src/widgets/map_view.cpp

/*
 * Copyright (C) 2014-2018 Christopho, Solarus - http://www.solarus-games.org
 *
 * Solarus Quest Editor is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Solarus Quest Editor is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */
#include "entities/tile.h"
#include "widgets/edit_entity_dialog.h"
#include "widgets/entity_item.h"
#include "widgets/enum_menus.h"
#include "widgets/gui_tools.h"
#include "widgets/map_scene.h"
#include "widgets/map_view.h"
#include "widgets/mouse_coordinates_tracking_tool.h"
#include "widgets/pan_tool.h"
#include "widgets/zoom_tool.h"
#include "point.h"
#include "quest.h"
#include "rectangle.h"
#include "tileset_model.h"
#include "view_settings.h"
#include <QAction>
#include <QActionGroup>
#include <QApplication>
#include <QClipboard>
#include <QDebug>
#include <QGraphicsItem>
#include <QMap>
#include <QMenu>
#include <QMouseEvent>
#include <QScrollBar>
#include <QtMath>
#include <QPainterPath>

namespace SolarusEditor {

namespace {

/**
 * @brief State of the map view corresponding to the user doing nothing special.
 *
 * He can select or unselect entities.
 */
class DoingNothingState : public MapView::State {

public:
  explicit DoingNothingState(MapView& view);

  void mouse_pressed(const QMouseEvent& event) override;
  void mouse_moved(const QMouseEvent& event) override;
  void mouse_released(const QMouseEvent& event) override;
  void context_menu_requested(const QPoint& where) override;
  void tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) override;

private:
  QPoint mouse_pressed_point;               /**< Point where the mouse was pressed, in view coordinates. */
  bool clicked_with_control_or_shift;
};

/**
 * @brief State of the map view of drawing a selection rectangle.
 */
class DrawingRectangleState : public MapView::State {

public:
  DrawingRectangleState(MapView& view, const QPoint& initial_point);

  void start() override;
  void stop() override;

  void mouse_moved(const QMouseEvent& event) override;
  void mouse_released(const QMouseEvent& event) override;

private:
  QPoint initial_point;                     /**< Point where the drawing started, in scene coordinates. */
  QPoint current_point;                     /**< Point where the dragging currently is, in scene coordinates. */
  QGraphicsRectItem* current_area_item;     /**< Graphic item of the rectangle the user is drawing
                                             * (belongs to the scene). */
  QList<QGraphicsItem*> initial_selection;  /**< Items that were selected before the drawing started. */
};

/**
 * @brief State of the map view of moving the selected entities.
 */
class MovingEntitiesState : public MapView::State {

public:
  MovingEntitiesState(MapView& view, const QPoint& initial_point);

  void cancel() override;

  void mouse_moved(const QMouseEvent& event) override;
  void mouse_released(const QMouseEvent& event) override;

private:
  QPoint initial_point;      /**< Point where the dragging started, in scene coordinates. */
  QPoint last_point;         /**< Point where the mouse was last time it moved, in scene coordinates. */
  bool first_move_done;      /**< Whether at least one move was done during the state. */
};

/**
 * @brief State of the map view of resizing entities.
 */
class ResizingEntitiesState : public MapView::State {

public:
  ResizingEntitiesState(MapView& view, const EntityIndexes& entities);
  void start() override;
  void cancel() override;

  void mouse_moved(const QMouseEvent& event) override;
  void mouse_released(const QMouseEvent& event) override;

private:
  void compute_center();
  void compute_leader();
  void compute_fixed_corner();
  void update_boxes(
      const QPoint& leader_expansion,
      bool horizontal_preferred
  );
  QRect update_box(
      const EntityIndex& index,
      const QPoint& leader_expansion,
      bool horizontal_preferred);
  QRect apply_smart_resizing(
      const EntityIndex& index,
      ResizeMode resize_mode,
      bool horizontal_preferred,
      const QPoint& leader_expansion
  );
  QRect get_box_from_expansion_and_translation(
      const EntityIndex& index,
      const QPoint& expansion,
      const QPoint& translation
  );
  QRect apply_constraints(
      const EntityIndex& index,
      ResizeMode resize_mode,
      bool horizontal_preferred,
      const QRect& box
  );
  static bool is_horizontally_resizable(
      ResizeMode resize_mode, bool horizontal_preferred);
  static bool is_vertically_resizable(
      ResizeMode resize_mode, bool horizontal_preferred);

  EntityIndexes entities;         /**< Entities to resize. */
  QMap<EntityIndex, QRect>
      old_boxes;                  /**< Bounding rectangle of each entity before resizing. */
  EntityIndex leader_index;       /**< Entity whose resizing follows the cursor position.
                                   * Other ones reproduce an equivalent change. */
  QPoint center;                  /**< Center of the bounding box of entities to resize. */
  QPoint fixed_corner;            /**< Which corner of the initial entities box
                                   * is fixed (+-1, +-1).
                                   * The opposite one follows the mouse. */
  bool first_resize_done;         /**< Whether at least one resizing was done during the state. */
  int num_free_entities;          /**< Number of entities freely resizable (mode ResizeMode::MULTI_DIMENSION_ALL). */

};

/**
 * @brief State of the map view of adding new entities.
 */
class AddingEntitiesState : public MapView::State {

public:
  AddingEntitiesState(MapView& view, EntityModels&& entities, bool guess_layer);
  void start() override;
  void stop() override;
  void mouse_pressed(const QMouseEvent& event) override;
  void mouse_moved(const QMouseEvent& event) override;
  void tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) override;

private:
  QPoint get_entities_center() const;
  void sort_entities();
  int find_best_layer(const EntityModel& entity) const;

  EntityModels entities;                    /**< Entities to be added. */
  std::vector<EntityItem*> entity_items;    /**< Graphic items of entities to be added. */
  QPoint last_point;                        /**< Point where the mouse was last time it moved, in scene coordinates. */
  bool guess_layer;                         /**< Whether the layer should be guessed or kept unchanged. */
};

}  // Anonymous namespace.

/**
 * @brief Creates a map view.
 * @param parent The parent widget or nullptr.
 */
MapView::MapView(QWidget* parent) :
  QGraphicsView(parent),
  map(),
  scene(nullptr),
  view_settings(nullptr),
  zoom(1.0),
  state(),
  common_actions(nullptr),
  edit_action(nullptr),
  resize_action(nullptr),
  convert_tiles_action(nullptr),
  set_layer_actions(),
  set_layer_actions_group(nullptr),
  up_one_layer_action(nullptr),
  down_one_layer_action(nullptr),
  bring_to_front_action(nullptr),
  bring_to_back_action(nullptr),
  remove_action(nullptr),
  cancel_action(nullptr) {

  setAlignment(Qt::AlignTop | Qt::AlignLeft);

  ViewSettings* view_settings = new ViewSettings(this);
  set_view_settings(*view_settings);

  // Necessary because we draw a custom background.
  setViewportUpdateMode(QGraphicsView::FullViewportUpdate);

  // Initialize actions.
  build_context_menu_actions();
}

/**
 * @brief Returns the map represented in this view.
 * @return The map model or nullptr if none was set.
 */
MapModel* MapView::get_map() {
  return map.data();
}

/**
 * @brief Sets the map to represent in this view.
 * @param map The map model, or nullptr to remove any model.
 * This class does not take ownership on the map.
 */
void MapView::set_map(MapModel* map) {

  if (this->map != nullptr) {
    this->map = nullptr;
    this->scene = nullptr;
  }

  this->map = map;

  if (map != nullptr) {
    // Create the scene from the map.
    scene = new MapScene(*map, this);
    setScene(scene);

    // Initialize layers.
    connect(map, &MapModel::layer_range_changed, [this]() {
      build_context_menu_layer_actions();
    });
    build_context_menu_layer_actions();

    // Enable useful features if there is an image.
    if (view_settings != nullptr) {
      view_settings->set_zoom(2.0);  // Initial zoom: x2.
    }
    horizontalScrollBar()->setValue(0);
    verticalScrollBar()->setValue(0);

    // Install panning and zooming helpers.
    new PanTool(this);
    new ZoomTool(this);
    new MouseCoordinatesTrackingTool(this);

    // Connect signals.
    connect(map, &MapModel::tileset_id_changed,
            this, &MapView::tileset_id_changed);
    tileset_id_changed(map->get_tileset_id());

    // Start the state mechanism.
    start_state_doing_nothing();
  }
}

/**
 * @brief Returns the map scene represented in this view.
 * @return The scene or nullptr if no map was set.
 */
MapScene* MapView::get_scene() {
  return scene;
}

/**
 * @brief Returns the view settings for this map view.
 * @return The view settings, or nullptr if none were set.
 */
const ViewSettings* MapView::get_view_settings() const {
  return view_settings;
}

/**
 * @brief Sets the view settings for this map view.
 *
 * When they change, the map view is updated accordingly.
 *
 * @param view_settings The settings to watch.
 */
void MapView::set_view_settings(ViewSettings& view_settings) {

  this->view_settings = &view_settings;

  connect(this->view_settings, &ViewSettings::zoom_changed,
          this, &MapView::update_zoom);
  update_zoom();

  connect(this->view_settings, &ViewSettings::grid_visibility_changed,
          this, &MapView::update_grid_visibility);
  connect(this->view_settings, &ViewSettings::grid_size_changed,
          this, &MapView::update_grid_visibility);
  connect(this->view_settings, &ViewSettings::grid_style_changed,
          this, &MapView::update_grid_visibility);
  connect(this->view_settings, &ViewSettings::grid_color_changed,
          this, &MapView::update_grid_visibility);
  update_grid_visibility();

  connect(this->view_settings, &ViewSettings::layer_visibility_changed,
          this, &MapView::update_layer_visibility);
  connect(this->view_settings, &ViewSettings::layer_locking_changed,
          this, &MapView::update_layer_locking);

  connect(this->view_settings, &ViewSettings::traversables_visibility_changed,
          this, &MapView::update_traversables_visibility);
  connect(this->view_settings, &ViewSettings::obstacles_visibility_changed,
          this, &MapView::update_obstacles_visibility);
  connect(this->view_settings, &ViewSettings::entity_type_visibility_changed,
          this, &MapView::update_entity_type_visibility);

  horizontalScrollBar()->setValue(0);
  verticalScrollBar()->setValue(0);
}

/**
 * @brief Returns the common actions of the editor.
 * @return The common actions or nullptr if unset.
 */
const QMap<QString, QAction*>* MapView::get_common_actions() const {
  return common_actions;
}

/**
 * @brief Sets the common actions of the editor.
 *
 * This function should be called at initialization time to make actions
 * available in the context menu.
 *
 * @param common_actions The common actions.
 */
void MapView::set_common_actions(const QMap<QString, QAction*>* common_actions) {
  this->common_actions = common_actions;
}

/**
 * @brief Changes the state of the view.
 *
 * The previous state if any is destroyed.
 *
 * @param state The new state.
 */
void MapView::set_state(std::unique_ptr<State> state) {

  if (this->state != nullptr) {
    this->state->stop();
  }

  this->state = std::move(state);

  if (this->state != nullptr) {
    this->state->start();
  }
}

/**
 * @brief Moves to the normal state of the map view.
 */
void MapView::start_state_doing_nothing() {

  set_state(std::unique_ptr<State>(new DoingNothingState(*this)));

  emit stopped_state();
}

/**
 * @brief Moves to the state of drawing a rectangle for a selection.
 * @param initial_point Where the user starts drawing the rectangle,
 * in view coordinates.
 */
void MapView::start_state_drawing_rectangle(const QPoint& initial_point) {

  set_state(std::unique_ptr<State>(new DrawingRectangleState(*this, initial_point)));
}

/**
 * @brief Moves to the state of moving the selected entities.
 * @param initial_point Where the user starts dragging the entities,
 */
void MapView::start_state_moving_entities(const QPoint& initial_point) {

  set_state(std::unique_ptr<State>(new MovingEntitiesState(*this, initial_point)));
}

/**
 * @brief Moves to the state of resizing the selected entities.
 *
 * Does nothing if there is no selected entity or if the selection is not
 * resizable.
 */
void MapView::start_state_resizing_entities() {

  const EntityIndexes selection = get_selected_entities();
  if (!are_entities_resizable(selection)) {
    // The selection is empty or not resizable.
    start_state_doing_nothing();
    return;
  }

  set_state(std::unique_ptr<State>(new ResizingEntitiesState(*this, selection)));
}

/**
 * @brief Moves to the state of adding new entities.
 * @param entities The entities to be added.
 * They must not belong to the map yet.
 * @param guess_layer Whether a layer should be guessed from the preferred
 * layer of entities and the mouse position.
 */
void MapView::start_state_adding_entities(EntityModels&& entities, bool guess_layer) {

  set_state(std::unique_ptr<State>(new AddingEntitiesState(
       *this,
       std::move(entities),
       guess_layer)));
}

/**
 * @brief Moves to the state of adding new entities, adding the specified tiles.
 * @param tileset_id Id of the tileset to use (empty means the one of the map).
 * @param indexes Indexes of the selected patterns.
 */
void MapView::start_adding_entities_from_tileset(const QString& tileset_id, const QList<int>& indexes) {

  if (indexes.isEmpty()) {
    return;
  }

  MapModel* map = get_map();
  if (map == nullptr) {
    return;
  }

  QString id = !tileset_id.isEmpty() ? tileset_id : map->get_tileset_id();
  TilesetModel* tileset = map->get_quest().get_tileset(id);
  if (tileset == nullptr) {
    return;
  }

  // Create a tile from each selected pattern.
  // Arrange the relative position of tiles as in the tileset.
  EntityModels tiles;

  bool has_common_preferred_layer = true;
  int common_preferred_layer = tileset->get_pattern_default_layer(indexes.first());
  for (int pattern_index : indexes) {
    QString pattern_id = tileset->index_to_id(pattern_index);
    if (pattern_id.isEmpty()) {
      continue;
    }

    // Create a tile from the pattern.
    QRect pattern_frame = tileset->get_pattern_frame(pattern_index);
    EntityModelPtr tile = EntityModel::create(*map, EntityType::TILE);
    tile->set_field("pattern", pattern_id);
    tile->set_size(pattern_frame.size());
    tile->set_xy(pattern_frame.topLeft());
    int preferred_layer = tileset->get_pattern_default_layer(pattern_index);
    tile->set_layer(preferred_layer);
    if (!tileset_id.isEmpty()) {
      // Not the default tileset of the map.
      tile->set_field("tileset", tileset_id);
    }
    tiles.emplace_back(std::move(tile));

    // Also check if they all have the same preferred layer.
    if (preferred_layer != common_preferred_layer) {
      has_common_preferred_layer = false;
    }
  }

  // Don't try to choose other layers if they are different at start.
  bool guess_layer = has_common_preferred_layer;

  start_state_adding_entities(std::move(tiles), guess_layer);
}

/**
 * @brief Returns whether at least one entity of a list is resizable.
 * @param indexes Indexes of entities to resize.
 * @return @c true at least one is resizable.
 */
bool MapView::are_entities_resizable(const EntityIndexes& indexes) const {

  for (const EntityIndex& index : indexes) {
    if (map->get_entity(index).is_resizable()) {
      return true;
    }
  }
  return false;
}

/**
 * @brief Creates all actions to be used by context menus.
 */
void MapView::build_context_menu_actions() {

  edit_action = new QAction(
        tr("Edit"), this);
  edit_action->setShortcut(Qt::Key_Return);
  edit_action->setShortcutContext(Qt::WidgetWithChildrenShortcut);
  connect(edit_action, &QAction::triggered,
          this, &MapView::edit_selected_entity);
  addAction(edit_action);

  resize_action = new QAction(
        tr("Resize"), this);
  resize_action->setShortcut(tr("R"));
  resize_action->setShortcutContext(Qt::WidgetWithChildrenShortcut);
  connect(resize_action, &QAction::triggered,
          this, &MapView::start_state_resizing_entities);
  addAction(resize_action);

  convert_tiles_action = new QAction(
        tr("Convert to dynamic tile"), this);
  connect(convert_tiles_action, &QAction::triggered,
          this, &MapView::convert_selected_tiles);
  addAction(convert_tiles_action);

  change_pattern_action = new QAction(
        tr("Change pattern..."), this);
  connect(change_pattern_action, &QAction::triggered, [this]() {
    emit change_tiles_pattern_requested(get_selected_entities());
  });
  addAction(change_pattern_action);

  change_pattern_all_action = new QAction(
        tr("Change pattern of similar tiles..."), this);
  connect(change_pattern_all_action, &QAction::triggered,
          this, &MapView::change_pattern_of_similar_tiles);
  addAction(change_pattern_action);

  add_border_action = new QAction(
        tr("Generate borders around selection"), this);
  add_border_action->setShortcut(tr("Ctrl+B"));
  add_border_action->setShortcutContext(Qt::WindowShortcut);
  connect(add_border_action, &QAction::triggered, [this]() {
    emit generate_borders_requested(get_selected_entities());
  });
  addAction(add_border_action);

  up_one_layer_action = new QAction(
        tr("One layer up"), this);
  up_one_layer_action->setShortcut(tr("+"));
  up_one_layer_action->setShortcutContext(Qt::WindowShortcut);
  connect(up_one_layer_action, &QAction::triggered, [this]() {
    emit increase_entities_layer_requested(get_selected_entities());
  });
  addAction(up_one_layer_action);

  down_one_layer_action = new QAction(
        tr("One layer down"), this);
  down_one_layer_action->setShortcut(tr("-"));
  down_one_layer_action->setShortcutContext(Qt::WindowShortcut);
  connect(down_one_layer_action, &QAction::triggered, [this]() {
    emit decrease_entities_layer_requested(get_selected_entities());
  });
  addAction(down_one_layer_action);

  bring_to_front_action = new QAction(
        tr("Bring to front"), this);
  bring_to_front_action->setShortcut(tr("T"));
  bring_to_front_action->setShortcutContext(Qt::WindowShortcut);
  connect(bring_to_front_action, &QAction::triggered, [this]() {
    emit bring_entities_to_front_requested(get_selected_entities());
  });
  addAction(bring_to_front_action);

  bring_to_back_action = new QAction(
        tr("Bring to back"), this);
  bring_to_back_action->setShortcut(tr("B"));
  bring_to_back_action->setShortcutContext(Qt::WindowShortcut);
  connect(bring_to_back_action, &QAction::triggered, [this]() {
    emit bring_entities_to_back_requested(get_selected_entities());
  });
  addAction(bring_to_back_action);

  remove_action = new QAction(
        QIcon(":/images/icon_delete.png"), tr("Delete"), this);
  remove_action->setShortcut(QKeySequence::Delete);
  remove_action->setShortcutContext(Qt::WidgetWithChildrenShortcut);
  connect(remove_action, &QAction::triggered,
          this, &MapView::remove_selected_entities);
  addAction(remove_action);

  cancel_action = new QAction(tr("Cancel"), this);
  cancel_action->setShortcut(Qt::Key_Escape);
  cancel_action->setShortcutContext(Qt::WindowShortcut);
  connect(cancel_action, &QAction::triggered,
          this, &MapView::cancel_state_requested);
  addAction(cancel_action);

  build_context_menu_layer_actions();
}

/**
 * @brief Creates all layer actions to be used by context menus.
 *
 * This function should be called when the number of layers of the map changes.
 */
void MapView::build_context_menu_layer_actions() {

  if (get_map() == nullptr) {
    return;
  }

  // Clean the old actions.
  delete set_layer_actions_group;
  set_layer_actions.clear();

  // Create new ones.
  set_layer_actions_group = new QActionGroup(this);
  set_layer_actions_group->setExclusive(true);
  for (int layer = get_map()->get_min_layer(); layer <= get_map()->get_max_layer(); ++layer) {
    QAction* action = new QAction(tr("Layer %1").arg(layer), set_layer_actions_group);
    action->setCheckable(true);
    connect(action, &QAction::triggered, [this, layer]() {
      emit set_entities_layer_requested(get_selected_entities(), layer);
    });
    set_layer_actions.push_back(action);
  }
}

/**
 * @brief Creates a context menu for the selected entities.
 * @return A context menu.
 */
QMenu* MapView::create_context_menu() {

  // Layout of the context menu (line breaks are separators):
  //
  // Edit, Resize, Direction
  // Change pattern, Change pattern of all, Convert to dynamic/static tile(s)
  // Cut, Copy, Paste
  // Borders
  // Layers, One layer up, One layer down
  // Bring to front, Bring to back
  // Delete

  QMenu* menu = new QMenu(this);
  const EntityIndexes& indexes = get_selected_entities();

  if (!is_selection_empty()) {

    // Edit.
    const bool single_selection = indexes.size() <= 1;
    Q_ASSERT(edit_action != nullptr);
    edit_action->setEnabled(single_selection);
    menu->addAction(edit_action);

    // Resize.
    const bool resizable = are_entities_resizable(indexes);
    resize_action->setEnabled(resizable);
    menu->addAction(resize_action);

    // Direction.
    QMenu* direction_menu = create_direction_context_menu(indexes);
    Q_ASSERT(direction_menu != nullptr);
    menu->addMenu(direction_menu);
    menu->addSeparator();

    // Convert to dynamic/static tile(s).
    bool tile_action_added = false;
    EntityType type;
    const bool show_convert_tiles_action = map->is_common_type(indexes, type) &&
        (type == EntityType::TILE || type == EntityType::DYNAMIC_TILE);
    if (show_convert_tiles_action) {
      QString text;
      if (type == EntityType::TILE) {
        text = single_selection ? tr("Convert to dynamic tile") : tr("Convert to dynamic tiles");
      }
      else {
        text = single_selection ? tr("Convert to static tile") : tr("Convert to static tiles");
      }
      convert_tiles_action->setText(text);
      menu->addAction(convert_tiles_action);
      tile_action_added = true;
    }

    if (map->are_tiles(indexes)) {

      bool same_pattern = true;
      const QString& pattern_id = map->get_entity_field(indexes.first(), "pattern").toString();
      for (const EntityIndex& index : indexes) {
        if (map->get_entity_field(index, "pattern").toString() != pattern_id) {
          same_pattern = false;
          break;
        }
      }

      bool same_tileset = true;
      const QString& tileset_id = map->get_entity_field(indexes.first(), "tileset").toString();
      for (const EntityIndex& index : indexes) {
        if (map->get_entity_field(index, "tileset").toString() != tileset_id) {
          same_tileset = false;
          break;
        }
      }

      // Change pattern.
      if (same_tileset) {
        menu->addAction(change_pattern_action);
        tile_action_added = true;
        // Change pattern of all similar tiles.
        if (same_pattern) {
          menu->addAction(change_pattern_all_action);
        }
      }
    }

    if (tile_action_added) {
      menu->addSeparator();
    }
  }

  // Cut, copy, paste.
  if (common_actions != nullptr) {
    // Global actions are available.
    menu->addAction(common_actions->value("cut"));
    menu->addAction(common_actions->value("copy"));
    menu->addAction(common_actions->value("paste"));
    menu->addSeparator();
  }

  if (!is_selection_empty()) {

    // Borders.
    menu->addAction(add_border_action);
    menu->addSeparator();

    // Layer.
    int common_layer = -1;
    bool has_common_layer = map->is_common_layer(indexes, common_layer);
    for (int i = 0; i < set_layer_actions.size(); ++i) {
      QAction* action = set_layer_actions[i];
      int layer = i + map->get_min_layer();
      action->setChecked(false);
      if (has_common_layer && layer == common_layer) {
        action->setChecked(true);
      }
      menu->addAction(action);
    }

    up_one_layer_action->setEnabled(!has_common_layer || common_layer < get_map()->get_max_layer());
    down_one_layer_action->setEnabled(!has_common_layer || common_layer > get_map()->get_min_layer());
    menu->addAction(up_one_layer_action);
    menu->addAction(down_one_layer_action);

    // Bring to front/back.
    menu->addAction(bring_to_front_action);
    menu->addAction(bring_to_back_action);
    menu->addSeparator();

    // Remove.
    menu->addAction(remove_action);
  }

  return menu;
}

/**
 * @brief Creates a context menu to select the direction of entities.
 *
 * Returns a disabled menu if the direction rules of the given entities are incompatible.
 *
 * @param indexes Indexes of entity to treat.
 * @return The direction context menu.
 */
QMenu* MapView::create_direction_context_menu(const EntityIndexes& indexes) {

  QMenu* menu = new QMenu(tr("Direction"), this);

  int num_directions = 0;
  QString no_direction_text;
  if (!map->is_common_direction_rules(indexes, num_directions, no_direction_text)) {
    // Directions rules are incompatible.
    menu->setEnabled(false);
    return menu;
  }

  if (num_directions == 0) {
    // There is no direction field on these entities.
    menu->setEnabled(false);
    return menu;
  }

  QStringList texts;
  if (num_directions == 4) {
    texts = QStringList{
      tr("Right"),
      tr("Up"),
      tr("Left"),
      tr("Down")
    };
  }
  else if (num_directions == 8) {
    texts = QStringList{
      tr("Right"),
      tr("Right-up"),
      tr("Up"),
      tr("Left-up"),
      tr("Left"),
      tr("Left-down"),
      tr("Down"),
      tr("Right-down"),
    };
  }
  else {
    for (int i = 0; i < num_directions; ++num_directions) {
      texts.append(QString::number(i));
    }
  }

  // Create the actions.
  if (!no_direction_text.isEmpty()) {
    // Special no-direction value.
    QAction* action = new QAction(no_direction_text, menu);
    action->setCheckable(true);
    connect(action, &QAction::triggered, [this, indexes]() {
      emit set_entities_direction_requested(indexes, -1);
    });
    menu->addAction(action);
  }
  for (int i = 0; i < num_directions; ++i) {
    // Normal direction.
    QAction* action = new QAction(texts[i], menu);
    action->setCheckable(true);
    connect(action, &QAction::triggered, [this, indexes, i]() {
      emit set_entities_direction_requested(indexes, i);
    });
    menu->addAction(action);
  }

  // Check the common direction if any.
  int direction = -1;
  if (map->is_common_direction(indexes, direction)) {
    int i = direction;
    if (!no_direction_text.isEmpty()) {
      ++i;
    }
    menu->actions().at(i)->setChecked(true);
  }

  return menu;
}

/**
 * @brief Exports the current view to an image.
 * @return The map image.
 */
QImage MapView::export_to_image() {

  if (scene == nullptr) {
    return QImage();
  }

  // Clear the selection first (we don't want selection markers.
  EntityIndexes selected_indexes = get_selected_entities();
  set_selected_entities(EntityIndexes());

  // Create the image.
  QImage image(map->get_size(), QImage::Format_ARGB32);
  image.fill(Qt::transparent);
  QPainter painter(&image);
  scene->render(&painter, image.rect(),
                QRect(scene->get_margin_top_left(), map->get_size()));

  // Restore the selection.
  set_selected_entities(selected_indexes);

  return image;
}

/**
 * @brief Copies the selected entities to the clipboard and removes them.
 */
void MapView::cut() {

  if (is_selection_empty()) {
    return;
  }

  copy();
  remove_selected_entities();
}

/**
 * @brief Copies the selected entities to the clipboard.
 */
void MapView::copy() {

  if (map == nullptr) {
    return;
  }

  EntityIndexes indexes = get_selected_entities();
  if (indexes.isEmpty()) {
    return;
  }

  // Sort entities to respect their relative order on the map when pasting.
  std::sort(indexes.begin(), indexes.end());

  QStringList entity_strings;
  for (const EntityIndex& index : indexes) {
    Q_ASSERT(map->entity_exists(index));
    const EntityModel& entity = map->get_entity(index);
    QString entity_string = entity.to_string();
    Q_ASSERT(!entity_string.isEmpty());
    entity_strings << entity_string;
  }

  QString text = entity_strings.join("");
  QApplication::clipboard()->setText(text);
}

/**
 * @brief Adds entities from the clipboard.
 */
void MapView::paste() {

  if (scene == nullptr) {
    return;
  }

  QString text = QApplication::clipboard()->text();
  if (text.isEmpty()) {
    return;
  }

  QStringList entity_strings = text.split(QRegExp("[\n\r]\\}[\n\r]"), QString::SkipEmptyParts);

  EntityModels entities;
  for (int i = 0; i < entity_strings.size(); ++i) {

    QString entity_string = entity_strings.at(i);

    if (entity_string.simplified().isEmpty()) {
      // Only whitespaces: skip.
      continue;
    }

    if (i < entity_strings.size() - 1) {
      entity_string = entity_string + "}";  // Restore the closing brace removed by split().
    }
    EntityModelPtr entity = EntityModel::create(*get_map(), entity_string);
    if (entity == nullptr) {
      // The text data from the clipboard is not a valid entity.
      return;
    }

    entities.push_back(std::move(entity));
  }

  if (entities.empty()) {
    return;
  }

  const bool guess_layer = false;  // Paste entities on the same layer.
  start_state_adding_entities(std::move(entities), guess_layer);
}

/**
 * @brief Sets the zoom level of the view from the settings.
 *
 * Zooming will be anchored at the mouse position.
 * The zoom value will be clamped between 0.25 and 4.0.
 */
void MapView::update_zoom() {

  if (view_settings == nullptr) {
    return;
  }

  double zoom = view_settings->get_zoom();
  zoom = qMin(4.0, qMax(0.25, zoom));

  if (zoom == this->zoom) {
    return;
  }

  setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
  double scale_factor = zoom / this->zoom;
  scale(scale_factor, scale_factor);
  this->zoom = zoom;
}

/**
 * @brief Scales the view by a factor of 2.
 *
 * Zooming will be anchored at the mouse position.
 * The maximum zoom value is 4.0: this function does nothing if you try to
 * zoom more.
 */
void MapView::zoom_in() {

  if (view_settings == nullptr) {
    return;
  }

  view_settings->set_zoom(view_settings->get_zoom() * 2.0);
}

/**
 * @brief Scales the view by a factor of 0.5.
 *
 * Zooming will be anchored at the mouse position.
 * The maximum zoom value is 0.25: this function does nothing if you try to
 * zoom less.
 */
void MapView::zoom_out() {

  if (view_settings == nullptr) {
    return;
  }

  view_settings->set_zoom(view_settings->get_zoom() / 2.0);
}

/**
 * @brief Slot called when the mouse coordinates on the view have changed.
 *
 * Translates the coordinates relative to the view into coordinates relative
 * to the map and emits mouse_map_coordinates_changed().
 *
 * @param xy The mouse coordinates relative to the widget.
 */
void MapView::mouse_coordinates_changed(const QPoint& xy) {

  QPoint map_xy = mapToScene(xy).toPoint() - MapScene::get_margin_top_left();
  emit mouse_map_coordinates_changed(map_xy);
}

/**
 * @brief Shows or hides the grid according to the view settings.
 */
void MapView::update_grid_visibility() {

  if (view_settings == nullptr) {
    return;
  }

  if (scene != nullptr) {
    // The foreground has changed.
    scene->invalidate();
  }
}

/**
 * @brief Shows or hides entities on a layer according to the view settings.
 * @param layer The layer to update.
 */
void MapView::update_layer_visibility(int layer) {

  if (scene == nullptr) {
    return;
  }

  scene->update_layer_visibility(layer, *view_settings);
}

/**
 * @brief Locks or unlock a layer according to the view settings.
 * @param layer The layer to update.
 */
void MapView::update_layer_locking(int layer) {

  if (scene == nullptr) {
    return;
  }

  scene->update_layer_locking(layer, *view_settings);
}

/**
 * @brief Shows or hides traversables according to the view settings.
 */
void MapView::update_traversables_visibility() {

  if (scene == nullptr) {
    return;
  }

  scene->update_traversables_visibility(*view_settings);
}

/**
 * @brief Shows or hides obstacles according to the view settings.
 */
void MapView::update_obstacles_visibility() {

  if (scene == nullptr) {
    return;
  }

  scene->update_obstacles_visibility(*view_settings);
}

/**
 * @brief Shows or hides entities of a type according to the view settings.
 * @param type The entity type to update.
 */
void MapView::update_entity_type_visibility(EntityType type) {

  scene->update_entity_type_visibility(type, *view_settings);
}
/**

 * @brief Function called when the pattern selection of the tileset is changed
 * by the user.
 *
 * Tiles with these new patterns are added if possible.
 *
 * @param tileset_id Id of the tileset to use (empty means the one of the map).
 * @param indexes Indexes of the selected patterns.
 */
void MapView::tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) {

  if (state == nullptr) {
    return;
  }

  state->tileset_selection_changed(tileset_id, indexes);
}

/**
 * @brief Slot called when another tileset is set on the map.
 * @param tileset_id The new tileset id.
 */
void MapView::tileset_id_changed(const QString& tileset_id) {

  Q_UNUSED(tileset_id);
  disconnect(this, SLOT(notify_tileset_changed()));

  if (map->get_tileset_model() != nullptr) {
    // Watch changes of this tileset.
    connect(map->get_tileset_model(), &TilesetModel::modelReset,
            this, &MapView::notify_tileset_changed);
  }

  // TODO only if there is really a change
  notify_tileset_changed();
}

/**
 * @brief Slot called when the tileset has changed.
 */
void MapView::notify_tileset_changed() {

  if (scene == nullptr) {
    return;
  }
  scene->update();

  start_state_doing_nothing();
}

/**
 * @brief Draws the map view.
 * @param event The paint event.
 */
void MapView::paintEvent(QPaintEvent* event) {

  QGraphicsView::paintEvent(event);

  if (view_settings == nullptr || !view_settings->is_grid_visible()) {
    return;
  }

  // Get the rect and convert to the scene.
  QRect rect = mapToScene(event->rect()).boundingRect().toRect();

  // Get grid and margin.
  QSize grid = view_settings->get_grid_size();
  QSize margin = scene != nullptr ? scene->get_margin_size() : QSize(0, 0);

  // Adjust the rect.
  rect.setTopLeft(QPoint(
    (margin.width() % grid.width()) - grid.width(),
    (margin.height() % grid.height()) - grid.height()));

  // Convert the rect from the scene.
  rect = mapFromScene(rect).boundingRect();
  grid *= zoom;

  // Draw the grid.
  QPainter painter(viewport());
  GuiTools::draw_grid(
    painter, rect, grid, view_settings->get_grid_color(),
    view_settings->get_grid_style());
}

/**
 * @brief Receives a key press event.
 * @param event The event to handle.
 */
void MapView::keyPressEvent(QKeyEvent* event) {

  switch (event->key()) {

  case Qt::Key_Enter:
    // Numpad enter key.
    // For some reason, this particular key does not work as a QAction shortcut
    // on all systems.
    edit_selected_entity();
    break;

  case Qt::Key_Plus:
    // Make sure that the numpad plus key works too.
    emit increase_entities_layer_requested(get_selected_entities());
    break;

  case Qt::Key_Minus:
    // Make sure that the numpad minus key works too.
    emit decrease_entities_layer_requested(get_selected_entities());
    break;

  default:
    break;
  }
}

/**
 * @brief Receives a mouse press event.
 * @param event The event to handle.
 */
void MapView::mousePressEvent(QMouseEvent* event) {

  if (map == nullptr || get_scene() == nullptr) {
    return;
  }

  if (!(QApplication::mouseButtons() & event->button())) {
    // The button that triggered this event is no longer pressed.
    // This is possible if pressing the button already triggered something
    // else like a modal dialog.
    return;
  }

  state->mouse_pressed(*event);

  // Don't forward the event to the parent because it would select the item
  // clicked. We only do this explicitly from specific states.
}

/**
 * @brief Receives a mouse release event.
 * @param event The event to handle.
 */
void MapView::mouseReleaseEvent(QMouseEvent* event) {

  if (map != nullptr && get_scene() != nullptr) {
    state->mouse_released(*event);
  }

  QGraphicsView::mouseReleaseEvent(event);
}

/**
 * @brief Receives a mouse move event.
 * @param event The event to handle.
 */
void MapView::mouseMoveEvent(QMouseEvent* event) {

  if (map != nullptr && get_scene() != nullptr) {
    state->mouse_moved(*event);
  }

  // The parent class tracks the mouse movements for internal needs
  // such as anchoring the viewport to the mouse when zooming.
  QGraphicsView::mouseMoveEvent(event);
}

/**
 * @brief Receives a mouse double click event.
 * @param event The event to handle.
 */
void MapView::mouseDoubleClickEvent(QMouseEvent* event) {

  if (get_num_selected_entities() == 1) {

    QList<QGraphicsItem*> items_under_mouse = items(
          QRect(event->pos(), QSize(1, 1)),
          Qt::IntersectsItemBoundingRect  // Pick transparent items too.
    );
    if (!items_under_mouse.isEmpty()) {
      QGraphicsItem* item = items_under_mouse.first();
      EntityModel* entity = scene->get_entity_from_item(*item);
      if (entity != nullptr) {
        start_state_doing_nothing();
        edit_selected_entity();
      }
    }
  }
}

/**
 * @brief Receives a context menu event.
 * @param event The event to handle.
 */
void MapView::contextMenuEvent(QContextMenuEvent* event) {

  if (map == nullptr || get_scene() == nullptr) {
    return;
  }

  QPoint where;
  if (event->pos() != QPoint(0, 0)) {
    where = event->pos() + QPoint(1, 1);
  }
  else {
    QList<QGraphicsItem*> selected_items = scene->selectedItems();
    where = mapFromScene(selected_items.first()->pos() + QPoint(8, 8));
  }

  state->context_menu_requested(viewport()->mapToGlobal(where));
}

/**
 * @brief Returns whether the selection is empty.
 * @return @c true if the number of selected entities is zero.
 */
bool MapView::is_selection_empty() const {

  if (scene == nullptr) {
    return true;
  }

  return scene->selectedItems().isEmpty();
}

/**
 * @brief Returns the number of selected entities.
 * @return The number of selected entities.
 */
int MapView::get_num_selected_entities() const {

  if (scene == nullptr) {
    return 0;
  }

  return scene->selectedItems().size();
}

/**
 * @brief Returns the indexes of selected entities.
 * @return The selected entities.
 */
EntityIndexes MapView::get_selected_entities() const {

  if (scene == nullptr) {
    return EntityIndexes();
  }

  return scene->get_selected_entities();
}

/**
 * @brief Selects the specified entities and unselect the rest.
 * @param indexes Indexes of the entities to make selecteded.
 */
void MapView::set_selected_entities(const EntityIndexes& indexes) {

  if (scene == nullptr) {
    return;
  }

  scene->set_selected_entities(indexes);
}

/**
 * @brief Selects the specified entity and unselects the rest.
 * @param index Index of the entity to make selecteded.
 */
void MapView::set_only_selected_entity(const EntityIndex& index) {

  EntityIndexes indexes;
  indexes << index;

  set_selected_entities(indexes);
}

/**
 * @brief Selects or unselects an entity.
 * @param entity The entity to change.
 * @param selected @c true to select it.
 */
void MapView::select_entity(const EntityIndex& index, bool selected) {

  if (scene == nullptr) {
    return;
  }

  scene->select_entity(index, selected);
}

/**
 * @brief Creates copies of all selected entities.
 *
 * The created copies are not on the map.
 *
 * @return The created copies.
 */
EntityModels MapView::clone_selected_entities() const {

  EntityModels clones;
  const EntityIndexes& indexes = get_selected_entities();
  for (const EntityIndex& index : indexes) {
    EntityModelPtr clone = EntityModel::clone(*map, index);
    clones.emplace_back(std::move(clone));
  }
  return clones;
}

/**
 * @brief Returns the index of the entity under the cursor if any.
 * @return The index of the entity under the cursor of an invalid index.
 */
EntityIndex MapView::get_entity_index_under_cursor() const {

  if (scene == nullptr) {
    return EntityIndex();
  }

  QPoint xy = mapFromGlobal(QCursor::pos());
  if (xy.x() < 0 ||
      xy.x() >= width() ||
      xy.y() < 0 ||
      xy.y() >= height()) {
    // The mouse is outside the widget.
    return EntityIndex();
  }

  QGraphicsItem* item = itemAt(xy);
  if (item == nullptr) {
    // No entity under the mouse.
    return EntityIndex();
  }

  EntityModel* entity = scene->get_entity_from_item(*item);
  if (entity == nullptr) {
    // Not an entity.
    return EntityIndex();
  }

  return entity->get_index();
}

/**
 * @brief Slot called when the user wants to cancel the current state.
 */
void MapView::cancel_state_requested() {

  if (state != nullptr) {
    state->cancel();
  }
  start_state_doing_nothing();
}

/**
 * @brief Undoes the last command in the undo/redo history.
 */
void MapView::undo_last_command() {
  emit undo_requested();
}

/**
 * @brief Opens a dialog to edit the selected entity.
 *
 * Does nothing if the number of selected entities is not 1.
 */
void MapView::edit_selected_entity() {

  if (map == nullptr) {
    return;
  }

  EntityIndexes indexes = get_selected_entities();
  if (indexes.size() != 1) {
    return;
  }

  EntityIndex index = indexes.first();
  EditEntityDialog dialog(map->get_entity(index));
  int result = dialog.exec();
  if (result == QDialog::Rejected) {
    return;
  }

  EntityModelPtr entity_after = dialog.get_entity_after();
  emit edit_entity_requested(index, entity_after);
}

/**
 * @brief Converts the selected tiles to dynamic tiles or to normal tiles.
 */
void MapView::convert_selected_tiles() {

  emit convert_tiles_requested(get_selected_entities());
}

/**
 * @brief Changes the pattern of tiles having the same pattern as the selection.
 */
void MapView::change_pattern_of_similar_tiles() {

  const EntityIndexes& indexes = get_selected_entities();
  if (indexes.empty()) {
    return;
  }

  const QString& pattern_id = get_map()->get_entity_field(indexes.first(), "pattern").toString();
  const QString& tileset_id = get_map()->get_entity_field(indexes.first(), "tileset").toString();

  // Find all tiles and dynamic tiles that also have this pattern.
  const EntityIndexes& tiles = map->find_entities_of_type(EntityType::TILE);
  EntityIndexes similar_tiles;
  for (const EntityIndex& tile : tiles) {
    if (get_map()->get_entity_field(tile, "pattern").toString() == pattern_id &&
        get_map()->get_entity_field(tile, "tileset").toString() == tileset_id ) {
      similar_tiles << tile;
    }
  }
  const EntityIndexes& dynamic_tiles = map->find_entities_of_type(EntityType::DYNAMIC_TILE);
  for (const EntityIndex& dynamic_tile : dynamic_tiles) {
    if (get_map()->get_entity_field(dynamic_tile, "pattern").toString() == pattern_id &&
        get_map()->get_entity_field(dynamic_tile, "tileset").toString() == tileset_id) {
      similar_tiles << dynamic_tile;
    }
  }

  emit change_tiles_pattern_requested(similar_tiles);
}

/**
 * @brief Requests to resize the given entities with the specified bounding boxes.
 * @param translation XY coordinates to add.
 * @param allow_merge_to_previous @c true to merge this move with the previous one if any.
 */
void MapView::move_selected_entities(const QPoint& translation, bool allow_merge_to_previous) {

  emit move_entities_requested(get_selected_entities(), translation, allow_merge_to_previous);
}

/**
 * @brief Requests to move the selected entities with the specified translation.
 * @param boxes The new bounding box to set to each entity.
 * @param allow_merge_to_previous @c true to merge this resizing with the previous one if any.
 */
void MapView::resize_entities(const QMap<EntityIndex, QRect>& boxes, bool allow_merge_to_previous) {

  emit resize_entities_requested(boxes, allow_merge_to_previous);
}

/**
 * @brief Requests to delete the selected entities.
 */
void MapView::remove_selected_entities() {

  emit remove_entities_requested(get_selected_entities());
}

/**
 * @brief Creates a state.
 * @param view The map view to manage.
 */
MapView::State::State(MapView& view) :
  view(view) {

}

/**
 * @brief Returns the map view managed by this state.
 * @return The map view.
 */
const MapView& MapView::State::get_view() const {
  return view;
}

/**
 * @overload
 *
 * Non-const version.
 */
MapView& MapView::State::get_view() {
  return view;
}

/**
 * @brief Returns the map scene managed by this state.
 * @return The map scene.
 */
const MapScene& MapView::State::get_scene() const {

  return *view.get_scene();
}

/**
 * @overload
 *
 * Non-const version.
 */
MapScene& MapView::State::get_scene() {

  return *view.get_scene();
}

/**
 * @brief Returns the map model represented in the view.
 * @return The map model.
 */
const MapModel& MapView::State::get_map() const {
  return *view.get_map();
}

/**
 * @overload
 *
 * Non-const version.
 */
MapModel& MapView::State::get_map() {
  return *view.get_map();
}

/**
 * @brief Returns the point of a mouse event in map coordinates.
 * @param mouse_event A mouse event.
 * @return The point in mouse coordinates.
 */
QPoint MapView::State::to_map_point(const QMouseEvent& mouse_event) const {

  // Need to floor to know exactly the square that has the mouse.
  QPointF map_point_f = view.mapToScene(mouse_event.pos()) - MapScene::get_margin_top_left();
  return QPoint(
        qFloor(map_point_f.x()),
        qFloor(map_point_f.y())
  );
}

/**
 * @brief Called when entering this state.
 *
 * Subclasses can reimplement this function to initialize data.
 */
void MapView::State::start() {
}

/**
 * @brief Called when leaving this state.
 *
 * Subclasses can reimplement this function to clean data.
 */
void MapView::State::stop() {
}

/**
 * @brief Called when the user cancels this state.
 *
 * Any ongoing action the state has should be undone here.
 */
void MapView::State::cancel() {
}

/**
 * @brief Called when the mouse is pressed in the map view during this state.
 *
 * Subclasses can reimplement this function to define what happens.
 *
 * @param event The event to handle.
 */
void MapView::State::mouse_pressed(const QMouseEvent& event) {
  Q_UNUSED(event);
}

/**
 * @brief Called when the mouse is released in the map view during this state.
 *
 * Subclasses can reimplement this function to define what happens.
 *
 * @param event The event to handle.
 */
void MapView::State::mouse_released(const QMouseEvent& event) {
  Q_UNUSED(event);
}

/**
 * @brief Called when the mouse is moved in the map view during this state.
 *
 * Subclasses can reimplement this function to define what happens.
 *
 * @param event The event to handle.
 */
void MapView::State::mouse_moved(const QMouseEvent& event) {
  Q_UNUSED(event);
}

/**
 * @brief Called when a context menu is requested in the map view during this
 * state.
 *
 * Subclasses can reimplement this function to show a context menu.
 *
 * @param where Where to show the context menu, in global coordinates.
 */
void MapView::State::context_menu_requested(const QPoint& where) {
  Q_UNUSED(where);
}

/**
 * @brief Called when the user changes the selection in the tileset.
 *
 * States may start or stop adding entities.
 *
 * @param tileset_id Id of the tileset to use (empty means the one of the map).
 * @param indexes Indexes of the selected patterns.
 */
void MapView::State::tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) {
  Q_UNUSED(tileset_id);
  Q_UNUSED(indexes);
}

/**
 * @brief Constructor.
 * @param view The map view to manage.
 */
DoingNothingState::DoingNothingState(MapView& view) :
  MapView::State(view),
  clicked_with_control_or_shift(false) {

}

/**
 * @copydoc MapView::State::mouse_pressed
 */
void DoingNothingState::mouse_pressed(const QMouseEvent& event) {

  if (event.button() != Qt::LeftButton && event.button() != Qt::RightButton) {
    return;
  }

  MapView& view = get_view();
  MapScene& scene = get_scene();

  mouse_pressed_point = event.pos();

  // Left or right button: possibly change the selection.
  QList<QGraphicsItem*> items_under_mouse = view.items(
        QRect(event.pos(), QSize(1, 1)),
        Qt::IntersectsItemBoundingRect  // Pick transparent items too.
  );
  QGraphicsItem* item = items_under_mouse.isEmpty() ? nullptr : items_under_mouse.first();
  const EntityItem* entity_item = qgraphicsitem_cast<const EntityItem*>(item);

  const bool control_or_shift = (event.modifiers() & (Qt::ControlModifier | Qt::ShiftModifier));

  bool keep_selected = false;
  if (control_or_shift) {
    // If ctrl or shift is pressed, keep the existing selection.
    keep_selected = true;
  }
  else if (item != nullptr && item->isSelected()) {
    // When clicking an already selected item, keep the existing selection too.
    keep_selected = true;
  }

  if (!keep_selected) {
    scene.clearSelection();
  }

  if (event.button() == Qt::LeftButton) {

    if (item != nullptr) {

      if (control_or_shift) {
        // Either toggle the clicked item or start a selection rectangle.
        // If will depend on wether the mouse moves before it is released.
        clicked_with_control_or_shift = true;
      }
      else {
        if (!item->isSelected()) {
          // Select the item.
          if (entity_item != nullptr) {
            const EntityIndex& index = entity_item->get_index();
            if (!view.get_view_settings()->is_layer_locked(index.layer)) {
              view.select_entity(index, true);
            }
            else {
              // Left click on a locked layer: trace a selection rectangle.
              view.start_state_drawing_rectangle(event.pos());
              return;
            }
          }
        }
        // Allow to move selected items.
        view.start_state_moving_entities(event.pos());
      }
    }
    else {
      // Left click outside items: trace a selection rectangle.
      view.start_state_drawing_rectangle(event.pos());
    }
  }

  else if (event.button() == Qt::RightButton) {

    if (entity_item != nullptr) {
      if (!entity_item->isSelected()) {
        // Select the right-clicked item.
        const EntityIndex& index = entity_item->get_index();
        if (!view.get_view_settings()->is_layer_locked(index.layer)) {
          view.select_entity(index, true);
        }
      }
    }
  }
}

/**
 * @copydoc MapView::State::mouse_moved
 */
void DoingNothingState::mouse_moved(const QMouseEvent& event) {

  if (clicked_with_control_or_shift) {

    // Moving the mouse while control or shift is pressed:
    // start a selection rectangle after a small distance threshold.
    QPoint current_point = event.pos();
    if ((current_point - mouse_pressed_point).manhattanLength() >= 4) {
      // Significant move: not a click.
      // Start a selection rectangle.
      MapView& view = get_view();
      view.start_state_drawing_rectangle(mouse_pressed_point);
    }
  }
}

/**
 * @copydoc MapView::State::mouse_released
 */
void DoingNothingState::mouse_released(const QMouseEvent& event) {

  if (event.button() != Qt::LeftButton) {
    return;
  }

  if (clicked_with_control_or_shift) {
    // Left-clicking an item while pressing control or shift: toggle it.
    // If the mouse had moved in the meantime, mouse_moved() would have started
    // a selection rectangle.
    MapView& view = get_view();

    QList<QGraphicsItem*> items_under_mouse = view.items(
          QRect(event.pos(), QSize(1, 1)),
          Qt::IntersectsItemBoundingRect  // Pick transparent items too.
    );
    QGraphicsItem* item = items_under_mouse.isEmpty() ? nullptr : items_under_mouse.first();
    const EntityItem* entity_item = qgraphicsitem_cast<const EntityItem*>(item);
    if (entity_item != nullptr) {
      const bool was_selected = item->isSelected();
      if (was_selected) {
        view.select_entity(entity_item->get_index(), false);
      }
      else {
        const bool layer_locked = view.get_view_settings()->is_layer_locked(entity_item->get_index().layer);
        if (!layer_locked) {
          view.select_entity(entity_item->get_index(), true);
        }
      }
    }
    clicked_with_control_or_shift = false;
  }
}

/**
 * @copydoc MapView::State::context_menu_requested
 */
void DoingNothingState::context_menu_requested(const QPoint& where) {

  MapView& view = get_view();
  QMenu* menu = view.create_context_menu();
  menu->popup(where);
}

/**
 * @copydoc MapView::State::tileset_selection_changed
 */
void DoingNothingState::tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) {

  // Create corresponding tiles.
  get_view().start_adding_entities_from_tileset(tileset_id, indexes);
}

/**
 * @brief Constructor.
 * @param view The map view to manage.
 * @param initial_point Point where the drawing started, in view coordinates.
 */
DrawingRectangleState::DrawingRectangleState(MapView& view, const QPoint& initial_point) :
  MapView::State(view),
  initial_point(view.mapToScene(initial_point).toPoint()),
  current_area_item(nullptr),
  initial_selection() {

}

/**
 * @copydoc MapView::State::start
 */
void DrawingRectangleState::start() {

  current_area_item = new QGraphicsRectItem();
  current_area_item->setZValue(get_map().get_max_layer() + 2);
  current_area_item->setPen(QPen(Qt::yellow));
  get_scene().addItem(current_area_item);
  initial_selection = get_scene().selectedItems();
}

/**
 * @copydoc MapView::State::stop
 */
void DrawingRectangleState::stop() {

  get_scene().removeItem(current_area_item);
  delete current_area_item;
  current_area_item = nullptr;
}

/**
 * @copydoc MapView::State::mouse_moved
 */
void DrawingRectangleState::mouse_moved(const QMouseEvent& event) {

  MapView& view = get_view();
  MapScene& scene = get_scene();

  // Compute the selected area.
  QPoint previous_point = current_point;
  current_point = view.mapToScene(event.pos()).toPoint();

  if (current_point == previous_point) {
    // No change.
    return;
  }

  // The area has changed: recalculate the rectangle.
  QRect area = Rectangle::from_two_points(initial_point, current_point);
  current_area_item->setRect(area);

  bool was_blocked = scene.signalsBlocked();
  if (!initial_selection.isEmpty()) {
    // Block QGraphicsScene::selectionChanged() signal for individual selects.
    scene.blockSignals(true);
  }

  // Select items strictly in the rectangle.
  scene.clearSelection();
  QPainterPath path;
  path.addRect(QRect(area.topLeft() - QPoint(1, 1),
                     area.size() + QSize(2, 2)));
  scene.setSelectionArea(path, Qt::ContainsItemBoundingRect);

  // But don't select entities on locked layers.
  const EntityIndexes selected_indexes = scene.get_selected_entities();
  const ViewSettings& view_settings = *view.get_view_settings();
  for (const EntityIndex& index : selected_indexes) {
    if (view_settings.is_layer_locked(index.layer)) {
      view.select_entity(index, false);
    }
  }

  // Also restore the initial selection.
  for (int i = 0; i < initial_selection.size(); ++i) {
    const EntityItem* entity_item = qgraphicsitem_cast<const EntityItem*>(initial_selection[i]);

    // Unblock signals before the last select.
    if (i == initial_selection.size() - 1 ) {
      // Last element.
      scene.blockSignals(was_blocked);
    }

    view.select_entity(entity_item->get_index(), true);
  }
}

/**
 * @copydoc MapView::State::mouse_released
 */
void DrawingRectangleState::mouse_released(const QMouseEvent& event) {

  Q_UNUSED(event);

  get_view().start_state_doing_nothing();
}

/**
 * @brief Constructor.
 * @param view The map view to manage.
 * @param initial_point Point where the dragging started, in view coordinates.
 */
MovingEntitiesState::MovingEntitiesState(MapView& view, const QPoint& initial_point) :
  MapView::State(view),
  initial_point(Point::floor_8(view.mapToScene(initial_point))),
  last_point(this->initial_point),
  first_move_done(false) {

}

/**
 * @copydoc MapView::State::cancel
 */
void MovingEntitiesState::cancel() {

  get_view().undo_last_command();
}

/**
 * @copydoc MapView::State::mouse_moved
 */
void MovingEntitiesState::mouse_moved(const QMouseEvent& event) {

  MapView& view = get_view();

  QPoint current_point = Point::floor_8(view.mapToScene(event.pos()));
  if (current_point == last_point) {
    // No change after rounding.
    return;
  }

  // Make selected entities follow the mouse while dragging.
  QPoint translation = current_point - last_point;
  last_point = current_point;

  // Merge undo actions of successive moves,
  // but don't merge the first one of this state instance to potential previous states.
  const bool allow_merge_to_previous = first_move_done;
  view.move_selected_entities(translation, allow_merge_to_previous);
  first_move_done = true;
}

/**
 * @copydoc MapView::State::mouse_released
 */
void MovingEntitiesState::mouse_released(const QMouseEvent& event) {

  Q_UNUSED(event);

  get_view().start_state_doing_nothing();
}

/**
 * @brief Constructor.
 * @param view The map view to manage.
 * @param entities The entities to resize.
 */
ResizingEntitiesState::ResizingEntitiesState(
    MapView& view, const EntityIndexes& entities) :
  MapView::State(view),
  entities(entities),
  old_boxes(),
  leader_index(),
  center(),
  first_resize_done(false),
  num_free_entities(0) {
}

/**
 * @copydoc MapView::State::cancel
 */
void ResizingEntitiesState::cancel() {

  get_view().undo_last_command();
}

/**
 * @brief Determines the center of the entities to resize.
 */
void ResizingEntitiesState::compute_center() {

  // Compute the total bounding box to determine its center.
  MapModel& map = get_map();
  QRect total_box = map.get_entity_bounding_box(entities.first());
  for (const EntityIndex& index : entities) {
    total_box |= map.get_entity_bounding_box(index);
  }
  center = total_box.center();
}

/**
 * @brief Determines the entity whose resizing follows the cursor position.
 * Other ones will reproduce an equivalent change.
 */
void ResizingEntitiesState::compute_leader() {

  // Among the most freely resizable entities,
  // the leader will be the closest to the mouse.
  const std::vector<ResizeMode> resize_modes_by_priority = {
    ResizeMode::MULTI_DIMENSION_ALL,
    ResizeMode::MULTI_DIMENSION_ONE,
    ResizeMode::SINGLE_DIMENSION,
    ResizeMode::SQUARE,
    ResizeMode::HORIZONTAL_ONLY,
    ResizeMode::VERTICAL_ONLY,
    ResizeMode::NONE
  };

  MapModel& map = get_map();
  MapView& view = get_view();

  const QPoint mouse_position_in_view = view.mapFromGlobal(QCursor::pos());
  QPoint mouse_position = view.mapToScene(mouse_position_in_view).toPoint() - MapScene::get_margin_top_left();

  bool found_leader = false;
  for (ResizeMode wanted_resize_mode : resize_modes_by_priority) {
    int min_distance = std::numeric_limits<int>::max();
    if (found_leader) {
      min_distance = 0;  // Don't search a leader with this resize mode.
    }
    for (const EntityIndex& index : entities) {
      const EntityModel& entity = map.get_entity(index);

      if (entity.get_resize_mode() != wanted_resize_mode) {
        continue;
      }

      // Save the initial position of entities.
      old_boxes.insert(index, entity.get_bounding_box());

      // Count entities whose resize mode is MULTI_DIMENSION_ALL.
      if (entity.get_resize_mode() == ResizeMode::MULTI_DIMENSION_ALL) {
        ++num_free_entities;
      }

      // Determine a leader if none was found with previous resize modes.
      found_leader = true;
      const QPoint& entity_center = entity.get_center();
      int distance = (entity_center - mouse_position).manhattanLength();
      if (distance < min_distance) {
        leader_index = index;
        min_distance = distance;
      }
    }
  }
  Q_ASSERT(leader_index.is_valid());
}

/**
 * Determines which corner of entities should be fixed
 * and which one should follow the mouse.
 */
void ResizingEntitiesState::compute_fixed_corner() {

  // Decide the resizing directions depending
  // on the mouse position relative to the leader.
  Q_ASSERT(leader_index.is_valid());

  MapModel& map = get_map();
  MapView& view = get_view();

  const QPoint mouse_position_in_view = view.mapFromGlobal(QCursor::pos());
  QPoint mouse_position = view.mapToScene(mouse_position_in_view).toPoint() - MapScene::get_margin_top_left();

  const EntityModel& entity = map.get_entity(leader_index);
  const QPoint& entity_center = entity.get_center();

  fixed_corner.setX(mouse_position.x() >= entity_center.x() ? -1 : 1);
  fixed_corner.setY(mouse_position.y() >= entity_center.y() ? -1 : 1);
}

/**
 * @copydoc MapView::State::start
 */
void ResizingEntitiesState::start() {

  // Determine the center of the entities to resize.
  compute_center();

  // Determine the leader entity.
  compute_leader();

  // Determine which corner of entities will be fixed
  // and which one will follow the mouse.
  compute_fixed_corner();
}

/**
 * @copydoc MapView::State::mouse_moved
 */
void ResizingEntitiesState::mouse_moved(const QMouseEvent& event) {

  const MapModel& map = get_map();
  const EntityModel& leader = map.get_entity(leader_index);
  const QSize& leader_base_size = leader.get_base_size();

  // Need to floor to know exactly which 8x8 square has the mouse.
  QPoint current_point = to_map_point(event);

  const QRect& old_leader_box = old_boxes.value(leader_index);

  // See which corner of the leader is following the mouse.
  QPoint leader_free_corner = old_leader_box.topLeft();
  if (fixed_corner.x() == -1) {
    // The left side is fixed, the right side moves.
    leader_free_corner.rx() += old_leader_box.width() - leader_base_size.width();
  }
  if (fixed_corner.y() == -1) {
    // The top side is fixed, the bottom side moves.
    leader_free_corner.ry() += old_leader_box.height() - leader_base_size.height();
  }

  QPoint leader_distance_to_mouse = current_point - leader_free_corner;

  // Choose once for all entitites the preferred dimension to use
  // in case resizing is constrained.
  bool horizontal_preferred = qAbs(leader_distance_to_mouse.x()) > qAbs(leader_distance_to_mouse.y());

  // Determine the change to apply to all selected entities.
  QSize reference_base_size(8, 8);
  ResizeMode leader_resize_mode = leader.get_resize_mode();
  if (is_horizontally_resizable(leader_resize_mode, horizontal_preferred)) {
    // If the leader has a base size of 16x16, it is better to make all
    // entities resize this way as well (if they can).
    reference_base_size.setWidth(leader_base_size.width());
  }
  if (is_vertically_resizable(leader_resize_mode, horizontal_preferred)) {
    reference_base_size.setHeight(leader_base_size.height());
  }

  QPoint leader_expansion = Point::round_down(leader_distance_to_mouse, reference_base_size);

  // Determine if at least one entity is resizable horizontally and
  // if at least one entity is resizable vertically.
  bool is_resizing_horizontally = false;
  bool is_resizing_vertically = false;
  for (auto it = old_boxes.constBegin(); it != old_boxes.constEnd(); ++it) {
    const EntityIndex& index = it.key();
    const EntityModel& entity = map.get_entity(index);
    is_resizing_horizontally |= is_horizontally_resizable(entity.get_resize_mode(), horizontal_preferred);
    is_resizing_vertically |= is_vertically_resizable(entity.get_resize_mode(), horizontal_preferred);

    if (is_resizing_horizontally && is_resizing_vertically) {
      break;
    }
  }
  if (!is_resizing_horizontally) {
    // Don't move anything horizontally if nothing can change horizontally.
    // We need to take care of this because with smart resizing,
    // non horizontally resizable entities could still be moved
    // to follow the ones that are.
    leader_expansion.setX(0);
  }
  if (!is_resizing_vertically) {
    // Same thing vertically.
    leader_expansion.setY(0);
  }

  // Apply the change to the entities.
  update_boxes(leader_expansion, horizontal_preferred);
}

/**
 * @copydoc MapView::State::mouse_released
 */
void ResizingEntitiesState::mouse_released(const QMouseEvent& event) {

  MapView& view = get_view();
  if (event.button() == Qt::RightButton) {
    // The right button was pressed during the resize:
    // add copies of the entities.
    EntityModels clones = view.clone_selected_entities();

    if (clones.size() == 1 && first_resize_done) {
      // A real resize was done.
      // We are probably adding successive entities like tiles and resizing
      // each one (contrary to just copying entities).
      // In this case, each new clone should be reset to the base size.
      const EntityModelPtr& clone = *clones.begin();
      clone->set_size(clone->get_base_size());
    }
    const bool guess_layer = false;
    view.start_state_adding_entities(std::move(clones), guess_layer);
  }
  else {
    get_view().start_state_doing_nothing();
  }
}

/**
 * @brief Applies the resizing to the bounding boxes of entities.
 * @param leader_expansion How much to expand the current box.
 * @param horizontal_preferred When only one of both dimensions can be resized, whether
 * this should be the horizontal or vertical dimension.
 *
 * This change will be applied at best, respecting the constraints of
 * each entity.
 */
void ResizingEntitiesState::update_boxes(
    const QPoint& leader_expansion,
    bool horizontal_preferred
) {

  // Compute the new size and position of each entity.
  QMap<EntityIndex, QRect> new_boxes;
  for (auto it = old_boxes.constBegin(); it != old_boxes.constEnd(); ++it) {
    const EntityIndex& index = it.key();
    QRect new_box = update_box(
          index,
          leader_expansion,
          horizontal_preferred
    );
    new_boxes.insert(index, new_box);
  }

  const bool allow_merge_to_previous = first_resize_done;
  get_view().resize_entities(new_boxes, allow_merge_to_previous);
  first_resize_done = true;
}

/**
 * @brief Updates with new coordinates the rectangle of one entity.
 * @param index Index of the entity to resize.
 * @param leader_expansion How much the user wants to expand.
 * This expansion will be applied at best, preserving constraints on
 * the specific entity: its size will remain a multiple of its base size,
 * and its resizing mode will be respected.
 * @param horizontal_preferred When only one of both dimensions can be resized,
 * whether this should be the horizontal or vertical dimension.
 * @return A new bounding box for the entity.
 * Returns a null rectangle in case of error.
 */
QRect ResizingEntitiesState::update_box(
    const EntityIndex& index,
    const QPoint& leader_expansion,
    bool horizontal_preferred) {

  MapModel& map = get_map();
  Q_ASSERT(map.entity_exists(index));
  EntityModel& entity = map.get_entity(index);

  // Choose the appropriate resize mode.
  ResizeMode resize_mode = entity.get_resize_mode();
  if (num_free_entities > 1 && resize_mode == ResizeMode::MULTI_DIMENSION_ALL) {
    // Multiple resize: restrict the resizing to only one dimension.
    resize_mode = ResizeMode::MULTI_DIMENSION_ONE;
  }

  QRect new_box = apply_smart_resizing(
      index,
      resize_mode,
      horizontal_preferred,
      leader_expansion
  );

  // Apply resize mode constraints to the bounding box.
  new_box = apply_constraints(index, resize_mode, horizontal_preferred, new_box);

  return new_box;
}

/**
 * @brief Decides how to expand or translate an entity.
 *
 * When trying to resize a non horizontally resizable entity located
 * on the right of horizontally resizable things, we move it instead.
 * This allows to resize a full room in only one operation:
 *     ______          ________________
 *     |....|          |..............|
 *     |....|   ===>   |..............|
 *     |____|          |______________|
 *
 * We call this "smart resizing".
 * Here, the right wall is not horizontally resizable,
 * but when resizing the full room, it moves
 * to the right instead of expanding to the right.
 * The expansion is replaced by a translation.
 *
 * @param index Index of the entity to resize.
 * @param resize_mode Current resize mode for the entity.
 * @param horizontal_preferred When only one of both dimensions can be resized,
 * whether this should be the horizontal or vertical dimension.
 * @param leader_expansion How the leader entity gets expanded
 * @return The resulting bounding box.
 */
QRect ResizingEntitiesState::apply_smart_resizing(
    const EntityIndex& index,
    ResizeMode resize_mode,
    bool horizontal_preferred,
    const QPoint& leader_expansion
) {
  MapModel& map = get_map();
  EntityModel& entity = map.get_entity(index);
  const QSize& base_size = entity.get_base_size();
  const QRect& old_box = old_boxes.value(index);

  // Expand like the leader, but keeping a multiple of the base size.
  QPoint expansion = Point::ceil(leader_expansion, base_size);
  QPoint translation(0, 0);

  // Horizontal smart resizing.
  if (!is_horizontally_resizable(resize_mode, horizontal_preferred)) {

    if (fixed_corner.x() == -1 &&
        old_box.center().x() > center.x()) {
      translation.setX(leader_expansion.x());
    }
    else if (fixed_corner.x() == 1 &&
        old_box.center().x() < center.x()) {
      translation.setX(leader_expansion.x());
    }
    expansion.setX(0);
  }

  // Vertical smart resizing.
  if (!is_vertically_resizable(resize_mode, horizontal_preferred)) {
    // Smart resizing.
    if (fixed_corner.y() == -1 &&
        old_box.center().y() > center.y()) {
      translation.setY(leader_expansion.y());
    }
    else if (fixed_corner.y() == 1 &&
        old_box.center().y() < center.y()) {
      translation.setY(leader_expansion.y());
    }
    expansion.setY(0);
  }

  // Compute the bounding box from the expansion and translation.
  return get_box_from_expansion_and_translation(index, expansion, translation);
}

/**
 * @brief Returns the bounding box of an entity expanded with the given amount.
 * @param index Index of an entity.
 * @param expansion How much to extend it in both directions, keeping the
 * current fixed corner.
 * @param translation How much to translate the entity.
 * @return The corresponding new bounding box.
 * The resize mode is not taken into account at this point
 * (this function acts like if the resize mode is the most permissive one:
 * ResizeMode::MULTI_DIMENSION_ALL).
 */
QRect ResizingEntitiesState::get_box_from_expansion_and_translation(
    const EntityIndex& index,
    const QPoint& expansion,
    const QPoint& translation
) {
  MapModel& map = get_map();
  EntityModel& entity = map.get_entity(index);
  const QSize& base_size = entity.get_base_size();
  const QRect& old_box = old_boxes.value(index);
  QRect new_box = old_box;

  // Expansion.
  if (fixed_corner.x() == -1) {
    // Left side fixed, right side free.
    int width = old_box.width() + expansion.x();
    if (width > 0) {
      new_box.setWidth(width);
    }
    else {
      new_box.setWidth(-width + 2 * base_size.width());
      new_box.translate(width - base_size.width(), 0);
    }
  }
  else {
    // Right side fixed, left side free.
    int width = old_box.width() - expansion.x();
    if (width > 0) {
      new_box.setWidth(width);
      new_box.translate(expansion.x(), 0);
    }
    else {
      new_box.setWidth(-width + 2 * base_size.width());
      new_box.translate(old_box.width() - base_size.width(), 0);
    }
  }
  if (fixed_corner.y() == -1) {
    // Top side fixed, bottom side free.
    int height = old_box.height() + expansion.y();
    if (height > 0) {
      new_box.setHeight(height);
    }
    else {
      new_box.setHeight(-height + 2 * base_size.height());
      new_box.translate(0, height - base_size.height());
    }
  }
  else {
    // Bottom side fixed, top side free.
    int height = old_box.height() - expansion.y();
    if (height > 0) {
      new_box.setHeight(height);
      new_box.translate(0, expansion.y());
    }
    else {
      new_box.setHeight(-height + 2 * base_size.height());
      new_box.translate(0, old_box.height() - base_size.height());
    }
  }

  // Translation.
  if (!translation.isNull()) {
    new_box.translate(translation);
  }

  return new_box;
}

/**
 * Ensures that a bounding box respects the constraints of the resize mode.
 * @param index Index of the entity to resize.
 * @param resize_mode Current resize mode for thi entity.
 * @param horizontal_preferred When only one of both dimensions can be resized,
 * whether this should be the horizontal or vertical dimension.
 * @param box The candidate bounding box, before applying constraints.
 * Assumed to be a multiple of the base size.
 * @return The resulting bounding box.
 */
QRect ResizingEntitiesState::apply_constraints(
    const EntityIndex& index,
    ResizeMode resize_mode,
    bool horizontal_preferred,
    const QRect& box
) {
  MapModel& map = get_map();
  EntityModel& entity = map.get_entity(index);
  const QSize& base_size = entity.get_base_size();
  const QRect& old_box = old_boxes.value(index);
  QRect new_box = box;

  // Only in one direction: choose which one.
  if (resize_mode == ResizeMode::SINGLE_DIMENSION) {
    resize_mode = horizontal_preferred ? ResizeMode::HORIZONTAL_ONLY : ResizeMode::VERTICAL_ONLY;
  }

  // If we are going to fix the size, first we need to decide where to anchor
  // the entity after the change of size.
  QRect base_box = old_box;
  base_box.setSize(base_size);
  if (fixed_corner.x() == 1) {
    base_box.setRight(old_box.right());
  }
  if (fixed_corner.y() == 1) {
    base_box.setBottom(old_box.bottom());
  }
  bool anchor_to_right = box.right() == base_box.right();
  bool anchor_to_bottom = box.bottom() == base_box.bottom();

  // Fix the size or not depending on the resize mode.
  switch (resize_mode) {

  case ResizeMode::SINGLE_DIMENSION:
  {
    // Already handled (see above).
    break;
  }

  case ResizeMode::MULTI_DIMENSION_ALL:
  {
    // No additional constraint.
    break;
  }

  case ResizeMode::NONE:
  {
    // The size must always be the base size.
    if (new_box.size() != base_size) {
      new_box.setSize(base_size);
      if (anchor_to_right) {
        new_box.moveRight(base_box.right());
      }
      if (anchor_to_bottom) {
        new_box.moveBottom(base_box.bottom());
      }
    }
    break;
  }

  case ResizeMode::HORIZONTAL_ONLY:
  {
    // The height must be the base height.
    if (new_box.height() != base_size.height()) {
      new_box.setHeight(base_size.height());
      if (anchor_to_bottom) {
        new_box.moveBottom(base_box.bottom());
      }
    }
    break;
  }

  case ResizeMode::VERTICAL_ONLY:
  {
    // The width must be the base width.
    if (new_box.width() != base_size.width()) {
      new_box.setWidth(base_size.width());
      if (anchor_to_right) {
        new_box.moveRight(base_box.right());
      }
    }
    break;
  }

  case ResizeMode::MULTI_DIMENSION_ONE:
  {
    // The width or height must remain unchanged.
    if (horizontal_preferred) {
      // The width must be the previous width.
      if (new_box.width() != old_box.width()) {
        new_box.setWidth(old_box.width());
        if (anchor_to_right) {
          new_box.moveBottom(base_box.bottom());
        }
      }
    }
    else {
      // The height must be the previous height.
      if (new_box.height() != old_box.height()) {
        new_box.setHeight(old_box.height());
        if (anchor_to_bottom) {
          new_box.moveBottom(base_box.bottom());
        }
      }
    }
    break;
  }

  case ResizeMode::SQUARE:
  {
    // The width and height must be equal.
    if (new_box.width() != new_box.height()) {
      int max = qMax(new_box.width(), new_box.height());
      new_box.setSize(QSize(max, max));
      if (anchor_to_right) {
        new_box.moveRight(base_box.right());
      }
      if (anchor_to_bottom) {
        new_box.moveBottom(base_box.bottom());
      }
    }
    break;
  }

  }  // switch

  return new_box;
}

/**
 * @brief Returns whether the given settings allow to resize horizontally.
 * @param resize_mode The resize mode to test.
 * @param horizontal_preferred When only one of both dimensions can be resized, whether
 * this should be the horizontal or vertical dimension.
 */
bool ResizingEntitiesState::is_horizontally_resizable(
    ResizeMode resize_mode, bool horizontal_preferred) {

  return resize_mode == ResizeMode::HORIZONTAL_ONLY ||
      resize_mode == ResizeMode::MULTI_DIMENSION_ALL ||
      resize_mode == ResizeMode::MULTI_DIMENSION_ONE ||
      resize_mode == ResizeMode::SQUARE ||
      (resize_mode == ResizeMode::SINGLE_DIMENSION && horizontal_preferred);
}

/**
 * @brief Returns whether the given settings allow to resize vertically.
 * @param resize_mode The resize mode to test.
 * @param horizontal_preferred When only one of both dimensions can be resized, whether
 * this should be the horizontal or vertical dimension.
 */
bool ResizingEntitiesState::is_vertically_resizable(
    ResizeMode resize_mode, bool horizontal_preferred) {

  return resize_mode == ResizeMode::VERTICAL_ONLY ||
      resize_mode == ResizeMode::MULTI_DIMENSION_ALL ||
      resize_mode == ResizeMode::MULTI_DIMENSION_ONE ||
      resize_mode == ResizeMode::SQUARE ||
      (resize_mode == ResizeMode::SINGLE_DIMENSION && !horizontal_preferred);
}

/**
 * @brief Constructor.
 * @param view The map view to manage.
 * @param entities The entities to be added to the map.
 * @param guess_layer Whether a layer should be guessed from the preferred
 * layer of entities and the mouse position.
 * If @c false, they will be added on their layer indicated by
 * EntityModel::get_layer().
 */
AddingEntitiesState::AddingEntitiesState(MapView& view, EntityModels&& entities, bool guess_layer) :
  MapView::State(view),
  entities(std::move(entities)),
  entity_items(),
  guess_layer(guess_layer) {

  for (const EntityModelPtr& entity : this->entities) {
    EntityItem* item = new EntityItem(*entity);
    item->setZValue(get_map().get_max_layer() + 1);
    entity_items.push_back(item);
  }
}

/**
 * @copydoc MapView::State::start
 */
void AddingEntitiesState::start() {

  MapView& view = get_view();
  QPoint mouse_position = view.mapFromGlobal(QCursor::pos());
  last_point = Point::floor_8(view.mapToScene(mouse_position));

  // Determine the center of all entities in their current position.
  QPoint center = get_entities_center();

  // Add the graphic item of each entity.
  for (EntityItem* item : entity_items) {
    get_scene().addItem(item);
    EntityModel& entity = item->get_entity();
    QPoint top_left_in_group = center - entity.get_top_left();
    QPoint top_left = last_point - top_left_in_group - MapScene::get_margin_top_left();
    top_left = Point::round_8(top_left);
    entity.set_top_left(top_left);
    item->update_xy();
  }
}

/**
 * @copydoc MapView::State::stop
 */
void AddingEntitiesState::stop() {

  for (EntityItem* item : entity_items) {
    get_scene().removeItem(item);
  }
}

/**
 * @brief Computes the center point of all entities to be added.
 * @return The center point.
 */
QPoint AddingEntitiesState::get_entities_center() const {

  QPoint top_left(1e9, 1e9);
  QPoint bottom_right(-1e9, -1e9);
  for (EntityItem* item : entity_items) {
    EntityModel& entity = item->get_entity();
    QRect box = entity.get_bounding_box();
    top_left.setX(qMin(box.left(), top_left.x()));
    top_left.setY(qMin(box.top(), top_left.y()));
    bottom_right.setX(qMax(box.right(), bottom_right.x()));
    bottom_right.setY(qMax(box.bottom(), bottom_right.y()));
  }
  return (top_left + bottom_right) / 2;
}

/**
 * @brief Ensures that the entities to be added are correctly sorted.
 *
 * The ones on lower layers come first, and on the same layer,
 * the non-dynamic ones come first.
 */
void AddingEntitiesState::sort_entities() {

  const size_t num_before = entities.size();

  std::map<int, EntityModels> entities_by_layer;
  for (EntityModelPtr& entity : entities) {
    if (!entity->is_dynamic()) {  // Non-dynamic ones first.
      int layer = entity->get_layer();
      entities_by_layer[layer].emplace_back(std::move(entity));
    }
  }
  for (EntityModelPtr& entity : entities) {
    if (entity != nullptr && entity->is_dynamic()) {  // Non-dynamic ones first.
      int layer = entity->get_layer();
      entities_by_layer[layer].emplace_back(std::move(entity));
    }
  }
  entities.clear();
  for (int layer = get_map().get_min_layer(); layer <= get_map().get_max_layer(); ++layer) {
    for (EntityModelPtr& entity : entities_by_layer[layer]) {
      entities.emplace_back(std::move(entity));
    }
  }

  Q_UNUSED(num_before);
  Q_ASSERT(entities.size() == num_before);
}

/**
 * @copydoc MapView::State::mouse_pressed
 */
void AddingEntitiesState::mouse_pressed(const QMouseEvent& event) {

  Q_UNUSED(event);
  MapModel& map = get_map();
  MapView& view = get_view();

  // Store the number of tiles and dynamic entities of each layer,
  // because every entity added will increment one of them.
  QMap<int, int> num_tiles_by_layer;     // Index where to append a tile.
  QMap<int, int> num_dynamic_entities_by_layer;  // Index where to append a dynamic entity.
  for (int layer = map.get_min_layer(); layer <= map.get_max_layer(); ++layer) {
    num_tiles_by_layer[layer] = map.get_num_tiles(layer);
    num_dynamic_entities_by_layer[layer] = map.get_num_dynamic_entities(layer);
  }

  // Determine the best layer of each entity.
  for (EntityModelPtr& entity : entities) {
    int layer = find_best_layer(*entity);
    entity->set_layer(layer);
  }
  // Now that their layer is known, sort them
  // to compute correct indexes below.
  sort_entities();

  // Clone them in case the user wants to add more entities.
  EntityModels clones;
  if (event.button() == Qt::RightButton) {
    for (EntityModelPtr& entity : entities) {
      Q_ASSERT(entity != nullptr);
      clones.emplace_back(entity->clone());
    }
  }

  // Make entities ready to be added at their specific index.
  AddableEntities addable_entities;
  EntityIndex previous_index;
  for (EntityModelPtr& entity : entities) {
    Q_ASSERT(entity != nullptr);
    int layer = entity->get_layer();

    int i = 0;
    if (entity->is_dynamic()) {
      i = num_tiles_by_layer[layer] + num_dynamic_entities_by_layer[layer];
      ++num_dynamic_entities_by_layer[layer];
    }
    else {
      i = num_tiles_by_layer[layer];
      ++num_tiles_by_layer[layer];
    }

    EntityIndex index = { layer, i };
    if (previous_index.is_valid()) {
      // Double-check that we are traversing entities in ascending order.
      // (If not, then sort_entities() above did not make its job and we risk
      // invalid indexes).
      Q_ASSERT(index > previous_index);
    }
    previous_index = index;
    addable_entities.emplace_back(std::move(entity), index);
  }

  // Add them.
  const bool control_or_shift = (event.modifiers() & (Qt::ControlModifier | Qt::ShiftModifier));
  const bool keep_selection = control_or_shift;
  view.add_entities_requested(addable_entities, !keep_selection);

  // Decide what to do next: resize them, add new ones or do nothing.
  if (view.are_entities_resizable(view.get_selected_entities()) &&
      !control_or_shift) {
    // Start resizing the newly added entities
    // (until the mouse button is released).
    view.start_state_resizing_entities();
  }
  else {
    if (event.button() == Qt::RightButton) {
      // Entities were added with the right mouse button: add new ones again.
      const bool guess_layer = false;
      view.start_state_adding_entities(std::move(clones), guess_layer);
    }
    else {
      // Get back to normal state.
      view.start_state_doing_nothing();
    }
  }
}

/**
 * @copydoc MapView::State::mouse_moved
 */
void AddingEntitiesState::mouse_moved(const QMouseEvent& event) {

  MapView& view = get_view();

  QPoint current_point = Point::floor_8(view.mapToScene(event.pos()));
  if (current_point == last_point) {
    // No change after rounding.
    return;
  }

  // Make entities being added follow the mouse.
  QPoint translation = current_point - last_point;
  last_point = current_point;

  for (EntityItem* item : entity_items) {
    EntityModel& entity = item->get_entity();
    QPoint xy = entity.get_xy() + translation;
    entity.set_xy(xy);
    item->update_xy();
  }
}

/**
 * @copydoc MapView::State::tileset_selection_changed
 */
void AddingEntitiesState::tileset_selection_changed(const QString& tileset_id, const QList<int>& indexes) {

  if (indexes.isEmpty()) {
    // Stop adding the tiles that were selected.
    get_view().start_state_doing_nothing();
    return;
  }

  // The user just selected some patterns in the tileset: create corresponding tiles.
  get_view().start_adding_entities_from_tileset(tileset_id, indexes);
}

/**
 * @brief Determines the appropriate layer where to add an entity.
 * @param entity The entity to add.
 * @return The layer. It is always a valid layer of the map.
 */
int AddingEntitiesState::find_best_layer(const EntityModel& entity) const {

  if (!guess_layer && get_map().is_valid_layer(entity.get_layer())) {
    // The entity does not want us to guess a layer.
    return entity.get_layer();
  }

  int layer_under = get_scene().get_layer_in_rectangle(
        entity.get_bounding_box()
  );
  if (!entity.get_has_preferred_layer()) {
    // The entity has no preferred layer.
    return layer_under;
  }

  // The entity has a preferred layer:
  // see if there is something above its preferred layer.
  int preferred_layer = entity.get_preferred_layer();
  if (!get_map().is_valid_layer(preferred_layer)) {
      // The preferred layer does not exist on this map.
      return layer_under;
  }

  if (layer_under > preferred_layer) {
      // The preferred layer is covered by other entities
      // on a higher layer.
      // Don't use the preferred layer in this case.
      return layer_under;
  }

  return preferred_layer;
}

}