core/scroll/scrollbar_theme.h

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_SCROLL_SCROLLBAR_THEME_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_SCROLL_SCROLLBAR_THEME_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/scroll/scroll_types.h"
#include "third_party/blink/renderer/core/scroll/scrollbar.h"
#include "third_party/blink/renderer/platform/geometry/int_rect.h"
#include "third_party/blink/renderer/platform/graphics/paint/display_item.h"
#include "third_party/blink/renderer/platform/graphics/scrollbar_theme_settings.h"

namespace blink {

class GraphicsContext;
class WebMouseEvent;

class CORE_EXPORT ScrollbarTheme {
  DISALLOW_COPY_AND_ASSIGN(ScrollbarTheme);
  USING_FAST_MALLOC(ScrollbarTheme);

 public:
  ScrollbarTheme() = default;
  virtual ~ScrollbarTheme() = default;

  // If true, then scrollbars with this theme will be painted every time
  // Scrollbar::SetNeedsPaintInvalidation is called. If false, then only parts
  // which are explicitly invalidated will be repainted.
  virtual bool ShouldRepaintAllPartsOnInvalidation() const { return true; }

  virtual void UpdateEnabledState(const Scrollbar&) {}

  // |context|'s current space is the space of the scrollbar's FrameRect().
  void Paint(const Scrollbar&,
             GraphicsContext& context,
             const IntPoint& paint_offset);

  ScrollbarPart HitTestRootFramePosition(const Scrollbar&, const IntPoint&);

  // This returns a fixed value regardless of device-scale-factor.
  // This returns thickness when scrollbar is painted.  i.e. It's not 0 even in
  // overlay scrollbar mode.
  // See also Scrollbar::scrollbarThickness().
  virtual int ScrollbarThickness(ScrollbarControlSize = kRegularScrollbar) {
    return 0;
  }
  virtual int ScrollbarMargin() const { return 0; }

  virtual bool IsSolidColor() const { return false; }
  virtual bool UsesOverlayScrollbars() const { return false; }
  virtual void UpdateScrollbarOverlayColorTheme(const Scrollbar&) {}

  // If true, scrollbars that become invisible (i.e. overlay scrollbars that
  // fade out) should be marked as disabled. This option exists since Mac and
  // Aura overlays implement the fade out differently, with Mac painting code
  // fading out the scrollbars. Aura scrollbars require disabling the scrollbar
  // to prevent painting it.
  virtual bool ShouldDisableInvisibleScrollbars() const { return true; }

  // If true, Blink is in charge of hiding/showing of overlay scrollbars.  As
  // above, this option exists because on Mac the visibility is controlled by
  // Mac painting code which Blink doesn't have an input into. In order to
  // prevent the two from getting out of sync we disable setting the Blink-side
  // parameter on Mac.
  virtual bool BlinkControlsOverlayVisibility() const { return true; }

  virtual bool InvalidateOnMouseEnterExit() { return false; }

  // Returns parts of the scrollbar which must be repainted following a change
  // in the thumb position, given scroll positions before and after.
  virtual ScrollbarPart PartsToInvalidateOnThumbPositionChange(
      const Scrollbar&,
      float old_position,
      float new_position) const {
    return kAllParts;
  }

  virtual void PaintScrollCorner(GraphicsContext&,
                                 const Scrollbar* vertical_scrollbar,
                                 const DisplayItemClient&,
                                 const IntRect& corner_rect,
                                 WebColorScheme color_scheme);
  virtual void PaintTickmarks(GraphicsContext&,
                              const Scrollbar&,
                              const IntRect&);

  virtual bool ShouldCenterOnThumb(const Scrollbar&, const WebMouseEvent&) {
    return false;
  }
  virtual bool ShouldSnapBackToDragOrigin(const Scrollbar&,
                                          const WebMouseEvent&) {
    return false;
  }
  virtual bool ShouldDragDocumentInsteadOfThumb(const Scrollbar&,
                                                const WebMouseEvent&) {
    return false;
  }

  virtual bool SupportsDragSnapBack() const { return false; }

  // The position of the thumb relative to the track.
  int ThumbPosition(const Scrollbar& scrollbar) {
    return ThumbPosition(scrollbar, scrollbar.CurrentPos());
  }
  virtual base::TimeDelta OverlayScrollbarFadeOutDelay() const;
  virtual base::TimeDelta OverlayScrollbarFadeOutDuration() const;
  // The position the thumb would have, relative to the track, at the specified
  // scroll position.
  virtual int ThumbPosition(const Scrollbar&, float scroll_position);
  // The length of the thumb along the axis of the scrollbar.
  virtual int ThumbLength(const Scrollbar&);
  // The position of the track relative to the scrollbar.
  virtual int TrackPosition(const Scrollbar&);
  // The length of the track along the axis of the scrollbar.
  virtual int TrackLength(const Scrollbar&);
  // The opacity to be applied to the scrollbar. A theme overriding Opacity()
  // should also override PaintThumbWithOpacity().
  virtual float Opacity(const Scrollbar&) const { return 1.0f; }

  // Whether the native theme of the OS has scrollbar buttons.
  virtual bool NativeThemeHasButtons() = 0;
  // Whether the scrollbar has buttons. It's the same as NativeThemeHasButtons()
  // except for custom scrollbars which can override the OS settings.
  virtual bool HasButtons(const Scrollbar&) { return NativeThemeHasButtons(); }

  virtual bool HasThumb(const Scrollbar&) = 0;

  // All these rects are in the same coordinate space as the scrollbar's
  // FrameRect.
  virtual IntRect BackButtonRect(const Scrollbar&) = 0;
  virtual IntRect ForwardButtonRect(const Scrollbar&) = 0;
  virtual IntRect TrackRect(const Scrollbar&) = 0;
  virtual IntRect ThumbRect(const Scrollbar&);
  virtual int ThumbThickness(const Scrollbar&);

  virtual int MinimumThumbLength(const Scrollbar&) = 0;

  virtual void SplitTrack(const Scrollbar&,
                          const IntRect& track,
                          IntRect& start_track,
                          IntRect& thumb,
                          IntRect& end_track);

  virtual void PaintThumb(GraphicsContext&, const Scrollbar&, const IntRect&) {}

  // |offset| is from the space of the scrollbar's FrameRect() to |context|'s
  // current space.
  void PaintTrackButtonsTickmarks(GraphicsContext& context,
                                  const Scrollbar&,
                                  const IntPoint& offset);

  virtual int MaxOverlapBetweenPages() {
    return std::numeric_limits<int>::max();
  }

  virtual base::TimeDelta InitialAutoscrollTimerDelay();
  virtual base::TimeDelta AutoscrollTimerDelay();

  virtual IntRect ConstrainTrackRectToTrackPieces(const Scrollbar&,
                                                  const IntRect& rect) {
    return rect;
  }

  virtual void RegisterScrollbar(Scrollbar&) {}

  virtual bool IsMockTheme() const { return false; }

  virtual bool UsesNinePatchThumbResource() const { return false; }

  // For a nine-patch scrollbar, this defines the painting canvas size which the
  // painting code will use to paint the scrollbar into. The actual scrollbar
  // dimensions will be ignored for purposes of painting since the resource can
  // be then resized without a repaint.
  virtual IntSize NinePatchThumbCanvasSize(const Scrollbar&) const {
    NOTREACHED();
    return IntSize();
  }

  // For a nine-patch resource, the aperture defines the center patch that will
  // be stretched out.
  virtual IntRect NinePatchThumbAperture(const Scrollbar&) const {
    NOTREACHED();
    return IntRect();
  }

  virtual bool AllowsHitTest() const { return true; }

 protected:
  // The point is in the same coordinate space as the scrollbar's FrameRect.
  virtual ScrollbarPart HitTest(const Scrollbar&, const IntPoint&);

  virtual int TickmarkBorderWidth() { return 0; }
  virtual void PaintTrack(GraphicsContext&, const Scrollbar&, const IntRect&) {}
  virtual void PaintButton(GraphicsContext&,
                           const Scrollbar&,
                           const IntRect&,
                           ScrollbarPart) {}

  // |offset| is the offset of the |context|'s current space to the space of
  // scrollbar's FrameRect().
  virtual void PaintTrackAndButtons(GraphicsContext& context,
                                    const Scrollbar&,
                                    const IntPoint& offset);

  // Paint the thumb with Opacity() applied.
  virtual void PaintThumbWithOpacity(GraphicsContext& context,
                                     const Scrollbar& scrollbar,
                                     const IntRect& rect) {
    // By default this method just calls PaintThumb(). A theme with custom
    // Opacity() should override this method to apply the opacity.
    DCHECK_EQ(1.0f, Opacity(scrollbar));
    PaintThumb(context, scrollbar, rect);
  }

 protected:
  // For GetTheme().
  friend class MockScrollableArea;
  friend class MockScrollableAreaForAnimatorTest;
  friend class Page;

  // Get the theme based on global scrollbar settings. We should always use
  // Page::GetScrollbarTheme() to get scrollbar theme because we support
  // different native scrollbar theme base on page settings.
  // See http://crrev.com/c/646727.
  static ScrollbarTheme& GetTheme();

  static bool OverlayScrollbarsEnabled() {
    return ScrollbarThemeSettings::OverlayScrollbarsEnabled();
  }
  static bool MockScrollbarsEnabled() {
    return ScrollbarThemeSettings::MockScrollbarsEnabled();
  }

 private:
  // Must be implemented to return the correct theme subclass.
  static ScrollbarTheme& NativeTheme();
};

}  // namespace blink
#endif