layout/mathml/nsMathMLFrame.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsMathMLFrame.h"

#include "gfxContext.h"
#include "gfxUtils.h"
#include "mozilla/gfx/2D.h"
#include "nsLayoutUtils.h"
#include "nsNameSpaceManager.h"
#include "nsMathMLChar.h"
#include "nsCSSPseudoElements.h"
#include "mozilla/dom/MathMLElement.h"
#include "gfxMathTable.h"
#include "nsPresContextInlines.h"

// used to map attributes into CSS rules
#include "mozilla/ServoStyleSet.h"
#include "nsDisplayList.h"

using namespace mozilla;
using namespace mozilla::gfx;

eMathMLFrameType nsMathMLFrame::GetMathMLFrameType() {
  // see if it is an embellished operator (mapped to 'Op' in TeX)
  if (mEmbellishData.coreFrame)
    return GetMathMLFrameTypeFor(mEmbellishData.coreFrame);

  // if it has a prescribed base, fetch the type from there
  if (mPresentationData.baseFrame)
    return GetMathMLFrameTypeFor(mPresentationData.baseFrame);

  // everything else is treated as ordinary (mapped to 'Ord' in TeX)
  return eMathMLFrameType_Ordinary;
}

NS_IMETHODIMP
nsMathMLFrame::InheritAutomaticData(nsIFrame* aParent) {
  mEmbellishData.flags = 0;
  mEmbellishData.coreFrame = nullptr;
  mEmbellishData.direction = NS_STRETCH_DIRECTION_UNSUPPORTED;
  mEmbellishData.leadingSpace = 0;
  mEmbellishData.trailingSpace = 0;

  mPresentationData.flags = 0;
  mPresentationData.baseFrame = nullptr;

  // by default, just inherit the display of our parent
  nsPresentationData parentData;
  GetPresentationDataFrom(aParent, parentData);

#if defined(DEBUG) && defined(SHOW_BOUNDING_BOX)
  mPresentationData.flags |= NS_MATHML_SHOW_BOUNDING_METRICS;
#endif

  return NS_OK;
}

NS_IMETHODIMP
nsMathMLFrame::UpdatePresentationData(uint32_t aFlagsValues,
                                      uint32_t aWhichFlags) {
  NS_ASSERTION(NS_MATHML_IS_COMPRESSED(aWhichFlags) ||
                   NS_MATHML_IS_DTLS_SET(aWhichFlags),
               "aWhichFlags should only be compression or dtls flag");

  if (NS_MATHML_IS_COMPRESSED(aWhichFlags)) {
    // updating the compression flag is allowed
    if (NS_MATHML_IS_COMPRESSED(aFlagsValues)) {
      // 'compressed' means 'prime' style in App. G, TeXbook
      mPresentationData.flags |= NS_MATHML_COMPRESSED;
    }
    // no else. the flag is sticky. it retains its value once it is set
  }
  // These flags determine whether the dtls font feature settings should
  // be applied.
  if (NS_MATHML_IS_DTLS_SET(aWhichFlags)) {
    if (NS_MATHML_IS_DTLS_SET(aFlagsValues)) {
      mPresentationData.flags |= NS_MATHML_DTLS;
    } else {
      mPresentationData.flags &= ~NS_MATHML_DTLS;
    }
  }
  return NS_OK;
}

// Helper to give a ComputedStyle suitable for doing the stretching of
// a MathMLChar. Frame classes that use this should ensure that the
// extra leaf ComputedStyle given to the MathMLChars are accessible to
// the Style System via the Get/Set AdditionalComputedStyle() APIs.
/* static */
void nsMathMLFrame::ResolveMathMLCharStyle(nsPresContext* aPresContext,
                                           nsIContent* aContent,
                                           ComputedStyle* aParentComputedStyle,
                                           nsMathMLChar* aMathMLChar) {
  PseudoStyleType pseudoType = PseudoStyleType::mozMathAnonymous;  // savings
  RefPtr<ComputedStyle> newComputedStyle;
  newComputedStyle = aPresContext->StyleSet()->ResolvePseudoElementStyle(
      *aContent->AsElement(), pseudoType, aParentComputedStyle);

  aMathMLChar->SetComputedStyle(newComputedStyle);
}

/* static */
void nsMathMLFrame::GetEmbellishDataFrom(nsIFrame* aFrame,
                                         nsEmbellishData& aEmbellishData) {
  // initialize OUT params
  aEmbellishData.flags = 0;
  aEmbellishData.coreFrame = nullptr;
  aEmbellishData.direction = NS_STRETCH_DIRECTION_UNSUPPORTED;
  aEmbellishData.leadingSpace = 0;
  aEmbellishData.trailingSpace = 0;

  if (aFrame && aFrame->IsFrameOfType(nsIFrame::eMathML)) {
    nsIMathMLFrame* mathMLFrame = do_QueryFrame(aFrame);
    if (mathMLFrame) {
      mathMLFrame->GetEmbellishData(aEmbellishData);
    }
  }
}

// helper to get the presentation data of a frame, by possibly walking up
// the frame hierarchy if we happen to be surrounded by non-MathML frames.
/* static */
void nsMathMLFrame::GetPresentationDataFrom(
    nsIFrame* aFrame, nsPresentationData& aPresentationData, bool aClimbTree) {
  // initialize OUT params
  aPresentationData.flags = 0;
  aPresentationData.baseFrame = nullptr;

  nsIFrame* frame = aFrame;
  while (frame) {
    if (frame->IsFrameOfType(nsIFrame::eMathML)) {
      nsIMathMLFrame* mathMLFrame = do_QueryFrame(frame);
      if (mathMLFrame) {
        mathMLFrame->GetPresentationData(aPresentationData);
        break;
      }
    }
    // stop if the caller doesn't want to lookup beyond the frame
    if (!aClimbTree) {
      break;
    }
    // stop if we reach the root <math> tag
    nsIContent* content = frame->GetContent();
    NS_ASSERTION(content || !frame->GetParent(),  // no assert for the root
                 "dangling frame without a content node");
    if (!content) break;

    if (content->IsMathMLElement(nsGkAtoms::math)) {
      break;
    }
    frame = frame->GetParent();
  }
  NS_WARNING_ASSERTION(
      frame && frame->GetContent(),
      "bad MathML markup - could not find the top <math> element");
}

/* static */
void nsMathMLFrame::GetRuleThickness(DrawTarget* aDrawTarget,
                                     nsFontMetrics* aFontMetrics,
                                     nscoord& aRuleThickness) {
  nscoord xHeight = aFontMetrics->XHeight();
  char16_t overBar = 0x00AF;
  nsBoundingMetrics bm = nsLayoutUtils::AppUnitBoundsOfString(
      &overBar, 1, *aFontMetrics, aDrawTarget);
  aRuleThickness = bm.ascent + bm.descent;
  if (aRuleThickness <= 0 || aRuleThickness >= xHeight) {
    // fall-back to the other version
    GetRuleThickness(aFontMetrics, aRuleThickness);
  }
}

/* static */
void nsMathMLFrame::GetAxisHeight(DrawTarget* aDrawTarget,
                                  nsFontMetrics* aFontMetrics,
                                  nscoord& aAxisHeight) {
  gfxFont* mathFont = aFontMetrics->GetThebesFontGroup()->GetFirstMathFont();
  if (mathFont) {
    aAxisHeight = mathFont->MathTable()->Constant(
        gfxMathTable::AxisHeight, aFontMetrics->AppUnitsPerDevPixel());
    return;
  }

  nscoord xHeight = aFontMetrics->XHeight();
  char16_t minus = 0x2212;  // not '-', but official Unicode minus sign
  nsBoundingMetrics bm = nsLayoutUtils::AppUnitBoundsOfString(
      &minus, 1, *aFontMetrics, aDrawTarget);
  aAxisHeight = bm.ascent - (bm.ascent + bm.descent) / 2;
  if (aAxisHeight <= 0 || aAxisHeight >= xHeight) {
    // fall-back to the other version
    GetAxisHeight(aFontMetrics, aAxisHeight);
  }
}

/* static */
nscoord nsMathMLFrame::CalcLength(nsPresContext* aPresContext,
                                  ComputedStyle* aComputedStyle,
                                  const nsCSSValue& aCSSValue,
                                  float aFontSizeInflation) {
  NS_ASSERTION(aCSSValue.IsLengthUnit(), "not a length unit");

  if (aCSSValue.IsPixelLengthUnit()) {
    return aCSSValue.GetPixelLength();
  }

  nsCSSUnit unit = aCSSValue.GetUnit();

  if (eCSSUnit_EM == unit) {
    const nsStyleFont* font = aComputedStyle->StyleFont();
    return NSToCoordRound(aCSSValue.GetFloatValue() * (float)font->mFont.size);
  } else if (eCSSUnit_XHeight == unit) {
    aPresContext->SetUsesExChUnits(true);
    RefPtr<nsFontMetrics> fm = nsLayoutUtils::GetFontMetricsForComputedStyle(
        aComputedStyle, aPresContext, aFontSizeInflation);
    nscoord xHeight = fm->XHeight();
    return NSToCoordRound(aCSSValue.GetFloatValue() * (float)xHeight);
  }

  // MathML doesn't specify other CSS units such as rem or ch
  NS_ERROR("Unsupported unit");
  return 0;
}

/* static */
void nsMathMLFrame::ParseNumericValue(const nsString& aString,
                                      nscoord* aLengthValue, uint32_t aFlags,
                                      nsPresContext* aPresContext,
                                      ComputedStyle* aComputedStyle,
                                      float aFontSizeInflation) {
  nsCSSValue cssValue;

  if (!dom::MathMLElement::ParseNumericValue(aString, cssValue, aFlags,
                                             aPresContext->Document())) {
    // Invalid attribute value. aLengthValue remains unchanged, so the default
    // length value is used.
    return;
  }

  nsCSSUnit unit = cssValue.GetUnit();

  if (unit == eCSSUnit_Percent || unit == eCSSUnit_Number) {
    // Relative units. A multiple of the default length value is used.
    *aLengthValue = NSToCoordRound(
        *aLengthValue * (unit == eCSSUnit_Percent ? cssValue.GetPercentValue()
                                                  : cssValue.GetFloatValue()));
    return;
  }

  // Absolute units.
  *aLengthValue =
      CalcLength(aPresContext, aComputedStyle, cssValue, aFontSizeInflation);
}

#if defined(DEBUG) && defined(SHOW_BOUNDING_BOX)
class nsDisplayMathMLBoundingMetrics final : public nsDisplayItem {
 public:
  nsDisplayMathMLBoundingMetrics(nsDisplayListBuilder* aBuilder,
                                 nsIFrame* aFrame, const nsRect& aRect)
      : nsDisplayItem(aBuilder, aFrame), mRect(aRect) {
    MOZ_COUNT_CTOR(nsDisplayMathMLBoundingMetrics);
  }
  MOZ_COUNTED_DTOR_OVERRIDE(nsDisplayMathMLBoundingMetrics)

  virtual void Paint(nsDisplayListBuilder* aBuilder, gfxContext* aCtx) override;
  NS_DISPLAY_DECL_NAME("MathMLBoundingMetrics", TYPE_MATHML_BOUNDING_METRICS)
 private:
  nsRect mRect;
};

void nsDisplayMathMLBoundingMetrics::Paint(nsDisplayListBuilder* aBuilder,
                                           gfxContext* aCtx) {
  DrawTarget* drawTarget = aCtx->GetDrawTarget();
  Rect r = NSRectToRect(mRect + ToReferenceFrame(),
                        mFrame->PresContext()->AppUnitsPerDevPixel());
  ColorPattern blue(ToDeviceColor(Color(0.f, 0.f, 1.f, 1.f)));
  drawTarget->StrokeRect(r, blue);
}

void nsMathMLFrame::DisplayBoundingMetrics(nsDisplayListBuilder* aBuilder,
                                           nsIFrame* aFrame, const nsPoint& aPt,
                                           const nsBoundingMetrics& aMetrics,
                                           const nsDisplayListSet& aLists) {
  if (!NS_MATHML_PAINT_BOUNDING_METRICS(mPresentationData.flags)) return;

  nscoord x = aPt.x + aMetrics.leftBearing;
  nscoord y = aPt.y - aMetrics.ascent;
  nscoord w = aMetrics.rightBearing - aMetrics.leftBearing;
  nscoord h = aMetrics.ascent + aMetrics.descent;

  aLists.Content()->AppendNewToTop<nsDisplayMathMLBoundingMetrics>(
      aBuilder, aFrame, nsRect(x, y, w, h));
}
#endif

class nsDisplayMathMLBar final : public nsPaintedDisplayItem {
 public:
  nsDisplayMathMLBar(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                     const nsRect& aRect)
      : nsPaintedDisplayItem(aBuilder, aFrame), mRect(aRect) {
    MOZ_COUNT_CTOR(nsDisplayMathMLBar);
  }
  MOZ_COUNTED_DTOR_OVERRIDE(nsDisplayMathMLBar)

  virtual void Paint(nsDisplayListBuilder* aBuilder, gfxContext* aCtx) override;
  NS_DISPLAY_DECL_NAME("MathMLBar", TYPE_MATHML_BAR)

 private:
  nsRect mRect;
};

void nsDisplayMathMLBar::Paint(nsDisplayListBuilder* aBuilder,
                               gfxContext* aCtx) {
  // paint the bar with the current text color
  DrawTarget* drawTarget = aCtx->GetDrawTarget();
  Rect rect = NSRectToNonEmptySnappedRect(
      mRect + ToReferenceFrame(), mFrame->PresContext()->AppUnitsPerDevPixel(),
      *drawTarget);
  ColorPattern color(ToDeviceColor(
      mFrame->GetVisitedDependentColor(&nsStyleText::mWebkitTextFillColor)));
  drawTarget->FillRect(rect, color);
}

void nsMathMLFrame::DisplayBar(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                               const nsRect& aRect,
                               const nsDisplayListSet& aLists,
                               uint32_t aIndex) {
  if (!aFrame->StyleVisibility()->IsVisible() || aRect.IsEmpty()) return;

  aLists.Content()->AppendNewToTopWithIndex<nsDisplayMathMLBar>(
      aBuilder, aFrame, aIndex, aRect);
}

void nsMathMLFrame::GetRadicalParameters(nsFontMetrics* aFontMetrics,
                                         bool aDisplayStyle,
                                         nscoord& aRadicalRuleThickness,
                                         nscoord& aRadicalExtraAscender,
                                         nscoord& aRadicalVerticalGap) {
  nscoord oneDevPixel = aFontMetrics->AppUnitsPerDevPixel();
  gfxFont* mathFont = aFontMetrics->GetThebesFontGroup()->GetFirstMathFont();

  // get the radical rulethickness
  if (mathFont) {
    aRadicalRuleThickness = mathFont->MathTable()->Constant(
        gfxMathTable::RadicalRuleThickness, oneDevPixel);
  } else {
    GetRuleThickness(aFontMetrics, aRadicalRuleThickness);
  }

  // get the leading to be left at the top of the resulting frame
  if (mathFont) {
    aRadicalExtraAscender = mathFont->MathTable()->Constant(
        gfxMathTable::RadicalExtraAscender, oneDevPixel);
  } else {
    // This seems more reliable than using aFontMetrics->GetLeading() on
    // suspicious fonts.
    nscoord em;
    GetEmHeight(aFontMetrics, em);
    aRadicalExtraAscender = nscoord(0.2f * em);
  }

  // get the clearance between rule and content
  if (mathFont) {
    aRadicalVerticalGap = mathFont->MathTable()->Constant(
        aDisplayStyle ? gfxMathTable::RadicalDisplayStyleVerticalGap
                      : gfxMathTable::RadicalVerticalGap,
        oneDevPixel);
  } else {
    // Rule 11, App. G, TeXbook
    aRadicalVerticalGap =
        aRadicalRuleThickness +
        (aDisplayStyle ? aFontMetrics->XHeight() : aRadicalRuleThickness) / 4;
  }
}