Quelle SVGTextFrame.cpp Sprache: C

/* -*- 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/. */

// Main header first:
#include "SVGTextFrame.h"

// Keep others in (case-insensitive) order:
#include "DOMSVGPoint.h"
#include "gfx2DGlue.h"
#include "gfxContext.h"
#include "gfxFont.h"
#include "gfxSkipChars.h"
#include "gfxTypes.h"
#include "gfxUtils.h"
#include "LookAndFeel.h"
#include "nsBidiPresUtils.h"
#include "nsBlockFrame.h"
#include "nsCaret.h"
#include "nsContentUtils.h"
#include "nsGkAtoms.h"
#include "SVGPaintServerFrame.h"
#include "nsTArray.h"
#include "nsTextFrame.h"
#include "SVGAnimatedNumberList.h"
#include "SVGContentUtils.h"
#include "SVGContextPaint.h"
#include "SVGLengthList.h"
#include "SVGNumberList.h"
#include "nsLayoutUtils.h"
#include "nsFrameSelection.h"
#include "nsStyleStructInlines.h"
#include "mozilla/CaretAssociationHint.h"
#include "mozilla/DisplaySVGItem.h"
#include "mozilla/Likely.h"
#include "mozilla/PresShell.h"
#include "mozilla/SVGObserverUtils.h"
#include "mozilla/SVGOuterSVGFrame.h"
#include "mozilla/SVGUtils.h"
#include "mozilla/dom/DOMPointBinding.h"
#include "mozilla/dom/Selection.h"
#include "mozilla/dom/SVGGeometryElement.h"
#include "mozilla/dom/SVGRect.h"
#include "mozilla/dom/SVGTextContentElementBinding.h"
#include "mozilla/dom/SVGTextPathElement.h"
#include "mozilla/dom/Text.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/PatternHelpers.h"
#include <algorithm>
#include <cmath>
#include <limits>

using namespace mozilla::dom;
using namespace mozilla::dom::SVGTextContentElement_Binding;
using namespace mozilla::gfx;
using namespace mozilla::image;

namespace mozilla {

// ============================================================================
// Utility functions

/**
* Using the specified gfxSkipCharsIterator, converts an offset and length
* in original char indexes to skipped char indexes.
*
* @param aIterator The gfxSkipCharsIterator to use for the conversion.
* @param aOriginalOffset The original offset.
* @param aOriginalLength The original length.
*/
static gfxTextRun::Range ConvertOriginalToSkipped(
    gfxSkipCharsIterator& aIterator, uint32_t aOriginalOffset,
    uint32_t aOriginalLength) {
  uint32_t start = aIterator.ConvertOriginalToSkipped(aOriginalOffset);
  aIterator.AdvanceOriginal(aOriginalLength);
  return gfxTextRun::Range(start, aIterator.GetSkippedOffset());
}

/**
* Converts an nsPoint from app units to user space units using the specified
* nsPresContext and returns it as a gfxPoint.
*/
static gfxPoint AppUnitsToGfxUnits(const nsPoint& aPoint,
                                   const nsPresContext* aContext) {
  return gfxPoint(aContext->AppUnitsToGfxUnits(aPoint.x),
                  aContext->AppUnitsToGfxUnits(aPoint.y));
}

/**
* Converts a gfxRect that is in app units to CSS pixels using the specified
* nsPresContext and returns it as a gfxRect.
*/
static gfxRect AppUnitsToFloatCSSPixels(const gfxRect& aRect,
                                        const nsPresContext* aContext) {
  return gfxRect(nsPresContext::AppUnitsToFloatCSSPixels(aRect.x),
                 nsPresContext::AppUnitsToFloatCSSPixels(aRect.y),
                 nsPresContext::AppUnitsToFloatCSSPixels(aRect.width),
                 nsPresContext::AppUnitsToFloatCSSPixels(aRect.height));
}

/**
* Returns whether a gfxPoint lies within a gfxRect.
*/
static bool Inside(const gfxRect& aRect, const gfxPoint& aPoint) {
  return aPoint.x >= aRect.x && aPoint.x < aRect.XMost() &&
         aPoint.y >= aRect.y && aPoint.y < aRect.YMost();
}

/**
* Gets the measured ascent and descent of the text in the given nsTextFrame
* in app units.
*
* @param aFrame The text frame.
* @param aAscent The ascent in app units (output).
* @param aDescent The descent in app units (output).
*/
static void GetAscentAndDescentInAppUnits(nsTextFrame* aFrame,
                                          gfxFloat& aAscent,
                                          gfxFloat& aDescent) {
  gfxSkipCharsIterator it = aFrame->EnsureTextRun(nsTextFrame::eInflated);
  gfxTextRun* textRun = aFrame->GetTextRun(nsTextFrame::eInflated);

  gfxTextRun::Range range = ConvertOriginalToSkipped(
      it, aFrame->GetContentOffset(), aFrame->GetContentLength());

  textRun->GetLineHeightMetrics(range, aAscent, aDescent);
}

/**
* Updates an interval by intersecting it with another interval.
* The intervals are specified using a start index and a length.
*/
static void IntersectInterval(uint32_t& aStart, uint32_t& aLength,
                              uint32_t aStartOther, uint32_t aLengthOther) {
  uint32_t aEnd = aStart + aLength;
  uint32_t aEndOther = aStartOther + aLengthOther;

  if (aStartOther >= aEnd || aStart >= aEndOther) {
    aLength = 0;
  } else {
    if (aStartOther >= aStart) {
      aStart = aStartOther;
    }
    aLength = std::min(aEnd, aEndOther) - aStart;
  }
}

/**
* Intersects an interval as IntersectInterval does but by taking
* the offset and length of the other interval from a
* nsTextFrame::TrimmedOffsets object.
*/
static void TrimOffsets(uint32_t& aStart, uint32_t& aLength,
                        const nsTextFrame::TrimmedOffsets& aTrimmedOffsets) {
  IntersectInterval(aStart, aLength, aTrimmedOffsets.mStart,
                    aTrimmedOffsets.mLength);
}

/**
* Returns the closest ancestor-or-self node that is not an SVG <a>
* element.
*/
static nsIContent* GetFirstNonAAncestor(nsIContent* aContent) {
  while (aContent && aContent->IsSVGElement(nsGkAtoms::a)) {
    aContent = aContent->GetParent();
  }
  return aContent;
}

/**
* Returns whether the given node is a text content element[1], taking into
* account whether it has a valid parent.
*
* For example, in:
*
*   <svg xmlns="http://www.w3.org/2000/svg">
*     <text><a/><text/></text>
*     <tspan/>
*   </svg>
*
* true would be returned for the outer <text> element and the <a> element,
* and false for the inner <text> element (since a <text> is not allowed
* to be a child of another <text>) and the <tspan> element (because it
* must be inside a <text> subtree).
*
* Note that we don't support the <tref> element yet and this function
* returns false for it.
*
* [1] https://svgwg.org/svg2-draft/intro.html#TermTextContentElement
*/
static bool IsTextContentElement(nsIContent* aContent) {
  if (aContent->IsSVGElement(nsGkAtoms::text)) {
    nsIContent* parent = GetFirstNonAAncestor(aContent->GetParent());
    return !parent || !IsTextContentElement(parent);
  }

  if (aContent->IsSVGElement(nsGkAtoms::textPath)) {
    nsIContent* parent = GetFirstNonAAncestor(aContent->GetParent());
    return parent && parent->IsSVGElement(nsGkAtoms::text);
  }

  return aContent->IsAnyOfSVGElements(nsGkAtoms::a, nsGkAtoms::tspan);
}

/**
* Returns whether the specified frame is an nsTextFrame that has some text
* content.
*/
static bool IsNonEmptyTextFrame(nsIFrame* aFrame) {
  nsTextFrame* textFrame = do_QueryFrame(aFrame);
  if (!textFrame) {
    return false;
  }

  return textFrame->GetContentLength() != 0;
}

/**
* Takes an nsIFrame and if it is a text frame that has some text content,
* returns it as an nsTextFrame and its corresponding Text.
*
* @param aFrame The frame to look at.
* @param aTextFrame aFrame as an nsTextFrame (output).
* @param aTextNode The Text content of aFrame (output).
* @return true if aFrame is a non-empty text frame, false otherwise.
*/
static bool GetNonEmptyTextFrameAndNode(nsIFrame* aFrame,
                                        nsTextFrame*& aTextFrame,
                                        Text*& aTextNode) {
  nsTextFrame* text = do_QueryFrame(aFrame);
  bool isNonEmptyTextFrame = text && text->GetContentLength() != 0;

  if (isNonEmptyTextFrame) {
    nsIContent* content = text->GetContent();
    NS_ASSERTION(content && content->IsText(),
                 "unexpected content type for nsTextFrame");

    Text* node = content->AsText();
    MOZ_ASSERT(node->TextLength() != 0,
               "frame's GetContentLength() should be 0 if the text node "
               "has no content");

    aTextFrame = text;
    aTextNode = node;
  }

  MOZ_ASSERT(IsNonEmptyTextFrame(aFrame) == isNonEmptyTextFrame,
             "our logic should agree with IsNonEmptyTextFrame");
  return isNonEmptyTextFrame;
}

/**
* Returns whether the specified atom is for one of the five
* glyph positioning attributes that can appear on SVG text
* elements -- x, y, dx, dy or rotate.
*/
static bool IsGlyphPositioningAttribute(nsAtom* aAttribute) {
  return aAttribute == nsGkAtoms::x || aAttribute == nsGkAtoms::y ||
         aAttribute == nsGkAtoms::dx || aAttribute == nsGkAtoms::dy ||
         aAttribute == nsGkAtoms::rotate;
}

/**
* Returns the position in app units of a given baseline (using an
* SVG dominant-baseline property value) for a given nsTextFrame.
*
* @param aFrame The text frame to inspect.
* @param aTextRun The text run of aFrame.
* @param aDominantBaseline The dominant-baseline value to use.
*/
static nscoord GetBaselinePosition(nsTextFrame* aFrame, gfxTextRun* aTextRun,
                                   StyleDominantBaseline aDominantBaseline,
                                   float aFontSizeScaleFactor) {
  WritingMode writingMode = aFrame->GetWritingMode();
  gfxFloat ascent, descent;
  aTextRun->GetLineHeightMetrics(ascent, descent);

  auto convertIfVerticalRL = [&](gfxFloat dominantBaseline) {
    return writingMode.IsVerticalRL() ? ascent + descent - dominantBaseline
                                      : dominantBaseline;
  };

  switch (aDominantBaseline) {
    case StyleDominantBaseline::Hanging:
      return convertIfVerticalRL(ascent * 0.2);
    case StyleDominantBaseline::TextBeforeEdge:
      return convertIfVerticalRL(0);

    case StyleDominantBaseline::Alphabetic:
      return writingMode.IsVerticalRL()
                 ? ascent * 0.5
                 : aFrame->GetLogicalBaseline(writingMode);

    case StyleDominantBaseline::Auto:
      return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode));

    case StyleDominantBaseline::Middle:
      return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode) -
                                 SVGContentUtils::GetFontXHeight(aFrame) / 2.0 *
                                     AppUnitsPerCSSPixel() *
                                     aFontSizeScaleFactor);

    case StyleDominantBaseline::TextAfterEdge:
    case StyleDominantBaseline::Ideographic:
      return writingMode.IsVerticalLR() ? 0 : ascent + descent;

    case StyleDominantBaseline::Central:
      return (ascent + descent) / 2.0;
    case StyleDominantBaseline::Mathematical:
      return convertIfVerticalRL(ascent / 2.0);
  }

  MOZ_ASSERT_UNREACHABLE("unexpected dominant-baseline value");
  return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode));
}

/**
* Truncates an array to be at most the length of another array.
*
* @param aArrayToTruncate The array to truncate.
* @param aReferenceArray The array whose length will be used to truncate
*   aArrayToTruncate to.
*/
template <typename T, typename U>
static void TruncateTo(nsTArray<T>& aArrayToTruncate,
                       const nsTArray<U>& aReferenceArray) {
  uint32_t length = aReferenceArray.Length();
  if (aArrayToTruncate.Length() > length) {
    aArrayToTruncate.TruncateLength(length);
  }
}

/**
* Asserts that the anonymous block child of the SVGTextFrame has been
* reflowed (or does not exist).  Returns null if the child has not been
* reflowed, and the frame otherwise.
*
* We check whether the kid has been reflowed and not the frame itself
* since we sometimes need to call this function during reflow, after the
* kid has been reflowed but before we have cleared the dirty bits on the
* frame itself.
*/
static SVGTextFrame* FrameIfAnonymousChildReflowed(SVGTextFrame* aFrame) {
  MOZ_ASSERT(aFrame, "aFrame must not be null");
  nsIFrame* kid = aFrame->PrincipalChildList().FirstChild();
  if (kid->IsSubtreeDirty()) {
    MOZ_ASSERT(false, "should have already reflowed the anonymous block child");
    return nullptr;
  }
  return aFrame;
}

// FIXME(emilio): SVG is a special-case where transforms affect layout. We don't
// want that to go outside the SVG stuff (and really we should aim to remove
// that).
static float GetContextScale(SVGTextFrame* aFrame) {
  if (aFrame->HasAnyStateBits(NS_FRAME_IS_NONDISPLAY)) {
    // When we are non-display, we could be painted in different coordinate
    // spaces, and we don't want to have to reflow for each of these.  We just
    // assume that the context scale is 1.0 for them all, so we don't get stuck
    // with a font size scale factor based on whichever referencing frame
    // happens to reflow first.
    return 1.0f;
  }
  auto matrix = nsLayoutUtils::GetTransformToAncestor(
      RelativeTo{aFrame}, RelativeTo{SVGUtils::GetOuterSVGFrame(aFrame)});
  Matrix transform2D;
  if (!matrix.CanDraw2D(&transform2D)) {
    return 1.0f;
  }
  auto scales = transform2D.ScaleFactors();
  return std::max(0.0f, std::max(scales.xScale, scales.yScale));
}

// ============================================================================
// Utility classes

// ----------------------------------------------------------------------------
// TextRenderedRun

/**
* A run of text within a single nsTextFrame whose glyphs can all be painted
* with a single call to nsTextFrame::PaintText.  A text rendered run can
* be created for a sequence of two or more consecutive glyphs as long as:
*
*   - Only the first glyph has (or none of the glyphs have) been positioned
*     with SVG text positioning attributes
*   - All of the glyphs have zero rotation
*   - The glyphs are not on a text path
*   - The glyphs correspond to content within the one nsTextFrame
*
* A TextRenderedRunIterator produces TextRenderedRuns required for painting a
* whole SVGTextFrame.
*/
struct TextRenderedRun {
  using Range = gfxTextRun::Range;

  /**
   * Constructs a TextRenderedRun that is uninitialized except for mFrame
   * being null.
   */
  TextRenderedRun() : mFrame(nullptr) {}

  /**
   * Constructs a TextRenderedRun with all of the information required to
   * paint it.  See the comments documenting the member variables below
   * for descriptions of the arguments.
   */
  TextRenderedRun(nsTextFrame* aFrame, const gfxPoint& aPosition,
                  float aLengthAdjustScaleFactor, double aRotate,
                  float aFontSizeScaleFactor, nscoord aBaseline,
                  uint32_t aTextFrameContentOffset,
                  uint32_t aTextFrameContentLength,
                  uint32_t aTextElementCharIndex)
      : mFrame(aFrame),
        mPosition(aPosition),
        mLengthAdjustScaleFactor(aLengthAdjustScaleFactor),
        mRotate(static_cast<float>(aRotate)),
        mFontSizeScaleFactor(aFontSizeScaleFactor),
        mBaseline(aBaseline),
        mTextFrameContentOffset(aTextFrameContentOffset),
        mTextFrameContentLength(aTextFrameContentLength),
        mTextElementCharIndex(aTextElementCharIndex) {}

  /**
   * Returns the text run for the text frame that this rendered run is part of.
   */
  gfxTextRun* GetTextRun() const {
    mFrame->EnsureTextRun(nsTextFrame::eInflated);
    return mFrame->GetTextRun(nsTextFrame::eInflated);
  }

  /**
   * Returns whether this rendered run is RTL.
   */
  bool IsRightToLeft() const { return GetTextRun()->IsRightToLeft(); }

  /**
   * Returns whether this rendered run is vertical.
   */
  bool IsVertical() const { return GetTextRun()->IsVertical(); }

  /**
   * Returns the transform that converts from a <text> element's user space into
   * the coordinate space that rendered runs can be painted directly in.
   *
   * The difference between this method and
   * GetTransformFromRunUserSpaceToUserSpace is that when calling in to
   * nsTextFrame::PaintText, it will already take into account any left clip
   * edge (that is, it doesn't just apply a visual clip to the rendered text, it
   * shifts the glyphs over so that they are painted with their left edge at the
   * x coordinate passed in to it). Thus we need to account for this in our
   * transform.
   *
   *
   * Assume that we have:
   *
   *   <text x="100" y="100" rotate="0 0 1 0 0 * 1">abcdef</text>.
   *
   * This would result in four text rendered runs:
   *
   *   - one for "ab"
   *   - one for "c"
   *   - one for "de"
   *   - one for "f"
   *
   * Assume now that we are painting the third TextRenderedRun.  It will have
   * a left clip edge that is the sum of the advances of "abc", and it will
   * have a right clip edge that is the advance of "f".  In
   * SVGTextFrame::PaintSVG(), we pass in nsPoint() (i.e., the origin)
   * as the point at which to paint the text frame, and we pass in the
   * clip edge values.  The nsTextFrame will paint the substring of its
   * text such that the top-left corner of the "d"'s glyph cell will be at
   * (0, 0) in the current coordinate system.
   *
   * Thus, GetTransformFromUserSpaceForPainting must return a transform from
   * whatever user space the <text> element is in to a coordinate space in
   * device pixels (as that's what nsTextFrame works in) where the origin is at
   * the same position as our user space mPositions[i].mPosition value for
   * the "d" glyph, which will be (100 + userSpaceAdvance("abc"), 100).
   * The translation required to do this (ignoring the scale to get from
   * user space to device pixels, and ignoring the
   * (100 + userSpaceAdvance("abc"), 100) translation) is:
   *
   *   (-leftEdge, -baseline)
   *
   * where baseline is the distance between the baseline of the text and the top
   * edge of the nsTextFrame.  We translate by -leftEdge horizontally because
   * the nsTextFrame will already shift the glyphs over by that amount and start
   * painting glyphs at x = 0.  We translate by -baseline vertically so that
   * painting the top edges of the glyphs at y = 0 will result in their
   * baselines being at our desired y position.
   *
   *
   * Now for an example with RTL text.  Assume our content is now
   * <text x="100" y="100" rotate="0 0 1 0 0 1">WERBEH</text>.  We'd have
   * the following text rendered runs:
   *
   *   - one for "EH"
   *   - one for "B"
   *   - one for "ER"
   *   - one for "W"
   *
   * Again, we are painting the third TextRenderedRun.  The left clip edge
   * is the advance of the "W" and the right clip edge is the sum of the
   * advances of "BEH".  Our translation to get the rendered "ER" glyphs
   * in the right place this time is:
   *
   *   (-frameWidth + rightEdge, -baseline)
   *
   * which is equivalent to:
   *
   *   (-(leftEdge + advance("ER")), -baseline)
   *
   * The reason we have to shift left additionally by the width of the run
   * of glyphs we are painting is that although the nsTextFrame is RTL,
   * we still supply the top-left corner to paint the frame at when calling
   * nsTextFrame::PaintText, even though our user space positions for each
   * glyph in mPositions specifies the origin of each glyph, which for RTL
   * glyphs is at the right edge of the glyph cell.
   *
   *
   * For any other use of an nsTextFrame in the context of a particular run
   * (such as hit testing, or getting its rectangle),
   * GetTransformFromRunUserSpaceToUserSpace should be used.
   *
   * @param aContext The context to use for unit conversions.
   */
  gfxMatrix GetTransformFromUserSpaceForPainting(
      nsPresContext* aContext, const nscoord aVisIStartEdge,
      const nscoord aVisIEndEdge) const;

  /**
   * Returns the transform that converts from "run user space" to a <text>
   * element's user space.  Run user space is a coordinate system that has the
   * same size as the <text>'s user space but rotated and translated such that
   * (0,0) is the top-left of the rectangle that bounds the text.
   *
   * @param aContext The context to use for unit conversions.
   */
  gfxMatrix GetTransformFromRunUserSpaceToUserSpace(
      nsPresContext* aContext) const;

  /**
   * Returns the transform that converts from "run user space" to float pixels
   * relative to the nsTextFrame that this rendered run is a part of.
   *
   * @param aContext The context to use for unit conversions.
   */
  gfxMatrix GetTransformFromRunUserSpaceToFrameUserSpace(
      nsPresContext* aContext) const;

  /**
   * Flag values used for the aFlags arguments of GetRunUserSpaceRect,
   * GetFrameUserSpaceRect and GetUserSpaceRect.
   */
  enum {
    // Includes the fill geometry of the text in the returned rectangle.
    eIncludeFill = 1,
    // Includes the stroke geometry of the text in the returned rectangle.
    eIncludeStroke = 2,
    // Don't include any horizontal glyph overflow in the returned rectangle.
    eNoHorizontalOverflow = 4
  };

  /**
   * Returns a rectangle that bounds the fill and/or stroke of the rendered run
   * in run user space.
   *
   * @param aContext The context to use for unit conversions.
   * @param aFlags A combination of the flags above (eIncludeFill and
   *   eIncludeStroke) indicating what parts of the text to include in
   *   the rectangle.
   */
  SVGBBox GetRunUserSpaceRect(nsPresContext* aContext, uint32_t aFlags) const;

  /**
   * Returns a rectangle that covers the fill and/or stroke of the rendered run
   * in "frame user space".
   *
   * Frame user space is a coordinate space of the same scale as the <text>
   * element's user space, but with its rotation set to the rotation of
   * the glyphs within this rendered run and its origin set to the position
   * such that placing the nsTextFrame there would result in the glyphs in
   * this rendered run being at their correct positions.
   *
   * For example, say we have <text x="100 150" y="100">ab</text>.  Assume
   * the advance of both the "a" and the "b" is 12 user units, and the
   * ascent of the text is 8 user units and its descent is 6 user units,
   * and that we are not measuing the stroke of the text, so that we stay
   * entirely within the glyph cells.
   *
   * There will be two text rendered runs, one for "a" and one for "b".
   *
   * The frame user space for the "a" run will have its origin at
   * (100, 100 - 8) in the <text> element's user space and will have its
   * axes aligned with the user space (since there is no rotate="" or
   * text path involve) and with its scale the same as the user space.
   * The rect returned by this method will be (0, 0, 12, 14), since the "a"
   * glyph is right at the left of the nsTextFrame.
   *
   * The frame user space for the "b" run will have its origin at
   * (150 - 12, 100 - 8), and scale/rotation the same as above.  The rect
   * returned by this method will be (12, 0, 12, 14), since we are
   * advance("a") horizontally in to the text frame.
   *
   * @param aContext The context to use for unit conversions.
   * @param aFlags A combination of the flags above (eIncludeFill and
   *   eIncludeStroke) indicating what parts of the text to include in
   *   the rectangle.
   */
  SVGBBox GetFrameUserSpaceRect(nsPresContext* aContext, uint32_t aFlags) const;

  /**
   * Returns a rectangle that covers the fill and/or stroke of the rendered run
   * in the <text> element's user space.
   *
   * @param aContext The context to use for unit conversions.
   * @param aFlags A combination of the flags above indicating what parts of
   *   the text to include in the rectangle.
   * @param aAdditionalTransform An additional transform to apply to the
   *   frame user space rectangle before its bounds are transformed into
   *   user space.
   */
  SVGBBox GetUserSpaceRect(
      nsPresContext* aContext, uint32_t aFlags,
      const gfxMatrix* aAdditionalTransform = nullptr) const;

  /**
   * Gets the app unit amounts to clip from the left and right edges of
   * the nsTextFrame in order to paint just this rendered run.
   *
   * Note that if clip edge amounts land in the middle of a glyph, the
   * glyph won't be painted at all.  The clip edges are thus more of
   * a selection mechanism for which glyphs will be painted, rather
   * than a geometric clip.
   */
  void GetClipEdges(nscoord& aVisIStartEdge, nscoord& aVisIEndEdge) const;

  /**
   * Returns the advance width of the whole rendered run.
   */
  nscoord GetAdvanceWidth() const;

  /**
   * Returns the index of the character into this rendered run whose
   * glyph cell contains the given point, or -1 if there is no such
   * character.  This does not hit test against any overflow.
   *
   * @param aContext The context to use for unit conversions.
   * @param aPoint The point in the user space of the <text> element.
   */
  int32_t GetCharNumAtPosition(nsPresContext* aContext,
                               const gfxPoint& aPoint) const;

  /**
   * The text frame that this rendered run lies within.
   */
  nsTextFrame* mFrame;

  /**
   * The point in user space that the text is positioned at.
   *
   * For a horizontal run:
   * The x coordinate is the left edge of a LTR run of text or the right edge of
   * an RTL run.  The y coordinate is the baseline of the text.
   * For a vertical run:
   * The x coordinate is the baseline of the text.
   * The y coordinate is the top edge of a LTR run, or bottom of RTL.
   */
  gfxPoint mPosition;

  /**
   * The horizontal scale factor to apply when painting glyphs to take
   * into account textLength="".
   */
  float mLengthAdjustScaleFactor;

  /**
   * The rotation in radians in the user coordinate system that the text has.
   */
  float mRotate;

  /**
   * The scale factor that was used to transform the text run's original font
   * size into a sane range for painting and measurement.
   */
  double mFontSizeScaleFactor;

  /**
   * The baseline in app units of this text run.  The measurement is from the
   * top of the text frame. (From the left edge if vertical.)
   */
  nscoord mBaseline;

  /**
   * The offset and length in mFrame's content Text that corresponds to
   * this text rendered run.  These are original char indexes.
   */
  uint32_t mTextFrameContentOffset;
  uint32_t mTextFrameContentLength;

  /**
   * The character index in the whole SVG <text> element that this text rendered
   * run begins at.
   */
  uint32_t mTextElementCharIndex;
};

gfxMatrix TextRenderedRun::GetTransformFromUserSpaceForPainting(
    nsPresContext* aContext, const nscoord aVisIStartEdge,
    const nscoord aVisIEndEdge) const {
  // We transform to device pixels positioned such that painting the text frame
  // at (0,0) with aItem will result in the text being in the right place.

  gfxMatrix m;
  if (!mFrame) {
    return m;
  }

  float cssPxPerDevPx =
      nsPresContext::AppUnitsToFloatCSSPixels(aContext->AppUnitsPerDevPixel());

  // Glyph position in user space.
  m.PreTranslate(mPosition / cssPxPerDevPx);

  // Take into account any font size scaling and scaling due to textLength="".
  m.PreScale(1.0 / mFontSizeScaleFactor, 1.0 / mFontSizeScaleFactor);

  // Rotation due to rotate="" or a <textPath>.
  m.PreRotate(mRotate);

  // Scale for textLength="" and translate to get the text frame
  // to the right place.
  nsPoint t;
  if (IsVertical()) {
    m.PreScale(1.0, mLengthAdjustScaleFactor);
    t = nsPoint(-mBaseline, IsRightToLeft()
                                ? -mFrame->GetRect().height + aVisIEndEdge
                                : -aVisIStartEdge);
  } else {
    m.PreScale(mLengthAdjustScaleFactor, 1.0);
    t = nsPoint(IsRightToLeft() ? -mFrame->GetRect().width + aVisIEndEdge
                                : -aVisIStartEdge,
                -mBaseline);
  }
  m.PreTranslate(AppUnitsToGfxUnits(t, aContext));

  return m;
}

gfxMatrix TextRenderedRun::GetTransformFromRunUserSpaceToUserSpace(
    nsPresContext* aContext) const {
  gfxMatrix m;
  if (!mFrame) {
    return m;
  }

  float cssPxPerDevPx =
      nsPresContext::AppUnitsToFloatCSSPixels(aContext->AppUnitsPerDevPixel());

  nscoord start, end;
  GetClipEdges(start, end);

  // Glyph position in user space.
  m.PreTranslate(mPosition);

  // Rotation due to rotate="" or a <textPath>.
  m.PreRotate(mRotate);

  // Scale for textLength="" and translate to get the text frame
  // to the right place.

  nsPoint t;
  if (IsVertical()) {
    m.PreScale(1.0, mLengthAdjustScaleFactor);
    t = nsPoint(-mBaseline,
                IsRightToLeft() ? -mFrame->GetRect().height + start + end : 0);
  } else {
    m.PreScale(mLengthAdjustScaleFactor, 1.0);
    t = nsPoint(IsRightToLeft() ? -mFrame->GetRect().width + start + end : 0,
                -mBaseline);
  }
  m.PreTranslate(AppUnitsToGfxUnits(t, aContext) * cssPxPerDevPx /
                 mFontSizeScaleFactor);

  return m;
}

gfxMatrix TextRenderedRun::GetTransformFromRunUserSpaceToFrameUserSpace(
    nsPresContext* aContext) const {
  gfxMatrix m;
  if (!mFrame) {
    return m;
  }

  nscoord start, end;
  GetClipEdges(start, end);

  // Translate by the horizontal distance into the text frame this
  // rendered run is.
  gfxFloat appPerCssPx = AppUnitsPerCSSPixel();
  gfxPoint t = IsVertical() ? gfxPoint(0, start / appPerCssPx)
                            : gfxPoint(start / appPerCssPx, 0);
  return m.PreTranslate(t);
}

SVGBBox TextRenderedRun::GetRunUserSpaceRect(nsPresContext* aContext,
                                             uint32_t aFlags) const {
  SVGBBox r;
  if (!mFrame) {
    return r;
  }

  // Determine the amount of overflow around frame's mRect.
  //
  // We need to call InkOverflowRectRelativeToSelf because this includes
  // overflowing decorations, which the MeasureText call below does not.
  nsRect self = mFrame->InkOverflowRectRelativeToSelf();
  nsRect rect = mFrame->GetRect();
  bool vertical = IsVertical();
  nsMargin inkOverflow(
      vertical ? -self.x : -self.y,
      vertical ? self.YMost() - rect.height : self.XMost() - rect.width,
      vertical ? self.XMost() - rect.width : self.YMost() - rect.height,
      vertical ? -self.y : -self.x);

  gfxSkipCharsIterator it = mFrame->EnsureTextRun(nsTextFrame::eInflated);
  gfxSkipCharsIterator start = it;
  gfxTextRun* textRun = mFrame->GetTextRun(nsTextFrame::eInflated);

  // Get the content range for this rendered run.
  Range range = ConvertOriginalToSkipped(it, mTextFrameContentOffset,
                                         mTextFrameContentLength);
  if (range.Length() == 0) {
    return r;
  }

  // FIXME(heycam): We could create a single PropertyProvider for all
  // TextRenderedRuns that correspond to the text frame, rather than recreate
  // it each time here.
  nsTextFrame::PropertyProvider provider(mFrame, start);

  // Measure that range.
  gfxTextRun::Metrics metrics = textRun->MeasureText(
      range, gfxFont::LOOSE_INK_EXTENTS, nullptr, &provider);
  // Make sure it includes the font-box.
  gfxRect fontBox(0, -metrics.mAscent, metrics.mAdvanceWidth,
                  metrics.mAscent + metrics.mDescent);
  metrics.mBoundingBox.UnionRect(metrics.mBoundingBox, fontBox);

  // Determine the rectangle that covers the rendered run's fill,
  // taking into account the measured overflow due to decorations.
  nscoord baseline =
      NSToCoordRoundWithClamp(metrics.mBoundingBox.y + metrics.mAscent);
  gfxFloat x, width;
  if (aFlags & eNoHorizontalOverflow) {
    x = 0.0;
    width = textRun->GetAdvanceWidth(range, &provider);
    if (width < 0.0) {
      x = width;
      width = -width;
    }
  } else {
    x = metrics.mBoundingBox.x;
    width = metrics.mBoundingBox.width;
  }
  nsRect fillInAppUnits(NSToCoordRoundWithClamp(x), baseline,
                        NSToCoordRoundWithClamp(width),
                        NSToCoordRoundWithClamp(metrics.mBoundingBox.height));
  fillInAppUnits.Inflate(inkOverflow);
  if (textRun->IsVertical()) {
    // Swap line-relative textMetrics dimensions to physical coordinates.
    std::swap(fillInAppUnits.x, fillInAppUnits.y);
    std::swap(fillInAppUnits.width, fillInAppUnits.height);
  }

  // Convert the app units rectangle to user units.
  gfxRect fill = AppUnitsToFloatCSSPixels(
      gfxRect(fillInAppUnits.x, fillInAppUnits.y, fillInAppUnits.width,
              fillInAppUnits.height),
      aContext);

  // Scale the rectangle up due to any mFontSizeScaleFactor.
  fill.Scale(1.0 / mFontSizeScaleFactor);

  // Include the fill if requested.
  if (aFlags & eIncludeFill) {
    r = fill;
  }

  // Include the stroke if requested.
  if ((aFlags & eIncludeStroke) && !fill.IsEmpty() &&
      SVGUtils::GetStrokeWidth(mFrame) > 0) {
    r.UnionEdges(
        SVGUtils::PathExtentsToMaxStrokeExtents(fill, mFrame, gfxMatrix()));
  }

  return r;
}

SVGBBox TextRenderedRun::GetFrameUserSpaceRect(nsPresContext* aContext,
                                               uint32_t aFlags) const {
  SVGBBox r = GetRunUserSpaceRect(aContext, aFlags);
  if (r.IsEmpty()) {
    return r;
  }
  gfxMatrix m = GetTransformFromRunUserSpaceToFrameUserSpace(aContext);
  return m.TransformBounds(r.ToThebesRect());
}

SVGBBox TextRenderedRun::GetUserSpaceRect(
    nsPresContext* aContext, uint32_t aFlags,
    const gfxMatrix* aAdditionalTransform) const {
  SVGBBox r = GetRunUserSpaceRect(aContext, aFlags);
  if (r.IsEmpty()) {
    return r;
  }
  gfxMatrix m = GetTransformFromRunUserSpaceToUserSpace(aContext);
  if (aAdditionalTransform) {
    m *= *aAdditionalTransform;
  }
  return m.TransformBounds(r.ToThebesRect());
}

void TextRenderedRun::GetClipEdges(nscoord& aVisIStartEdge,
                                   nscoord& aVisIEndEdge) const {
  uint32_t contentLength = mFrame->GetContentLength();
  if (mTextFrameContentOffset == 0 &&
      mTextFrameContentLength == contentLength) {
    // If the rendered run covers the entire content, we know we don't need
    // to clip without having to measure anything.
    aVisIStartEdge = 0;
    aVisIEndEdge = 0;
    return;
  }

  gfxSkipCharsIterator it = mFrame->EnsureTextRun(nsTextFrame::eInflated);
  gfxTextRun* textRun = mFrame->GetTextRun(nsTextFrame::eInflated);
  nsTextFrame::PropertyProvider provider(mFrame, it);

  // Get the covered content offset/length for this rendered run in skipped
  // characters, since that is what GetAdvanceWidth expects.
  Range runRange = ConvertOriginalToSkipped(it, mTextFrameContentOffset,
                                            mTextFrameContentLength);

  // Get the offset/length of the whole nsTextFrame.
  uint32_t frameOffset = mFrame->GetContentOffset();
  uint32_t frameLength = mFrame->GetContentLength();

  // Trim the whole-nsTextFrame offset/length to remove any leading/trailing
  // white space, as the nsTextFrame when painting does not include them when
  // interpreting clip edges.
  nsTextFrame::TrimmedOffsets trimmedOffsets =
      mFrame->GetTrimmedOffsets(mFrame->TextFragment());
  TrimOffsets(frameOffset, frameLength, trimmedOffsets);

  // Convert the trimmed whole-nsTextFrame offset/length into skipped
  // characters.
  Range frameRange = ConvertOriginalToSkipped(it, frameOffset, frameLength);

  // Measure the advance width in the text run between the start of
  // frame's content and the start of the rendered run's content,
  nscoord startEdge = textRun->GetAdvanceWidth(
      Range(frameRange.start, runRange.start), &provider);

  // and between the end of the rendered run's content and the end
  // of the frame's content.
  nscoord endEdge =
      textRun->GetAdvanceWidth(Range(runRange.end, frameRange.end), &provider);

  if (textRun->IsRightToLeft()) {
    aVisIStartEdge = endEdge;
    aVisIEndEdge = startEdge;
  } else {
    aVisIStartEdge = startEdge;
    aVisIEndEdge = endEdge;
  }
}

nscoord TextRenderedRun::GetAdvanceWidth() const {
  gfxSkipCharsIterator it = mFrame->EnsureTextRun(nsTextFrame::eInflated);
  gfxTextRun* textRun = mFrame->GetTextRun(nsTextFrame::eInflated);
  nsTextFrame::PropertyProvider provider(mFrame, it);

  Range range = ConvertOriginalToSkipped(it, mTextFrameContentOffset,
                                         mTextFrameContentLength);

  return textRun->GetAdvanceWidth(range, &provider);
}

int32_t TextRenderedRun::GetCharNumAtPosition(nsPresContext* aContext,
                                              const gfxPoint& aPoint) const {
  if (mTextFrameContentLength == 0) {
    return -1;
  }

  float cssPxPerDevPx =
      nsPresContext::AppUnitsToFloatCSSPixels(aContext->AppUnitsPerDevPixel());

  // Convert the point from user space into run user space, and take
  // into account any mFontSizeScaleFactor.
  gfxMatrix m = GetTransformFromRunUserSpaceToUserSpace(aContext);
  if (!m.Invert()) {
    return -1;
  }
  gfxPoint p = m.TransformPoint(aPoint) / cssPxPerDevPx * mFontSizeScaleFactor;

  // First check that the point lies vertically between the top and bottom
  // edges of the text.
  gfxFloat ascent, descent;
  GetAscentAndDescentInAppUnits(mFrame, ascent, descent);

  WritingMode writingMode = mFrame->GetWritingMode();
  if (writingMode.IsVertical()) {
    gfxFloat leftEdge = mFrame->GetLogicalBaseline(writingMode) -
                        (writingMode.IsVerticalRL() ? ascent : descent);
    gfxFloat rightEdge = leftEdge + ascent + descent;
    if (p.x < aContext->AppUnitsToGfxUnits(leftEdge) ||
        p.x > aContext->AppUnitsToGfxUnits(rightEdge)) {
      return -1;
    }
  } else {
    gfxFloat topEdge = mFrame->GetLogicalBaseline(writingMode) - ascent;
    gfxFloat bottomEdge = topEdge + ascent + descent;
    if (p.y < aContext->AppUnitsToGfxUnits(topEdge) ||
        p.y > aContext->AppUnitsToGfxUnits(bottomEdge)) {
      return -1;
    }
  }

  gfxSkipCharsIterator it = mFrame->EnsureTextRun(nsTextFrame::eInflated);
  gfxTextRun* textRun = mFrame->GetTextRun(nsTextFrame::eInflated);
  nsTextFrame::PropertyProvider provider(mFrame, it);

  // Next check that the point lies horizontally within the left and right
  // edges of the text.
  Range range = ConvertOriginalToSkipped(it, mTextFrameContentOffset,
                                         mTextFrameContentLength);
  gfxFloat runAdvance =
      aContext->AppUnitsToGfxUnits(textRun->GetAdvanceWidth(range, &provider));

  gfxFloat pos = writingMode.IsVertical() ? p.y : p.x;
  if (pos < 0 || pos >= runAdvance) {
    return -1;
  }

  // Finally, measure progressively smaller portions of the rendered run to
  // find which glyph it lies within.  This will need to change once we
  // support letter-spacing and word-spacing.
  bool rtl = textRun->IsRightToLeft();
  for (int32_t i = mTextFrameContentLength - 1; i >= 0; i--) {
    range = ConvertOriginalToSkipped(it, mTextFrameContentOffset, i);
    gfxFloat advance = aContext->AppUnitsToGfxUnits(
        textRun->GetAdvanceWidth(range, &provider));
    if ((rtl && pos < runAdvance - advance) || (!rtl && pos >= advance)) {
      return i;
    }
  }
  return -1;
}

// ----------------------------------------------------------------------------
// TextNodeIterator

enum SubtreePosition { eBeforeSubtree, eWithinSubtree, eAfterSubtree };

/**
* An iterator class for Text that are descendants of a given node, the
* root.  Nodes are iterated in document order.  An optional subtree can be
* specified, in which case the iterator will track whether the current state of
* the traversal over the tree is within that subtree or is past that subtree.
*/
class TextNodeIterator {
public:
  /**
   * Constructs a TextNodeIterator with the specified root node and optional
   * subtree.
   */
  explicit TextNodeIterator(nsIContent* aRoot, nsIContent* aSubtree = nullptr)
      : mRoot(aRoot),
        mSubtree(aSubtree == aRoot ? nullptr : aSubtree),
        mCurrent(aRoot),
        mSubtreePosition(mSubtree ? eBeforeSubtree : eWithinSubtree) {
    NS_ASSERTION(aRoot, "expected non-null root");
    if (!aRoot->IsText()) {
      Next();
    }
  }

  /**
   * Returns the current Text, or null if the iterator has finished.
   */
  Text* Current() const { return mCurrent ? mCurrent->AsText() : nullptr; }

  /**
   * Advances to the next Text and returns it, or null if the end of
   * iteration has been reached.
   */
  Text* Next();

  /**
   * Returns whether the iterator is currently within the subtree rooted
   * at mSubtree.  Returns true if we are not tracking a subtree (we consider
   * that we're always within the subtree).
   */
  bool IsWithinSubtree() const { return mSubtreePosition == eWithinSubtree; }

  /**
   * Returns whether the iterator is past the subtree rooted at mSubtree.
   * Returns false if we are not tracking a subtree.
   */
  bool IsAfterSubtree() const { return mSubtreePosition == eAfterSubtree; }

private:
  /**
   * The root under which all Text will be iterated over.
   */
  nsIContent* const mRoot;

  /**
   * The node rooting the subtree to track.
   */
  nsIContent* const mSubtree;

  /**
   * The current node during iteration.
   */
  nsIContent* mCurrent;

  /**
   * The current iterator position relative to mSubtree.
   */
  SubtreePosition mSubtreePosition;
};

Text* TextNodeIterator::Next() {
  // Starting from mCurrent, we do a non-recursive traversal to the next
  // Text beneath mRoot, updating mSubtreePosition appropriately if we
  // encounter mSubtree.
  if (mCurrent) {
    do {
      nsIContent* next =
          IsTextContentElement(mCurrent) ? mCurrent->GetFirstChild() : nullptr;
      if (next) {
        mCurrent = next;
        if (mCurrent == mSubtree) {
          mSubtreePosition = eWithinSubtree;
        }
      } else {
        for (;;) {
          if (mCurrent == mRoot) {
            mCurrent = nullptr;
            break;
          }
          if (mCurrent == mSubtree) {
            mSubtreePosition = eAfterSubtree;
          }
          next = mCurrent->GetNextSibling();
          if (next) {
            mCurrent = next;
            if (mCurrent == mSubtree) {
              mSubtreePosition = eWithinSubtree;
            }
            break;
          }
          if (mCurrent == mSubtree) {
            mSubtreePosition = eAfterSubtree;
          }
          mCurrent = mCurrent->GetParent();
        }
      }
    } while (mCurrent && !mCurrent->IsText());
  }

  return mCurrent ? mCurrent->AsText() : nullptr;
}

// ----------------------------------------------------------------------------
// TextNodeCorrespondenceRecorder

/**
* TextNodeCorrespondence is used as the value of a frame property that
* is stored on all its descendant nsTextFrames.  It stores the number of DOM
* characters between it and the previous nsTextFrame that did not have an
* nsTextFrame created for them, due to either not being in a correctly
* parented text content element, or because they were display:none.
* These are called "undisplayed characters".
*
* See also TextNodeCorrespondenceRecorder below, which is what sets the
* frame property.
*/
struct TextNodeCorrespondence {
  explicit TextNodeCorrespondence(uint32_t aUndisplayedCharacters)
      : mUndisplayedCharacters(aUndisplayedCharacters) {}

  uint32_t mUndisplayedCharacters;
};

NS_DECLARE_FRAME_PROPERTY_DELETABLE(TextNodeCorrespondenceProperty,
                                    TextNodeCorrespondence)

/**
* Returns the number of undisplayed characters before the specified
* nsTextFrame.
*/
static uint32_t GetUndisplayedCharactersBeforeFrame(nsTextFrame* aFrame) {
  void* value = aFrame->GetProperty(TextNodeCorrespondenceProperty());
  TextNodeCorrespondence* correspondence =
      static_cast<TextNodeCorrespondence*>(value);
  if (!correspondence) {
    // FIXME bug 903785
    NS_ERROR(
        "expected a TextNodeCorrespondenceProperty on nsTextFrame "
        "used for SVG text");
    return 0;
  }
  return correspondence->mUndisplayedCharacters;
}

/**
* Traverses the nsTextFrames for an SVGTextFrame and records a
* TextNodeCorrespondenceProperty on each for the number of undisplayed DOM
* characters between each frame.  This is done by iterating simultaneously
* over the Text and nsTextFrames and noting when Text (or
* parts of them) are skipped when finding the next nsTextFrame.
*/
class TextNodeCorrespondenceRecorder {
public:
  /**
   * Entry point for the TextNodeCorrespondenceProperty recording.
   */
  static void RecordCorrespondence(SVGTextFrame* aRoot);

private:
  explicit TextNodeCorrespondenceRecorder(SVGTextFrame* aRoot)
      : mNodeIterator(aRoot->GetContent()),
        mPreviousNode(nullptr),
        mNodeCharIndex(0) {}

  void Record(SVGTextFrame* aRoot);
  void TraverseAndRecord(nsIFrame* aFrame);

  /**
   * Returns the next non-empty Text.
   */
  Text* NextNode();

  /**
   * The iterator over the Text that we use as we simultaneously
   * iterate over the nsTextFrames.
   */
  TextNodeIterator mNodeIterator;

  /**
   * The previous Text we iterated over.
   */
  Text* mPreviousNode;

  /**
   * The index into the current Text's character content.
   */
  uint32_t mNodeCharIndex;
};

/* static */
void TextNodeCorrespondenceRecorder::RecordCorrespondence(SVGTextFrame* aRoot) {
  if (aRoot->HasAnyStateBits(NS_STATE_SVG_TEXT_CORRESPONDENCE_DIRTY)) {
    // Resolve bidi so that continuation frames are created if necessary:
    aRoot->MaybeResolveBidiForAnonymousBlockChild();
    TextNodeCorrespondenceRecorder recorder(aRoot);
    recorder.Record(aRoot);
    aRoot->RemoveStateBits(NS_STATE_SVG_TEXT_CORRESPONDENCE_DIRTY);
  }
}

void TextNodeCorrespondenceRecorder::Record(SVGTextFrame* aRoot) {
  if (!mNodeIterator.Current()) {
    // If there are no Text nodes then there is nothing to do.
    return;
  }

  // Traverse over all the nsTextFrames and record the number of undisplayed
  // characters.
  TraverseAndRecord(aRoot);

  // Find how many undisplayed characters there are after the final nsTextFrame.
  uint32_t undisplayed = 0;
  if (mNodeIterator.Current()) {
    if (mPreviousNode && mPreviousNode->TextLength() != mNodeCharIndex) {
      // The last nsTextFrame ended part way through a Text node.  The
      // remaining characters count as undisplayed.
      NS_ASSERTION(mNodeCharIndex < mPreviousNode->TextLength(),
                   "incorrect tracking of undisplayed characters in "
                   "text nodes");
      undisplayed += mPreviousNode->TextLength() - mNodeCharIndex;
    }
    // All the remaining Text that we iterate must also be undisplayed.
    for (Text* textNode = mNodeIterator.Current(); textNode;
         textNode = NextNode()) {
      undisplayed += textNode->TextLength();
    }
  }

  // Record the trailing number of undisplayed characters on the
  // SVGTextFrame.
  aRoot->mTrailingUndisplayedCharacters = undisplayed;
}

Text* TextNodeCorrespondenceRecorder::NextNode() {
  mPreviousNode = mNodeIterator.Current();
  Text* next;
  do {
    next = mNodeIterator.Next();
  } while (next && next->TextLength() == 0);
  return next;
}

void TextNodeCorrespondenceRecorder::TraverseAndRecord(nsIFrame* aFrame) {
  // Recursively iterate over the frame tree, for frames that correspond
  // to text content elements.
  if (IsTextContentElement(aFrame->GetContent())) {
    for (nsIFrame* f : aFrame->PrincipalChildList()) {
      TraverseAndRecord(f);
    }
    return;
  }

  nsTextFrame* frame;  // The current text frame.
  Text* node;          // The text node for the current text frame.
  if (!GetNonEmptyTextFrameAndNode(aFrame, frame, node)) {
    // If this isn't an nsTextFrame, or is empty, nothing to do.
    return;
  }

  NS_ASSERTION(frame->GetContentOffset() >= 0,
               "don't know how to handle negative content indexes");

  uint32_t undisplayed = 0;
  if (!mPreviousNode) {
    // Must be the very first text frame.
    NS_ASSERTION(mNodeCharIndex == 0,
                 "incorrect tracking of undisplayed "
                 "characters in text nodes");
    if (!mNodeIterator.Current()) {
      MOZ_ASSERT_UNREACHABLE(
          "incorrect tracking of correspondence between "
          "text frames and text nodes");
    } else {
      // Each whole Text we find before we get to the text node for the
      // first text frame must be undisplayed.
      while (mNodeIterator.Current() != node) {
        undisplayed += mNodeIterator.Current()->TextLength();
        NextNode();
      }
      // If the first text frame starts at a non-zero content offset, then those
      // earlier characters are also undisplayed.
      undisplayed += frame->GetContentOffset();
      NextNode();
    }
  } else if (mPreviousNode == node) {
    // Same text node as last time.
    if (static_cast<uint32_t>(frame->GetContentOffset()) != mNodeCharIndex) {
      // We have some characters in the middle of the text node
      // that are undisplayed.
      NS_ASSERTION(
          mNodeCharIndex < static_cast<uint32_t>(frame->GetContentOffset()),
          "incorrect tracking of undisplayed characters in "
          "text nodes");
      undisplayed = frame->GetContentOffset() - mNodeCharIndex;
    }
  } else {
    // Different text node from last time.
    if (mPreviousNode->TextLength() != mNodeCharIndex) {
      NS_ASSERTION(mNodeCharIndex < mPreviousNode->TextLength(),
                   "incorrect tracking of undisplayed characters in "
                   "text nodes");
      // Any trailing characters at the end of the previous Text are
      // undisplayed.
      undisplayed = mPreviousNode->TextLength() - mNodeCharIndex;
    }
    // Each whole Text we find before we get to the text node for
    // the current text frame must be undisplayed.
    while (mNodeIterator.Current() && mNodeIterator.Current() != node) {
      undisplayed += mNodeIterator.Current()->TextLength();
      NextNode();
    }
    // If the current text frame starts at a non-zero content offset, then those
    // earlier characters are also undisplayed.
    undisplayed += frame->GetContentOffset();
    NextNode();
  }

  // Set the frame property.
  frame->SetProperty(TextNodeCorrespondenceProperty(),
                     new TextNodeCorrespondence(undisplayed));

  // Remember how far into the current Text we are.
  mNodeCharIndex = frame->GetContentEnd();
}

// ----------------------------------------------------------------------------
// TextFrameIterator

/**
* An iterator class for nsTextFrames that are descendants of an
* SVGTextFrame.  The iterator can optionally track whether the
* current nsTextFrame is for a descendant of, or past, a given subtree
* content node or frame.  (This functionality is used for example by the SVG
* DOM text methods to get only the nsTextFrames for a particular <tspan>.)
*
* TextFrameIterator also tracks and exposes other information about the
* current nsTextFrame:
*
*   * how many undisplayed characters came just before it
*   * its position (in app units) relative to the SVGTextFrame's anonymous
*     block frame
*   * what nsInlineFrame corresponding to a <textPath> element it is a
*     descendant of
*   * what computed dominant-baseline value applies to it
*
* Note that any text frames that are empty -- whose ContentLength() is 0 --
* will be skipped over.
*/
class MOZ_STACK_CLASS TextFrameIterator {
public:
  /**
   * Constructs a TextFrameIterator for the specified SVGTextFrame
   * with an optional frame subtree to restrict iterated text frames to.
   */
  explicit TextFrameIterator(SVGTextFrame* aRoot,
                             const nsIFrame* aSubtree = nullptr)
      : mRootFrame(aRoot),
        mSubtree(aSubtree),
        mCurrentFrame(aRoot),
        mSubtreePosition(mSubtree ? eBeforeSubtree : eWithinSubtree) {
    Init();
  }

  /**
   * Constructs a TextFrameIterator for the specified SVGTextFrame
   * with an optional frame content subtree to restrict iterated text frames to.
   */
  TextFrameIterator(SVGTextFrame* aRoot, nsIContent* aSubtree)
      : mRootFrame(aRoot),
        mSubtree(aRoot && aSubtree && aSubtree != aRoot->GetContent()
                     ? aSubtree->GetPrimaryFrame()
                     : nullptr),
        mCurrentFrame(aRoot),
        mSubtreePosition(mSubtree ? eBeforeSubtree : eWithinSubtree) {
    Init();
  }

  /**
   * Returns the root SVGTextFrame this TextFrameIterator is iterating over.
   */
  SVGTextFrame* Root() const { return mRootFrame; }

  /**
   * Returns the current nsTextFrame.
   */
  nsTextFrame* Current() const { return do_QueryFrame(mCurrentFrame); }

  /**
   * Returns the number of undisplayed characters in the DOM just before the
   * current frame.
   */
  uint32_t UndisplayedCharacters() const;

  /**
   * Returns the current frame's position, in app units, relative to the
   * root SVGTextFrame's anonymous block frame.
   */
  nsPoint Position() const { return mCurrentPosition; }

  /**
   * Advances to the next nsTextFrame and returns it.
   */
  nsTextFrame* Next();

  /**
   * Returns whether the iterator is within the subtree.
   */
  bool IsWithinSubtree() const { return mSubtreePosition == eWithinSubtree; }

  /**
   * Returns whether the iterator is past the subtree.
   */
  bool IsAfterSubtree() const { return mSubtreePosition == eAfterSubtree; }

  /**
   * Returns the frame corresponding to the <textPath> element, if we
   * are inside one.
   */
  nsIFrame* TextPathFrame() const {
    return mTextPathFrames.IsEmpty() ? nullptr : mTextPathFrames.LastElement();
  }

  /**
   * Returns the current frame's computed dominant-baseline value.
   */
  StyleDominantBaseline DominantBaseline() const {
    return mBaselines.LastElement();
  }

  /**
   * Finishes the iterator.
   */
  void Close() { mCurrentFrame = nullptr; }

private:
  /**
   * Initializes the iterator and advances to the first item.
   */
  void Init() {
    if (!mRootFrame) {
      return;
    }

    mBaselines.AppendElement(mRootFrame->StyleSVG()->mDominantBaseline);
    Next();
  }

  /**
   * Pushes the specified frame's computed dominant-baseline value.
   * If the value of the property is "auto", then the parent frame's
   * computed value is used.
   */
  void PushBaseline(nsIFrame* aNextFrame);

  /**
   * Pops the current dominant-baseline off the stack.
   */
  void PopBaseline();

  /**
   * The root frame we are iterating through.
   */
  SVGTextFrame* const mRootFrame;

  /**
   * The frame for the subtree we are also interested in tracking.
   */
  const nsIFrame* const mSubtree;

  /**
   * The current value of the iterator.
   */
  nsIFrame* mCurrentFrame;

  /**
   * The position, in app units, of the current frame relative to mRootFrame.
   */
  nsPoint mCurrentPosition;

  /**
   * Stack of frames corresponding to <textPath> elements that are in scope
   * for the current frame.
   */
  AutoTArray<nsIFrame*, 1> mTextPathFrames;

  /**
   * Stack of dominant-baseline values to record as we traverse through the
   * frame tree.
   */
  AutoTArray<StyleDominantBaseline, 8> mBaselines;

  /**
   * The iterator's current position relative to mSubtree.
   */
  SubtreePosition mSubtreePosition;
};

uint32_t TextFrameIterator::UndisplayedCharacters() const {
  MOZ_ASSERT(
      !mRootFrame->HasAnyStateBits(NS_STATE_SVG_TEXT_CORRESPONDENCE_DIRTY),
      "Text correspondence must be up to date");

  if (!mCurrentFrame) {
    return mRootFrame->mTrailingUndisplayedCharacters;
  }

  nsTextFrame* frame = do_QueryFrame(mCurrentFrame);
  return GetUndisplayedCharactersBeforeFrame(frame);
}

nsTextFrame* TextFrameIterator::Next() {
  // Starting from mCurrentFrame, we do a non-recursive traversal to the next
  // nsTextFrame beneath mRoot, updating mSubtreePosition appropriately if we
  // encounter mSubtree.
  if (mCurrentFrame) {
    do {
      nsIFrame* next = IsTextContentElement(mCurrentFrame->GetContent())
                           ? mCurrentFrame->PrincipalChildList().FirstChild()
                           : nullptr;
      if (next) {
        // Descend into this frame, and accumulate its position.
        mCurrentPosition += next->GetPosition();
        if (next->GetContent()->IsSVGElement(nsGkAtoms::textPath)) {
          // Record this <textPath> frame.
          mTextPathFrames.AppendElement(next);
        }
        // Record the frame's baseline.
        PushBaseline(next);
        mCurrentFrame = next;
        if (mCurrentFrame == mSubtree) {
          // If the current frame is mSubtree, we have now moved into it.
          mSubtreePosition = eWithinSubtree;
        }
      } else {
        for (;;) {
          // We want to move past the current frame.
          if (mCurrentFrame == mRootFrame) {
            // If we've reached the root frame, we're finished.
            mCurrentFrame = nullptr;
            break;
          }
          // Remove the current frame's position.
          mCurrentPosition -= mCurrentFrame->GetPosition();
          if (mCurrentFrame->GetContent()->IsSVGElement(nsGkAtoms::textPath)) {
            // Pop off the <textPath> frame if this is a <textPath>.
            mTextPathFrames.RemoveLastElement();
          }
          // Pop off the current baseline.
          PopBaseline();
          if (mCurrentFrame == mSubtree) {
            // If this was mSubtree, we have now moved past it.
            mSubtreePosition = eAfterSubtree;
          }
          next = mCurrentFrame->GetNextSibling();
          if (next) {
            // Moving to the next sibling.
            mCurrentPosition += next->GetPosition();
            if (next->GetContent()->IsSVGElement(nsGkAtoms::textPath)) {
              // Record this <textPath> frame.
              mTextPathFrames.AppendElement(next);
            }
            // Record the frame's baseline.
            PushBaseline(next);
            mCurrentFrame = next;
            if (mCurrentFrame == mSubtree) {
              // If the current frame is mSubtree, we have now moved into it.
              mSubtreePosition = eWithinSubtree;
            }
            break;
          }
          if (mCurrentFrame == mSubtree) {
            // If there is no next sibling frame, and the current frame is
            // mSubtree, we have now moved past it.
            mSubtreePosition = eAfterSubtree;
          }
          // Ascend out of this frame.
          mCurrentFrame = mCurrentFrame->GetParent();
        }
      }
    } while (mCurrentFrame && !IsNonEmptyTextFrame(mCurrentFrame));
  }

  return Current();
}

void TextFrameIterator::PushBaseline(nsIFrame* aNextFrame) {
  StyleDominantBaseline baseline = aNextFrame->StyleSVG()->mDominantBaseline;
  mBaselines.AppendElement(baseline);
}

void TextFrameIterator::PopBaseline() {
  NS_ASSERTION(!mBaselines.IsEmpty(), "popped too many baselines");
  mBaselines.RemoveLastElement();
}

// -----------------------------------------------------------------------------
// TextRenderedRunIterator

/**
* Iterator for TextRenderedRun objects for the SVGTextFrame.
*/
class TextRenderedRunIterator {
public:
  /**
   * Values for the aFilter argument of the constructor, to indicate which
   * frames we should be limited to iterating TextRenderedRun objects for.
   */
  enum RenderedRunFilter {
    // Iterate TextRenderedRuns for all nsTextFrames.
    eAllFrames,
    // Iterate only TextRenderedRuns for nsTextFrames that are
    // visibility:visible.
    eVisibleFrames
  };

  /**
   * Constructs a TextRenderedRunIterator with an optional frame subtree to
   * restrict iterated rendered runs to.
   *
   * @param aSVGTextFrame The SVGTextFrame whose rendered runs to iterate
   *   through.
   * @param aFilter Indicates whether to iterate rendered runs for non-visible
   *   nsTextFrames.
   * @param aSubtree An optional frame subtree to restrict iterated rendered
   *   runs to.
   */
  explicit TextRenderedRunIterator(SVGTextFrame* aSVGTextFrame,
                                   RenderedRunFilter aFilter = eAllFrames,
                                   const nsIFrame* aSubtree = nullptr)
      : mFrameIterator(FrameIfAnonymousChildReflowed(aSVGTextFrame), aSubtree),
        mFilter(aFilter),
        mTextElementCharIndex(0),
        mFrameStartTextElementCharIndex(0),
        mFontSizeScaleFactor(aSVGTextFrame->mFontSizeScaleFactor),
        mCurrent(First()) {}

  /**
   * Constructs a TextRenderedRunIterator with a content subtree to restrict
   * iterated rendered runs to.
   *
   * @param aSVGTextFrame The SVGTextFrame whose rendered runs to iterate
   *   through.
   * @param aFilter Indicates whether to iterate rendered runs for non-visible
   *   nsTextFrames.
   * @param aSubtree A content subtree to restrict iterated rendered runs to.
   */
  TextRenderedRunIterator(SVGTextFrame* aSVGTextFrame,
                          RenderedRunFilter aFilter, nsIContent* aSubtree)
      : mFrameIterator(FrameIfAnonymousChildReflowed(aSVGTextFrame), aSubtree),
        mFilter(aFilter),
        mTextElementCharIndex(0),
        mFrameStartTextElementCharIndex(0),
        mFontSizeScaleFactor(aSVGTextFrame->mFontSizeScaleFactor),
        mCurrent(First()) {}

  /**
   * Returns the current TextRenderedRun.
   */
  TextRenderedRun Current() const { return mCurrent; }

  /**
   * Advances to the next TextRenderedRun and returns it.
   */
  TextRenderedRun Next();

private:
  /**
   * Returns the root SVGTextFrame this iterator is for.
   */
  SVGTextFrame* Root() const { return mFrameIterator.Root(); }

  /**
   * Advances to the first TextRenderedRun and returns it.
   */
  TextRenderedRun First();

  /**
   * The frame iterator to use.
   */
  TextFrameIterator mFrameIterator;

  /**
   * The filter indicating which TextRenderedRuns to return.
   */
  RenderedRunFilter mFilter;

  /**
   * The character index across the entire <text> element we are currently
   * up to.
   */
  uint32_t mTextElementCharIndex;

  /**
   * The character index across the entire <text> for the start of the current
   * frame.
   */
  uint32_t mFrameStartTextElementCharIndex;

  /**
   * The font-size scale factor we used when constructing the nsTextFrames.
   */
  double mFontSizeScaleFactor;

  /**
   * The current TextRenderedRun.
   */
  TextRenderedRun mCurrent;
};

TextRenderedRun TextRenderedRunIterator::Next() {
  if (!mFrameIterator.Current()) {
    // If there are no more frames, then there are no more rendered runs to
    // return.
    mCurrent = TextRenderedRun();
    return mCurrent;
  }

  // The values we will use to initialize the TextRenderedRun with.
  nsTextFrame* frame;
  gfxPoint pt;
  double rotate;
  nscoord baseline;
  uint32_t offset, length;
  uint32_t charIndex;

  // We loop, because we want to skip over rendered runs that either aren't
  // within our subtree of interest, because they don't match the filter,
  // or because they are hidden due to having fallen off the end of a
  // <textPath>.
  for (;;) {
    if (mFrameIterator.IsAfterSubtree()) {
      mCurrent = TextRenderedRun();
      return mCurrent;
    }

    frame = mFrameIterator.Current();

    charIndex = mTextElementCharIndex;

    // Find the end of the rendered run, by looking through the
    // SVGTextFrame's positions array until we find one that is recorded
    // as a run boundary.
    uint32_t runStart,
        runEnd;  // XXX Replace runStart with mTextElementCharIndex.
    runStart = mTextElementCharIndex;
    runEnd = runStart + 1;
    while (runEnd < Root()->mPositions.Length() &&
           !Root()->mPositions[runEnd].mRunBoundary) {
      runEnd++;
    }

    // Convert the global run start/end indexes into an offset/length into the
    // current frame's Text.
    offset =
        frame->GetContentOffset() + runStart - mFrameStartTextElementCharIndex;
    length = runEnd - runStart;

    // If the end of the frame's content comes before the run boundary we found
    // in SVGTextFrame's position array, we need to shorten the rendered run.
    uint32_t contentEnd = frame->GetContentEnd();
    if (offset + length > contentEnd) {
      length = contentEnd - offset;
    }

    NS_ASSERTION(offset >= uint32_t(frame->GetContentOffset()),
                 "invalid offset");
    NS_ASSERTION(offset + length <= contentEnd, "invalid offset or length");

    // Get the frame's baseline position.
    frame->EnsureTextRun(nsTextFrame::eInflated);
    baseline = GetBaselinePosition(
        frame, frame->GetTextRun(nsTextFrame::eInflated),
        mFrameIterator.DominantBaseline(), mFontSizeScaleFactor);

    // Trim the offset/length to remove any leading/trailing white space.
    uint32_t untrimmedOffset = offset;
    uint32_t untrimmedLength = length;
    nsTextFrame::TrimmedOffsets trimmedOffsets =
        frame->GetTrimmedOffsets(frame->TextFragment());
    TrimOffsets(offset, length, trimmedOffsets);
    charIndex += offset - untrimmedOffset;

    // Get the position and rotation of the character that begins this
    // rendered run.
    pt = Root()->mPositions[charIndex].mPosition;
    rotate = Root()->mPositions[charIndex].mAngle;

    // Determine if we should skip this rendered run.
    bool skip = !mFrameIterator.IsWithinSubtree() ||
                Root()->mPositions[mTextElementCharIndex].mHidden;
    if (mFilter == eVisibleFrames) {
      skip = skip || !frame->StyleVisibility()->IsVisible();
    }

    // Update our global character index to move past the characters
    // corresponding to this rendered run.
    mTextElementCharIndex += untrimmedLength;

    // If we have moved past the end of the current frame's content, we need to
--> --------------------

--> maximum size reached

--> --------------------

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