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/* -*- 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 */
#include "mozilla/Attributes.h"
#include "mozilla/PresShellForwards.h"
#include "mozilla/RefPtr.h"
#include "mozilla/SVGContainerFrame.h"
#include "mozilla/gfx/2D.h"
#include "gfxMatrix.h"
#include "gfxRect.h"
#include "gfxTextRun.h"
#include "nsIContent.h" // for GetContent
#include "nsStubMutationObserver.h"
#include "nsTextFrame.h"
class gfxContext;
namespace mozilla {
class CharIterator;
class DisplaySVGText;
class SVGTextFrame;
class TextFrameIterator;
class TextNodeCorrespondenceRecorder;
struct TextRenderedRun;
class TextRenderedRunIterator;
namespace dom {
struct DOMPointInit;
class DOMSVGPoint;
class SVGRect;
class SVGGeometryElement;
} // namespace dom
} // namespace mozilla
nsIFrame* NS_NewSVGTextFrame(mozilla::PresShell* aPresShell,
mozilla::ComputedStyle* aStyle);
namespace mozilla {
* Information about the positioning for a single character in an SVG <text>
* element.
* During SVG text layout, we use infinity values to represent positions and
* rotations that are not explicitly specified with x/y/rotate attributes.
struct CharPosition {
: mAngle(0),
mStartOfChunk(false) {}
CharPosition(gfxPoint aPosition, double aAngle)
: mPosition(aPosition),
mStartOfChunk(false) {}
static CharPosition Unspecified(bool aUnaddressable) {
CharPosition cp(UnspecifiedPoint(), UnspecifiedAngle());
cp.mUnaddressable = aUnaddressable;
return cp;
bool IsAngleSpecified() const { return mAngle != UnspecifiedAngle(); }
bool IsXSpecified() const { return mPosition.x != UnspecifiedCoord(); }
bool IsYSpecified() const { return mPosition.y != UnspecifiedCoord(); }
gfxPoint mPosition;
double mAngle;
// not displayed due to falling off the end of a <textPath>
bool mHidden;
// skipped in positioning attributes due to being collapsed-away white space
bool mUnaddressable;
// a preceding character is what positioning attributes address
bool mClusterOrLigatureGroupMiddle;
// rendering is split here since an explicit position or rotation was given
bool mRunBoundary;
// an anchored chunk begins here
bool mStartOfChunk;
static gfxFloat UnspecifiedCoord() {
return std::numeric_limits<gfxFloat>::infinity();
static double UnspecifiedAngle() {
return std::numeric_limits<double>::infinity();
static gfxPoint UnspecifiedPoint() {
return gfxPoint(UnspecifiedCoord(), UnspecifiedCoord());
* A runnable to mark glyph positions as needing to be recomputed
* and to invalid the bounds of the SVGTextFrame frame.
class GlyphMetricsUpdater : public Runnable {
explicit GlyphMetricsUpdater(SVGTextFrame* aFrame)
: Runnable("GlyphMetricsUpdater"), mFrame(aFrame) {}
static void Run(SVGTextFrame* aFrame);
void Revoke() { mFrame = nullptr; }
SVGTextFrame* mFrame;
* Frame class for SVG <text> elements.
* An SVGTextFrame manages SVG text layout, painting and interaction for
* all descendent text content elements. The frame tree will look like this:
* SVGTextFrame -- for <text>
* <anonymous block frame>
* ns{Block,Inline,Text}Frames -- for text nodes, <tspan>s, <a>s, etc.
* SVG text layout is done by:
* 1. Reflowing the anonymous block frame.
* 2. Inspecting the (app unit) positions of the glyph for each character in
* the nsTextFrames underneath the anonymous block frame.
* 3. Determining the (user unit) positions for each character in the <text>
* using the x/y/dx/dy/rotate attributes on all the text content elements,
* and using the step 2 results to fill in any gaps.
* 4. Applying any other SVG specific text layout (anchoring and text paths)
* to the positions computed in step 3.
* Rendering of the text is done by splitting up each nsTextFrame into ranges
* that can be contiguously painted. (For example <text x="10 20">abcd</text>
* would have two contiguous ranges: one for the "a" and one for the "bcd".)
* Each range is called a "text rendered run", represented by a TextRenderedRun
* object. The TextRenderedRunIterator class performs that splitting and
* returns a TextRenderedRun for each bit of text to be painted separately.
* Each rendered run is painted by calling nsTextFrame::PaintText. If the text
* formatting is simple enough (solid fill, no stroking, etc.), PaintText will
* itself do the painting. Otherwise, a DrawPathCallback is passed to
* PaintText so that we can fill the text geometry with SVG paint servers.
class SVGTextFrame final : public SVGDisplayContainerFrame {
friend nsIFrame* ::NS_NewSVGTextFrame(mozilla::PresShell* aPresShell,
ComputedStyle* aStyle);
friend class CharIterator;
friend class DisplaySVGText;
friend class GlyphMetricsUpdater;
friend class MutationObserver;
friend class TextFrameIterator;
friend class TextNodeCorrespondenceRecorder;
friend struct TextRenderedRun;
friend class TextRenderedRunIterator;
using Range = gfxTextRun::Range;
using DrawTarget = gfx::DrawTarget;
using Path = gfx::Path;
using Point = gfx::Point;
using Rect = gfx::Rect;
explicit SVGTextFrame(ComputedStyle* aStyle, nsPresContext* aPresContext)
: SVGDisplayContainerFrame(aStyle, aPresContext, kClassID),
mLengthAdjustScaleFactor(1.0f) {
~SVGTextFrame() = default;
// nsIFrame:
void Init(nsIContent* aContent, nsContainerFrame* aParent,
nsIFrame* aPrevInFlow) override;
nsresult AttributeChanged(int32_t aNamespaceID, nsAtom* aAttribute,
int32_t aModType) override;
nsContainerFrame* GetContentInsertionFrame() override {
return PrincipalChildList().FirstChild()->GetContentInsertionFrame();
void BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) override;
nsresult GetFrameName(nsAString& aResult) const override {
return MakeFrameName(u"SVGText"_ns, aResult);
* Finds the nsTextFrame for the closest rendered run to the specified point.
void FindCloserFrameForSelection(
const nsPoint& aPoint, FrameWithDistance* aCurrentBestFrame) override;
// ISVGDisplayableFrame interface:
void NotifySVGChanged(uint32_t aFlags) override;
void PaintSVG(gfxContext& aContext, const gfxMatrix& aTransform,
imgDrawingParams& aImgParams) override;
nsIFrame* GetFrameForPoint(const gfxPoint& aPoint) override;
void ReflowSVG() override;
SVGBBox GetBBoxContribution(const Matrix& aToBBoxUserspace,
uint32_t aFlags) override;
// SVG DOM text methods:
uint32_t GetNumberOfChars(nsIContent* aContent);
float GetComputedTextLength(nsIContent* aContent);
MOZ_CAN_RUN_SCRIPT_BOUNDARY void SelectSubString(nsIContent* aContent,
uint32_t charnum,
uint32_t nchars,
ErrorResult& aRv);
bool RequiresSlowFallbackForSubStringLength();
float GetSubStringLengthFastPath(nsIContent* aContent, uint32_t charnum,
uint32_t nchars, ErrorResult& aRv);
* This fallback version of GetSubStringLength takes
* into account glyph positioning and requires us to have flushed layout
* before calling it. As per the SVG 2 spec, typically glyph
* positioning does not affect the results of getSubStringLength, but one
* exception is text in a textPath where we need to ignore characters that
* fall off the end of the textPath path.
float GetSubStringLengthSlowFallback(nsIContent* aContent, uint32_t charnum,
uint32_t nchars, ErrorResult& aRv);
int32_t GetCharNumAtPosition(nsIContent* aContent,
const dom::DOMPointInit& aPoint);
already_AddRefed<dom::DOMSVGPoint> GetStartPositionOfChar(
nsIContent* aContent, uint32_t aCharNum, ErrorResult& aRv);
already_AddRefed<dom::DOMSVGPoint> GetEndPositionOfChar(nsIContent* aContent,
uint32_t aCharNum,
ErrorResult& aRv);
already_AddRefed<dom::SVGRect> GetExtentOfChar(nsIContent* aContent,
uint32_t aCharNum,
ErrorResult& aRv);
float GetRotationOfChar(nsIContent* aContent, uint32_t aCharNum,
ErrorResult& aRv);
// SVGTextFrame methods:
* Handles a base or animated attribute value change to a descendant
* text content element.
void HandleAttributeChangeInDescendant(dom::Element* aElement,
int32_t aNameSpaceID,
nsAtom* aAttribute);
* Calls ScheduleReflowSVGNonDisplayText if this is a non-display frame,
* and SVGUtils::ScheduleReflowSVG otherwise.
void ScheduleReflowSVG();
* Reflows the anonymous block frame of this non-display SVGTextFrame.
* When we are under SVGDisplayContainerFrame::ReflowSVG, we need to
* reflow any SVGTextFrame frames in the subtree in case they are
* being observed (by being for example in a <mask>) and the change
* that caused the reflow would not already have caused a reflow.
* Note that displayed SVGTextFrames are reflowed as needed, when PaintSVG
* is called or some SVG DOM method is called on the element.
void ReflowSVGNonDisplayText();
* This is a function that behaves similarly to SVGUtils::ScheduleReflowSVG,
* but which will skip over any ancestor non-display container frames on the
* way to the SVGOuterSVGFrame. It exists for the situation where a
* non-display <text> element has changed and needs to ensure ReflowSVG will
* be called on its closest display container frame, so that
* SVGDisplayContainerFrame::ReflowSVG will call ReflowSVGNonDisplayText on
* it.
* We have to do this in two cases: in response to a style change on a
* non-display <text>, where aReason will be
* IntrinsicDirty::FrameAncestorsAndDescendants (the common case), and also in
* response to glyphs changes on non-display <text> (i.e., animated
* SVG-in-OpenType glyphs), in which case aReason will be None, since layout
* doesn't need to be recomputed.
void ScheduleReflowSVGNonDisplayText(IntrinsicDirty aReason);
* Updates the mFontSizeScaleFactor value by looking at the range of
* font-sizes used within the <text>.
* @return Whether mFontSizeScaleFactor changed.
bool UpdateFontSizeScaleFactor();
double GetFontSizeScaleFactor() const;
* Takes a point from the <text> element's user space and
* converts it to the appropriate frame user space of aChildFrame,
* according to which rendered run the point hits.
Point TransformFramePointToTextChild(const Point& aPoint,
const nsIFrame* aChildFrame);
* Takes an app unit rectangle in the coordinate space of a given descendant
* frame of this frame, and returns a rectangle in the <text> element's user
* space that covers all parts of rendered runs that intersect with the
* rectangle.
gfxRect TransformFrameRectFromTextChild(const nsRect& aRect,
const nsIFrame* aChildFrame);
/** As above, but taking and returning a device px rect. */
Rect TransformFrameRectFromTextChild(const Rect& aRect,
const nsIFrame* aChildFrame);
/** As above, but with a single point */
Point TransformFramePointFromTextChild(const Point& aPoint,
const nsIFrame* aChildFrame);
// Return our ::-moz-svg-text anonymous box.
void AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult) override;
* Mutation observer used to watch for text positioning attribute changes
* on descendent text content elements (like <tspan>s).
class MutationObserver final : public nsStubMutationObserver {
explicit MutationObserver(SVGTextFrame* aFrame) : mFrame(aFrame) {
MOZ_ASSERT(mFrame, "MutationObserver needs a non-null frame");
SetEnabledCallbacks(kCharacterDataChanged | kAttributeChanged |
kContentAppended | kContentInserted |
// nsISupports
// nsIMutationObserver
~MutationObserver() { mFrame->GetContent()->RemoveMutationObserver(this); }
SVGTextFrame* const mFrame;
* Resolves Bidi for the anonymous block child if it needs it.
void MaybeResolveBidiForAnonymousBlockChild();
* Reflows the anonymous block child if it is dirty or has dirty
* children, or if the SVGTextFrame itself is dirty.
void MaybeReflowAnonymousBlockChild();
* Performs the actual work of reflowing the anonymous block child.
void DoReflow();
* Schedules mPositions to be recomputed and the covered region to be
* updated.
void NotifyGlyphMetricsChange(bool aUpdateTextCorrespondence);
* Recomputes mPositions by calling DoGlyphPositioning if this information
* is out of date.
void UpdateGlyphPositioning();
* Populates mPositions with positioning information for each character
* within the <text>.
void DoGlyphPositioning();
* Converts the specified index into mPositions to an addressable
* character index (as can be used with the SVG DOM text methods)
* relative to the specified text child content element.
* @param aIndex The global character index.
* @param aContent The descendant text child content element that
* the returned addressable index will be relative to; null
* means the same as the <text> element.
* @return The addressable index, or -1 if the index cannot be
* represented as an addressable index relative to aContent.
int32_t ConvertTextElementCharIndexToAddressableIndex(int32_t aIndex,
nsIContent* aContent);
* Recursive helper for ResolvePositions below.
* @param aContent The current node.
* @param aIndex (in/out) The current character index.
* @param aInTextPath Whether we are currently under a <textPath> element.
* @param aForceStartOfChunk (in/out) Whether the next character we find
* should start a new anchored chunk.
* @param aDeltas (in/out) Receives the resolved dx/dy values for each
* character.
* @return false if we discover that mPositions did not have enough
* elements; true otherwise.
bool ResolvePositionsForNode(nsIContent* aContent, uint32_t& aIndex,
bool aInTextPath, bool& aForceStartOfChunk,
nsTArray<gfxPoint>& aDeltas);
* Initializes mPositions with character position information based on
* x/y/rotate attributes, leaving unspecified values in the array if a
* position was not given for that character. Also fills aDeltas with values
* based on dx/dy attributes.
* @param aDeltas (in/out) Receives the resolved dx/dy values for each
* character.
* @param aRunPerGlyph Whether mPositions should record that a new run begins
* at each glyph.
* @return false if we did not record any positions (due to having no
* displayed characters) or if we discover that mPositions did not have
* enough elements; true otherwise.
bool ResolvePositions(nsTArray<gfxPoint>& aDeltas, bool aRunPerGlyph);
* Determines the position, in app units, of each character in the <text> as
* laid out by reflow, and appends them to aPositions. Any characters that
* are undisplayed or trimmed away just get the last position.
void DetermineCharPositions(nsTArray<nsPoint>& aPositions);
* Sets mStartOfChunk to true for each character in mPositions that starts a
* line of text.
void AdjustChunksForLineBreaks();
* Adjusts recorded character positions in mPositions to account for glyph
* boundaries. Four things are done:
* 1. mClusterOrLigatureGroupMiddle is set to true for all such characters.
* 2. Any run and anchored chunk boundaries that begin in the middle of a
* cluster/ligature group get moved to the start of the next
* cluster/ligature group.
* 3. The position of any character in the middle of a cluster/ligature
* group is updated to take into account partial ligatures and any
* rotation the glyph as a whole has. (The values that come out of
* DetermineCharPositions which then get written into mPositions in
* ResolvePositions store the same position value for each part of the
* ligature.)
* 4. The rotation of any character in the middle of a cluster/ligature
* group is set to the rotation of the first character.
void AdjustPositionsForClusters();
* Updates the character positions stored in mPositions to account for
* text anchoring.
void DoAnchoring();
* Updates character positions in mPositions for those characters inside a
* <textPath>.
void DoTextPathLayout();
* Returns whether we need to render the text using
* nsTextFrame::DrawPathCallbacks rather than directly painting
* the text frames.
* @param aShouldPaintSVGGlyphs (out) Whether SVG glyphs in the text
* should be painted.
bool ShouldRenderAsPath(nsTextFrame* aFrame, bool& aShouldPaintSVGGlyphs);
// Methods to get information for a <textPath> frame.
already_AddRefed<Path> GetTextPath(nsIFrame* aTextPathFrame);
gfxFloat GetOffsetScale(nsIFrame* aTextPathFrame);
gfxFloat GetStartOffset(nsIFrame* aTextPathFrame);
* The MutationObserver we have registered for the <text> element subtree.
RefPtr<MutationObserver> mMutationObserver;
* The number of characters in the DOM after the final nsTextFrame. For
* example, with
* <text>abcd<tspan display="none">ef</tspan></text>
* mTrailingUndisplayedCharacters would be 2.
uint32_t mTrailingUndisplayedCharacters;
* Computed position information for each DOM character within the <text>.
nsTArray<CharPosition> mPositions;
* mFontSizeScaleFactor is used to cause the nsTextFrames to create text
* runs with a font size different from the actual font-size property value.
* This is used so that, for example with:
* <svg>
* <g transform="scale(2)">
* <text font-size="10">abc</text>
* </g>
* </svg>
* a font size of 20 would be used. It's preferable to use a font size that
* is identical or close to the size that the text will appear on the screen,
* because at very small or large font sizes, text metrics will be computed
* differently due to the limited precision that text runs have.
* mFontSizeScaleFactor is the amount the actual font-size property value
* should be multiplied by to cause the text run font size to (a) be within a
* "reasonable" range, and (b) be close to the actual size to be painted on
* screen. (The "reasonable" range as determined by some #defines in
* SVGTextFrame.cpp is 8..200.)
float mFontSizeScaleFactor;
* The scale of the context that we last used to compute mFontSizeScaleFactor.
* We record this so that we can tell when our scale transform has changed
* enough to warrant reflowing the text.
float mLastContextScale;
* The amount that we need to scale each rendered run to account for
* lengthAdjust="spacingAndGlyphs".
float mLengthAdjustScaleFactor;
} // namespace mozilla