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gecko-dev/layout/mathml/nsMathMLmfracFrame.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "nsMathMLmfracFrame.h"
#include "nsPresContext.h"
#include "nsRenderingContext.h"
#include "nsDisplayList.h"
#include "gfxContext.h"
#include "nsMathMLElement.h"
#include <algorithm>
//
// <mfrac> -- form a fraction from two subexpressions - implementation
//
// various fraction line thicknesses (multiplicative values of the default rule thickness)
#define THIN_FRACTION_LINE 0.5f
#define THIN_FRACTION_LINE_MINIMUM_PIXELS 1 // minimum of 1 pixel
#define THICK_FRACTION_LINE 2.0f
#define THICK_FRACTION_LINE_MINIMUM_PIXELS 2 // minimum of 2 pixels
nsIFrame*
NS_NewMathMLmfracFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
{
return new (aPresShell) nsMathMLmfracFrame(aContext);
}
NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmfracFrame)
nsMathMLmfracFrame::~nsMathMLmfracFrame()
{
}
eMathMLFrameType
nsMathMLmfracFrame::GetMathMLFrameType()
{
// frac is "inner" in TeXBook, Appendix G, rule 15e. See also page 170.
return eMathMLFrameType_Inner;
}
NS_IMETHODIMP
nsMathMLmfracFrame::TransmitAutomaticData()
{
// 1. The REC says:
// The <mfrac> element sets displaystyle to "false", or if it was already
// false increments scriptlevel by 1, within numerator and denominator.
// 2. The TeXbook (Ch 17. p.141) says the numerator inherits the compression
// while the denominator is compressed
bool increment = !NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags);
SetIncrementScriptLevel(0, increment);
SetIncrementScriptLevel(1, increment);
UpdatePresentationDataFromChildAt(0, -1,
~NS_MATHML_DISPLAYSTYLE,
NS_MATHML_DISPLAYSTYLE);
UpdatePresentationDataFromChildAt(1, 1,
NS_MATHML_COMPRESSED,
NS_MATHML_COMPRESSED);
// if our numerator is an embellished operator, let its state bubble to us
GetEmbellishDataFrom(mFrames.FirstChild(), mEmbellishData);
if (NS_MATHML_IS_EMBELLISH_OPERATOR(mEmbellishData.flags)) {
// even when embellished, we need to record that <mfrac> won't fire
// Stretch() on its embellished child
mEmbellishData.direction = NS_STRETCH_DIRECTION_UNSUPPORTED;
}
return NS_OK;
}
nscoord
nsMathMLmfracFrame::CalcLineThickness(nsPresContext* aPresContext,
nsStyleContext* aStyleContext,
nsString& aThicknessAttribute,
nscoord onePixel,
nscoord aDefaultRuleThickness)
{
nscoord defaultThickness = aDefaultRuleThickness;
nscoord lineThickness = aDefaultRuleThickness;
nscoord minimumThickness = onePixel;
// linethickness
//
// "Specifies the thickness of the horizontal 'fraction bar', or 'rule'. The
// default value is 'medium', 'thin' is thinner, but visible, 'thick' is
// thicker; the exact thickness of these is left up to the rendering agent."
//
// values: length | "thin" | "medium" | "thick"
// default: medium
//
if (!aThicknessAttribute.IsEmpty()) {
if (aThicknessAttribute.EqualsLiteral("thin")) {
lineThickness = NSToCoordFloor(defaultThickness * THIN_FRACTION_LINE);
minimumThickness = onePixel * THIN_FRACTION_LINE_MINIMUM_PIXELS;
// should visually decrease by at least one pixel, if default is not a pixel
if (defaultThickness > onePixel && lineThickness > defaultThickness - onePixel)
lineThickness = defaultThickness - onePixel;
}
else if (aThicknessAttribute.EqualsLiteral("medium")) {
// medium is default
}
else if (aThicknessAttribute.EqualsLiteral("thick")) {
lineThickness = NSToCoordCeil(defaultThickness * THICK_FRACTION_LINE);
minimumThickness = onePixel * THICK_FRACTION_LINE_MINIMUM_PIXELS;
// should visually increase by at least one pixel
if (lineThickness < defaultThickness + onePixel)
lineThickness = defaultThickness + onePixel;
}
else {
// length value
lineThickness = defaultThickness;
ParseNumericValue(aThicknessAttribute, &lineThickness,
nsMathMLElement::PARSE_ALLOW_UNITLESS,
aPresContext, aStyleContext);
}
}
// use minimum if the lineThickness is a non-zero value less than minimun
if (lineThickness && lineThickness < minimumThickness)
lineThickness = minimumThickness;
return lineThickness;
}
void
nsMathMLmfracFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsRect& aDirtyRect,
const nsDisplayListSet& aLists)
{
/////////////
// paint the numerator and denominator
nsMathMLContainerFrame::BuildDisplayList(aBuilder, aDirtyRect, aLists);
/////////////
// paint the fraction line
if (mIsBevelled) {
DisplaySlash(aBuilder, this, mLineRect, mLineThickness, aLists);
} else {
DisplayBar(aBuilder, this, mLineRect, aLists);
}
}
/* virtual */ nsresult
nsMathMLmfracFrame::MeasureForWidth(nsRenderingContext& aRenderingContext,
nsHTMLReflowMetrics& aDesiredSize)
{
return PlaceInternal(aRenderingContext,
false,
aDesiredSize,
true);
}
nscoord
nsMathMLmfracFrame::FixInterFrameSpacing(nsHTMLReflowMetrics& aDesiredSize)
{
nscoord gap = nsMathMLContainerFrame::FixInterFrameSpacing(aDesiredSize);
if (!gap) return 0;
mLineRect.MoveBy(gap, 0);
return gap;
}
/* virtual */ nsresult
nsMathMLmfracFrame::Place(nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize)
{
return PlaceInternal(aRenderingContext,
aPlaceOrigin,
aDesiredSize,
false);
}
nsresult
nsMathMLmfracFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize,
bool aWidthOnly)
{
////////////////////////////////////
// Get the children's desired sizes
nsBoundingMetrics bmNum, bmDen;
nsHTMLReflowMetrics sizeNum;
nsHTMLReflowMetrics sizeDen;
nsIFrame* frameDen = nullptr;
nsIFrame* frameNum = mFrames.FirstChild();
if (frameNum)
frameDen = frameNum->GetNextSibling();
if (!frameNum || !frameDen || frameDen->GetNextSibling()) {
// report an error, encourage people to get their markups in order
if (aPlaceOrigin) {
ReportChildCountError();
}
return ReflowError(aRenderingContext, aDesiredSize);
}
GetReflowAndBoundingMetricsFor(frameNum, sizeNum, bmNum);
GetReflowAndBoundingMetricsFor(frameDen, sizeDen, bmDen);
nsPresContext* presContext = PresContext();
nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
nsRefPtr<nsFontMetrics> fm;
nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
aRenderingContext.SetFont(fm);
nscoord defaultRuleThickness, axisHeight;
GetRuleThickness(aRenderingContext, fm, defaultRuleThickness);
GetAxisHeight(aRenderingContext, fm, axisHeight);
nsEmbellishData coreData;
GetEmbellishDataFrom(mEmbellishData.coreFrame, coreData);
// see if the linethickness attribute is there
nsAutoString value;
GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::linethickness_,
value);
mLineThickness = CalcLineThickness(presContext, mStyleContext, value,
onePixel, defaultRuleThickness);
// bevelled attribute
GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::bevelled_,
value);
mIsBevelled = value.EqualsLiteral("true");
if (!mIsBevelled) {
mLineRect.height = mLineThickness;
// by default, leave at least one-pixel padding at either end, or use
// lspace & rspace that may come from <mo> if we are an embellished
// container (we fetch values from the core since they may use units that
// depend on style data, and style changes could have occurred in the
// core since our last visit there)
nscoord leftSpace = std::max(onePixel, StyleVisibility()->mDirection ?
coreData.trailingSpace : coreData.leadingSpace);
nscoord rightSpace = std::max(onePixel, StyleVisibility()->mDirection ?
coreData.leadingSpace : coreData.trailingSpace);
//////////////////
// Get shifts
nscoord numShift = 0;
nscoord denShift = 0;
// Rule 15b, App. G, TeXbook
nscoord numShift1, numShift2, numShift3;
nscoord denShift1, denShift2;
GetNumeratorShifts(fm, numShift1, numShift2, numShift3);
GetDenominatorShifts(fm, denShift1, denShift2);
if (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
// C > T
numShift = numShift1;
denShift = denShift1;
}
else {
numShift = (0 < mLineRect.height) ? numShift2 : numShift3;
denShift = denShift2;
}
nscoord minClearance = 0;
nscoord actualClearance = 0;
nscoord actualRuleThickness = mLineThickness;
if (0 == actualRuleThickness) {
// Rule 15c, App. G, TeXbook
// min clearance between numerator and denominator
minClearance = (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) ?
7 * defaultRuleThickness : 3 * defaultRuleThickness;
actualClearance =
(numShift - bmNum.descent) - (bmDen.ascent - denShift);
// actualClearance should be >= minClearance
if (actualClearance < minClearance) {
nscoord halfGap = (minClearance - actualClearance)/2;
numShift += halfGap;
denShift += halfGap;
}
}
else {
// Rule 15d, App. G, TeXbook
// min clearance between numerator or denominator and middle of bar
// TeX has a different interpretation of the thickness.
// Try $a \above10pt b$ to see. Here is what TeX does:
// minClearance = (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) ?
// 3 * actualRuleThickness : actualRuleThickness;
// we slightly depart from TeX here. We use the defaultRuleThickness instead
// of the value coming from the linethickness attribute, i.e., we recover what
// TeX does if the user hasn't set linethickness. But when the linethickness
// is set, we avoid the wide gap problem.
minClearance = (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) ?
3 * defaultRuleThickness : defaultRuleThickness + onePixel;
// adjust numShift to maintain minClearance if needed
actualClearance =
(numShift - bmNum.descent) - (axisHeight + actualRuleThickness/2);
if (actualClearance < minClearance) {
numShift += (minClearance - actualClearance);
}
// adjust denShift to maintain minClearance if needed
actualClearance =
(axisHeight - actualRuleThickness/2) - (bmDen.ascent - denShift);
if (actualClearance < minClearance) {
denShift += (minClearance - actualClearance);
}
}
//////////////////
// Place Children
// XXX Need revisiting the width. TeX uses the exact width
// e.g. in $$\huge\frac{\displaystyle\int}{i}$$
nscoord width = std::max(bmNum.width, bmDen.width);
nscoord dxNum = leftSpace + (width - sizeNum.width)/2;
nscoord dxDen = leftSpace + (width - sizeDen.width)/2;
width += leftSpace + rightSpace;
// see if the numalign attribute is there
GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::numalign_,
value);
if (value.EqualsLiteral("left"))
dxNum = leftSpace;
else if (value.EqualsLiteral("right"))
dxNum = width - rightSpace - sizeNum.width;
// see if the denomalign attribute is there
GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::denomalign_,
value);
if (value.EqualsLiteral("left"))
dxDen = leftSpace;
else if (value.EqualsLiteral("right"))
dxDen = width - rightSpace - sizeDen.width;
mBoundingMetrics.rightBearing =
std::max(dxNum + bmNum.rightBearing, dxDen + bmDen.rightBearing);
if (mBoundingMetrics.rightBearing < width - rightSpace)
mBoundingMetrics.rightBearing = width - rightSpace;
mBoundingMetrics.leftBearing =
std::min(dxNum + bmNum.leftBearing, dxDen + bmDen.leftBearing);
if (mBoundingMetrics.leftBearing > leftSpace)
mBoundingMetrics.leftBearing = leftSpace;
mBoundingMetrics.ascent = bmNum.ascent + numShift;
mBoundingMetrics.descent = bmDen.descent + denShift;
mBoundingMetrics.width = width;
aDesiredSize.ascent = sizeNum.ascent + numShift;
aDesiredSize.height = aDesiredSize.ascent +
sizeDen.height - sizeDen.ascent + denShift;
aDesiredSize.width = mBoundingMetrics.width;
aDesiredSize.mBoundingMetrics = mBoundingMetrics;
mReference.x = 0;
mReference.y = aDesiredSize.ascent;
if (aPlaceOrigin) {
nscoord dy;
// place numerator
dy = 0;
FinishReflowChild(frameNum, presContext, nullptr, sizeNum, dxNum, dy, 0);
// place denominator
dy = aDesiredSize.height - sizeDen.height;
FinishReflowChild(frameDen, presContext, nullptr, sizeDen, dxDen, dy, 0);
// place the fraction bar - dy is top of bar
dy = aDesiredSize.ascent - (axisHeight + actualRuleThickness/2);
mLineRect.SetRect(leftSpace, dy, width - (leftSpace + rightSpace),
actualRuleThickness);
}
} else {
nscoord numShift = 0.0;
nscoord denShift = 0.0;
nscoord padding = 3 * defaultRuleThickness;
nscoord slashRatio = 3;
// Define the constant used in the expression of the maximum width
nscoord em = fm->EmHeight();
nscoord slashMaxWidthConstant = 2 * em;
// For large line thicknesses the minimum slash height is limited to the
// largest expected height of a fraction
nscoord slashMinHeight = slashRatio *
std::min(2 * mLineThickness, slashMaxWidthConstant);
nscoord leadingSpace = std::max(padding, coreData.leadingSpace);
nscoord trailingSpace = std::max(padding, coreData.trailingSpace);
nscoord delta;
// ___________
// | | /
// {|-NUMERATOR-| /
// {|___________| S
// { L
// numShift{ A
// ------------------------------------------------------- baseline
// S _____________ } denShift
// H | |}
// / |-DENOMINATOR-|}
// / |_____________|
//
// first, ensure that the top of the numerator is at least as high as the
// top of the denominator (and the reverse for the bottoms)
delta = std::max(bmDen.ascent - bmNum.ascent,
bmNum.descent - bmDen.descent) / 2;
if (delta > 0) {
numShift += delta;
denShift += delta;
}
if (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
delta = std::min(bmDen.ascent + bmDen.descent,
bmNum.ascent + bmNum.descent) / 2;
numShift += delta;
denShift += delta;
} else {
nscoord xHeight = fm->XHeight();
numShift += xHeight / 2;
denShift += xHeight / 4;
}
// Set the ascent/descent of our BoundingMetrics.
mBoundingMetrics.ascent = bmNum.ascent + numShift;
mBoundingMetrics.descent = bmDen.descent + denShift;
// At this point the height of the slash is
// mBoundingMetrics.ascent + mBoundingMetrics.descent
// Ensure that it is greater than slashMinHeight
delta = (slashMinHeight -
(mBoundingMetrics.ascent + mBoundingMetrics.descent)) / 2;
if (delta > 0) {
mBoundingMetrics.ascent += delta;
mBoundingMetrics.descent += delta;
}
// Set the width of the slash
if (aWidthOnly) {
mLineRect.width = mLineThickness + slashMaxWidthConstant;
} else {
mLineRect.width = mLineThickness +
std::min(slashMaxWidthConstant,
(mBoundingMetrics.ascent + mBoundingMetrics.descent) /
slashRatio);
}
// Set horizontal bounding metrics
if (StyleVisibility()->mDirection) {
mBoundingMetrics.leftBearing = trailingSpace + bmDen.leftBearing;
mBoundingMetrics.rightBearing = trailingSpace + bmDen.width + mLineRect.width + bmNum.rightBearing;
} else {
mBoundingMetrics.leftBearing = leadingSpace + bmNum.leftBearing;
mBoundingMetrics.rightBearing = leadingSpace + bmNum.width + mLineRect.width + bmDen.rightBearing;
}
mBoundingMetrics.width =
leadingSpace + bmNum.width + mLineRect.width + bmDen.width +
trailingSpace;
// Set aDesiredSize
aDesiredSize.ascent = mBoundingMetrics.ascent + padding;
aDesiredSize.height =
mBoundingMetrics.ascent + mBoundingMetrics.descent + 2 * padding;
aDesiredSize.width = mBoundingMetrics.width;
aDesiredSize.mBoundingMetrics = mBoundingMetrics;
mReference.x = 0;
mReference.y = aDesiredSize.ascent;
if (aPlaceOrigin) {
nscoord dx, dy;
// place numerator
dx = MirrorIfRTL(aDesiredSize.width, sizeNum.width,
leadingSpace);
dy = aDesiredSize.ascent - numShift - sizeNum.ascent;
FinishReflowChild(frameNum, presContext, nullptr, sizeNum, dx, dy, 0);
// place the fraction bar
dx = MirrorIfRTL(aDesiredSize.width, mLineRect.width,
leadingSpace + bmNum.width);
dy = aDesiredSize.ascent - mBoundingMetrics.ascent;
mLineRect.SetRect(dx, dy,
mLineRect.width, aDesiredSize.height - 2 * padding);
// place denominator
dx = MirrorIfRTL(aDesiredSize.width, sizeDen.width,
leadingSpace + bmNum.width + mLineRect.width);
dy = aDesiredSize.ascent + denShift - sizeDen.ascent;
FinishReflowChild(frameDen, presContext, nullptr, sizeDen, dx, dy, 0);
}
}
return NS_OK;
}
NS_IMETHODIMP
nsMathMLmfracFrame::UpdatePresentationDataFromChildAt(int32_t aFirstIndex,
int32_t aLastIndex,
uint32_t aFlagsValues,
uint32_t aFlagsToUpdate)
{
// The REC says "The <mfrac> element sets displaystyle to "false" within
// numerator and denominator"
#if 0
// At one point I thought that it meant that the displaystyle state of
// the numerator and denominator cannot be modified by an ancestor, i.e.,
// to change the displaystyle, one has to use displaystyle="true" with mstyle:
// <mfrac> <mstyle>numerator</mstyle> <mstyle>denominator</mstyle> </mfrac>
// Commenting out for now until it is clear what the intention really is.
// See also the variants for <mover>, <munder>, <munderover>
aFlagsToUpdate &= ~NS_MATHML_DISPLAYSTYLE;
aFlagsValues &= ~NS_MATHML_DISPLAYSTYLE;
#endif
return nsMathMLContainerFrame::
UpdatePresentationDataFromChildAt(aFirstIndex, aLastIndex,
aFlagsValues, aFlagsToUpdate);
}
class nsDisplayMathMLSlash : public nsDisplayItem {
public:
nsDisplayMathMLSlash(nsDisplayListBuilder* aBuilder,
nsIFrame* aFrame, const nsRect& aRect,
nscoord aThickness, bool aRTL)
: nsDisplayItem(aBuilder, aFrame), mRect(aRect), mThickness(aThickness),
mRTL(aRTL) {
MOZ_COUNT_CTOR(nsDisplayMathMLSlash);
}
#ifdef NS_BUILD_REFCNT_LOGGING
virtual ~nsDisplayMathMLSlash() {
MOZ_COUNT_DTOR(nsDisplayMathMLSlash);
}
#endif
virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx);
NS_DISPLAY_DECL_NAME("MathMLSlash", TYPE_MATHML_SLASH)
private:
nsRect mRect;
nscoord mThickness;
bool mRTL;
};
void nsDisplayMathMLSlash::Paint(nsDisplayListBuilder* aBuilder,
nsRenderingContext* aCtx)
{
// get the gfxRect
nsPresContext* presContext = mFrame->PresContext();
gfxRect rect = presContext->AppUnitsToGfxUnits(mRect + ToReferenceFrame());
// paint with the current text color
aCtx->SetColor(mFrame->GetVisitedDependentColor(eCSSProperty_color));
// draw the slash as a parallelogram
gfxContext *gfxCtx = aCtx->ThebesContext();
gfxPoint delta = gfxPoint(presContext->AppUnitsToGfxUnits(mThickness), 0);
gfxCtx->NewPath();
if (mRTL) {
gfxCtx->MoveTo(rect.TopLeft());
gfxCtx->LineTo(rect.TopLeft() + delta);
gfxCtx->LineTo(rect.BottomRight());
gfxCtx->LineTo(rect.BottomRight() - delta);
} else {
gfxCtx->MoveTo(rect.BottomLeft());
gfxCtx->LineTo(rect.BottomLeft() + delta);
gfxCtx->LineTo(rect.TopRight());
gfxCtx->LineTo(rect.TopRight() - delta);
}
gfxCtx->ClosePath();
gfxCtx->Fill();
}
void
nsMathMLmfracFrame::DisplaySlash(nsDisplayListBuilder* aBuilder,
nsIFrame* aFrame, const nsRect& aRect,
nscoord aThickness,
const nsDisplayListSet& aLists) {
if (!aFrame->StyleVisibility()->IsVisible() || aRect.IsEmpty())
return;
aLists.Content()->AppendNewToTop(new (aBuilder)
nsDisplayMathMLSlash(aBuilder, aFrame, aRect, aThickness,
StyleVisibility()->mDirection));
}
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