gecko-dev/layout/mathml/nsMathMLmsubsupFrame.cpp

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C++

/* -*- 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 "nsCOMPtr.h"
#include "nsFrame.h"
#include "nsPresContext.h"
#include "nsStyleContext.h"
#include "nsStyleConsts.h"
#include "nsRenderingContext.h"
#include "nsMathMLmsubsupFrame.h"
//
// <msubsup> -- attach a subscript-superscript pair to a base - implementation
//
nsIFrame*
NS_NewMathMLmsubsupFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
{
return new (aPresShell) nsMathMLmsubsupFrame(aContext);
}
NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmsubsupFrame)
nsMathMLmsubsupFrame::~nsMathMLmsubsupFrame()
{
}
NS_IMETHODIMP
nsMathMLmsubsupFrame::TransmitAutomaticData()
{
// if our base is an embellished operator, let its state bubble to us
mPresentationData.baseFrame = mFrames.FirstChild();
GetEmbellishDataFrom(mPresentationData.baseFrame, mEmbellishData);
// 1. The REC says:
// The <msubsup> element increments scriptlevel by 1, and sets displaystyle to
// "false", within subscript and superscript, but leaves both attributes
// unchanged within base.
// 2. The TeXbook (Ch 17. p.141) says the superscript inherits the compression
// while the subscript is compressed
UpdatePresentationDataFromChildAt(1, -1,
~NS_MATHML_DISPLAYSTYLE,
NS_MATHML_DISPLAYSTYLE);
UpdatePresentationDataFromChildAt(1, 1,
NS_MATHML_COMPRESSED,
NS_MATHML_COMPRESSED);
return NS_OK;
}
/* virtual */ nsresult
nsMathMLmsubsupFrame::Place(nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize)
{
// extra spacing between base and sup/subscript
nscoord scriptSpace = 0;
// subscriptshift
//
// "Specifies the minimum amount to shift the baseline of subscript down; the
// default is for the rendering agent to use its own positioning rules."
//
// values: length
// default: automatic
//
// We use 0 as the default value so unitless values can be ignored.
// XXXfredw Should we forbid negative values? (bug 411227)
//
nsAutoString value;
nscoord subScriptShift = 0;
GetAttribute(mContent, mPresentationData.mstyle,
nsGkAtoms::subscriptshift_, value);
if (!value.IsEmpty()) {
ParseNumericValue(value, &subScriptShift,
nsMathMLElement::PARSE_ALLOW_NEGATIVE,
PresContext(), mStyleContext);
}
// superscriptshift
//
// "Specifies the minimum amount to shift the baseline of superscript up; the
// default is for the rendering agent to use its own positioning rules."
//
// values: length
// default: automatic
//
// We use 0 as the default value so unitless values can be ignored.
// XXXfredw Should we forbid negative values? (bug 411227)
//
nscoord supScriptShift = 0;
GetAttribute(mContent, mPresentationData.mstyle,
nsGkAtoms::superscriptshift_, value);
if (!value.IsEmpty()) {
ParseNumericValue(value, &supScriptShift,
nsMathMLElement::PARSE_ALLOW_NEGATIVE,
PresContext(), mStyleContext);
}
return nsMathMLmsubsupFrame::PlaceSubSupScript(PresContext(),
aRenderingContext,
aPlaceOrigin,
aDesiredSize,
this,
subScriptShift,
supScriptShift,
scriptSpace);
}
// exported routine that both munderover and msubsup share.
// munderover uses this when movablelimits is set.
nsresult
nsMathMLmsubsupFrame::PlaceSubSupScript(nsPresContext* aPresContext,
nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize,
nsMathMLContainerFrame* aFrame,
nscoord aUserSubScriptShift,
nscoord aUserSupScriptShift,
nscoord aScriptSpace)
{
// force the scriptSpace to be atleast 1 pixel
nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
aScriptSpace = NS_MAX(onePixel, aScriptSpace);
////////////////////////////////////
// Get the children's desired sizes
nsHTMLReflowMetrics baseSize;
nsHTMLReflowMetrics subScriptSize;
nsHTMLReflowMetrics supScriptSize;
nsBoundingMetrics bmBase, bmSubScript, bmSupScript;
nsIFrame* subScriptFrame = nsnull;
nsIFrame* supScriptFrame = nsnull;
nsIFrame* baseFrame = aFrame->GetFirstPrincipalChild();
if (baseFrame)
subScriptFrame = baseFrame->GetNextSibling();
if (subScriptFrame)
supScriptFrame = subScriptFrame->GetNextSibling();
if (!baseFrame || !subScriptFrame || !supScriptFrame ||
supScriptFrame->GetNextSibling()) {
// report an error, encourage people to get their markups in order
return aFrame->ReflowError(aRenderingContext, aDesiredSize);
}
GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
GetReflowAndBoundingMetricsFor(subScriptFrame, subScriptSize, bmSubScript);
GetReflowAndBoundingMetricsFor(supScriptFrame, supScriptSize, bmSupScript);
// get the subdrop from the subscript font
nscoord subDrop;
GetSubDropFromChild(subScriptFrame, subDrop);
// parameter v, Rule 18a, App. G, TeXbook
nscoord minSubScriptShift = bmBase.descent + subDrop;
// get the supdrop from the supscript font
nscoord supDrop;
GetSupDropFromChild(supScriptFrame, supDrop);
// parameter u, Rule 18a, App. G, TeXbook
nscoord minSupScriptShift = bmBase.ascent - supDrop;
//////////////////
// Place Children
//////////////////
//////////////////////////////////////////////////
// Get subscript shift
// slightly different from nsMathMLmsubFrame.cpp
//////////////////////////////////////////////////
// subScriptShift{1,2}
// = minimum amount to shift the subscript down
// = sub{1,2} in TeXbook
// subScriptShift1 = subscriptshift attribute * x-height
nscoord subScriptShift1, subScriptShift2;
nsRefPtr<nsFontMetrics> fm;
nsLayoutUtils::GetFontMetricsForFrame(baseFrame, getter_AddRefs(fm));
aRenderingContext.SetFont(fm);
// get x-height (an ex)
nscoord xHeight = fm->XHeight();
nscoord ruleSize;
GetRuleThickness (aRenderingContext, fm, ruleSize);
// Get subScriptShift{1,2} default from font
GetSubScriptShifts (fm, subScriptShift1, subScriptShift2);
if (0 < aUserSubScriptShift) {
// the user has set the subscriptshift attribute
float scaler = ((float) subScriptShift2) / subScriptShift1;
subScriptShift1 = NS_MAX(subScriptShift1, aUserSubScriptShift);
subScriptShift2 = NSToCoordRound(scaler * subScriptShift1);
}
// get a tentative value for subscriptshift
// Rule 18d, App. G, TeXbook
nscoord subScriptShift =
NS_MAX(minSubScriptShift,NS_MAX(subScriptShift1,subScriptShift2));
//////////////////////////////////////////////////
// Get supscript shift
// same code from nsMathMLmsupFrame.cpp
//////////////////////////////////////////////////
// get min supscript shift limit from x-height
// = d(x) + 1/4 * sigma_5, Rule 18c, App. G, TeXbook
nscoord minShiftFromXHeight = (nscoord)
(bmSupScript.descent + (1.0f/4.0f) * xHeight);
// supScriptShift{1,2,3}
// = minimum amount to shift the supscript up
// = sup{1,2,3} in TeX
// supScriptShift1 = superscriptshift attribute * x-height
// Note that there are THREE values for supscript shifts depending
// on the current style
nscoord supScriptShift1, supScriptShift2, supScriptShift3;
// Set supScriptShift{1,2,3} default from font
GetSupScriptShifts (fm, supScriptShift1, supScriptShift2, supScriptShift3);
if (0 < aUserSupScriptShift) {
// the user has set the superscriptshift attribute
float scaler2 = ((float) supScriptShift2) / supScriptShift1;
float scaler3 = ((float) supScriptShift3) / supScriptShift1;
supScriptShift1 = NS_MAX(supScriptShift1, aUserSupScriptShift);
supScriptShift2 = NSToCoordRound(scaler2 * supScriptShift1);
supScriptShift3 = NSToCoordRound(scaler3 * supScriptShift1);
}
// get sup script shift depending on current script level and display style
// Rule 18c, App. G, TeXbook
nscoord supScriptShift;
nsPresentationData presentationData;
aFrame->GetPresentationData(presentationData);
if ( aFrame->GetStyleFont()->mScriptLevel == 0 &&
NS_MATHML_IS_DISPLAYSTYLE(presentationData.flags) &&
!NS_MATHML_IS_COMPRESSED(presentationData.flags)) {
// Style D in TeXbook
supScriptShift = supScriptShift1;
}
else if (NS_MATHML_IS_COMPRESSED(presentationData.flags)) {
// Style C' in TeXbook = D',T',S',SS'
supScriptShift = supScriptShift3;
}
else {
// everything else = T,S,SS
supScriptShift = supScriptShift2;
}
// get tentative value for superscriptshift
// Rule 18c, App. G, TeXbook
supScriptShift =
NS_MAX(minSupScriptShift,NS_MAX(supScriptShift,minShiftFromXHeight));
//////////////////////////////////////////////////
// Negotiate between supScriptShift and subScriptShift
// so that there will be enough gap between them
// Rule 18e, App. G, TeXbook
//////////////////////////////////////////////////
nscoord gap =
(supScriptShift - bmSupScript.descent) -
(bmSubScript.ascent - subScriptShift);
if (gap < 4.0f * ruleSize) {
// adjust subScriptShift to get a gap of (4.0 * ruleSize)
subScriptShift += NSToCoordRound ((4.0f * ruleSize) - gap);
}
// next we want to ensure that the bottom of the superscript
// will be > (4/5) * x-height above baseline
gap = NSToCoordRound ((4.0f/5.0f) * xHeight -
(supScriptShift - bmSupScript.descent));
if (gap > 0) {
supScriptShift += gap;
subScriptShift -= gap;
}
//////////////////////////////////////////////////
// Do the Placing
//////////////////////////////////////////////////
// get bounding box for base + subscript + superscript
nsBoundingMetrics boundingMetrics;
boundingMetrics.ascent =
NS_MAX(bmBase.ascent, (bmSupScript.ascent + supScriptShift));
boundingMetrics.descent =
NS_MAX(bmBase.descent, (bmSubScript.descent + subScriptShift));
// leave aScriptSpace after both super/subscript
// add italicCorrection between base and superscript
// add "a little to spare" as well (see TeXbook Ch.11, p.64), as we
// estimate the italic creation ourselves and it isn't the same as TeX
nscoord italicCorrection;
GetItalicCorrection(bmBase, italicCorrection);
italicCorrection += onePixel;
boundingMetrics.width = bmBase.width + aScriptSpace +
NS_MAX((italicCorrection + bmSupScript.width), bmSubScript.width);
boundingMetrics.leftBearing = bmBase.leftBearing;
boundingMetrics.rightBearing = bmBase.width +
NS_MAX((italicCorrection + bmSupScript.rightBearing), bmSubScript.rightBearing);
aFrame->SetBoundingMetrics(boundingMetrics);
// reflow metrics
aDesiredSize.ascent =
NS_MAX(baseSize.ascent,
NS_MAX(subScriptSize.ascent - subScriptShift,
supScriptSize.ascent + supScriptShift));
aDesiredSize.height = aDesiredSize.ascent +
NS_MAX(baseSize.height - baseSize.ascent,
NS_MAX(subScriptSize.height - subScriptSize.ascent + subScriptShift,
supScriptSize.height - subScriptSize.ascent - supScriptShift));
aDesiredSize.width = boundingMetrics.width;
aDesiredSize.mBoundingMetrics = boundingMetrics;
aFrame->SetReference(nsPoint(0, aDesiredSize.ascent));
if (aPlaceOrigin) {
nscoord dx, dy;
// now place the base ...
dx = aFrame->MirrorIfRTL(aDesiredSize.width, baseSize.width, 0);
dy = aDesiredSize.ascent - baseSize.ascent;
FinishReflowChild(baseFrame, aPresContext, nsnull,
baseSize, dx, dy, 0);
// ... and subscript
dx = aFrame->MirrorIfRTL(aDesiredSize.width, subScriptSize.width,
bmBase.width);
dy = aDesiredSize.ascent - (subScriptSize.ascent - subScriptShift);
FinishReflowChild(subScriptFrame, aPresContext, nsnull,
subScriptSize, dx, dy, 0);
// ... and the superscript
dx = aFrame->MirrorIfRTL(aDesiredSize.width, supScriptSize.width,
bmBase.width + italicCorrection);
dy = aDesiredSize.ascent - (supScriptSize.ascent + supScriptShift);
FinishReflowChild(supScriptFrame, aPresContext, nsnull,
supScriptSize, dx, dy, 0);
}
return NS_OK;
}