gecko-dev/layout/mathml/nsMathMLmsupFrame.cpp

230 строки
8.6 KiB
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 "nsMathMLmsupFrame.h"
//
// <msup> -- attach a superscript to a base - implementation
//
nsIFrame*
NS_NewMathMLmsupFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
{
return new (aPresShell) nsMathMLmsupFrame(aContext);
}
NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmsupFrame)
nsMathMLmsupFrame::~nsMathMLmsupFrame()
{
}
NS_IMETHODIMP
nsMathMLmsupFrame::TransmitAutomaticData()
{
// if our base is an embellished operator, its flags bubble to us
mPresentationData.baseFrame = mFrames.FirstChild();
GetEmbellishDataFrom(mPresentationData.baseFrame, mEmbellishData);
// 1. The REC says:
// The <msup> element increments scriptlevel by 1, and sets displaystyle to
// "false", within superscript, but leaves both attributes unchanged within base.
// 2. The TeXbook (Ch 17. p.141) says the superscript *inherits* the compression,
// so we don't set the compression flag. Our parent will propagate its own.
UpdatePresentationDataFromChildAt(1, -1,
~NS_MATHML_DISPLAYSTYLE,
NS_MATHML_DISPLAYSTYLE);
return NS_OK;
}
/* virtual */ nsresult
nsMathMLmsupFrame::Place(nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize)
{
// extra spacing after sup/subscript
nscoord scriptSpace = nsPresContext::CSSPointsToAppUnits(0.5f); // 0.5pt as in plain TeX
// 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)
//
nsAutoString value;
nscoord supScriptShift = 0;
GetAttribute(mContent, mPresentationData.mstyle,
nsGkAtoms::superscriptshift_, value);
if (!value.IsEmpty()) {
ParseNumericValue(value, &supScriptShift,
nsMathMLElement::PARSE_ALLOW_NEGATIVE,
PresContext(), mStyleContext);
}
return nsMathMLmsupFrame::PlaceSuperScript(PresContext(),
aRenderingContext,
aPlaceOrigin,
aDesiredSize,
this,
supScriptShift,
scriptSpace);
}
// exported routine that both mover and msup share.
// mover uses this when movablelimits is set.
nsresult
nsMathMLmsupFrame::PlaceSuperScript(nsPresContext* aPresContext,
nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize,
nsMathMLContainerFrame* aFrame,
nscoord aUserSupScriptShift,
nscoord aScriptSpace)
{
// force the scriptSpace to be at least 1 pixel
nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
aScriptSpace = NS_MAX(onePixel, aScriptSpace);
////////////////////////////////////
// Get the children's desired sizes
nsHTMLReflowMetrics baseSize;
nsHTMLReflowMetrics supScriptSize;
nsBoundingMetrics bmBase, bmSupScript;
nsIFrame* supScriptFrame = nullptr;
nsIFrame* baseFrame = aFrame->GetFirstPrincipalChild();
if (baseFrame)
supScriptFrame = baseFrame->GetNextSibling();
if (!baseFrame || !supScriptFrame || supScriptFrame->GetNextSibling()) {
// report an error, encourage people to get their markups in order
return aFrame->ReflowError(aRenderingContext, aDesiredSize);
}
GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
GetReflowAndBoundingMetricsFor(supScriptFrame, supScriptSize, bmSupScript);
// 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 min supscript shift limit from x-height
// = d(x) + 1/4 * sigma_5, Rule 18c, App. G, TeXbook
nscoord xHeight = 0;
nsRefPtr<nsFontMetrics> fm;
nsLayoutUtils::GetFontMetricsForFrame(baseFrame, getter_AddRefs(fm));
xHeight = fm->XHeight();
nscoord minShiftFromXHeight = (nscoord)
(bmSupScript.descent + (1.0f/4.0f) * xHeight);
nscoord italicCorrection;
GetItalicCorrection(bmBase, italicCorrection);
// 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 actual supscriptshift to be used
// Rule 18c, App. G, TeXbook
nscoord actualSupScriptShift =
NS_MAX(minSupScriptShift,NS_MAX(supScriptShift,minShiftFromXHeight));
// bounding box
nsBoundingMetrics boundingMetrics;
boundingMetrics.ascent =
NS_MAX(bmBase.ascent, (bmSupScript.ascent + actualSupScriptShift));
boundingMetrics.descent =
NS_MAX(bmBase.descent, (bmSupScript.descent - actualSupScriptShift));
// leave aScriptSpace after superscript
// 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
italicCorrection += onePixel;
boundingMetrics.width = bmBase.width + italicCorrection +
bmSupScript.width + aScriptSpace;
boundingMetrics.leftBearing = bmBase.leftBearing;
boundingMetrics.rightBearing = bmBase.width + italicCorrection +
bmSupScript.rightBearing;
aFrame->SetBoundingMetrics(boundingMetrics);
// reflow metrics
aDesiredSize.ascent =
NS_MAX(baseSize.ascent, (supScriptSize.ascent + actualSupScriptShift));
aDesiredSize.height = aDesiredSize.ascent +
NS_MAX(baseSize.height - baseSize.ascent,
(supScriptSize.height - supScriptSize.ascent - actualSupScriptShift));
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, nullptr, baseSize, dx, dy, 0);
// ... and supscript
dx = aFrame->MirrorIfRTL(aDesiredSize.width, supScriptSize.width,
bmBase.width + italicCorrection);
dy = aDesiredSize.ascent - (supScriptSize.ascent + actualSupScriptShift);
FinishReflowChild (supScriptFrame, aPresContext, nullptr, supScriptSize, dx, dy, 0);
}
return NS_OK;
}