gecko-dev/layout/mathml/nsMathMLmsubFrame.cpp

194 lines
7.0 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 "nsMathMLmsubFrame.h"
#include <algorithm>
//
// <msub> -- attach a subscript to a base - implementation
//
nsIFrame*
NS_NewMathMLmsubFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
{
return new (aPresShell) nsMathMLmsubFrame(aContext);
}
NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmsubFrame)
nsMathMLmsubFrame::~nsMathMLmsubFrame()
{
}
NS_IMETHODIMP
nsMathMLmsubFrame::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 <msub> element increments scriptlevel by 1, and sets displaystyle to
// "false", within subscript, but leaves both attributes unchanged within base.
// 2. The TeXbook (Ch 17. p.141) says the subscript is compressed
UpdatePresentationDataFromChildAt(1, -1,
~NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED,
NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED);
return NS_OK;
}
/* virtual */ nsresult
nsMathMLmsubFrame::Place (nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize)
{
// extra spacing after sup/subscript
nscoord scriptSpace = nsPresContext::CSSPointsToAppUnits(0.5f); // 0.5pt as in plain TeX
// 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.
// As a minimum, negative values can be ignored.
//
nscoord subScriptShift = 0;
nsAutoString value;
GetAttribute(mContent, mPresentationData.mstyle,
nsGkAtoms::subscriptshift_, value);
if (!value.IsEmpty()) {
ParseNumericValue(value, &subScriptShift, 0, PresContext(), mStyleContext);
}
return nsMathMLmsubFrame::PlaceSubScript(PresContext(),
aRenderingContext,
aPlaceOrigin,
aDesiredSize,
this,
subScriptShift,
scriptSpace);
}
// exported routine that both munder and msub share.
// munder uses this when movablelimits is set.
nsresult
nsMathMLmsubFrame::PlaceSubScript (nsPresContext* aPresContext,
nsRenderingContext& aRenderingContext,
bool aPlaceOrigin,
nsHTMLReflowMetrics& aDesiredSize,
nsMathMLContainerFrame* aFrame,
nscoord aUserSubScriptShift,
nscoord aScriptSpace)
{
// force the scriptSpace to be atleast 1 pixel
aScriptSpace = std::max(nsPresContext::CSSPixelsToAppUnits(1), aScriptSpace);
////////////////////////////////////
// Get the children's desired sizes
nsBoundingMetrics bmBase, bmSubScript;
nsHTMLReflowMetrics baseSize;
nsHTMLReflowMetrics subScriptSize;
nsIFrame* baseFrame = aFrame->GetFirstPrincipalChild();
nsIFrame* subScriptFrame = nullptr;
if (baseFrame)
subScriptFrame = baseFrame->GetNextSibling();
if (!baseFrame || !subScriptFrame || subScriptFrame->GetNextSibling()) {
// report an error, encourage people to get their markups in order
if (aPlaceOrigin) {
aFrame->ReportChildCountError();
}
return aFrame->ReflowError(aRenderingContext, aDesiredSize);
}
GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
GetReflowAndBoundingMetricsFor(subScriptFrame, subScriptSize, bmSubScript);
// get the subdrop from the subscript font
nscoord subDrop;
GetSubDropFromChild(subScriptFrame, subDrop);
// parameter v, Rule 18a, App. G, TeXbook
nscoord minSubScriptShift = bmBase.descent + subDrop;
//////////////////
// Place Children
// get min subscript shift limit from x-height
// = h(x) - 4/5 * sigma_5, Rule 18b, App. G, TeXbook
nscoord xHeight = 0;
nsRefPtr<nsFontMetrics> fm;
nsLayoutUtils::GetFontMetricsForFrame(baseFrame, getter_AddRefs(fm));
xHeight = fm->XHeight();
nscoord minShiftFromXHeight = (nscoord)
(bmSubScript.ascent - (4.0f/5.0f) * xHeight);
// subScriptShift
// = minimum amount to shift the subscript down set by user or from the font
// = sub1 in TeX
// = subscriptshift attribute * x-height
nscoord subScriptShift, dummy;
// get subScriptShift default from font
GetSubScriptShifts (fm, subScriptShift, dummy);
subScriptShift =
std::max(subScriptShift, aUserSubScriptShift);
// get actual subscriptshift to be used
// Rule 18b, App. G, TeXbook
nscoord actualSubScriptShift =
std::max(minSubScriptShift,std::max(subScriptShift,minShiftFromXHeight));
// get bounding box for base + subscript
nsBoundingMetrics boundingMetrics;
boundingMetrics.ascent =
std::max(bmBase.ascent, bmSubScript.ascent - actualSubScriptShift);
boundingMetrics.descent =
std::max(bmBase.descent, bmSubScript.descent + actualSubScriptShift);
// add aScriptSpace to the subscript's width
boundingMetrics.width = bmBase.width + bmSubScript.width + aScriptSpace;
boundingMetrics.leftBearing = bmBase.leftBearing;
boundingMetrics.rightBearing = std::max(bmBase.rightBearing, bmBase.width +
std::max(bmSubScript.width + aScriptSpace, bmSubScript.rightBearing));
aFrame->SetBoundingMetrics (boundingMetrics);
// reflow metrics
aDesiredSize.ascent =
std::max(baseSize.ascent, subScriptSize.ascent - actualSubScriptShift);
aDesiredSize.height = aDesiredSize.ascent +
std::max(baseSize.height - baseSize.ascent,
subScriptSize.height - subScriptSize.ascent + actualSubScriptShift);
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 subscript
dx = aFrame->MirrorIfRTL(aDesiredSize.width, subScriptSize.width,
bmBase.width);
dy = aDesiredSize.ascent - (subScriptSize.ascent - actualSubScriptShift);
FinishReflowChild (subScriptFrame, aPresContext, nullptr, subScriptSize, dx, dy, 0);
}
return NS_OK;
}