layout/mathml/base/src/nsMathMLmsubFrame.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is Mozilla MathML Project.
  16  *
  17  * The Initial Developer of the Original Code is
  18  * The University Of Queensland.
  19  * Portions created by the Initial Developer are Copyright (C) 1999
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *   Roger B. Sidje <rbs@maths.uq.edu.au>
  24  *   David J. Fiddes <D.J.Fiddes@hw.ac.uk>
  25  *   Shyjan Mahamud <mahamud@cs.cmu.edu> (added TeX rendering rules)
  26  *
  27  * Alternatively, the contents of this file may be used under the terms of
  28  * either of the GNU General Public License Version 2 or later (the "GPL"),
  29  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  30  * in which case the provisions of the GPL or the LGPL are applicable instead
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  36  * the provisions above, a recipient may use your version of this file under
  37  * the terms of any one of the MPL, the GPL or the LGPL.
  38  *
  39  * ***** END LICENSE BLOCK ***** */
  40
  41
  42 #include "nsCOMPtr.h"
  43 #include "nsFrame.h"
  44 #include "nsPresContext.h"
  45 #include "nsStyleContext.h"
  46 #include "nsStyleConsts.h"
  47 #include "nsIRenderingContext.h"
  48 #include "nsIFontMetrics.h"
  49
  50 #include "nsMathMLmsubFrame.h"
  51
  52 //
  53 // <msub> -- attach a subscript to a base - implementation
  54 //
  55
  56 nsIFrame*
  57 NS_NewMathMLmsubFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
  58 {
  59   return new (aPresShell) nsMathMLmsubFrame(aContext);
  60 }
  61
  62 nsMathMLmsubFrame::~nsMathMLmsubFrame()
  63 {
  64 }
  65
  66 NS_IMETHODIMP
  67 nsMathMLmsubFrame::TransmitAutomaticData()
  68 {
  69   // if our base is an embellished operator, let its state bubble to us
  70   mPresentationData.baseFrame = mFrames.FirstChild();
  71   GetEmbellishDataFrom(mPresentationData.baseFrame, mEmbellishData);
  72
  73   // 1. The REC says:
  74   // The <msub> element increments scriptlevel by 1, and sets displaystyle to
  75   // "false", within subscript, but leaves both attributes unchanged within base.
  76   // 2. The TeXbook (Ch 17. p.141) says the subscript is compressed
  77   UpdatePresentationDataFromChildAt(1, -1,
  78     ~NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED,
  79      NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED);
  80
  81   return NS_OK;
  82 }
  83
  84 /* virtual */ nsresult
  85 nsMathMLmsubFrame::Place (nsIRenderingContext& aRenderingContext,
  86                           PRBool               aPlaceOrigin,
  87                           nsHTMLReflowMetrics& aDesiredSize)
  88 {
  89   // extra spacing after sup/subscript
  90   nscoord scriptSpace = PresContext()->PointsToAppUnits(0.5f); // 0.5pt as in plain TeX
  91
  92   // check if the subscriptshift attribute is there
  93   nscoord subScriptShift = 0;
  94   nsAutoString value;
  95   GetAttribute(mContent, mPresentationData.mstyle,
  96                nsGkAtoms::subscriptshift_, value);
  97   if (!value.IsEmpty()) {
  98     nsCSSValue cssValue;
  99     if (ParseNumericValue(value, cssValue) && cssValue.IsLengthUnit()) {
 100       subScriptShift = CalcLength(PresContext(), mStyleContext, cssValue);
 101     }
 102   }
 103
 104   return nsMathMLmsubFrame::PlaceSubScript(PresContext(),
 105                                            aRenderingContext,
 106                                            aPlaceOrigin,
 107                                            aDesiredSize,
 108                                            this,
 109                                            subScriptShift,
 110                                            scriptSpace);
 111 }
 112
 113 // exported routine that both munder and msub share.
 114 // munder uses this when movablelimits is set.
 115 nsresult
 116 nsMathMLmsubFrame::PlaceSubScript (nsPresContext*      aPresContext,
 117                                    nsIRenderingContext& aRenderingContext,
 118                                    PRBool               aPlaceOrigin,
 119                                    nsHTMLReflowMetrics& aDesiredSize,
 120                                    nsMathMLContainerFrame* aFrame,
 121                                    nscoord              aUserSubScriptShift,
 122                                    nscoord              aScriptSpace)
 123 {
 124   // force the scriptSpace to be atleast 1 pixel
 125   aScriptSpace = PR_MAX(nsPresContext::CSSPixelsToAppUnits(1), aScriptSpace);
 126
 127   ////////////////////////////////////
 128   // Get the children's desired sizes
 129
 130   nsBoundingMetrics bmBase, bmSubScript;
 131   nsHTMLReflowMetrics baseSize;
 132   nsHTMLReflowMetrics subScriptSize;
 133   nsIFrame* baseFrame = aFrame->GetFirstChild(nsnull);
 134   nsIFrame* subScriptFrame = nsnull;
 135   if (baseFrame)
 136     subScriptFrame = baseFrame->GetNextSibling();
 137   if (!baseFrame || !subScriptFrame || subScriptFrame->GetNextSibling()) {
 138     // report an error, encourage people to get their markups in order
 139     return aFrame->ReflowError(aRenderingContext, aDesiredSize);
 140   }
 141   GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
 142   GetReflowAndBoundingMetricsFor(subScriptFrame, subScriptSize, bmSubScript);
 143
 144   // get the subdrop from the subscript font
 145   nscoord subDrop;
 146   GetSubDropFromChild(subScriptFrame, subDrop);
 147   // parameter v, Rule 18a, App. G, TeXbook
 148   nscoord minSubScriptShift = bmBase.descent + subDrop;
 149
 150   //////////////////
 151   // Place Children
 152
 153   // get min subscript shift limit from x-height
 154   // = h(x) - 4/5 * sigma_5, Rule 18b, App. G, TeXbook
 155   nscoord xHeight = 0;
 156   nsCOMPtr<nsIFontMetrics> fm =
 157     aPresContext->GetMetricsFor(baseFrame->GetStyleFont()->mFont);
 158
 159   fm->GetXHeight (xHeight);
 160   nscoord minShiftFromXHeight = (nscoord)
 161     (bmSubScript.ascent - (4.0f/5.0f) * xHeight);
 162
 163   // subScriptShift
 164   // = minimum amount to shift the subscript down set by user or from the font
 165   // = sub1 in TeX
 166   // = subscriptshift attribute * x-height
 167   nscoord subScriptShift, dummy;
 168   // get subScriptShift default from font
 169   GetSubScriptShifts (fm, subScriptShift, dummy);
 170
 171   subScriptShift =
 172     PR_MAX(subScriptShift, aUserSubScriptShift);
 173
 174   // get actual subscriptshift to be used
 175   // Rule 18b, App. G, TeXbook
 176   nscoord actualSubScriptShift =
 177     PR_MAX(minSubScriptShift,PR_MAX(subScriptShift,minShiftFromXHeight));
 178   // get bounding box for base + subscript
 179   nsBoundingMetrics boundingMetrics;
 180   boundingMetrics.ascent =
 181     PR_MAX(bmBase.ascent, bmSubScript.ascent - actualSubScriptShift);
 182   boundingMetrics.descent =
 183     PR_MAX(bmBase.descent, bmSubScript.descent + actualSubScriptShift);
 184
 185   // add aScriptSpace to the subscript's width
 186   boundingMetrics.width = bmBase.width + bmSubScript.width + aScriptSpace;
 187   boundingMetrics.leftBearing = bmBase.leftBearing;
 188   boundingMetrics.rightBearing = PR_MAX(bmBase.rightBearing, bmBase.width +
 189     PR_MAX(bmSubScript.width + aScriptSpace, bmSubScript.rightBearing));
 190   aFrame->SetBoundingMetrics (boundingMetrics);
 191
 192   // reflow metrics
 193   aDesiredSize.ascent =
 194     PR_MAX(baseSize.ascent, subScriptSize.ascent - actualSubScriptShift);
 195   aDesiredSize.height = aDesiredSize.ascent +
 196     PR_MAX(baseSize.height - baseSize.ascent,
 197            subScriptSize.height - subScriptSize.ascent + actualSubScriptShift);
 198   aDesiredSize.width = boundingMetrics.width;
 199   aDesiredSize.mBoundingMetrics = boundingMetrics;
 200
 201   aFrame->SetReference(nsPoint(0, aDesiredSize.ascent));
 202
 203   if (aPlaceOrigin) {
 204     nscoord dx, dy;
 205     // now place the base ...
 206     dx = 0; dy = aDesiredSize.ascent - baseSize.ascent;
 207     FinishReflowChild (baseFrame, aPresContext, nsnull, baseSize, dx, dy, 0);
 208     // ... and subscript
 209     dx = bmBase.width;
 210     dy = aDesiredSize.ascent - (subScriptSize.ascent - actualSubScriptShift);
 211     FinishReflowChild (subScriptFrame, aPresContext, nsnull, subScriptSize, dx, dy, 0);
 212   }
 213
 214   return NS_OK;
 215 }