layout/mathml/nsMathMLmsupFrame.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
  31  * of those above. If you wish to allow use of your version of this file only
  32  * under the terms of either the GPL or the LGPL, and not to allow others to
  33  * use your version of this file under the terms of the MPL, indicate your
  34  * decision by deleting the provisions above and replace them with the notice
  35  * and other provisions required by the GPL or the LGPL. If you do not delete
  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 #include "nsCOMPtr.h"
  42 #include "nsFrame.h"
  43 #include "nsPresContext.h"
  44 #include "nsStyleContext.h"
  45 #include "nsStyleConsts.h"
  46 #include "nsIRenderingContext.h"
  47 #include "nsIFontMetrics.h"
  48
  49 #include "nsMathMLmsupFrame.h"
  50
  51 //
  52 // <msup> -- attach a superscript to a base - implementation
  53 //
  54
  55 nsIFrame*
  56 NS_NewMathMLmsupFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
  57 {
  58   return new (aPresShell) nsMathMLmsupFrame(aContext);
  59 }
  60
  61 NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmsupFrame)
  62
  63 nsMathMLmsupFrame::~nsMathMLmsupFrame()
  64 {
  65 }
  66
  67 NS_IMETHODIMP
  68 nsMathMLmsupFrame::TransmitAutomaticData()
  69 {
  70   // if our base is an embellished operator, its flags bubble to us
  71   mPresentationData.baseFrame = mFrames.FirstChild();
  72   GetEmbellishDataFrom(mPresentationData.baseFrame, mEmbellishData);
  73
  74   // 1. The REC says:
  75   // The <msup> element increments scriptlevel by 1, and sets displaystyle to
  76   // "false", within superscript, but leaves both attributes unchanged within base.
  77   // 2. The TeXbook (Ch 17. p.141) says the superscript *inherits* the compression,
  78   // so we don't set the compression flag. Our parent will propagate its own.
  79   UpdatePresentationDataFromChildAt(1, -1,
  80     ~NS_MATHML_DISPLAYSTYLE,
  81      NS_MATHML_DISPLAYSTYLE);
  82
  83   return NS_OK;
  84 }
  85
  86 /* virtual */ nsresult
  87 nsMathMLmsupFrame::Place(nsIRenderingContext& aRenderingContext,
  88                          PRBool               aPlaceOrigin,
  89                          nsHTMLReflowMetrics& aDesiredSize)
  90 {
  91   // extra spacing after sup/subscript
  92   nscoord scriptSpace = nsPresContext::CSSPointsToAppUnits(0.5f); // 0.5pt as in plain TeX
  93
  94   // check if the superscriptshift attribute is there
  95   nsAutoString value;
  96   nscoord supScriptShift = 0;
  97   GetAttribute(mContent, mPresentationData.mstyle,
  98                nsGkAtoms::superscriptshift_, value);
  99   if (!value.IsEmpty()) {
 100     nsCSSValue cssValue;
 101     if (ParseNumericValue(value, cssValue) && cssValue.IsLengthUnit()) {
 102       supScriptShift = CalcLength(PresContext(), mStyleContext, cssValue);
 103     }
 104   }
 105
 106   return nsMathMLmsupFrame::PlaceSuperScript(PresContext(),
 107                                              aRenderingContext,
 108                                              aPlaceOrigin,
 109                                              aDesiredSize,
 110                                              this,
 111                                              supScriptShift,
 112                                              scriptSpace);
 113 }
 114
 115 // exported routine that both mover and msup share.
 116 // mover uses this when movablelimits is set.
 117 nsresult
 118 nsMathMLmsupFrame::PlaceSuperScript(nsPresContext*      aPresContext,
 119                                     nsIRenderingContext& aRenderingContext,
 120                                     PRBool               aPlaceOrigin,
 121                                     nsHTMLReflowMetrics& aDesiredSize,
 122                                     nsMathMLContainerFrame* aFrame,
 123                                     nscoord              aUserSupScriptShift,
 124                                     nscoord              aScriptSpace)
 125 {
 126   // force the scriptSpace to be at least 1 pixel
 127   nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
 128   aScriptSpace = NS_MAX(onePixel, aScriptSpace);
 129
 130   ////////////////////////////////////
 131   // Get the children's desired sizes
 132
 133   nsHTMLReflowMetrics baseSize;
 134   nsHTMLReflowMetrics supScriptSize;
 135   nsBoundingMetrics bmBase, bmSupScript;
 136   nsIFrame* supScriptFrame = nsnull;
 137   nsIFrame* baseFrame = aFrame->GetFirstChild(nsnull);
 138   if (baseFrame)
 139     supScriptFrame = baseFrame->GetNextSibling();
 140   if (!baseFrame || !supScriptFrame || supScriptFrame->GetNextSibling()) {
 141     // report an error, encourage people to get their markups in order
 142     return aFrame->ReflowError(aRenderingContext, aDesiredSize);
 143   }
 144   GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
 145   GetReflowAndBoundingMetricsFor(supScriptFrame, supScriptSize, bmSupScript);
 146
 147   // get the supdrop from the supscript font
 148   nscoord supDrop;
 149   GetSupDropFromChild(supScriptFrame, supDrop);
 150   // parameter u, Rule 18a, App. G, TeXbook
 151   nscoord minSupScriptShift = bmBase.ascent - supDrop;
 152
 153   //////////////////
 154   // Place Children
 155
 156   // get min supscript shift limit from x-height
 157   // = d(x) + 1/4 * sigma_5, Rule 18c, App. G, TeXbook
 158   nscoord xHeight = 0;
 159   nsCOMPtr<nsIFontMetrics> fm =
 160     aPresContext->GetMetricsFor(baseFrame->GetStyleFont()->mFont);
 161
 162   fm->GetXHeight (xHeight);
 163   nscoord minShiftFromXHeight = (nscoord)
 164     (bmSupScript.descent + (1.0f/4.0f) * xHeight);
 165   nscoord italicCorrection;
 166   GetItalicCorrection(bmBase, italicCorrection);
 167
 168   // supScriptShift{1,2,3}
 169   // = minimum amount to shift the supscript up
 170   // = sup{1,2,3} in TeX
 171   // supScriptShift1 = superscriptshift attribute * x-height
 172   // Note that there are THREE values for supscript shifts depending
 173   // on the current style
 174   nscoord supScriptShift1, supScriptShift2, supScriptShift3;
 175   // Set supScriptShift{1,2,3} default from font
 176   GetSupScriptShifts (fm, supScriptShift1, supScriptShift2, supScriptShift3);
 177
 178   if (0 < aUserSupScriptShift) {
 179     // the user has set the superscriptshift attribute
 180     float scaler2 = ((float) supScriptShift2) / supScriptShift1;
 181     float scaler3 = ((float) supScriptShift3) / supScriptShift1;
 182     supScriptShift1 =
 183       NS_MAX(supScriptShift1, aUserSupScriptShift);
 184     supScriptShift2 = NSToCoordRound(scaler2 * supScriptShift1);
 185     supScriptShift3 = NSToCoordRound(scaler3 * supScriptShift1);
 186   }
 187
 188   // get sup script shift depending on current script level and display style
 189   // Rule 18c, App. G, TeXbook
 190   nscoord supScriptShift;
 191   nsPresentationData presentationData;
 192   aFrame->GetPresentationData (presentationData);
 193   if ( aFrame->GetStyleFont()->mScriptLevel == 0 &&
 194        NS_MATHML_IS_DISPLAYSTYLE(presentationData.flags) &&
 195       !NS_MATHML_IS_COMPRESSED(presentationData.flags)) {
 196     // Style D in TeXbook
 197     supScriptShift = supScriptShift1;
 198   }
 199   else if (NS_MATHML_IS_COMPRESSED(presentationData.flags)) {
 200     // Style C' in TeXbook = D',T',S',SS'
 201     supScriptShift = supScriptShift3;
 202   }
 203   else {
 204     // everything else = T,S,SS
 205     supScriptShift = supScriptShift2;
 206   }
 207
 208   // get actual supscriptshift to be used
 209   // Rule 18c, App. G, TeXbook
 210   nscoord actualSupScriptShift =
 211     NS_MAX(minSupScriptShift,NS_MAX(supScriptShift,minShiftFromXHeight));
 212
 213   // bounding box
 214   nsBoundingMetrics boundingMetrics;
 215   boundingMetrics.ascent =
 216     NS_MAX(bmBase.ascent, (bmSupScript.ascent + actualSupScriptShift));
 217   boundingMetrics.descent =
 218     NS_MAX(bmBase.descent, (bmSupScript.descent - actualSupScriptShift));
 219
 220   // leave aScriptSpace after superscript
 221   // add italicCorrection between base and superscript
 222   // add "a little to spare" as well (see TeXbook Ch.11, p.64), as we
 223   // estimate the italic creation ourselves and it isn't the same as TeX
 224   italicCorrection += onePixel;
 225   boundingMetrics.width = bmBase.width + italicCorrection +
 226                           bmSupScript.width + aScriptSpace;
 227   boundingMetrics.leftBearing = bmBase.leftBearing;
 228   boundingMetrics.rightBearing = bmBase.width + italicCorrection +
 229                                  bmSupScript.rightBearing;
 230   aFrame->SetBoundingMetrics(boundingMetrics);
 231
 232   // reflow metrics
 233   aDesiredSize.ascent =
 234     NS_MAX(baseSize.ascent, (supScriptSize.ascent + actualSupScriptShift));
 235   aDesiredSize.height = aDesiredSize.ascent +
 236     NS_MAX(baseSize.height - baseSize.ascent,
 237            (supScriptSize.height - supScriptSize.ascent - actualSupScriptShift));
 238   aDesiredSize.width = boundingMetrics.width;
 239   aDesiredSize.mBoundingMetrics = boundingMetrics;
 240
 241   aFrame->SetReference(nsPoint(0, aDesiredSize.ascent));
 242
 243   if (aPlaceOrigin) {
 244     nscoord dx, dy;
 245     // now place the base ...
 246     dx = 0; dy = aDesiredSize.ascent - baseSize.ascent;
 247     FinishReflowChild (baseFrame, aPresContext, nsnull, baseSize, dx, dy, 0);
 248     // ... and supscript
 249     dx = bmBase.width + italicCorrection;
 250     dy = aDesiredSize.ascent - (supScriptSize.ascent + actualSupScriptShift);
 251     FinishReflowChild (supScriptFrame, aPresContext, nsnull, supScriptSize, dx, dy, 0);
 252   }
 253
 254   return NS_OK;
 255 }