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