layout/mathml/nsMathMLmrootFrame.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6
   7 #include "nsCOMPtr.h"
   8 #include "nsFrame.h"
   9 #include "nsPresContext.h"
  10 #include "nsStyleContext.h"
  11 #include "nsStyleConsts.h"
  12 #include "nsRenderingContext.h"
  13
  14 #include "nsMathMLmrootFrame.h"
  15
  16 //
  17 // <msqrt> and <mroot> -- form a radical - implementation
  18 //
  19
  20 //NOTE:
  21 //  The code assumes that TeX fonts are picked.
  22 //  There is no fall-back to draw the branches of the sqrt explicitly
  23 //  in the case where TeX fonts are not there. In general, there are no
  24 //  fall-back(s) in MathML when some (freely-downloadable) fonts are missing.
  25 //  Otherwise, this will add much work and unnecessary complexity to the core
  26 //  MathML  engine. Assuming that authors have the free fonts is part of the
  27 //  deal. We are not responsible for cases of misconfigurations out there.
  28
  29 // additional style context to be used by our MathMLChar.
  30 #define NS_SQR_CHAR_STYLE_CONTEXT_INDEX   0
  31
  32 static const PRUnichar kSqrChar = PRUnichar(0x221A);
  33
  34 nsIFrame*
  35 NS_NewMathMLmrootFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
  36 {
  37   return new (aPresShell) nsMathMLmrootFrame(aContext);
  38 }
  39
  40 NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmrootFrame)
  41
  42 nsMathMLmrootFrame::nsMathMLmrootFrame(nsStyleContext* aContext) :
  43   nsMathMLContainerFrame(aContext),
  44   mSqrChar(),
  45   mBarRect()
  46 {
  47 }
  48
  49 nsMathMLmrootFrame::~nsMathMLmrootFrame()
  50 {
  51 }
  52
  53 NS_IMETHODIMP
  54 nsMathMLmrootFrame::Init(nsIContent*      aContent,
  55                          nsIFrame*        aParent,
  56                          nsIFrame*        aPrevInFlow)
  57 {
  58   nsresult rv = nsMathMLContainerFrame::Init(aContent, aParent, aPrevInFlow);
  59
  60   nsPresContext *presContext = PresContext();
  61
  62   // No need to track the style context given to our MathML char.
  63   // The Style System will use Get/SetAdditionalStyleContext() to keep it
  64   // up-to-date if dynamic changes arise.
  65   nsAutoString sqrChar; sqrChar.Assign(kSqrChar);
  66   mSqrChar.SetData(presContext, sqrChar);
  67   ResolveMathMLCharStyle(presContext, mContent, mStyleContext, &mSqrChar, true);
  68
  69   return rv;
  70 }
  71
  72 NS_IMETHODIMP
  73 nsMathMLmrootFrame::TransmitAutomaticData()
  74 {
  75   // 1. The REC says:
  76   //    The <mroot> element increments scriptlevel by 2, and sets displaystyle to
  77   //    "false", within index, but leaves both attributes unchanged within base.
  78   // 2. The TeXbook (Ch 17. p.141) says \sqrt is compressed
  79   UpdatePresentationDataFromChildAt(1, 1,
  80     ~NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED,
  81      NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED);
  82   UpdatePresentationDataFromChildAt(0, 0,
  83      NS_MATHML_COMPRESSED, NS_MATHML_COMPRESSED);
  84
  85   return NS_OK;
  86 }
  87
  88 NS_IMETHODIMP
  89 nsMathMLmrootFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
  90                                      const nsRect&           aDirtyRect,
  91                                      const nsDisplayListSet& aLists)
  92 {
  93   /////////////
  94   // paint the content we are square-rooting
  95   nsresult rv = nsMathMLContainerFrame::BuildDisplayList(aBuilder, aDirtyRect, aLists);
  96   NS_ENSURE_SUCCESS(rv, rv);
  97
  98   /////////////
  99   // paint the sqrt symbol
 100   if (!NS_MATHML_HAS_ERROR(mPresentationData.flags)) {
 101     rv = mSqrChar.Display(aBuilder, this, aLists, 0);
 102     NS_ENSURE_SUCCESS(rv, rv);
 103
 104     rv = DisplayBar(aBuilder, this, mBarRect, aLists);
 105     NS_ENSURE_SUCCESS(rv, rv);
 106
 107 #if defined(DEBUG) && defined(SHOW_BOUNDING_BOX)
 108     // for visual debug
 109     nsRect rect;
 110     mSqrChar.GetRect(rect);
 111     nsBoundingMetrics bm;
 112     mSqrChar.GetBoundingMetrics(bm);
 113     rv = DisplayBoundingMetrics(aBuilder, this, rect.TopLeft(), bm, aLists);
 114 #endif
 115   }
 116
 117   return rv;
 118 }
 119
 120 static void
 121 GetRadicalXOffsets(nscoord aIndexWidth, nscoord aSqrWidth,
 122                    nsFontMetrics* aFontMetrics,
 123                    nscoord* aIndexOffset, nscoord* aSqrOffset)
 124 {
 125   // The index is tucked in closer to the radical while making sure
 126   // that the kern does not make the index and radical collide
 127   nscoord dxIndex, dxSqr;
 128   nscoord xHeight = aFontMetrics->XHeight();
 129   nscoord indexRadicalKern = NSToCoordRound(1.35f * xHeight);
 130   if (indexRadicalKern > aIndexWidth) {
 131     dxIndex = indexRadicalKern - aIndexWidth;
 132     dxSqr = 0;
 133   }
 134   else {
 135     dxIndex = 0;
 136     dxSqr = aIndexWidth - indexRadicalKern;
 137   }
 138   // avoid collision by leaving a minimum space between index and radical
 139   nscoord minimumClearance = aSqrWidth/2;
 140   if (dxIndex + aIndexWidth + minimumClearance > dxSqr + aSqrWidth) {
 141     if (aIndexWidth + minimumClearance < aSqrWidth) {
 142       dxIndex = aSqrWidth - (aIndexWidth + minimumClearance);
 143       dxSqr = 0;
 144     }
 145     else {
 146       dxIndex = 0;
 147       dxSqr = (aIndexWidth + minimumClearance) - aSqrWidth;
 148     }
 149   }
 150
 151   if (aIndexOffset)
 152     *aIndexOffset = dxIndex;
 153   if (aSqrOffset)
 154     *aSqrOffset = dxSqr;
 155 }
 156
 157 NS_IMETHODIMP
 158 nsMathMLmrootFrame::Reflow(nsPresContext*          aPresContext,
 159                            nsHTMLReflowMetrics&     aDesiredSize,
 160                            const nsHTMLReflowState& aReflowState,
 161                            nsReflowStatus&          aStatus)
 162 {
 163   nsresult rv = NS_OK;
 164   nsSize availSize(aReflowState.ComputedWidth(), NS_UNCONSTRAINEDSIZE);
 165   nsReflowStatus childStatus;
 166
 167   aDesiredSize.width = aDesiredSize.height = 0;
 168   aDesiredSize.ascent = 0;
 169
 170   nsBoundingMetrics bmSqr, bmBase, bmIndex;
 171   nsRenderingContext& renderingContext = *aReflowState.rendContext;
 172
 173   //////////////////
 174   // Reflow Children
 175
 176   int32_t count = 0;
 177   nsIFrame* baseFrame = nullptr;
 178   nsIFrame* indexFrame = nullptr;
 179   nsHTMLReflowMetrics baseSize;
 180   nsHTMLReflowMetrics indexSize;
 181   nsIFrame* childFrame = mFrames.FirstChild();
 182   while (childFrame) {
 183     // ask our children to compute their bounding metrics
 184     nsHTMLReflowMetrics childDesiredSize(aDesiredSize.mFlags
 185                                          | NS_REFLOW_CALC_BOUNDING_METRICS);
 186     nsHTMLReflowState childReflowState(aPresContext, aReflowState,
 187                                        childFrame, availSize);
 188     rv = ReflowChild(childFrame, aPresContext,
 189                      childDesiredSize, childReflowState, childStatus);
 190     //NS_ASSERTION(NS_FRAME_IS_COMPLETE(childStatus), "bad status");
 191     if (NS_FAILED(rv)) {
 192       // Call DidReflow() for the child frames we successfully did reflow.
 193       DidReflowChildren(mFrames.FirstChild(), childFrame);
 194       return rv;
 195     }
 196     if (0 == count) {
 197       // base
 198       baseFrame = childFrame;
 199       baseSize = childDesiredSize;
 200       bmBase = childDesiredSize.mBoundingMetrics;
 201     }
 202     else if (1 == count) {
 203       // index
 204       indexFrame = childFrame;
 205       indexSize = childDesiredSize;
 206       bmIndex = childDesiredSize.mBoundingMetrics;
 207     }
 208     count++;
 209     childFrame = childFrame->GetNextSibling();
 210   }
 211   if (2 != count) {
 212     // report an error, encourage people to get their markups in order
 213     rv = ReflowError(renderingContext, aDesiredSize);
 214     aStatus = NS_FRAME_COMPLETE;
 215     NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
 216     // Call DidReflow() for the child frames we successfully did reflow.
 217     DidReflowChildren(mFrames.FirstChild(), childFrame);
 218     return rv;
 219   }
 220
 221   ////////////
 222   // Prepare the radical symbol and the overline bar
 223
 224   nsRefPtr<nsFontMetrics> fm;
 225   nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
 226   renderingContext.SetFont(fm);
 227
 228   // For radical glyphs from TeX fonts and some of the radical glyphs from
 229   // Mathematica fonts, the thickness of the overline can be obtained from the
 230   // ascent of the glyph.  Most fonts however have radical glyphs above the
 231   // baseline so no assumption can be made about the meaning of the ascent.
 232   nscoord ruleThickness, leading, em;
 233   GetRuleThickness(renderingContext, fm, ruleThickness);
 234
 235   PRUnichar one = '1';
 236   nsBoundingMetrics bmOne = renderingContext.GetBoundingMetrics(&one, 1);
 237
 238   // get the leading to be left at the top of the resulting frame
 239   // this seems more reliable than using fm->GetLeading() on suspicious fonts
 240   GetEmHeight(fm, em);
 241   leading = nscoord(0.2f * em);
 242
 243   // Rule 11, App. G, TeXbook
 244   // psi = clearance between rule and content
 245   nscoord phi = 0, psi = 0;
 246   if (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags))
 247     phi = fm->XHeight();
 248   else
 249     phi = ruleThickness;
 250   psi = ruleThickness + phi/4;
 251
 252   // built-in: adjust clearance psi to emulate \mathstrut using '1' (TexBook, p.131)
 253   if (bmOne.ascent > bmBase.ascent)
 254     psi += bmOne.ascent - bmBase.ascent;
 255
 256   // make sure that the rule appears on on screen
 257   nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
 258   if (ruleThickness < onePixel) {
 259     ruleThickness = onePixel;
 260   }
 261
 262   // adjust clearance psi to get an exact number of pixels -- this
 263   // gives a nicer & uniform look on stacked radicals (bug 130282)
 264   nscoord delta = psi % onePixel;
 265   if (delta)
 266     psi += onePixel - delta; // round up
 267
 268   // Stretch the radical symbol to the appropriate height if it is not big enough.
 269   nsBoundingMetrics contSize = bmBase;
 270   contSize.descent = bmBase.ascent + bmBase.descent + psi;
 271   contSize.ascent = ruleThickness;
 272
 273   // height(radical) should be >= height(base) + psi + ruleThickness
 274   nsBoundingMetrics radicalSize;
 275   mSqrChar.Stretch(aPresContext, renderingContext,
 276                    NS_STRETCH_DIRECTION_VERTICAL,
 277                    contSize, radicalSize,
 278                    NS_STRETCH_LARGER,
 279                    NS_MATHML_IS_RTL(mPresentationData.flags));
 280   // radicalSize have changed at this point, and should match with
 281   // the bounding metrics of the char
 282   mSqrChar.GetBoundingMetrics(bmSqr);
 283
 284   // Update the desired size for the container (like msqrt, index is not yet included)
 285   // the baseline will be that of the base.
 286   mBoundingMetrics.ascent = bmBase.ascent + psi + ruleThickness;
 287   mBoundingMetrics.descent =
 288     NS_MAX(bmBase.descent,
 289            (bmSqr.ascent + bmSqr.descent - mBoundingMetrics.ascent));
 290   mBoundingMetrics.width = bmSqr.width + bmBase.width;
 291   mBoundingMetrics.leftBearing = bmSqr.leftBearing;
 292   mBoundingMetrics.rightBearing = bmSqr.width +
 293     NS_MAX(bmBase.width, bmBase.rightBearing); // take also care of the rule
 294
 295   aDesiredSize.ascent = mBoundingMetrics.ascent + leading;
 296   aDesiredSize.height = aDesiredSize.ascent +
 297     NS_MAX(baseSize.height - baseSize.ascent,
 298            mBoundingMetrics.descent + ruleThickness);
 299   aDesiredSize.width = mBoundingMetrics.width;
 300
 301   /////////////
 302   // Re-adjust the desired size to include the index.
 303
 304   // the index is raised by some fraction of the height
 305   // of the radical, see \mroot macro in App. B, TexBook
 306   nscoord raiseIndexDelta = NSToCoordRound(0.6f * (bmSqr.ascent + bmSqr.descent));
 307   nscoord indexRaisedAscent = mBoundingMetrics.ascent // top of radical
 308     - (bmSqr.ascent + bmSqr.descent) // to bottom of radical
 309     + raiseIndexDelta + bmIndex.ascent + bmIndex.descent; // to top of raised index
 310
 311   nscoord indexClearance = 0;
 312   if (mBoundingMetrics.ascent < indexRaisedAscent) {
 313     indexClearance =
 314       indexRaisedAscent - mBoundingMetrics.ascent; // excess gap introduced by a tall index
 315     mBoundingMetrics.ascent = indexRaisedAscent;
 316     nscoord descent = aDesiredSize.height - aDesiredSize.ascent;
 317     aDesiredSize.ascent = mBoundingMetrics.ascent + leading;
 318     aDesiredSize.height = aDesiredSize.ascent + descent;
 319   }
 320
 321   nscoord dxIndex, dxSqr;
 322   GetRadicalXOffsets(bmIndex.width, bmSqr.width, fm, &dxIndex, &dxSqr);
 323
 324   mBoundingMetrics.width = dxSqr + bmSqr.width + bmBase.width;
 325   mBoundingMetrics.leftBearing =
 326     NS_MIN(dxIndex + bmIndex.leftBearing, dxSqr + bmSqr.leftBearing);
 327   mBoundingMetrics.rightBearing = dxSqr + bmSqr.width +
 328     NS_MAX(bmBase.width, bmBase.rightBearing);
 329
 330   aDesiredSize.width = mBoundingMetrics.width;
 331   aDesiredSize.mBoundingMetrics = mBoundingMetrics;
 332   GatherAndStoreOverflow(&aDesiredSize);
 333
 334   // place the index
 335   nscoord dx = dxIndex;
 336   nscoord dy = aDesiredSize.ascent - (indexRaisedAscent + indexSize.ascent - bmIndex.ascent);
 337   FinishReflowChild(indexFrame, aPresContext, nullptr, indexSize,
 338                     MirrorIfRTL(aDesiredSize.width, indexSize.width, dx),
 339                     dy, 0);
 340
 341   // place the radical symbol and the radical bar
 342   dx = dxSqr;
 343   dy = indexClearance + leading; // leave a leading at the top
 344   mSqrChar.SetRect(nsRect(MirrorIfRTL(aDesiredSize.width, bmSqr.width, dx),
 345                           dy, bmSqr.width, bmSqr.ascent + bmSqr.descent));
 346   dx += bmSqr.width;
 347   mBarRect.SetRect(MirrorIfRTL(aDesiredSize.width, bmBase.width, dx),
 348                    dy, bmBase.width, ruleThickness);
 349
 350   // place the base
 351   dy = aDesiredSize.ascent - baseSize.ascent;
 352   FinishReflowChild(baseFrame, aPresContext, nullptr, baseSize,
 353                     MirrorIfRTL(aDesiredSize.width, baseSize.width, dx),
 354                     dy, 0);
 355
 356   mReference.x = 0;
 357   mReference.y = aDesiredSize.ascent;
 358
 359   aStatus = NS_FRAME_COMPLETE;
 360   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
 361   return NS_OK;
 362 }
 363
 364 /* virtual */ nscoord
 365 nsMathMLmrootFrame::GetIntrinsicWidth(nsRenderingContext* aRenderingContext)
 366 {
 367   nsIFrame* baseFrame = mFrames.FirstChild();
 368   nsIFrame* indexFrame = nullptr;
 369   if (baseFrame)
 370     indexFrame = baseFrame->GetNextSibling();
 371   if (!indexFrame || indexFrame->GetNextSibling()) {
 372     nsHTMLReflowMetrics desiredSize;
 373     ReflowError(*aRenderingContext, desiredSize);
 374     return desiredSize.width;
 375   }
 376
 377   nscoord baseWidth =
 378     nsLayoutUtils::IntrinsicForContainer(aRenderingContext, baseFrame,
 379                                          nsLayoutUtils::PREF_WIDTH);
 380   nscoord indexWidth =
 381     nsLayoutUtils::IntrinsicForContainer(aRenderingContext, indexFrame,
 382                                          nsLayoutUtils::PREF_WIDTH);
 383   nscoord sqrWidth = mSqrChar.GetMaxWidth(PresContext(), *aRenderingContext);
 384
 385   nscoord dxSqr;
 386   GetRadicalXOffsets(indexWidth, sqrWidth, aRenderingContext->FontMetrics(),
 387                      nullptr, &dxSqr);
 388
 389   return dxSqr + sqrWidth + baseWidth;
 390 }
 391
 392 // ----------------------
 393 // the Style System will use these to pass the proper style context to our MathMLChar
 394 nsStyleContext*
 395 nsMathMLmrootFrame::GetAdditionalStyleContext(int32_t aIndex) const
 396 {
 397   switch (aIndex) {
 398   case NS_SQR_CHAR_STYLE_CONTEXT_INDEX:
 399     return mSqrChar.GetStyleContext();
 400     break;
 401   default:
 402     return nullptr;
 403   }
 404 }
 405
 406 void
 407 nsMathMLmrootFrame::SetAdditionalStyleContext(int32_t          aIndex,
 408                                               nsStyleContext*  aStyleContext)
 409 {
 410   switch (aIndex) {
 411   case NS_SQR_CHAR_STYLE_CONTEXT_INDEX:
 412     mSqrChar.SetStyleContext(aStyleContext);
 413     break;
 414   }
 415 }