Basic bidi support for SVG. Bug 620446, r=roc, a=roc

gfx/thebes/Makefile.in

@@ -36,6 +36,7 @@ EXPORTS	= \
 	gfxTypes.h \
 	gfxTextRunCache.h \
 	gfxTextRunWordCache.h \
+	gfxUnicodeProperties.h \
 	gfxUtils.h \
 	gfxUserFontSet.h \
 	GLDefs.h \

gfx/thebes/gfxUnicodeProperties.h

@@ -39,8 +39,9 @@
 #define GFX_UNICODEPROPERTIES_H
 
 #include "prtypes.h"
+#include "gfxTypes.h"
 
-class gfxUnicodeProperties
+class THEBES_API gfxUnicodeProperties
 {
 public:
     static PRUint32 GetMirroredChar(PRUint32 aCh);

layout/base/nsBidi.cpp

@@ -1116,15 +1116,15 @@ void nsBidi::AdjustWSLevels()
     }
   }
 }
-#ifdef FULL_BIDI_ENGINE
-
-/* -------------------------------------------------------------------------- */
 
 nsresult nsBidi::GetDirection(nsBidiDirection* aDirection)
 {
   *aDirection = mDirection;
   return NS_OK;
 }
+#ifdef FULL_BIDI_ENGINE
+
+/* -------------------------------------------------------------------------- */
 
 nsresult nsBidi::GetLength(PRInt32* aLength)
 {

layout/base/nsBidi.h

@@ -510,6 +510,17 @@ class nsBidi
    */
   nsresult SetPara(const PRUnichar *aText, PRInt32 aLength, nsBidiLevel aParaLevel, nsBidiLevel *aEmbeddingLevels);
 
+  /**
+   * Get the directionality of the text.
+   *
+   * @param aDirection receives a <code>NSBIDI_XXX</code> value that indicates if the entire text
+   *       represented by this object is unidirectional,
+   *       and which direction, or if it is mixed-directional.
+   *
+   * @see nsBidiDirection
+   */
+  nsresult GetDirection(nsBidiDirection* aDirection);
+
 #ifdef FULL_BIDI_ENGINE
   /**
    * <code>SetLine</code> sets an <code>nsBidi</code> to
@@ -546,17 +557,6 @@ class nsBidi
    */
   nsresult SetLine(nsIBidi* aParaBidi, PRInt32 aStart, PRInt32 aLimit);  
 
-  /**
-   * Get the directionality of the text.
-   *
-   * @param aDirection receives a <code>NSBIDI_XXX</code> value that indicates if the entire text
-   *       represented by this object is unidirectional,
-   *       and which direction, or if it is mixed-directional.
-   *
-   * @see nsBidiDirection
-   */
-  nsresult GetDirection(nsBidiDirection* aDirection);
-
   /**
    * Get the length of the text.
    *

layout/base/nsBidiPresUtils.cpp

@@ -55,6 +55,7 @@
 #include "nsPlaceholderFrame.h"
 #include "nsContainerFrame.h"
 #include "nsFirstLetterFrame.h"
+#include "gfxUnicodeProperties.h"
 
 using namespace mozilla;
 
@@ -1683,6 +1684,139 @@ nsresult nsBidiPresUtils::ProcessTextForRenderingContext(const PRUnichar*
                      aMode, aPosResolve, aPosResolveCount, aWidth);
 }
 
+/* static */
+void nsBidiPresUtils::WriteReverse(const PRUnichar* aSrc,
+                                   PRUint32 aSrcLength,
+                                   PRUnichar* aDest)
+{
+  const PRUnichar* src = aSrc + aSrcLength;
+  PRUnichar* dest = aDest;
+  PRUint32 UTF32Char;
+
+  while (--src >= aSrc) {
+    if (NS_IS_LOW_SURROGATE(*src)) {
+      if (src > aSrc && NS_IS_HIGH_SURROGATE(*(src - 1))) {
+        UTF32Char = SURROGATE_TO_UCS4(*(src - 1), *src);
+        --src;
+      } else {
+        UTF32Char = UCS2_REPLACEMENT_CHAR;
+      }
+    } else if (NS_IS_HIGH_SURROGATE(*src)) {
+      // paired high surrogates are handled above, so this is a lone high surrogate
+      UTF32Char = UCS2_REPLACEMENT_CHAR;
+    } else {
+      UTF32Char = *src;
+    }
+
+    UTF32Char = gfxUnicodeProperties::GetMirroredChar(UTF32Char);
+
+    if (IS_IN_BMP(UTF32Char)) {
+      *(dest++) = UTF32Char;
+    } else {
+      *(dest++) = H_SURROGATE(UTF32Char);
+      *(dest++) = L_SURROGATE(UTF32Char);
+    }
+  }
+
+  NS_ASSERTION(dest - aDest == aSrcLength, "Whole string not copied");
+}
+
+/* static */
+PRBool nsBidiPresUtils::WriteLogicalToVisual(const PRUnichar* aSrc,
+                                             PRUint32 aSrcLength,
+                                             PRUnichar* aDest,
+                                             nsBidiLevel aBaseDirection,
+                                             nsBidi* aBidiEngine)
+{
+  const PRUnichar* src = aSrc;
+  nsresult rv = aBidiEngine->SetPara(src, aSrcLength, aBaseDirection, nsnull);
+  if (NS_FAILED(rv)) {
+    return PR_FALSE;
+  }
+
+  nsBidiDirection dir;
+  rv = aBidiEngine->GetDirection(&dir);
+  // NSBIDI_LTR returned from GetDirection means the whole text is LTR
+  if (NS_FAILED(rv) || dir == NSBIDI_LTR) {
+    return PR_FALSE;
+  }
+
+  PRInt32 runCount;
+  rv = aBidiEngine->CountRuns(&runCount);
+  if (NS_FAILED(rv)) {
+    return PR_FALSE;
+  }
+
+  PRInt32 runIndex, start, length;
+  PRUnichar* dest = aDest;
+
+  for (runIndex = 0; runIndex < runCount; ++runIndex) {
+    rv = aBidiEngine->GetVisualRun(runIndex, &start, &length, &dir);
+    if (NS_FAILED(rv)) {
+      return PR_FALSE;
+    }
+
+    src = aSrc + start;
+
+    if (dir == NSBIDI_RTL) {
+      WriteReverse(src, length, dest);
+      dest += length;
+    } else {
+      do {
+        NS_ASSERTION(src >= aSrc && src < aSrc + aSrcLength,
+                     "logical index out of range");
+        NS_ASSERTION(dest < aDest + aSrcLength, "visual index out of range");
+        *(dest++) = *(src++);
+      } while (--length);
+    }
+  }
+
+  NS_ASSERTION(dest - aDest == aSrcLength, "whole string not copied");
+  return PR_TRUE;
+}
+
+void nsBidiPresUtils::CopyLogicalToVisual(const nsAString& aSource,
+                                          nsAString& aDest,
+                                          nsBidiLevel aBaseDirection,
+                                          PRBool aOverride)
+{
+  aDest.SetLength(0);
+  PRUint32 srcLength = aSource.Length();
+  if (srcLength == 0)
+    return;
+  if (!EnsureStringLength(aDest, srcLength)) {
+    return;
+  }
+  nsAString::const_iterator fromBegin, fromEnd;
+  nsAString::iterator toBegin;
+  aSource.BeginReading(fromBegin);
+  aSource.EndReading(fromEnd);
+  aDest.BeginWriting(toBegin);
+
+  if (aOverride) {
+    if (aBaseDirection == NSBIDI_RTL) {
+      // no need to use the converter -- just copy the string in reverse order
+      WriteReverse(fromBegin.get(), srcLength, toBegin.get());
+    } else {
+      // if aOverride && aBaseDirection == NSBIDI_LTR, fall through to the
+      // simple copy
+      aDest.SetLength(0);
+    }
+  } else {
+    if (!WriteLogicalToVisual(fromBegin.get(), srcLength, toBegin.get(),
+                             aBaseDirection, mBidiEngine)) {
+      aDest.SetLength(0);
+    }
+  }
+
+  if (aDest.IsEmpty()) {
+    // Either there was an error or the source is unidirectional
+    //  left-to-right. In either case, just copy source to dest.
+    CopyUnicodeTo(aSource.BeginReading(fromBegin), aSource.EndReading(fromEnd),
+                  aDest);
+  }
+}
+
 PRUint32 nsBidiPresUtils::EstimateMemoryUsed()
 {
   PRUint32 size = 0;

layout/base/nsBidiPresUtils.h

@@ -317,6 +317,24 @@ class nsBidiPresUtils {
                        PRInt32                aPosResolveCount,
                        nscoord*               aWidth);
 
+  /**
+   * Make a copy of a string, converting from logical to visual order
+   *
+   * @param aSource the source string
+   * @param aDest the destination string
+   * @param aBaseDirection the base direction of the string
+   *       (NSBIDI_LTR or NSBIDI_RTL to force the base direction;
+   *        NSBIDI_DEFAULT_LTR or NSBIDI_DEFAULT_RTL to let the bidi engine
+   *        determine the direction from rules P2 and P3 of the bidi algorithm.
+   *  @see nsBidi::GetPara
+   * @param aOverride if TRUE, the text has a bidi override, according to
+   *                    the direction in aDir
+   */
+  void CopyLogicalToVisual(const nsAString& aSource,
+                           nsAString& aDest,
+                           nsBidiLevel aBaseDirection,
+                           PRBool aOverride);
+
   /**
    * Guess at how much memory is being used by this nsBidiPresUtils instance,
    * including memory used by nsBidi.
@@ -477,6 +495,17 @@ class nsBidiPresUtils {
 
   void StripBidiControlCharacters(PRUnichar* aText,
                                   PRInt32&   aTextLength) const;
+
+  static PRBool WriteLogicalToVisual(const PRUnichar* aSrc,
+                                     PRUint32 aSrcLength,
+                                     PRUnichar* aDest,
+                                     nsBidiLevel aBaseDirection,
+                                     nsBidi* aBidiEngine);
+
+ static void WriteReverse(const PRUnichar* aSrc,
+                          PRUint32 aSrcLength,
+                          PRUnichar* aDest);
+
   nsAutoString    mBuffer;
   nsTArray<nsIFrame*> mLogicalFrames;
   nsTArray<nsIFrame*> mVisualFrames;

layout/svg/base/src/nsSVGGlyphFrame.cpp

@@ -39,6 +39,7 @@
 #include "nsSVGTextFrame.h"
 #include "nsILookAndFeel.h"
 #include "nsTextFragment.h"
+#include "nsBidiPresUtils.h"
 #include "nsSVGUtils.h"
 #include "SVGLengthList.h"
 #include "nsIDOMSVGLength.h"
@@ -1548,6 +1549,50 @@ nsSVGGlyphFrame::EnsureTextRun(float *aDrawScale, float *aMetricsScale,
     if (!GetCharacterData(text))
       return PR_FALSE;
 
+    nsBidiPresUtils* bidiUtils = presContext->GetBidiUtils();
+    if (bidiUtils) {
+      nsAutoString visualText;
+
+      /*
+       * XXXsmontagu: The SVG spec says:
+       *
+       * http://www.w3.org/TR/SVG11/text.html#DirectionProperty
+       *  "For the 'direction' property to have any effect, the 'unicode-bidi'
+       *   property's value must be embed or bidi-override."
+       *
+       * The SVGTiny spec, on the other hand, says 
+       *
+       * http://www.w3.org/TR/SVGTiny12/text.html#DirectionProperty
+       *  "For the 'direction' property to have any effect on an element that 
+       *   does not by itself establish a new text chunk (such as the 'tspan'
+       *   element in SVG 1.2 Tiny), the 'unicode-bidi' property's value must
+       *   be embed or bidi-override."
+       *
+       * Note that this is different from HTML/CSS, where setting the 'dir'
+       *  attribute on an inline element automatically sets unicode-bidi: embed
+       *
+       * Our current implementation of bidi in SVG does not distinguish between
+       * different text elements, but treats every text container frame as a
+       * new text chunk, so we always set the base direction according to the
+       * direction property
+       *
+       * See also XXXsmontagu comments in nsSVGTextFrame::UpdateGlyphPositioning
+       */
+
+      // Get the unicodeBidi property from the parent, because it doesn't
+      // inherit
+      PRBool bidiOverride = (mParent->GetStyleTextReset()->mUnicodeBidi ==
+                             NS_STYLE_UNICODE_BIDI_OVERRIDE);
+      nsBidiLevel baseDirection =
+        GetStyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL ?
+          NSBIDI_RTL : NSBIDI_LTR;
+      bidiUtils->CopyLogicalToVisual(text, visualText,
+                                     baseDirection, bidiOverride);
+      if (!visualText.IsEmpty()) {
+        text = visualText;
+      }
+    }
+
     gfxMatrix m;
     if (aForceGlobalTransform ||
         !(GetStateBits() & NS_STATE_SVG_NONDISPLAY_CHILD)) {

layout/svg/base/src/nsSVGTextFrame.cpp

@@ -341,6 +341,39 @@ nsSVGTextFrame::UpdateGlyphPositioning(PRBool aForceGlobalTransform)
 
     PRUint8 anchor = firstFragment->GetTextAnchor();
 
+    /**
+     * XXXsmontagu: The SVG spec is very vague as to how 'text-anchor'
+     *  interacts with bidirectional text. It says:
+     *
+     *   "For scripts that are inherently right to left such as Hebrew and
+     *   Arabic [text-anchor: start] is equivalent to right alignment."
+     * and
+     *   "For scripts that are inherently right to left such as Hebrew and
+     *   Arabic, [text-anchor: end] is equivalent to left alignment.
+     *
+     * It's not clear how this should be implemented in terms of defined
+     * properties, i.e. how one should determine that a particular element
+     * contains a script that is inherently right to left.
+     *
+     * The code below follows http://www.w3.org/TR/SVGTiny12/text.html#TextAnchorProperty
+     * and swaps the values of text-anchor: end and  text-anchor: start
+     * whenever the 'direction' property is rtl.
+     *
+     * This is probably the "right" thing to do, but other browsers don't do it,
+     * so I am leaving it inside #if 0 for now for interoperability.
+     *
+     * See also XXXsmontagu comments in nsSVGGlyphFrame::EnsureTextRun
+     */
+#if 0
+    if (GetStyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL) {
+      if (anchor == NS_STYLE_TEXT_ANCHOR_END) {
+        anchor = NS_STYLE_TEXT_ANCHOR_START;
+      } else if (anchor == NS_STYLE_TEXT_ANCHOR_START) {
+        anchor = NS_STYLE_TEXT_ANCHOR_END;
+      }
+    }
+#endif
+
     float chunkLength = 0.0f;
     if (anchor != NS_STYLE_TEXT_ANCHOR_START) {
       // need to get the total chunk length