Bug 850655 - Make CharIterator::Next() not crash when at the end of text. r=longsonr

--HG--
extra : rebase_source : 830fa0fda257401a77c1aae8686aa5ab6db18d86

content/svg/content/src/SVGTextContentElement.cpp

@@ -75,16 +75,9 @@ SVGTextContentElement::GetSubStringLength(uint32_t charnum, uint32_t nchars, Err
     if (!textFrame)
       return 0.0f;
 
-    uint32_t charcount = textFrame->GetNumberOfChars(this);
-    if (charcount <= charnum || nchars > charcount - charnum) {
-      rv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
-      return 0.0f;
-    }
-
-    if (nchars == 0)
-      return 0.0f;
-
-    return textFrame->GetSubStringLength(this, charnum, nchars);
+    float length = 0.0f;
+    rv = textFrame->GetSubStringLength(this, charnum, nchars, &length);
+    return length;
   } else {
     nsSVGTextContainerFrame* metrics = GetTextContainerFrame();
     if (!metrics)

layout/svg/nsSVGTextFrame2.cpp

@@ -2293,6 +2293,9 @@ CharIterator::Next()
 bool
 CharIterator::Next(uint32_t aCount)
 {
+  if (aCount == 0 && AtEnd()) {
+    return false;
+  }
   while (aCount) {
     if (!Next()) {
       return false;
@@ -2479,6 +2482,10 @@ CharIterator::GetGlyphPartialAdvance(uint32_t aPartOffset, uint32_t aPartLength,
 bool
 CharIterator::NextCharacter()
 {
+  if (AtEnd()) {
+    return false;
+  }
+
   mTextElementCharIndex++;
 
   // Advance within the current text run.
@@ -3646,9 +3653,10 @@ nsSVGTextFrame2::GetComputedTextLength(nsIContent* aContent)
  * Implements the SVG DOM GetSubStringLength method for the specified
  * text content element.
  */
-float
+nsresult
 nsSVGTextFrame2::GetSubStringLength(nsIContent* aContent,
-                                    uint32_t charnum, uint32_t nchars)
+                                    uint32_t charnum, uint32_t nchars,
+                                    float* aResult)
 {
   UpdateGlyphPositioning(false);
 
@@ -3656,11 +3664,16 @@ nsSVGTextFrame2::GetSubStringLength(nsIContent* aContent,
   // aContent to global character indices.
   CharIterator chit(this, CharIterator::eAddressable, aContent);
   if (!chit.AdvanceToSubtree() ||
-      chit.AtEnd() ||
       !chit.Next(charnum) ||
       chit.IsAfterSubtree()) {
-    return 0.0f;
+    return NS_ERROR_DOM_INDEX_SIZE_ERR;
   }
+
+  if (nchars == 0) {
+    *aResult = 0.0f;
+    return NS_OK;
+  }
+
   charnum = chit.TextElementCharIndex();
   chit.NextWithinSubtree(nchars);
   nchars = chit.TextElementCharIndex() - charnum;
@@ -3703,8 +3716,9 @@ nsSVGTextFrame2::GetSubStringLength(nsIContent* aContent,
   float cssPxPerDevPx = presContext->
     AppUnitsToFloatCSSPixels(presContext->AppUnitsPerDevPixel());
 
-  return presContext->AppUnitsToGfxUnits(textLength) *
-           cssPxPerDevPx / mFontSizeScaleFactor;
+  *aResult = presContext->AppUnitsToGfxUnits(textLength) *
+               cssPxPerDevPx / mFontSizeScaleFactor;
+  return NS_OK;
 }
 
 /**
@@ -3752,7 +3766,6 @@ nsSVGTextFrame2::GetStartPositionOfChar(nsIContent* aContent,
 
   CharIterator it(this, CharIterator::eAddressable, aContent);
   if (!it.AdvanceToSubtree() ||
-      it.AtEnd() ||
       !it.Next(aCharNum)) {
     return NS_ERROR_DOM_INDEX_SIZE_ERR;
   }
@@ -3777,7 +3790,6 @@ nsSVGTextFrame2::GetEndPositionOfChar(nsIContent* aContent,
 
   CharIterator it(this, CharIterator::eAddressable, aContent);
   if (!it.AdvanceToSubtree() ||
-      it.AtEnd() ||
       !it.Next(aCharNum)) {
     return NS_ERROR_DOM_INDEX_SIZE_ERR;
   }
@@ -3815,7 +3827,6 @@ nsSVGTextFrame2::GetExtentOfChar(nsIContent* aContent,
 
   CharIterator it(this, CharIterator::eAddressable, aContent);
   if (!it.AdvanceToSubtree() ||
-      it.AtEnd() ||
       !it.Next(aCharNum)) {
     return NS_ERROR_DOM_INDEX_SIZE_ERR;
   }
@@ -3867,7 +3878,6 @@ nsSVGTextFrame2::GetRotationOfChar(nsIContent* aContent,
 
   CharIterator it(this, CharIterator::eAddressable, aContent);
   if (!it.AdvanceToSubtree() ||
-      it.AtEnd() ||
       !it.Next(aCharNum)) {
     return NS_ERROR_DOM_INDEX_SIZE_ERR;
   }

layout/svg/nsSVGTextFrame2.h

@@ -259,7 +259,8 @@ public:
   // SVG DOM text methods:
   uint32_t GetNumberOfChars(nsIContent* aContent);
   float GetComputedTextLength(nsIContent* aContent);
-  float GetSubStringLength(nsIContent* aContent, uint32_t charnum, uint32_t nchars);
+  nsresult GetSubStringLength(nsIContent* aContent, uint32_t charnum,
+                              uint32_t nchars, float* aResult);
   int32_t GetCharNumAtPosition(nsIContent* aContent, mozilla::nsISVGPoint* point);
 
   nsresult GetStartPositionOfChar(nsIContent* aContent, uint32_t aCharNum,