Canvas fillText and measureText handle ideographic spaces differently.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index 8456aba1db2b4de549857a809bf166dec4e1618a..b50c659131612b902e53fd4e4b13dfa008e815a5 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -2024,6 +2024,32 @@ void CanvasRenderingContext2D::strokeText(const String& text, float x, float y,
     drawTextInternal(text, x, y, false, maxWidth, true);
 }
 
+static inline bool isSpaceCharacters(UChar c)

[Justin Novosad, 2014/05/21 15:14:46]

Remove 's' at the end of name. There is just one character.

+{
+    // According to specification all space characters should be replaced with 0x0020 space character.
+    // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#text-preparation-algorithm
+    // The space characters according to specification are : U+0020, U+0009, U+000A, U+000C, and U+000D.
+    // http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#space-character
+    // This function returns true for 0x000B also, so that this is backward compatible.
+    // Otherwise, the test LayoutTests/canvas/philip/tests/2d.text.draw.space.collapse.space.html will fail
+    return c == 0x0009 || c == 0x000A || c == 0x000B || c == 0x000C || c == 0x000D;
+}
+
+static String normalizeSpaces(const String& text)
+{
+    unsigned textLength = text.length();
+    Vector<UChar> charVector(textLength);
+
+    for (unsigned i = 0; i < textLength; i++) {
+        if (isSpaceCharacters(text[i]))
+            charVector[i] = ' ';
+        else
+            charVector[i] = text[i];
+    }
+
+    return String(charVector);
+}
+
 PassRefPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text)
 {
     RefPtr<TextMetrics> metrics = TextMetrics::create();
@@ -2035,7 +2061,8 @@ PassRefPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text
     FontCachePurgePreventer fontCachePurgePreventer;
     canvas()->document().updateRenderTreeIfNeeded();
     const Font& font = accessFont();
-    const TextRun textRun(text);
+    String normalizedText = normalizeSpaces(text);
+    const TextRun textRun(normalizedText);
     FloatRect textBounds = font.selectionRectForText(textRun, FloatPoint(), font.fontDescription().computedSize(), 0, -1, true);
 
     // x direction
@@ -2065,16 +2092,6 @@ PassRefPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text
     return metrics.release();
 }
 
-static void replaceCharacterInString(String& text, WTF::CharacterMatchFunctionPtr matchFunction, const String& replacement)
-{
-    const size_t replacementLength = replacement.length();
-    size_t index = 0;
-    while ((index = text.find(matchFunction, index)) != kNotFound) {
-        text.replace(index, 1, replacement);
-        index += replacementLength;
-    }
-}
-
 void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, float y, bool fill, float maxWidth, bool useMaxWidth)
 {
     // The style resolution required for rendering text is not available in frame-less documents.
@@ -2109,9 +2126,7 @@ void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, flo
 
     const Font& font = accessFont();
     const FontMetrics& fontMetrics = font.fontMetrics();
-    // According to spec, all the space characters must be replaced with U+0020 SPACE characters.
-    String normalizedText = text;
-    replaceCharacterInString(normalizedText, isSpaceOrNewline, " ");
+    String normalizedText = normalizeSpaces(text);
 
     // FIXME: Need to turn off font smoothing.