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..0f172667fb46aa460c714621f9ab459c02280fd5 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -2065,6 +2065,17 @@ PassRefPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text
     return metrics.release();
 }
 
+static inline bool isSpaceCharacters(UChar c)
+{
+    // 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 void replaceCharacterInString(String& text, WTF::CharacterMatchFunctionPtr matchFunction, const String& replacement)
 {
     const size_t replacementLength = replacement.length();
@@ -2111,7 +2122,7 @@ void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, flo
     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, " ");
+    replaceCharacterInString(normalizedText, isSpaceCharacters, " ");

[Justin Novosad, 2014/05/20 18:29:50]

What exactly is wrong with isSpaceOrNewline? Why are you defining a new function
instead of correcting isSpaceOrNewline?

 
     // FIXME: Need to turn off font smoothing.