Implement canvas2d direction attribute

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 4eea12475e641bce52e6482f6efa3b73d6060b7e..b86d7cb7f3719cfa8112de03068d2532bdb191f6 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -83,6 +83,13 @@ static bool contextLostRestoredEventsEnabled()
     return RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled();
 }
 
+static inline TextDirection inheritedDirection(HTMLCanvasElement& canvasElement)
+{
+    canvasElement.document().updateRenderTreeIfNeeded();
+    RenderStyle* computedStyle = canvasElement.computedStyle();
+    return computedStyle ? computedStyle->direction() : LTR;
+}
+
 CanvasRenderingContext2D::CanvasRenderingContext2D(HTMLCanvasElement* canvas, const Canvas2DContextAttributes* attrs, bool usesCSSCompatibilityParseMode)
     : CanvasRenderingContext(canvas)
     , m_usesCSSCompatibilityParseMode(usesCSSCompatibilityParseMode)
@@ -239,7 +246,7 @@ void CanvasRenderingContext2D::reset()
 // StrokeData. The default values that StrokeData uses may not the same values
 // that the canvas 2d spec specifies. Make sure to sync the initial state of the
 // GraphicsContext in HTMLCanvasElement::createImageBuffer()!
-CanvasRenderingContext2D::State::State()
+CanvasRenderingContext2D::State::State(Direction direction)

[Stephen White, 2014/08/21 14:04:38]

This seems out of keeping with the other State parameters, none of 
which are passed as constructor arguments. What makes Direction 
special?

     : m_unrealizedSaveCount(0)
     , m_strokeStyle(CanvasStyle::createFromRGBA(Color::black))
     , m_fillStyle(CanvasStyle::createFromRGBA(Color::black))
@@ -257,6 +264,7 @@ CanvasRenderingContext2D::State::State()
     , m_imageSmoothingEnabled(true)
     , m_textAlign(StartTextAlign)
     , m_textBaseline(AlphabeticTextBaseline)
+    , m_direction(direction)
     , m_unparsedFont(defaultFont)
     , m_realizedFont(false)
     , m_hasClip(false)
@@ -286,6 +294,7 @@ CanvasRenderingContext2D::State::State(const State& other)
     , m_imageSmoothingEnabled(other.m_imageSmoothingEnabled)
     , m_textAlign(other.m_textAlign)
     , m_textBaseline(other.m_textBaseline)
+    , m_direction(other.m_direction)
     , m_unparsedFont(other.m_unparsedFont)
     , m_font(other.m_font)
     , m_realizedFont(other.m_realizedFont)
@@ -325,6 +334,7 @@ CanvasRenderingContext2D::State& CanvasRenderingContext2D::State::operator=(cons
     m_imageSmoothingEnabled = other.m_imageSmoothingEnabled;
     m_textAlign = other.m_textAlign;
     m_textBaseline = other.m_textBaseline;
+    m_direction = other.m_direction;
     m_unparsedFont = other.m_unparsedFont;
     m_font = other.m_font;
     m_realizedFont = other.m_realizedFont;
@@ -2016,6 +2026,42 @@ void CanvasRenderingContext2D::setTextBaseline(const String& s)
     modifiableState().m_textBaseline = baseline;
 }
 
+String CanvasRenderingContext2D::direction() const
+{
+    TextDirection direction = LTR;
+    switch (state().m_direction) {
+    case DirectionInherit:
+        direction = inheritedDirection(*canvas());
+        break;
+    case DirectionRTL:
+        direction = RTL;
+        break;
+    case DirectionLTR:
+        direction = LTR;
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
+    return direction == RTL ? "rtl" : "ltr";
+}
+
+void CanvasRenderingContext2D::setDirection(const String& directionString)
+{
+    Direction direction;
+    if (directionString == "inherit")
+        direction = DirectionInherit;
+    else if (directionString == "rtl")
+        direction = DirectionRTL;
+    else if (directionString == "ltr")
+        direction = DirectionLTR;
+    else
+        return;
+
+    realizeSaves();
+    modifiableState().m_direction = direction;
+}
+
 void CanvasRenderingContext2D::fillText(const String& text, float x, float y)
 {
     drawTextInternal(text, x, y, true);
@@ -2142,8 +2188,24 @@ void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, flo
 
     // FIXME: Need to turn off font smoothing.
 
+    if (state().m_direction == DirectionInherit)
+        canvas()->document().updateRenderTreeIfNeeded();
     RenderStyle* computedStyle = canvas()->computedStyle();
-    TextDirection direction = computedStyle ? computedStyle->direction() : LTR;
+    TextDirection direction = LTR;
+    switch (state().m_direction) {
+    case DirectionInherit:
+        direction = computedStyle ? computedStyle->direction() : LTR;
+        break;
+    case DirectionRTL:
+        direction = RTL;
+        break;
+    case DirectionLTR:
+        direction = LTR;
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
     bool isRTL = direction == RTL;
     bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;