Implement canvas2d direction attribute

Source/core/html/canvas/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
@@ skipping 239 matching lines @@
     , m_shadowBlur(0)
     , m_shadowColor(Color::transparent)
     , m_globalAlpha(1)
     , m_globalComposite(CompositeSourceOver)
     , m_globalBlend(blink::WebBlendModeNormal)
     , m_invertibleCTM(true)
     , m_lineDashOffset(0)
     , m_imageSmoothingEnabled(true)
     , m_textAlign(StartTextAlign)
     , m_textBaseline(AlphabeticTextBaseline)
+    , m_direction(Inherit)
     , m_unparsedFont(defaultFont)
     , m_realizedFont(false)
     , m_hasClip(false)
 {
 }
 
 CanvasRenderingContext2D::State::State(const State& other)
     : CSSFontSelectorClient()
     , m_unrealizedSaveCount(other.m_unrealizedSaveCount)
     , m_unparsedStrokeColor(other.m_unparsedStrokeColor)
     , m_unparsedFillColor(other.m_unparsedFillColor)
     , m_strokeStyle(other.m_strokeStyle)
     , m_fillStyle(other.m_fillStyle)
     , m_lineWidth(other.m_lineWidth)
     , m_lineCap(other.m_lineCap)
     , m_lineJoin(other.m_lineJoin)
     , m_miterLimit(other.m_miterLimit)
     , m_shadowOffset(other.m_shadowOffset)
     , m_shadowBlur(other.m_shadowBlur)
     , m_shadowColor(other.m_shadowColor)
     , m_globalAlpha(other.m_globalAlpha)
     , m_globalComposite(other.m_globalComposite)
     , m_globalBlend(other.m_globalBlend)
     , m_transform(other.m_transform)
     , m_invertibleCTM(other.m_invertibleCTM)
     , m_lineDashOffset(other.m_lineDashOffset)
     , 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)
     , m_hasClip(other.m_hasClip)
 {
     if (m_realizedFont)
         static_cast<CSSFontSelector*>(m_font.fontSelector())->registerForInvalidationCallbacks(this);
 }
 
 CanvasRenderingContext2D::State& CanvasRenderingContext2D::State::operator=(const State& other)
@@ skipping 19 matching lines @@
     m_shadowBlur = other.m_shadowBlur;
     m_shadowColor = other.m_shadowColor;
     m_globalAlpha = other.m_globalAlpha;
     m_globalComposite = other.m_globalComposite;
     m_globalBlend = other.m_globalBlend;
     m_transform = other.m_transform;
     m_invertibleCTM = other.m_invertibleCTM;
     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;
     m_hasClip = other.m_hasClip;
 
     if (m_realizedFont)
         static_cast<CSSFontSelector*>(m_font.fontSelector())->registerForInvalidationCallbacks(this);
 
     return *this;
 }
@@ skipping 1671 matching lines @@
 {
     TextBaseline baseline;
     if (!parseTextBaseline(s, baseline))
         return;
     if (state().m_textBaseline == baseline)
         return;
     realizeSaves();
     modifiableState().m_textBaseline = baseline;
 }
 
+TextDirection CanvasRenderingContext2D::toTextDirection(Direction direction, RenderStyle*& computedStyle, bool updateRenderTree) const

[Stephen White, 2014/08/22 17:45:35]

I'm not fond of non-const references, although they are not banned by the blink
style guide. Would you mind using a RenderStyle** instead, for clarity at the
call site?

[Justin Novosad, 2014/08/22 18:15:02]

Does Blink really need to have an additional enum (Direction)? RTL vs. Rtl is a
bit unclear. I mean blink already has enough enums for this: WritingDirection,
TextDirection, WebTextDirection.

[vivekg, 2014/08/26 11:31:52]

We wanted to be explicit with "inherit" hence ended up adding the Direction enum
which is only visible to CanvasRenderingContext2D being private.

[vivekg, 2014/08/26 11:31:52]

Done.

+{
+    if (updateRenderTree)
+        canvas()->document().updateRenderTreeIfNeeded();
+    computedStyle = canvas()->computedStyle();
+    switch (direction) {
+    case Inherit:
+        return computedStyle ? computedStyle->direction() : LTR;
+    case Rtl:
+        return RTL;
+    case Ltr:
+        return LTR;
+    }
+    ASSERT_NOT_REACHED();
+    return LTR;
+}
+
+String CanvasRenderingContext2D::direction() const
+{
+    RenderStyle* computedStyle = nullptr;
+    return toTextDirection(state().m_direction, computedStyle) == RTL ? "rtl" : "ltr";
+}
+
+void CanvasRenderingContext2D::setDirection(const String& directionString)
+{
+    Direction direction;
+    if (directionString == "inherit")
+        direction = Inherit;
+    else if (directionString == "rtl")

[Justin Novosad, 2014/08/22 18:15:02]

This literal is in more than one place. A constant would be appropriate.

[vivekg, 2014/08/26 11:31:52]

Done.

+        direction = Rtl;
+    else if (directionString == "ltr")
+        direction = Ltr;
+    else
+        return;
+
+    realizeSaves();
+    modifiableState().m_direction = direction;
+}
+
 void CanvasRenderingContext2D::fillText(const String& text, float x, float y)
 {
     drawTextInternal(text, x, y, true);
 }
 
 void CanvasRenderingContext2D::fillText(const String& text, float x, float y, float maxWidth)
 {
     drawTextInternal(text, x, y, true, maxWidth, true);
 }
 
@@ skipping 106 matching lines @@
         return;
 
     FontCachePurgePreventer fontCachePurgePreventer;
 
     const Font& font = accessFont();
     const FontMetrics& fontMetrics = font.fontMetrics();
     String normalizedText = normalizeSpaces(text);
 
     // FIXME: Need to turn off font smoothing.
 
-    RenderStyle* computedStyle = canvas()->computedStyle();
-    TextDirection direction = computedStyle ? computedStyle->direction() : LTR;
+    RenderStyle* computedStyle = nullptr;
+    TextDirection direction = toTextDirection(state().m_direction, computedStyle, false);

[Stephen White, 2014/08/22 17:45:35]

Passing a boolean constant is not self-documenting: "Prefer enums to bools on
function parameters if callers are likely to be passing constants, since named
constants are easier to read at the call site."

Could you just get rid of this argument altogether, and put the code at the call
site where it's needed?

[vivekg, 2014/08/26 11:31:52]

Done.

     bool isRTL = direction == RTL;
     bool override = computedStyle ? isOverride(computedStyle->unicodeBidi()) : false;
 
     TextRun textRun(normalizedText, 0, 0, TextRun::AllowTrailingExpansion, direction, override, true);
     // Draw the item text at the correct point.
     FloatPoint location(x, y + getFontBaseline(fontMetrics));
 
     float fontWidth = font.width(TextRun(normalizedText, 0, 0, TextRun::AllowTrailingExpansion, direction, override));
 
     useMaxWidth = (useMaxWidth && maxWidth < fontWidth);
@@ skipping 287 matching lines @@
 
 unsigned CanvasRenderingContext2D::hitRegionsCount() const
 {
     if (m_hitRegionManager)
         return m_hitRegionManager->getHitRegionsCount();
 
     return 0;
 }
 
 } // namespace blink