Avoid redundant initialization of GraphicsContextState.

When creating a new GraphicsContextState the constructor initializes the state
with various default values. In GraphicsContext::realizePaintState we immediately
overwrite these values after creation. This patch adds a copy constructor to
GraphicsContextState to avoid that.

Even though this seems like a clear win, the benefits are not visible when
profiling. Looks like the overhead of the redundant initialization is
not very large. Still seems worth fixing though.

BUG=377687

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174985

Review URL: https://codereview.chromium.org/303613002

git-svn-id: svn://svn.chromium.org/blink/trunk@175894 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/graphics/GraphicsContext.h

@@ -463,11 +463,14 @@ private:
         if (m_paintState->saveCount()) {
             m_paintState->decrementSaveCount();
             ++m_paintStateIndex;
-            if (m_paintStateStack.size() == m_paintStateIndex)
-                m_paintStateStack.append(GraphicsContextState::create());
-            GraphicsContextState* priorPaintState = m_paintState;
-            m_paintState = m_paintStateStack[m_paintStateIndex].get();
-            m_paintState->copy(priorPaintState);
+            if (m_paintStateStack.size() == m_paintStateIndex) {
+                m_paintStateStack.append(GraphicsContextState::createAndCopy(*m_paintState));
+                m_paintState = m_paintStateStack[m_paintStateIndex].get();
+            } else {
+                GraphicsContextState* priorPaintState = m_paintState;
+                m_paintState = m_paintStateStack[m_paintStateIndex].get();
+                m_paintState->copy(*priorPaintState);
+            }
         }
     }
 

third_party/WebKit/Source/platform/graphics/GraphicsContextState.cpp

@@ -36,27 +36,30 @@ GraphicsContextState::GraphicsContextState()
     m_fillPaint.setAntiAlias(m_shouldAntialias);
 }
 
-void GraphicsContextState::copy(GraphicsContextState* source)
-{
-    m_strokePaint = source->m_strokePaint;
-    m_fillPaint = source->m_fillPaint;
-    m_strokeData = source->m_strokeData;
-    m_fillColor = source->m_fillColor;
-    m_fillRule = source->m_fillRule;
-    m_fillGradient = source->m_fillGradient;
-    m_fillPattern = source->m_fillPattern;
-    m_looper = source->m_looper;
-    m_textDrawingMode = source->m_textDrawingMode;
-    m_alpha = source->m_alpha;
-    m_xferMode = source->m_xferMode;
-    m_colorFilter = source->m_colorFilter;
-    m_compositeOperator = source->m_compositeOperator;
-    m_blendMode = source->m_blendMode;
-    m_interpolationQuality = source->m_interpolationQuality;
-    m_saveCount = 0;
-    m_shouldAntialias = source->m_shouldAntialias;
-    m_shouldSmoothFonts = source->m_shouldSmoothFonts;
-    m_shouldClampToSourceRect = source->m_shouldClampToSourceRect;
+GraphicsContextState::GraphicsContextState(const GraphicsContextState& other)
+    : m_strokePaint(other.m_strokePaint)
+    , m_fillPaint(other.m_fillPaint)
+    , m_strokeData(other.m_strokeData)
+    , m_fillColor(other.m_fillColor)
+    , m_fillRule(other.m_fillRule)
+    , m_fillGradient(other.m_fillGradient)
+    , m_fillPattern(other.m_fillPattern)
+    , m_looper(other.m_looper)
+    , m_textDrawingMode(other.m_textDrawingMode)
+    , m_alpha(other.m_alpha)
+    , m_xferMode(other.m_xferMode)
+    , m_colorFilter(other.m_colorFilter)
+    , m_compositeOperator(other.m_compositeOperator)
+    , m_blendMode(other.m_blendMode)
+    , m_interpolationQuality(other.m_interpolationQuality)
+    , m_saveCount(0)
+    , m_shouldAntialias(other.m_shouldAntialias)
+    , m_shouldSmoothFonts(other.m_shouldSmoothFonts)
+    , m_shouldClampToSourceRect(other.m_shouldClampToSourceRect) { }
+
+void GraphicsContextState::copy(const GraphicsContextState& source)
+{
+    new (this) GraphicsContextState(source);
 }
 
 const SkPaint& GraphicsContextState::strokePaint(int strokedPathLength) const

third_party/WebKit/Source/platform/graphics/GraphicsContextState.h

@@ -46,14 +46,18 @@ namespace WebCore {
 // Encapsulates the state information we store for each pushed graphics state.
 // Only GraphicsContext can use this class.
 class PLATFORM_EXPORT GraphicsContextState FINAL {
-    WTF_MAKE_NONCOPYABLE(GraphicsContextState);
 public:
     static PassOwnPtr<GraphicsContextState> create()
     {
         return adoptPtr(new GraphicsContextState());
     }
 
-    void copy(GraphicsContextState*);
+    static PassOwnPtr<GraphicsContextState> createAndCopy(const GraphicsContextState& other)
+    {
+        return adoptPtr(new GraphicsContextState(other));
+    }
+
+    void copy(const GraphicsContextState&);
 
     // SkPaint objects that reflect the current state. If the length of the
     // path to be stroked is known, pass it in for correct dash or dot placement.
@@ -142,6 +146,8 @@ public:
 
 private:
     GraphicsContextState();
+    explicit GraphicsContextState(const GraphicsContextState&);
+    GraphicsContextState& operator=(const GraphicsContextState&);
 
     // Helper function for applying the state's alpha value to the given input
     // color to produce a new output color.