context.addHitRegion() is not working when using transform operation.

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 72 matching lines @@
 }
 
 CanvasRenderingContext2D::CanvasRenderingContext2D(HTMLCanvasElement* canvas, const Canvas2DContextAttributes* attrs, bool usesCSSCompatibilityParseMode)
     : CanvasRenderingContext(canvas)
     , m_usesCSSCompatibilityParseMode(usesCSSCompatibilityParseMode)
     , m_hasAlpha(!attrs || attrs->alpha())
     , m_isContextLost(false)
     , m_contextRestorable(true)
     , m_storageMode(!attrs ? PersistentStorage : attrs->parsedStorage())
     , m_tryRestoreContextAttemptCount(0)
+    , m_clipCount(0)
     , m_dispatchContextLostEventTimer(this, &CanvasRenderingContext2D::dispatchContextLostEvent)
     , m_dispatchContextRestoredEventTimer(this, &CanvasRenderingContext2D::dispatchContextRestoredEvent)
     , m_tryRestoreContextEventTimer(this, &CanvasRenderingContext2D::tryRestoreContextEvent)
 {
     m_stateStack.append(adoptPtrWillBeNoop(new State()));
     ScriptWrappable::init(this);
 }
 
 void CanvasRenderingContext2D::unwindStateStack()
 {
@@ skipping 121 matching lines @@
     }
 }
 
 void CanvasRenderingContext2D::reset()
 {
     validateStateStack();
     unwindStateStack();
     m_stateStack.resize(1);
     m_stateStack.first() = adoptPtrWillBeNoop(new State());
     m_path.clear();
+    m_clipCount = 0;
     validateStateStack();
 }
 
 // Important: Several of these properties are also stored in GraphicsContext's
 // 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()
     : m_unrealizedSaveCount(0)
     , m_strokeStyle(CanvasStyle::createFromRGBA(Color::black))
@@ skipping 121 matching lines @@
         GraphicsContext* context = drawingContext();
         if (context)
             context->save();
         validateStateStack();
     }
 }
 
 void CanvasRenderingContext2D::restore()
 {
     validateStateStack();
+    if (isClipMode())
+        --m_clipCount;

[Justin Novosad, 2014/07/02 15:12:31]

I don't think this is correct. There could be multiple clips on the same state
stack level.  There could also be 0 clips (this clip may come from a higher a
higher state stack level).
In order to restore properly, I think you need to save the the clipCount in the
state stack rather than in CanvasRenderingContext2D.

     if (state().m_unrealizedSaveCount) {
         // We never realized the save, so just record that it was unnecessary.
         --m_stateStack.last()->m_unrealizedSaveCount;
         return;
     }
     ASSERT(m_stateStack.size() >= 1);
     if (m_stateStack.size() <= 1)
         return;
     m_path.transform(state().m_transform);
     m_stateStack.removeLast();
@@ skipping 704 matching lines @@
     GraphicsContext* c = drawingContext();
     if (!c) {
         return;
     }
     if (!state().m_invertibleCTM) {
         return;
     }
 
     realizeSaves();
     c->canvasClip(path, parseWinding(windingRuleString));
+    ++m_clipCount;
 }
 
 void CanvasRenderingContext2D::clip(const String& windingRuleString)
 {
     clipInternal(m_path, windingRuleString);
 }
 
 void CanvasRenderingContext2D::clip(Path2D* domPath, const String& windingRuleString)
 {
     clipInternal(domPath->path(), windingRuleString);
@@ skipping 1269 matching lines @@
 
     if (m_path.isEmpty() || !context || !state().m_invertibleCTM
         || !context->getTransformedClipBounds(&clipBounds)) {
         exceptionState.throwDOMException(NotSupportedError, "The specified path has no pixels.");
         return;
     }
 
     Path specifiedPath = m_path;
     specifiedPath.transform(state().m_transform);
 
-    if (context->isClipMode()) {
+    if (isClipMode()) {
         // FIXME: The hit regions should take clipping region into account.
         // However, we have no way to get the region from canvas state stack by now.
         // See http://crbug.com/387057
         exceptionState.throwDOMException(NotSupportedError, "The specified path has no pixels.");
         return;
     }
 
     passOptions.path = specifiedPath;
     addHitRegionInternal(passOptions, exceptionState);
 }
@@ skipping 34 matching lines @@
 
 unsigned CanvasRenderingContext2D::hitRegionsCount() const
 {
     if (m_hitRegionManager)
         return m_hitRegionManager->getHitRegionsCount();
 
     return 0;
 }
 
 } // namespace WebCore