Fix zoom in CSS paint worklets

third_party/WebKit/Source/modules/csspaint/CSSPaintDefinition.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/csspaint/CSSPaintDefinition.h"
 
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8BindingMacros.h"
 #include "bindings/core/v8/V8ObjectConstructor.h"
 #include "core/css/CSSComputedStyleDeclaration.h"
 #include "core/css/cssom/FilteredComputedStylePropertyMap.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/layout/LayoutObject.h"
 #include "modules/csspaint/PaintRenderingContext2D.h"
 #include "modules/csspaint/PaintSize.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "platform/graphics/PaintGeneratedImage.h"
 #include "platform/graphics/RecordingImageBufferSurface.h"
 #include "wtf/PtrUtil.h"
 
 namespace blink {
 
+namespace {
+
+IntSize adjustSizeForZoom(const IntSize& size, float zoom)
+{
+    IntSize newSize(size);
+    newSize.scale(1 / zoom);
+    return newSize;
+}
+
+} // namespace
+
 CSSPaintDefinition* CSSPaintDefinition::create(ScriptState* scriptState, v8::Local<v8::Function> constructor, v8::Local<v8::Function> paint, Vector<CSSPropertyID>& nativeInvalidationProperties, Vector<AtomicString>& customInvalidationProperties)
 {
     return new CSSPaintDefinition(scriptState, constructor, paint, nativeInvalidationProperties, customInvalidationProperties);
 }
 
 CSSPaintDefinition::CSSPaintDefinition(ScriptState* scriptState, v8::Local<v8::Function> constructor, v8::Local<v8::Function> paint, Vector<CSSPropertyID>& nativeInvalidationProperties, Vector<AtomicString>& customInvalidationProperties)
     : m_scriptState(scriptState)
     , m_constructor(scriptState->isolate(), constructor)
     , m_paint(scriptState->isolate(), paint)
 {
     m_nativeInvalidationProperties.swap(nativeInvalidationProperties);
     m_customInvalidationProperties.swap(customInvalidationProperties);
 }
 
 CSSPaintDefinition::~CSSPaintDefinition()
 {
 }
 
-PassRefPtr<Image> CSSPaintDefinition::paint(const LayoutObject& layoutObject, const IntSize& size)
+PassRefPtr<Image> CSSPaintDefinition::paint(const LayoutObject& layoutObject, const IntSize& size, float zoom)
 {
+    const auto adjustedSize = adjustSizeForZoom(size, zoom);

[ikilpatrick, 2016/06/30 17:24:54]

add a comment as to why we are doing this.

[Gleb Lanbin, 2016/06/30 23:57:20]

renamed the function and variable to make clear our intention here.

+
     ScriptState::Scope scope(m_scriptState.get());
 
     maybeCreatePaintInstance();
 
     v8::Isolate* isolate = m_scriptState->isolate();
     v8::Local<v8::Object> instance = m_instance.newLocal(isolate);
 
     // We may have failed to create an instance class, in which case produce an
     // invalid image.
     if (isUndefinedOrNull(instance))
         return nullptr;
 
     DCHECK(layoutObject.node());
 
     PaintRenderingContext2D* renderingContext = PaintRenderingContext2D::create(
-        ImageBuffer::create(wrapUnique(new RecordingImageBufferSurface(size))));
-    PaintSize* paintSize = PaintSize::create(size);
+        ImageBuffer::create(wrapUnique(new RecordingImageBufferSurface(size))), zoom);
+    PaintSize* paintSize = PaintSize::create(adjustedSize);
     StylePropertyMap* styleMap = FilteredComputedStylePropertyMap::create(
         CSSComputedStyleDeclaration::create(layoutObject.node()),
         m_nativeInvalidationProperties, m_customInvalidationProperties);
 
     v8::Local<v8::Value> argv[] = {
         toV8(renderingContext, m_scriptState->context()->Global(), isolate),
         toV8(paintSize, m_scriptState->context()->Global(), isolate),
         toV8(styleMap, m_scriptState->context()->Global(), isolate)
     };
 
     v8::Local<v8::Function> paint = m_paint.newLocal(isolate);
 
     v8::TryCatch block(isolate);
     block.SetVerbose(true);
 
     V8ScriptRunner::callFunction(paint, m_scriptState->getExecutionContext(), instance, 3, argv, isolate);
 
     // The paint function may have produced an error, in which case produce an
     // invalid image.
     if (block.HasCaught()) {
         return nullptr;
     }
 
-    return PaintGeneratedImage::create(renderingContext->imageBuffer()->getPicture(), size);
+    return PaintGeneratedImage::create(renderingContext->imageBuffer()->getPicture(), adjustedSize);
 }
 
 void CSSPaintDefinition::maybeCreatePaintInstance()
 {
     if (m_didCallConstructor)
         return;
 
     DCHECK(m_instance.isEmpty());
 
     v8::Isolate* isolate = m_scriptState->isolate();
     v8::Local<v8::Function> constructor = m_constructor.newLocal(isolate);
     DCHECK(!isUndefinedOrNull(constructor));
 
     v8::Local<v8::Object> paintInstance;
     if (V8ObjectConstructor::newInstance(isolate, constructor).ToLocal(&paintInstance)) {
         m_instance.set(isolate, paintInstance);
     }
 
     m_didCallConstructor = true;
 }
 
 } // namespace blink