Adding the 'filter' context attribute to 2D canvas

Source/core/html/canvas/CanvasRenderingContext2DState.cpp

 // Copyright 2015 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 "config.h"
 
 #include "core/html/canvas/CanvasRenderingContext2DState.h"
 
 #include "core/css/CSSFontSelector.h"
+#include "core/css/resolver/FilterOperationResolver.h"
+#include "core/css/resolver/StyleBuilder.h"
+#include "core/css/resolver/StyleResolverState.h"
 #include "core/html/canvas/CanvasGradient.h"
 #include "core/html/canvas/CanvasPattern.h"
 #include "core/html/canvas/CanvasStyle.h"
+#include "core/paint/FilterEffectBuilder.h"
+#include "core/style/ComputedStyle.h"
 #include "platform/graphics/DrawLooperBuilder.h"
+#include "platform/graphics/filters/SkiaImageFilterBuilder.h"
 #include "platform/graphics/skia/SkiaUtils.h"
 #include "third_party/skia/include/effects/SkDashPathEffect.h"
 #include "third_party/skia/include/effects/SkDropShadowImageFilter.h"
 
 static const char defaultFont[] = "10px sans-serif";
+static const char defaultFilter[] = "none";
 
 namespace blink {
 
 CanvasRenderingContext2DState::CanvasRenderingContext2DState()
     : m_unrealizedSaveCount(0)
     , m_strokeStyle(CanvasStyle::createFromRGBA(SK_ColorBLACK))
     , m_fillStyle(CanvasStyle::createFromRGBA(SK_ColorBLACK))
     , m_shadowBlur(0)
     , m_shadowColor(Color::transparent)
     , m_globalAlpha(1)
     , m_lineDashOffset(0)
     , m_unparsedFont(defaultFont)
+    , m_unparsedFilter(defaultFilter)
     , m_textAlign(StartTextAlign)
     , m_textBaseline(AlphabeticTextBaseline)
     , m_direction(DirectionInherit)
     , m_realizedFont(false)
     , m_isTransformInvertible(true)
     , m_hasClip(false)
     , m_hasComplexClip(false)
     , m_fillStyleDirty(true)
     , m_strokeStyleDirty(true)
     , m_lineDashDirty(false)
@@ skipping 27 matching lines @@
     , m_emptyDrawLooper(other.m_emptyDrawLooper)
     , m_shadowOnlyDrawLooper(other.m_shadowOnlyDrawLooper)
     , m_shadowAndForegroundDrawLooper(other.m_shadowAndForegroundDrawLooper)
     , m_shadowOnlyImageFilter(other.m_shadowOnlyImageFilter)
     , m_shadowAndForegroundImageFilter(other.m_shadowAndForegroundImageFilter)
     , m_globalAlpha(other.m_globalAlpha)
     , m_transform(other.m_transform)
     , m_lineDashOffset(other.m_lineDashOffset)
     , m_unparsedFont(other.m_unparsedFont)
     , m_font(other.m_font)
+    , m_unparsedFilter(other.m_unparsedFilter)
+    , m_filterValue(other.m_filterValue)
+    , m_resolvedFilter(other.m_resolvedFilter)
     , m_textAlign(other.m_textAlign)
     , m_textBaseline(other.m_textBaseline)
     , m_direction(other.m_direction)
     , m_realizedFont(other.m_realizedFont)
     , m_isTransformInvertible(other.m_isTransformInvertible)
     , m_hasClip(other.m_hasClip)
     , m_hasComplexClip(other.m_hasComplexClip)
     , m_fillStyleDirty(other.m_fillStyleDirty)
     , m_strokeStyleDirty(other.m_strokeStyleDirty)
     , m_lineDashDirty(other.m_lineDashDirty)
@@ skipping 61 matching lines @@
         static_cast<CSSFontSelector*>(m_font.fontSelector())->unregisterForInvalidationCallbacks(this);
 #endif
 }
 
 void CanvasRenderingContext2DState::fontsNeedUpdate(CSSFontSelector* fontSelector)
 {
     ASSERT_ARG(fontSelector, fontSelector == m_font.fontSelector());
     ASSERT(m_realizedFont);
 
     m_font.update(fontSelector);
+    // FIXME: We only really need to invalidate the resolved filter if the font
+    // update above changed anything and the filter uses font-dependent units.
+    m_resolvedFilter.clear();
 }
 
 DEFINE_TRACE(CanvasRenderingContext2DState)
 {
     visitor->trace(m_strokeStyle);
     visitor->trace(m_fillStyle);
     CSSFontSelectorClient::trace(visitor);
 }
 
 void CanvasRenderingContext2DState::setLineDashOffset(float offset)
@@ skipping 110 matching lines @@
 void CanvasRenderingContext2DState::setFont(const Font& font, CSSFontSelector* selector)
 {
 #if !ENABLE(OILPAN)
     if (m_realizedFont)
         static_cast<CSSFontSelector*>(m_font.fontSelector())->unregisterForInvalidationCallbacks(this);
 #endif
     m_font = font;
     m_font.update(selector);
     m_realizedFont = true;
     selector->registerForInvalidationCallbacks(this);
+    // FIXME: We only really need to invalidate the resolved filter if it
+    // uses font-relative units.
+    m_resolvedFilter.clear();
 }
 
 const Font& CanvasRenderingContext2DState::font() const
 {
     ASSERT(m_realizedFont);
     return m_font;
 }
 
 void CanvasRenderingContext2DState::setTransform(const AffineTransform& transform)
 {
     m_isTransformInvertible = transform.isInvertible();
     m_transform = transform;
 }
 
 void CanvasRenderingContext2DState::resetTransform()
 {
     m_transform.makeIdentity();
     m_isTransformInvertible = true;
 }
 
+SkImageFilter* CanvasRenderingContext2DState::getFilter(Element* styleResolutionHost, const Font& font) const
+{
+    if (!m_filterValue)
+        return nullptr;
+
+    if (!m_resolvedFilter) {
+        RefPtr<ComputedStyle> filterStyle = ComputedStyle::create();
+        // Must set font in case the filter uses any font-relative units (em, ex)
+        filterStyle->setFont(font);
+
+        StyleResolverState resolverState(styleResolutionHost->document(), styleResolutionHost, filterStyle.get());
+        resolverState.setStyle(filterStyle);
+
+        // TODO(junov): crbug.com/502877 Feed m_fillStyle and m_strokeStyle into FillPaint and
+        // StrokePaint respectively for filters that reference SVG.
+        StyleBuilder::applyProperty(CSSPropertyWebkitFilter, resolverState, m_filterValue.get());
+        RefPtrWillBeRawPtr<FilterEffectBuilder> filterEffectBuilder = FilterEffectBuilder::create();
+        const float effectiveZoom = 1.0f; // Deliberately ignore zoom on the canvas element
+        filterEffectBuilder->build(styleResolutionHost, filterStyle->filter(), effectiveZoom);
+
+        SkiaImageFilterBuilder imageFilterBuilder;
+        RefPtrWillBeRawPtr<FilterEffect> lastEffect = filterEffectBuilder->lastEffect();
+        m_resolvedFilter = imageFilterBuilder.build(lastEffect.get(), ColorSpaceDeviceRGB);
+    }
+
+    return m_resolvedFilter.get();
+}
+
 SkDrawLooper* CanvasRenderingContext2DState::emptyDrawLooper() const
 {
     if (!m_emptyDrawLooper) {
         OwnPtr<DrawLooperBuilder> drawLooperBuilder = DrawLooperBuilder::create();
         m_emptyDrawLooper = drawLooperBuilder->detachDrawLooper();
     }
     return m_emptyDrawLooper.get();
 }
 
 SkDrawLooper* CanvasRenderingContext2DState::shadowOnlyDrawLooper() const
@@ skipping 60 matching lines @@
     m_shadowBlur = shadowBlur;
     shadowParameterChanged();
 }
 
 void CanvasRenderingContext2DState::setShadowColor(SkColor shadowColor)
 {
     m_shadowColor = shadowColor;
     shadowParameterChanged();
 }
 
+void CanvasRenderingContext2DState::setFilter(PassRefPtrWillBeRawPtr<CSSValue> filterValue)
+{
+    m_filterValue = filterValue;
+    m_resolvedFilter.clear();
+}
+
 void CanvasRenderingContext2DState::setGlobalComposite(SkXfermode::Mode mode)
 {
     m_strokePaint.setXfermodeMode(mode);
     m_fillPaint.setXfermodeMode(mode);
     m_imagePaint.setXfermodeMode(mode);
 }
 
 SkXfermode::Mode CanvasRenderingContext2DState::globalComposite() const
 {
     SkXfermode* xferMode = m_strokePaint.getXfermode();
@@ skipping 48 matching lines @@
         return paint;
     }
 
     if (!shouldDrawShadows() && shadowMode == DrawShadowOnly) {
         paint->setLooper(emptyDrawLooper()); // draw nothing
         paint->setImageFilter(0);
         return paint;
     }
 
     if (shadowMode == DrawShadowOnly) {
-        if (imageType == NonOpaqueImage) {
+        if (imageType == NonOpaqueImage || m_filterValue) {
             paint->setLooper(0);
             paint->setImageFilter(shadowOnlyImageFilter());
             return paint;
         }
         paint->setLooper(shadowOnlyDrawLooper());
         paint->setImageFilter(0);
         return paint;
     }
 
     ASSERT(shadowMode == DrawShadowAndForeground);
     if (imageType == NonOpaqueImage) {
         paint->setLooper(0);
         paint->setImageFilter(shadowAndForegroundImageFilter());
         return paint;
     }
     paint->setLooper(shadowAndForegroundDrawLooper());
     paint->setImageFilter(0);
     return paint;
 }
 
 } // blink