[Cairo] Create Cairo patterns from Gradient objects on-the-fly

https://bugs.webkit.org/show_bug.cgi?id=177947

Reviewed by Carlos Garcia Campos.

Stop caching cairo_pattern_t objects for a specific global alpha value
in the Gradient class. Instead, create these as required, for whatever
alpha value. This drops some efficiency benefits in exchange for better
Cairo operation isolation, while also matching the same approach that
is used in the Pattern implementation for Cairo.

Introduce the createPlatformGradient() method for Cairo, resuing the
implementation of platformGradient() that's now removed. The
Cairo-specific setPlatformGradientSpaceTransform() method is also
removed since there's no cached cairo_pattern_t object that we can
update. The Cairo-specific m_platformGradientAlpha member float is also
deleted.

Gradient::fill() and prepareCairoContextSource() are the only two places
that need to create a cairo_pattern_t object off of Gradient, so they
are updated accordingly.

No new tests -- no changes in behavior.

* platform/graphics/Gradient.cpp:
(WebCore::Gradient::setGradientSpaceTransform):
(WebCore::Gradient::setPlatformGradientSpaceTransform): Deleted.
* platform/graphics/Gradient.h:
* platform/graphics/cairo/GradientCairo.cpp:
(WebCore::Gradient::platformDestroy):
(WebCore::Gradient::createPlatformGradient):
(WebCore::Gradient::fill):
(WebCore::Gradient::platformGradient): Deleted.
(WebCore::Gradient::setPlatformGradientSpaceTransform): Deleted.
* platform/graphics/cairo/PlatformContextCairo.cpp:
(WebCore::prepareCairoContextSource):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@222975 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Author: [email protected]

Source/WebCore/ChangeLog

@@ -1,3 +1,42 @@
+2017-10-06  Zan Dobersek  <[email protected]>
+
+        [Cairo] Create Cairo patterns from Gradient objects on-the-fly
+        https://bugs.webkit.org/show_bug.cgi?id=177947
+
+        Reviewed by Carlos Garcia Campos.
+
+        Stop caching cairo_pattern_t objects for a specific global alpha value
+        in the Gradient class. Instead, create these as required, for whatever
+        alpha value. This drops some efficiency benefits in exchange for better
+        Cairo operation isolation, while also matching the same approach that
+        is used in the Pattern implementation for Cairo.
+
+        Introduce the createPlatformGradient() method for Cairo, resuing the
+        implementation of platformGradient() that's now removed. The
+        Cairo-specific setPlatformGradientSpaceTransform() method is also
+        removed since there's no cached cairo_pattern_t object that we can
+        update. The Cairo-specific m_platformGradientAlpha member float is also
+        deleted.
+
+        Gradient::fill() and prepareCairoContextSource() are the only two places
+        that need to create a cairo_pattern_t object off of Gradient, so they
+        are updated accordingly.
+
+        No new tests -- no changes in behavior.
+
+        * platform/graphics/Gradient.cpp:
+        (WebCore::Gradient::setGradientSpaceTransform):
+        (WebCore::Gradient::setPlatformGradientSpaceTransform): Deleted.
+        * platform/graphics/Gradient.h:
+        * platform/graphics/cairo/GradientCairo.cpp:
+        (WebCore::Gradient::platformDestroy):
+        (WebCore::Gradient::createPlatformGradient):
+        (WebCore::Gradient::fill):
+        (WebCore::Gradient::platformGradient): Deleted.
+        (WebCore::Gradient::setPlatformGradientSpaceTransform): Deleted.
+        * platform/graphics/cairo/PlatformContextCairo.cpp:
+        (WebCore::prepareCairoContextSource):
+
 2017-10-06  Ms2ger  <[email protected]>
 
         Create bindings for WebGL2's versions of compressedTexImage2D.

Source/WebCore/platform/graphics/Gradient.cpp

@@ -163,17 +163,10 @@ void Gradient::setGradientSpaceTransform(const AffineTransform& gradientSpaceTra
         return;
 
     m_gradientSpaceTransformation = gradientSpaceTransformation;
-    setPlatformGradientSpaceTransform(gradientSpaceTransformation);
 
     invalidateHash();
 }
 
-#if !USE(CAIRO)
-void Gradient::setPlatformGradientSpaceTransform(const AffineTransform&)
-{
-}
-#endif
-
 unsigned Gradient::hash() const
 {
     if (m_cachedHash)

Source/WebCore/platform/graphics/Gradient.h

@@ -159,8 +159,6 @@ namespace WebCore {
         void fill(GraphicsContext*, const FloatRect&);
         void adjustParametersForTiledDrawing(FloatSize&, FloatRect&, const FloatSize& spacing);
 
-        void setPlatformGradientSpaceTransform(const AffineTransform& gradientSpaceTransformation);
-
         unsigned hash() const;
         void invalidateHash() { m_cachedHash = 0; }
 
@@ -170,7 +168,7 @@ namespace WebCore {
 #elif USE(DIRECT2D)
         PlatformGradient createPlatformGradientIfNecessary(ID2D1RenderTarget*);
 #elif USE(CAIRO)
-        PlatformGradient platformGradient(float globalAlpha);
+        PlatformGradient createPlatformGradient(float globalAlpha);
 #endif
 
     private:
@@ -201,11 +199,6 @@ namespace WebCore {
         mutable unsigned m_cachedHash;
 
         PlatformGradient m_gradient;
-
-#if USE(CAIRO)
-        float m_platformGradientAlpha;
-#endif
-
     };
 
 } //namespace

Source/WebCore/platform/graphics/cairo/GradientCairo.cpp

@@ -37,77 +37,57 @@ namespace WebCore {
 
 void Gradient::platformDestroy()
 {
-    if (m_gradient) {
-        cairo_pattern_destroy(m_gradient);
-        m_gradient = 0;
-    }
-}
-
-cairo_pattern_t* Gradient::platformGradient()
-{
-    return platformGradient(1);
 }
 
-cairo_pattern_t* Gradient::platformGradient(float globalAlpha)
+cairo_pattern_t* Gradient::createPlatformGradient(float globalAlpha)
 {
-    if (m_gradient && m_platformGradientAlpha == globalAlpha)
-        return m_gradient;
-
-    platformDestroy();
-    m_platformGradientAlpha = globalAlpha;
-
+    cairo_pattern_t* gradient;
     if (m_radial)
-        m_gradient = cairo_pattern_create_radial(m_p0.x(), m_p0.y(), m_r0, m_p1.x(), m_p1.y(), m_r1);
+        gradient = cairo_pattern_create_radial(m_p0.x(), m_p0.y(), m_r0, m_p1.x(), m_p1.y(), m_r1);
     else
-        m_gradient = cairo_pattern_create_linear(m_p0.x(), m_p0.y(), m_p1.x(), m_p1.y());
+        gradient = cairo_pattern_create_linear(m_p0.x(), m_p0.y(), m_p1.x(), m_p1.y());
 
     for (const auto& stop : m_stops) {
         if (stop.color.isExtended()) {
-            cairo_pattern_add_color_stop_rgba(m_gradient, stop.offset, stop.color.asExtended().red(), stop.color.asExtended().green(), stop.color.asExtended().blue(),
+            cairo_pattern_add_color_stop_rgba(gradient, stop.offset, stop.color.asExtended().red(), stop.color.asExtended().green(), stop.color.asExtended().blue(),
                 stop.color.asExtended().alpha() * globalAlpha);
         } else {
             float r, g, b, a;
             stop.color.getRGBA(r, g, b, a);
-            cairo_pattern_add_color_stop_rgba(m_gradient, stop.offset, r, g, b, a * globalAlpha);
+            cairo_pattern_add_color_stop_rgba(gradient, stop.offset, r, g, b, a * globalAlpha);
         }
     }
 
     switch (m_spreadMethod) {
     case SpreadMethodPad:
-        cairo_pattern_set_extend(m_gradient, CAIRO_EXTEND_PAD);
+        cairo_pattern_set_extend(gradient, CAIRO_EXTEND_PAD);
         break;
     case SpreadMethodReflect:
-        cairo_pattern_set_extend(m_gradient, CAIRO_EXTEND_REFLECT);
+        cairo_pattern_set_extend(gradient, CAIRO_EXTEND_REFLECT);
         break;
     case SpreadMethodRepeat:
-        cairo_pattern_set_extend(m_gradient, CAIRO_EXTEND_REPEAT);
+        cairo_pattern_set_extend(gradient, CAIRO_EXTEND_REPEAT);
         break;
     }
 
     cairo_matrix_t matrix = toCairoMatrix(m_gradientSpaceTransformation);
     cairo_matrix_invert(&matrix);
-    cairo_pattern_set_matrix(m_gradient, &matrix);
-
-    return m_gradient;
-}
+    cairo_pattern_set_matrix(gradient, &matrix);
 
-void Gradient::setPlatformGradientSpaceTransform(const AffineTransform& gradientSpaceTransformation)
-{
-    if (m_gradient) {
-        cairo_matrix_t matrix = toCairoMatrix(gradientSpaceTransformation);
-        cairo_matrix_invert(&matrix);
-        cairo_pattern_set_matrix(m_gradient, &matrix);
-    }
+    return gradient;
 }
 
 void Gradient::fill(GraphicsContext* context, const FloatRect& rect)
 {
-    cairo_t* cr = context->platformContext()->cr();
+    RefPtr<cairo_pattern_t> gradient = adoptRef(createPlatformGradient(1.0));
 
     context->save();
-    cairo_set_source(cr, platformGradient());
+
+    cairo_t* cr = context->platformContext()->cr();
+    cairo_set_source(cr, gradient.get());
     cairo_rectangle(cr, rect.x(), rect.y(), rect.width(), rect.height());
     cairo_fill(cr);
+
     context->restore();
 }
 

Source/WebCore/platform/graphics/cairo/PlatformContextCairo.cpp

@@ -269,12 +269,13 @@ static inline void reduceSourceByAlpha(cairo_t* cr, float alpha)
 static void prepareCairoContextSource(cairo_t* cr, Pattern* pattern, Gradient* gradient, const Color& color, float globalAlpha)
 {
     if (pattern) {
-        RefPtr<cairo_pattern_t> cairoPattern(adoptRef(pattern->createPlatformPattern(AffineTransform())));
+        RefPtr<cairo_pattern_t> cairoPattern = adoptRef(pattern->createPlatformPattern(AffineTransform()));
         cairo_set_source(cr, cairoPattern.get());
         reduceSourceByAlpha(cr, globalAlpha);
-    } else if (gradient)
-        cairo_set_source(cr, gradient->platformGradient(globalAlpha));
-    else { // Solid color source.
+    } else if (gradient) {
+        RefPtr<cairo_pattern_t> cairoPattern = adoptRef(gradient->createPlatformGradient(globalAlpha));
+        cairo_set_source(cr, cairoPattern.get());
+    } else { // Solid color source.
         if (globalAlpha < 1)
             setSourceRGBAFromColor(cr, colorWithOverrideAlpha(color.rgb(), color.alpha() / 255.f * globalAlpha));
         else