Introduce SVGPaintServer

Source/core/paint/SVGPaintServer.h

+// Copyright 2014 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.
+
+#ifndef SVGPaintServer_h
+#define SVGPaintServer_h
+
+#include "core/rendering/svg/RenderSVGResource.h"
+#include "platform/graphics/Gradient.h"
+#include "platform/graphics/Pattern.h"
+
+namespace blink {
+
+class GraphicsContext;
+class GraphicsContextStateSaver;
+
+class SVGPaintServer {
+public:
+    SVGPaintServer();

[pdr., 2014/10/09 01:00:50]

This can be private.

+
+    static bool existsForRenderer(RenderObject&, const RenderStyle*, RenderSVGResourceMode);
+
+    // Update the GC state (on |context|) for painting |renderer|
+    // using |style|. |resourceModeFlags| is used to decide between fill/stroke.
+    // Previous state will be saved (if needed) using |stateSaver|.
+    static bool updateGraphicsContext(GraphicsContext*, RenderStyle*, RenderObject&, RenderSVGResourceModeFlags, GraphicsContextStateSaver&);

[pdr., 2014/10/09 01:00:50]

Passing in both a context and a statesaver that holds the context is messy. Can
we just expose the context on GraphicsContextStateSaver and just pass that in?

[fs, 2014/10/09 07:23:08]

It's already exposed, I just don't find it particularly clean to do it that
way...

[fs, 2014/10/10 13:08:59]

Dropped GC*, moved GCSS in the argument list. (I hope to eventually be able to
split "fetch paint-server" from "apply paint-server".)

+
+    void setColor(Color);
+    void setGradient(const PassRefPtr<Gradient>);
+    void setPattern(const PassRefPtr<Pattern>);
+
+    void apply(GraphicsContext&, RenderSVGResourceMode, GraphicsContextStateSaver* = 0);
+
+private:
+    static bool requestForRenderer(RenderObject&, RenderStyle*, RenderSVGResourceModeFlags, SVGPaintServer&);
+
+    RefPtr<Gradient> m_gradient;
+    RefPtr<Pattern> m_pattern;
+    Color m_color;

[pdr., 2014/10/09 01:00:50]

This makes me a little sad because a paint server for the color black is 12
bytes. Because this won't simultaneously contain a gradient and a pattern, can
we do something smarter?

[fs, 2014/10/09 07:23:08]

I'm glad you asked =). It'd be possible to add a common superclass for
Gradient/Pattern, and then we'd only need 8 bytes... (or 16 vs. 24 for 64-bit).
This is not intended for longer term (heap) storage though, so I'd
probably/actually worry more of number of destructors to call etc.

[fs, 2014/10/10 13:08:58]

I haven't done anything about this. If "people" find the above suggestion (about
adding a common base for Gradient and Pattern) reasonable I'll upload a separate
CL for that (should shrink/simplify GC-state as well.)

+};
+
+} // namespace blink
+
+#endif // SVGPaintServer_h