Add a basic custom painting facility to Sky

sky/engine/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 971 matching lines @@
         return BackgroundBleedBackgroundOverBorder;
 
     return BackgroundBleedClipBackground;
 }
 
 void RenderBox::paintBoxDecorationBackground(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     LayoutRect paintRect = borderBoxRect();
     paintRect.moveBy(paintOffset);
     paintBoxDecorationBackgroundWithRect(paintInfo, paintOffset, paintRect);
+    // TODO(abarth): Currently we only draw m_customPainting if we happen to

[ojan, 2015/03/19 22:30:04]

I think we want to do this before we do any other painting. I think in the final
result we'll probably want 3 different callbacks. beforePaint, paint and
afterPaint.

beforePaint: happens before the default paint (including backgrounds, etc.
paint: the default paint. if you set this callback then we skip the default
paint code.
afterPaint: happens after paint. :)

We can fix this in followup patches of course.

[abarth-chromium, 2015/03/19 22:34:27]

Yeah, the main design question is whether these paint callbacks should be
synchronous.  One idea is to make them asynchronous (as implemented in this CL),
and basically generate SkPictures that get played back at these times.  The
script is then responsible for invalidating the SkPictures as appropriate. 
Presumably we'll want to make it easy to invalidate your picture when the size
of your box changes.

+    // have a box decoration or a background. Instead, we should probably have
+    // another function like paintBoxDecorationBackground that subclasses can
+    // call to draw m_customPainting.
+    if (m_customPainting)
+        paintInfo.context->drawDisplayList(m_customPainting.get(), paintRect.location());
 }
 
 void RenderBox::paintBoxDecorationBackgroundWithRect(PaintInfo& paintInfo, const LayoutPoint& paintOffset, const LayoutRect& paintRect)
 {
     RenderStyle* style = this->style();
     BoxDecorationData boxDecorationData(*style);
     BackgroundBleedAvoidance bleedAvoidance = determineBackgroundBleedAvoidance(paintInfo.context, boxDecorationData);
 
     // FIXME: Should eventually give the theme control over whether the box shadow should paint, since controls could have
     // custom shadows of their own.
@@ skipping 2070 matching lines @@
 
 RenderBox::BoxDecorationData::BoxDecorationData(const RenderStyle& style)
 {
     backgroundColor = style.colorIncludingFallback(CSSPropertyBackgroundColor);
     hasBackground = backgroundColor.alpha() || style.hasBackgroundImage();
     ASSERT(hasBackground == style.hasBackground());
     hasBorder = style.hasBorder();
 }
 
 } // namespace blink