Flush the cairo surface before we try to write to it.

skia/ext/bitmap_platform_device_linux.cc

 // Copyright (c) 2010 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 "skia/ext/bitmap_platform_device_linux.h"
 
 #include "skia/ext/bitmap_platform_device_data.h"
 
 #include <cairo/cairo.h>
 
@@ skipping 135 matching lines @@
   return SkNEW(BitmapPlatformDeviceFactory);
 }
 
 bool BitmapPlatformDevice::IsVectorial() {
   return false;
 }
 
 cairo_t* BitmapPlatformDevice::beginPlatformPaint() {
   data_->LoadConfig();
   cairo_t* cairo = data_->bitmap_context();
-  // Tell Cairo that we've (probably) modified its pixel buffer without
-  // its knowledge.
-  cairo_surface_mark_dirty(cairo_get_target(cairo));
+  cairo_surface_t* surface = cairo_get_target(cairo);
+  // Tell cairo to flush anything it has pending.
+  cairo_surface_flush(surface);

[Evan Martin, 2010/12/14 22:27:11]

Doesn't this belong in endPlatformPaint()?
It seems from the docs that you're supposed to call it before using non-cairo
APIs to work on the surface... I guess that's what the mark_dirty is for,
though, huh.

[vandebo (ex-Chrome), 2010/12/14 22:47:53]

I read the Docs the other way around.  flush needs to be called before you
modify the surface directly (cairo may have things it hasn't finalized to the
surface).  Then, if you modify the surface, you need to call mark_dirty before
making further cairo calls so that cairo knows to invalidate any cached state it
has.  Asserts in new versions of mark_dirty reinforce this interpretation.

Linux doesn't currently have an endPlatformPaint.  I assume this is ok and
currently works because mark_dirty just flushes cairo caches and doesn't
recompute anything.

+  // Tell Cairo that we (probably) modified (actually, will modify) its pixel
+  // buffer directly.
+  cairo_surface_mark_dirty(surface);
   return cairo;
 }
 
 void BitmapPlatformDevice::setMatrixClip(const SkMatrix& transform,
                                          const SkRegion& region) {
   data_->SetMatrixClip(transform, region);
 }
 
 BitmapPlatformDevice& BitmapPlatformDevice::operator=(
     const BitmapPlatformDevice& other) {
   data_ = other.data_;
   return *this;
 }
 
 }  // namespace skia