WIP RasterCanvasLayerAllocator experiment 2

skia/ext/layer_allocator_cairo.cc

Index: skia/ext/layer_allocator_cairo.cc
diff --git a/skia/ext/layer_allocator_cairo.cc b/skia/ext/layer_allocator_cairo.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7519f5bebe9cb82ed722b1b9f34e0bb6cf027ef4
--- /dev/null
+++ b/skia/ext/layer_allocator_cairo.cc
@@ -0,0 +1,112 @@
+// Copyright 2016 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 "build/build_config.h"
+#include "skia/ext/layer_allocator_cairo.h"
+#include "third_party/skia/include/core/SkMatrix.h"
+#include "third_party/skia/include/core/SkRect.h"
+
+#if defined(OS_OPENBSD)
+#include <cairo.h>
+#else
+#include <cairo/cairo.h>
+#endif
+
+typedef struct _cairo_surface cairo_surface_t;
+
+namespace {
+
+void LoadMatrixToContext(cairo_t* context, const SkMatrix& matrix) {
+  cairo_matrix_t cairo_matrix;
+  cairo_matrix_init(&cairo_matrix,
+                    SkScalarToFloat(matrix.getScaleX()),
+                    SkScalarToFloat(matrix.getSkewY()),
+                    SkScalarToFloat(matrix.getSkewX()),
+                    SkScalarToFloat(matrix.getScaleY()),
+                    SkScalarToFloat(matrix.getTranslateX()),
+                    SkScalarToFloat(matrix.getTranslateY()));
+  cairo_set_matrix(context, &cairo_matrix);
+}
+
+void LoadClipToContext(cairo_t* context, const SkIRect& clip_bounds) {
+  cairo_reset_clip(context);
+
+  cairo_rectangle(context, clip_bounds.fLeft, clip_bounds.fTop,
+                  clip_bounds.width(), clip_bounds.height());
+  cairo_clip(context);
+}
+
+void FreeCairoBacking(void* context) {
+  if (!context)
+    return;
+  cairo_surface_destroy(cairo_get_target((cairo_t*) context));
+  cairo_destroy((cairo_t*) context);
+}
+
+}  // namespace
+
+namespace skia {
+
+LayerAllocator::LayerAllocator() { }
+
+LayerAllocator::~LayerAllocator() { }
+
+void* LayerAllocator::getNativeContext(void* buffer,
+                                       const SkMatrix& transform,
+                                       const SkIRect& clip_bounds) {
+  if (!buffer)
+    return nullptr;
+
+  context_map_t::iterator context_iterator = contexts_.find(buffer);
+  if (context_iterator == contexts_.end())
+    return nullptr;
+
+  LoadClipToContext(context_iterator->second, clip_bounds);
+  LoadMatrixToContext(context_iterator->second, transform);
+  cairo_surface_t* surface = cairo_get_target(context_iterator->second);
+  cairo_surface_flush(surface);
+  cairo_surface_mark_dirty(surface);
+  return context_iterator->second;
+}
+
+void* LayerAllocator::allocateLayer(const SkImageInfo& info,
+                                    size_t* rowBytes,
+                                    void (**deallocator)(void*),
+                                    void** deallocatorPayload,
+                                    void* initialData) {
+  SkASSERT(info.colorType() == kN32_SkColorType);
+
+  cairo_surface_t* surface;
+  if (initialData)
+    surface = cairo_image_surface_create_for_data(
+        (unsigned char*) initialData,
+        CAIRO_FORMAT_ARGB32,
+        info.width(),
+        info.height(),
+        cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, info.width()));
+  else
+    surface = cairo_image_surface_create(
+        CAIRO_FORMAT_ARGB32, info.width(), info.height());
+  if (!surface)
+    return nullptr;
+
+  if (rowBytes)
+    *rowBytes = cairo_image_surface_get_stride(surface);
+
+  cairo_t* context = cairo_create(surface);
+  if (!context) {
+    cairo_surface_destroy(surface);
+    return nullptr;
+  }
+  void* buffer = cairo_image_surface_get_data(surface);
+  contexts_.insert({buffer, context});
+
+  *deallocator = FreeCairoBacking;
+  *deallocatorPayload = context;
+
+  return buffer;
+}
+
+}  // namespace skia
+