WIP RasterCanvasLayerAllocator experiment 2

skia/ext/layer_allocator_win.cc

+// 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_win.h"
+#include "third_party/skia/include/core/SkMatrix.h"
+#include "third_party/skia/include/core/SkRect.h"
+
+namespace {
+
+void LoadClippingRegionToDC(HDC context,
+                            const SkMatrix& transformation,
+                            const SkIRect& clip_bounds) {
+  HRGN hrgn = CreateRectRgnIndirect(&skia::SkIRectToRECT(clip_bounds));
+  int result = SelectClipRgn(context, hrgn);
+  SkASSERT(result != ERROR);
+  result = DeleteObject(hrgn);
+  SkASSERT(result != 0);
+}
+
+// Old implementation restored the previously-selected bitmap
+// but it's not clear whether that is necessary.
+void FreeWindowsBacking(void* context) {
+  if (!context)
+    return;
+  HBITMAP bitmap;
+  bitmap = SelectObject(hbitmap, nullptr);
+  DeleteObject(hbitmap);
+  DeleteObject(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 it = contexts_.find(buffer);
+  if (it == contexts_.end())
+    return nullptr;
+
+  skia::LoadTransformToDC(it->second, transform);
+  LoadClippingRegionToDC(it->second, transform, clip_bounds);
+
+  // This is where we should flush the bitmap & mark it dirty,
+  // but the old implementation didn't seem to do so.
+
+  return it->second;
+}
+
+void* LayerAllocator::allocateLayer(const SkImageInfo& info,
+                                    size_t* rowBytes,
+                                    void (**deallocator)(void*),
+                                    void** deallocatorPayload,
+                                    void* initialData) {
+  SkASSERT(info.colorType() == kN32_SkColorType);
+
+  void* buffer = nullptr;
+  HDC context = nullptr;
+
+/*
+  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 = FreeWindowsBacking;
+  *deallocatorPayload = context;
+
+  return buffer;
+}
+
+}  // namespace skia
+