use SkRasterHandleAllocator to support GDI drawing in SkCanvas

skia/ext/raster_handle_allocator_win.cc

+// Copyright (c) 2017 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 <windows.h>
+#include <psapi.h>
+#include <stddef.h>
+
+#include "base/debug/gdi_debug_util_win.h"
+#include "base/memory/ptr_util.h"
+#include "base/logging.h"
+#include "base/win/win_util.h"
+#include "skia/ext/platform_canvas.h"
+#include "skia/ext/skia_utils_win.h"
+#include "third_party/skia/include/core/SkMatrix.h"
+#include "third_party/skia/include/core/SkPath.h"
+#include "third_party/skia/include/core/SkRefCnt.h"
+#include "third_party/skia/include/core/SkRect.h"
+
+namespace {
+
+static void DeleteHDCCallback(void*, void* context) {
+  HDC hdc = static_cast<HDC>(context);
+  HBITMAP hbitmap = static_cast<HBITMAP>(SelectObject(hdc, nullptr));
+  DeleteObject(hbitmap);
+  DeleteDC(hdc);
+}
+
+// Allocate the layer and fill in the fields for the Rec, or return false
+// on error.
+static bool Create(int width,
+                   int height,
+                   bool is_opaque,
+                   HANDLE shared_section,
+                   bool do_clear,
+                   SkRasterHandleAllocator::Rec* rec) {
+  void* pixels;
+  HBITMAP hbitmap =
+      skia::CreateHBitmap(width, height, is_opaque, shared_section, &pixels);
+  if (!hbitmap) {
+    LOG(ERROR) << "CreateHBitmap failed";
+    return false;
+  }
+
+  size_t row_bytes = skia::PlatformCanvasStrideForWidth(width);
+  if (do_clear)
+    sk_bzero(pixels, row_bytes * height);
+
+  HDC hdc = CreateCompatibleDC(nullptr);
+  if (!hdc) {
+    DeleteObject(hbitmap);
+    return false;
+  }
+  SetGraphicsMode(hdc, GM_ADVANCED);
+  SelectObject(hdc, hbitmap);
+
+  rec->fReleaseProc = DeleteHDCCallback;
+  rec->fReleaseCtx = hdc;
+  rec->fPixels = pixels;
+  rec->fRowBytes = row_bytes;
+  rec->fHandle = hdc;
+  return true;
+}
+
+/**
+ *  Subclass of SkRasterHandleAllocator that returns an HDC as its "handle".
+ */
+class GDIAllocator : public SkRasterHandleAllocator {
+ public:
+  GDIAllocator() {}
+
+  bool allocHandle(const SkImageInfo& info, Rec* rec) override {
+    SkASSERT(info.colorType() == kN32_SkColorType);
+    return Create(info.width(), info.height(), info.isOpaque(), nullptr,
+                  !info.isOpaque(), rec);
+  }
+
+  void updateHandle(Handle handle,
+                    const SkMatrix& ctm,
+                    const SkIRect& clip_bounds) override {
+    HDC hdc = static_cast<HDC>(handle);
+    skia::LoadTransformToDC(hdc, ctm);
+
+    HRGN hrgn = CreateRectRgnIndirect(&skia::SkIRectToRECT(clip_bounds));
+    int result = SelectClipRgn(hdc, hrgn);
+    DCHECK(result != ERROR);
+    result = DeleteObject(hrgn);
+    DCHECK(result != 0);
+  }
+};
+
+}  // namespace
+
+namespace skia {
+
+std::unique_ptr<SkCanvas> CreatePlatformCanvasWithSharedSection(
+    int width,
+    int height,
+    bool is_opaque,
+    HANDLE shared_section,
+    OnFailureType failure_type) {
+  SkAlphaType alpha = is_opaque ? kPremul_SkAlphaType : kOpaque_SkAlphaType;
+  SkImageInfo info = SkImageInfo::MakeN32(width, height, alpha);
+  size_t row_bytes = PlatformCanvasStrideForWidth(width);
+
+  // This function contains an implementation of a Skia platform bitmap for
+  // drawing and compositing graphics. The original implementation uses Windows
+  // GDI to create the backing bitmap memory, however it's possible for a
+  // process to not have access to GDI which will cause this code to fail. It's
+  // possible to detect when GDI is unavailable and instead directly map the
+  // shared memory as the bitmap.
+  if (base::win::IsUser32AndGdi32Available()) {
+    SkRasterHandleAllocator::Rec rec;
+    if (Create(width, height, is_opaque, shared_section, false, &rec))
+      return SkRasterHandleAllocator::MakeCanvas(
+          base::MakeUnique<GDIAllocator>(), info, &rec);
+  } else {
+    DCHECK(shared_section != NULL);
+    void* pixels =
+        MapViewOfFile(shared_section, FILE_MAP_WRITE, 0, 0, row_bytes * height);
+    if (pixels)
+      return SkCanvas::MakeRasterDirect(info, pixels, row_bytes);
+  }
+
+  if (failure_type == CRASH_ON_FAILURE)
+    SK_CRASH();
+  return nullptr;
+}
+
+HDC GetNativeDrawingContext(SkCanvas* canvas) {
+  return canvas ? static_cast<HDC>(canvas->accessTopRasterHandle()) : nullptr;
+}
+
+}  // namespace skia