Introduce PlatformBitmap, which is a minimal helper class that wraps an SkBitmap

skia/ext/bitmap_platform_device_win.cc

Index: skia/ext/bitmap_platform_device_win.cc
===================================================================
--- skia/ext/bitmap_platform_device_win.cc	(revision 160846)
+++ skia/ext/bitmap_platform_device_win.cc	(working copy)
@@ -6,13 +6,46 @@
 #include <psapi.h>
 
 #include "skia/ext/bitmap_platform_device_win.h"
-
 #include "skia/ext/bitmap_platform_device_data.h"
+#include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "third_party/skia/include/core/SkUtils.h"
 
+static HBITMAP CreateHBitmap(int width, int height, bool is_opaque,
+                             HANDLE shared_section, SkBitmap* output) {
+  // CreateDIBSection appears to get unhappy if we create an empty bitmap, so
+  // just create a minimal bitmap
+  if ((width == 0) || (height == 0)) {
+    width = 1;
+    height = 1;
+  }
+    
+  BITMAPINFOHEADER hdr = {0};
+  hdr.biSize = sizeof(BITMAPINFOHEADER);
+  hdr.biWidth = width;
+  hdr.biHeight = -height;  // minus means top-down bitmap
+  hdr.biPlanes = 1;
+  hdr.biBitCount = 32;
+  hdr.biCompression = BI_RGB;  // no compression
+  hdr.biSizeImage = 0;
+  hdr.biXPelsPerMeter = 1;
+  hdr.biYPelsPerMeter = 1;
+  hdr.biClrUsed = 0;
+  hdr.biClrImportant = 0;
+
+  void* data = NULL;
+  HBITMAP hbitmap = CreateDIBSection(NULL, reinterpret_cast<BITMAPINFO*>(&hdr),
+                                     0, &data, shared_section, 0);
+  if (hbitmap) {
+    output->setConfig(SkBitmap::kARGB_8888_Config, width, height);
+    output->setPixels(data);
+    output->setIsOpaque(is_opaque);
+  }
+  return hbitmap;
+}
+
 namespace skia {
 
 BitmapPlatformDevice::BitmapPlatformDeviceData::BitmapPlatformDeviceData(
@@ -94,38 +127,11 @@
     HANDLE shared_section) {
   SkBitmap bitmap;
 
-  // CreateDIBSection appears to get unhappy if we create an empty bitmap, so
-  // just create a minimal bitmap
-  if ((width == 0) || (height == 0)) {
-    width = 1;
-    height = 1;
-  }
-
-  BITMAPINFOHEADER hdr = {0};
-  hdr.biSize = sizeof(BITMAPINFOHEADER);
-  hdr.biWidth = width;
-  hdr.biHeight = -height;  // minus means top-down bitmap
-  hdr.biPlanes = 1;
-  hdr.biBitCount = 32;
-  hdr.biCompression = BI_RGB;  // no compression
-  hdr.biSizeImage = 0;
-  hdr.biXPelsPerMeter = 1;
-  hdr.biYPelsPerMeter = 1;
-  hdr.biClrUsed = 0;
-  hdr.biClrImportant = 0;
-
-  void* data = NULL;
-  HBITMAP hbitmap = CreateDIBSection(NULL,
-                                     reinterpret_cast<BITMAPINFO*>(&hdr), 0,
-                                     &data,
-                                     shared_section, 0);
+  HBITMAP hbitmap = CreateHBitmap(width, height, is_opaque, shared_section,
+                                  &bitmap);
   if (!hbitmap)
     return NULL;
 
-  bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
-  bitmap.setPixels(data);
-  bitmap.setIsOpaque(is_opaque);
-
 #ifndef NDEBUG
   // If we were given data, then don't clobber it!
   if (!shared_section && is_opaque)
@@ -262,4 +268,26 @@
   return bitmap_device;
 }
 
+// Port of PlatformBitmap to win
+
+PlatformBitmap::~PlatformBitmap() {
+  if (surface_)
+    DeleteDC(surface_);
+}
+
+bool PlatformBitmap::Allocate(int width, int height, bool is_opaque) {
+  HBITMAP hbitmap = CreateHBitmap(width, height, is_opaque, 0, &bitmap_);
+  if (!hbitmap)
+    return false;
+
+  surface_ = CreateCompatibleDC(NULL);
+  InitializeDC(surface_);
+  HGDIOBJ old_bitmap = SelectObject(surface_, hbitmap);
+  // When the memory DC is created, its display surface is exactly one
+  // monochrome pixel wide and one monochrome pixel high. Since we select our
+  // own bitmap, we must delete the previous one.
+  DeleteObject(old_bitmap);
+  return true;
+}
+
 }  // namespace skia