Consolidate Windows bitmap and DC code

skia/ext/skia_utils_win.cc

Index: skia/ext/skia_utils_win.cc
diff --git a/skia/ext/skia_utils_win.cc b/skia/ext/skia_utils_win.cc
index 9873373725705fe6f8e4491a54ebd56916829276..c53bb3e35838a22e3018acbceaaa7b67236c56a0 100644
--- a/skia/ext/skia_utils_win.cc
+++ b/skia/ext/skia_utils_win.cc
@@ -7,7 +7,10 @@
 #include <stddef.h>
 #include <windows.h>
 
+#include "base/debug/gdi_debug_util_win.h"
+#include "base/win/win_util.h"
 #include "third_party/skia/include/core/SkRect.h"
+#include "third_party/skia/include/core/SkSurface.h"
 #include "third_party/skia/include/core/SkTypes.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 
@@ -23,8 +26,42 @@ static_assert(sizeof(RECT().right) == sizeof(SkIRect().fRight), "o7");
 static_assert(sizeof(RECT().bottom) == sizeof(SkIRect().fBottom), "o8");
 static_assert(sizeof(RECT) == sizeof(SkIRect), "o9");
 
-}  // namespace
+HBITMAP CreateHBitmap(int width, int height) {
+  // 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;
+
+  HBITMAP hbitmap = CreateDIBSection(nullptr, reinterpret_cast<BITMAPINFO*>(&hdr),

[Peter Kasting, 2016/02/16 21:12:10]

Nit: 80 columns

[tomhudson, 2016/06/21 22:20:22]

Done.

+                                     0, nullptr, nullptr, 0);
+
+#if !defined(_WIN64)
+  // If CreateDIBSection() failed, try to get some useful

[Peter Kasting, 2016/02/16 21:12:10]

Nit: Wrap as late as possible

[tomhudson, 2016/06/21 22:20:22]

Done.

+  // information out before we crash for post-mortem analysis.
+  if (!hbitmap)
+    base::debug::GDIBitmapAllocFailure(&hdr, nullptr);
+#endif
+
+  return hbitmap;
+}
 
+
+}  // namespace
 namespace skia {
 
 POINT SkPointToPOINT(const SkPoint& point) {
@@ -73,7 +110,7 @@ void InitializeDC(HDC context) {
   SkASSERT(res != 0);
   // As per SetStretchBltMode() documentation, SetBrushOrgEx() must be called
   // right after.
-  res = SetBrushOrgEx(context, 0, 0, NULL);
+  res = SetBrushOrgEx(context, 0, 0, nullptr);
   SkASSERT(res != 0);
 
   // Sets up default orientation.
@@ -97,5 +134,94 @@ void InitializeDC(HDC context) {
   SkASSERT(res != 0);
 }
 
+#if 0
+namespace {
+
+bool PrepareAllocation(HDC context, SkImageInfo* size, BITMAP* backing) {
+  HBITMAP backing_handle =
+      static_cast<HBITMAP>(GetCurrentObject(context, OBJ_BITMAP));
+  if (GetObject(backing_handle, sizeof(*backing),
+                             backing) != sizeof(*backing))
+    return false;
+  *size = SkImageInfo::MakeN32Premul(backing->bmWidth,
+                                     backing->bmHeight);
+  return true;
+}
+
+}
+
+SkSurface* MapPlatformSurface(HDC context) {
+  SkImageInfo size;
+  Bitmap backing;
+  if (!PrepareAllocation(HDC, &size, &backing))
+    return nullptr;
+  return SkSurface::NewRasterDirect(size, backing.bmBits,
+                                    backing.bmWidthBytes);
+}
+  
+SkBitmap MapPlatformBitmap(HDC context) {
+  SkImageInfo size;
+  Bitmap backing;
+  SkBitmap bitmap;
+  if (PrepareAllocation(HDC, &size, &backing))
+    bitmap.installPixels(size, backing.bmBits, size.minRowBytes());
+  return bitmap;
+}
+#endif
+
+SkSurface* MapPlatformSurface(HDC context) {
+  HBITMAP backing_handle =
+      static_cast<HBITMAP>(GetCurrentObject(context, OBJ_BITMAP));
+  BITMAP backing;
+  if (GetObject(backing_handle, sizeof(backing),
+                &backing) != sizeof(backing))
+    return nullptr;
+  return SkSurface::NewRasterDirect(
+      SkImageInfo::MakeN32Premul(backing.bmWidth, backing.bmHeight),
+      backing.bmBits, backing.bmWidthBytes);
+}
+
+SkBitmap MapPlatformBitmap(HDC context) {
+  HBITMAP backing_handle =
+    static_cast<HBITMAP>(GetCurrentObject(context, OBJ_BITMAP));
+  BITMAP backing;
+  SkBitmap bitmap;
+  if (GetObject(backing_handle, sizeof(backing),
+                &backing) == sizeof(backing)) {
+    SkImageInfo size = SkImageInfo::MakeN32Premul(backing.bmWidth,
+                                                  backing.bmHeight);
+    bitmap.installPixels(size, backing.bmBits, size.minRowBytes());
+  }
+  return bitmap;
+}
+
+HDC CreateOffscreenSurface(int width, int height) {
+  HBITMAP bitmap = nullptr;
+
+  // If this process doesn't have access to GDI, we'll have to use a shared
+  // memory segment instead.
+  if (!base::win::IsUser32AndGdi32Available())
+    return nullptr;
+
+  bitmap = CreateHBitmap(width, height);
+  if (!bitmap)
+    return nullptr;
+
+  HDC hdc = CreateCompatibleDC(nullptr);
+  SkASSERT(hdc);
+  InitializeDC(hdc);
+  HRGN clip = CreateRectRgn(0, 0, width, height);
+  int result = SelectClipRgn(hdc, clip);
+  SkASSERT(result != ERROR);
+  result = DeleteObject(clip);
+  SkASSERT(result);
+
+  SelectObject(hdc, bitmap);
+
+  // need to clean up by calling DeleteDC(hdc) else we leak!
+
+  return hdc;
+}
+
 }  // namespace skia