Make scoped dc objects smarter.

base/win/scoped_hdc_unittest.cc

Index: base/win/scoped_hdc_unittest.cc
===================================================================
--- base/win/scoped_hdc_unittest.cc	(revision 0)
+++ base/win/scoped_hdc_unittest.cc	(revision 0)
@@ -0,0 +1,86 @@
+// Copyright (c) 2012 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 "base/basictypes.h"
+#include "base/win/scoped_hdc.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+
+namespace {
+// Helper class that allows testing ScopedDC<T>.
+class TestScopedDC : public base::win::ScopedDC<TestScopedDC> {
+ public:
+  explicit TestScopedDC(HDC hdc)
+    : ScopedDC(hdc) {
+  }
+
+ private:
+  friend class base::win::ScopedDC<TestScopedDC>;
+
+  void DisposeDC(HDC hdc) {
+    // We leak the DC, so we can test its state. The test itself
+    // will dispose of the dc later.
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(TestScopedDC);
+};
+
+bool IsValidDC(HDC hdc) {
+  // The theory here is that any (cheap) GDI operation should fail for
+  // an invalid dc.
+  return GetCurrentObject(hdc, OBJ_BITMAP) != NULL;
+}
+
+}  // namespace.
+
+TEST(BaseWinScopedDC, CreateDestroy) {
+  HDC hdc1;
+  {
+    base::win::ScopedGetDC dc1(NULL);
+    hdc1 = dc1.Get();
+    EXPECT_TRUE(IsValidDC(hdc1));
+  }
+  EXPECT_FALSE(IsValidDC(hdc1));
+
+  HDC hdc2 = CreateDC(L"DISPLAY", NULL, NULL, NULL);
+  ASSERT_TRUE(IsValidDC(hdc2));
+  {
+    base::win::ScopedCreateDC dc2(hdc2);
+    EXPECT_TRUE(IsValidDC(hdc2));
+  }
+  EXPECT_FALSE(IsValidDC(hdc2));
+}
+
+TEST(BaseWinScopedDC, SelectObjects) {
+  HDC hdc = CreateCompatibleDC(NULL);
+  ASSERT_TRUE(IsValidDC(hdc));
+  HGDIOBJ bitmap = GetCurrentObject(hdc, OBJ_BITMAP);
+  HGDIOBJ brush = GetCurrentObject(hdc, OBJ_BRUSH);
+  HGDIOBJ pen = GetCurrentObject(hdc, OBJ_PEN);
+  HGDIOBJ font = GetCurrentObject(hdc, OBJ_FONT);
+
+  HBITMAP compat_bitmap = CreateCompatibleBitmap(hdc, 24, 24);
+  ASSERT_TRUE(compat_bitmap != NULL);
+  HBRUSH solid_brush = CreateSolidBrush(RGB(22, 33, 44));
+  ASSERT_TRUE(solid_brush != NULL);
+
+  {
+    TestScopedDC dc2(hdc);
+    dc2.SelectBitmap(compat_bitmap);
+    dc2.SelectBrush(solid_brush);
+    EXPECT_TRUE(bitmap != GetCurrentObject(hdc, OBJ_BITMAP));
+    EXPECT_TRUE(brush != GetCurrentObject(hdc, OBJ_BRUSH));
+  }
+
+  EXPECT_TRUE(bitmap == GetCurrentObject(hdc, OBJ_BITMAP));
+  EXPECT_TRUE(brush == GetCurrentObject(hdc, OBJ_BRUSH));
+  EXPECT_TRUE(pen == GetCurrentObject(hdc, OBJ_PEN));
+  EXPECT_TRUE(font == GetCurrentObject(hdc, OBJ_FONT));
+
+  EXPECT_TRUE(DeleteDC(hdc));
+  EXPECT_TRUE(DeleteObject(compat_bitmap));
+  EXPECT_TRUE(DeleteObject(solid_brush));
+}