base/win/scoped_hdc.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_WIN_SCOPED_HDC_H_
   6 #define BASE_WIN_SCOPED_HDC_H_
   7
   8 #include <windows.h>
   9
  10 #include "base/basictypes.h"
  11 #include "base/logging.h"
  12 #include "base/win/scoped_handle.h"
  13
  14 namespace base {
  15 namespace win {
  16
  17 // Like ScopedHandle but for HDC.  Only use this on HDCs returned from
  18 // GetDC.
  19 class ScopedGetDC {
  20  public:
  21   explicit ScopedGetDC(HWND hwnd)
  22       : hwnd_(hwnd),
  23         hdc_(GetDC(hwnd)) {
  24     if (hwnd_) {
  25       DCHECK(IsWindow(hwnd_));
  26       DCHECK(hdc_);
  27     } else {
  28       // If GetDC(NULL) returns NULL, something really bad has happened, like
  29       // GDI handle exhaustion.  In this case Chrome is going to behave badly no
  30       // matter what, so we may as well just force a crash now.
  31       CHECK(hdc_);
  32     }
  33   }
  34
  35   ~ScopedGetDC() {
  36     if (hdc_)
  37       ReleaseDC(hwnd_, hdc_);
  38   }
  39
  40   operator HDC() { return hdc_; }
  41
  42  private:
  43   HWND hwnd_;
  44   HDC hdc_;
  45
  46   DISALLOW_COPY_AND_ASSIGN(ScopedGetDC);
  47 };
  48
  49 // Like ScopedHandle but for HDC.  Only use this on HDCs returned from
  50 // CreateCompatibleDC, CreateDC and CreateIC.
  51 class CreateDCTraits {
  52  public:
  53   typedef HDC Handle;
  54
  55   static bool CloseHandle(HDC handle) {
  56     return ::DeleteDC(handle) != FALSE;
  57   }
  58
  59   static bool IsHandleValid(HDC handle) {
  60     return handle != NULL;
  61   }
  62
  63   static HDC NullHandle() {
  64     return NULL;
  65   }
  66
  67  private:
  68   DISALLOW_IMPLICIT_CONSTRUCTORS(CreateDCTraits);
  69 };
  70
  71 typedef GenericScopedHandle<CreateDCTraits, VerifierTraits> ScopedCreateDC;
  72
  73 }  // namespace win
  74 }  // namespace base
  75
  76 #endif  // BASE_WIN_SCOPED_HDC_H_