base/win/scoped_hdc.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_WIN_SCOPED_HDC_H_
#define BASE_WIN_SCOPED_HDC_H_

#include <windows.h>

#include "base/check.h"
#include "base/debug/gdi_debug_util_win.h"
#include "base/win/scoped_handle.h"

namespace base {
namespace win {

// Like ScopedHandle but for HDC.  Only use this on HDCs returned from
// GetDC.
class ScopedGetDC {
 public:
  explicit ScopedGetDC(HWND hwnd) : hwnd_(hwnd), hdc_(GetDC(hwnd)) {
    if (hwnd_) {
      DCHECK(IsWindow(hwnd_));
      DCHECK(hdc_);
    } else {
      // If GetDC(NULL) returns NULL, something really bad has happened, like
      // GDI handle exhaustion.  In this case Chrome is going to behave badly no
      // matter what, so we may as well just force a crash now.
      if (!hdc_)
        base::debug::CollectGDIUsageAndDie();
    }
  }

  ScopedGetDC(const ScopedGetDC&) = delete;
  ScopedGetDC& operator=(const ScopedGetDC&) = delete;

  ~ScopedGetDC() {
    if (hdc_)
      ReleaseDC(hwnd_, hdc_);
  }

  operator HDC() { return hdc_; }

 private:
  HWND hwnd_;
  HDC hdc_;
};

// Like ScopedHandle but for HDC.  Only use this on HDCs returned from
// CreateCompatibleDC, CreateDC and CreateIC.
class CreateDCTraits {
 public:
  typedef HDC Handle;

  CreateDCTraits() = delete;
  CreateDCTraits(const CreateDCTraits&) = delete;
  CreateDCTraits& operator=(const CreateDCTraits&) = delete;

  static bool CloseHandle(HDC handle) { return ::DeleteDC(handle) != FALSE; }

  static bool IsHandleValid(HDC handle) { return handle != NULL; }

  static HDC NullHandle() { return NULL; }
};

typedef GenericScopedHandle<CreateDCTraits, DummyVerifierTraits> ScopedCreateDC;

}  // namespace win
}  // namespace base

#endif  // BASE_WIN_SCOPED_HDC_H_