關於BS_OWNERDRAW的用法

轉：http://blog.csdn.net/kof2001kop/article/details/7233844

BS_OWNERDRAW用於自繪按鈕，通常與WM_CTLCOLORBTN消息連用,如下:

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND button0;

    switch (message)
    {
    case WM_CREATE:
        button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_OWNERDRAW, 20, 20, 400, 200,
                                hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
        return 0;

    case WM_CTLCOLORBTN:
        return (LRESULT)CreateSolidBrush(RGB(0, 255, 0));

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HWND button0;

	switch (message)
	{
	case WM_CREATE:
		button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_OWNERDRAW, 20, 20, 400, 200,
								hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);	
		return 0;

	case WM_CTLCOLORBTN:
		return (LRESULT)CreateSolidBrush(RGB(0, 255, 0));
			
	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, message, wParam, lParam);
}

 上述代碼的結果會顯示出一個綠色的按鈕。

但如果想在按鈕上顯示一個位圖或圖標，則不能使用BS_OWNERDRAW，而要用BS_ICON或BS_BITMAP，並和SendMessage函數連用，如下：

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND button0;

    switch (message)
    {
    case WM_CREATE:
        button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_ICON, 20, 20, 400, 200,
                                hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
        SendMessage(button0, BM_SETIMAGE, IMAGE_ICON, (LPARAM)LoadIcon(NULL, IDI_ERROR));
        return 0;

    case WM_CTLCOLORBTN:                                  //因爲沒有了BS_OWNERDRAW,所以被忽略了
        return (LRESULT)CreateSolidBrush(RGB(0, 255, 0)); //不起任何作用

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HWND button0;

	switch (message)
	{
	case WM_CREATE:
		button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_ICON, 20, 20, 400, 200,
								hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);	
		SendMessage(button0, BM_SETIMAGE, IMAGE_ICON, (LPARAM)LoadIcon(NULL, IDI_ERROR));
		return 0;

	case WM_CTLCOLORBTN:                                  //因爲沒有了BS_OWNERDRAW,所以被忽略了
		return (LRESULT)CreateSolidBrush(RGB(0, 255, 0)); //不起任何作用
			
	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, message, wParam, lParam);
}

 上述代碼會顯示出一個帶有錯誤標記的按鈕，而WM_CTLCOLORBTN的觸發標誌是按鈕被重繪，因爲沒有了BS_OWNERDRAW，所以按鈕不能被重繪，即WM_CTLCOLORBTN消息不會被觸發。

但如果在上述代碼中，再加入BS_OWNERDRAW，那麼按鈕會既有位圖，又有自繪顏色嗎？

即：

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND button0;

    switch (message)
    {
    case WM_CREATE:
        button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_OWNERDRAW | BS_ICON, 20, 20, 400,
                               200, hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
        SendMessage(button0, BM_SETIMAGE, IMAGE_ICON, (LPARAM)LoadIcon(NULL, IDI_ERROR)); //因爲有了BS_OWNERDRAW,導致不起作用
        return 0;

    case WM_CTLCOLORBTN:                                  //因爲有了BS_OWNERDRAW,再次被觸發
        return (LRESULT)CreateSolidBrush(RGB(0, 255, 0));

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HWND button0;

	switch (message)
	{
	case WM_CREATE:
		button0 = CreateWindow(L"button", NULL, WS_CHILD | WS_VISIBLE | BS_OWNERDRAW | BS_ICON, 20, 20, 400,
							   200, hwnd, (HMENU)1, ((LPCREATESTRUCT)lParam)->hInstance, NULL);	
		SendMessage(button0, BM_SETIMAGE, IMAGE_ICON, (LPARAM)LoadIcon(NULL, IDI_ERROR)); //因爲有了BS_OWNERDRAW,導致不起作用
		return 0;

	case WM_CTLCOLORBTN:                                  //因爲有了BS_OWNERDRAW,再次被觸發
		return (LRESULT)CreateSolidBrush(RGB(0, 255, 0)); 

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, message, wParam, lParam);
}

上述代碼的結果是顯示一綠色的按鈕，而按鈕上不見任何的位圖。所以，如果在創建按鈕的窗口句柄時，在CreateWindow中使用了BS_OWNERDRAW，那麼就不能用SendMessage函數在按鈕上載入位圖或圖標了，即使有BS_ICON也不能載入。
 

PS: 在WM_CTLCOLORBTN內所做的一切代碼，只與設備環境句柄（HDC）有關，如果嘗試通過窗口句柄（HWND）來更改什麼，例如用SetWindowText（用到hwnd）來改變按鈕內文字，都將無效或陷入死循環。