Thread: Why CS_OWNDC doesnt work?

Code:

HDC hDC;
	HBITMAP hbitmap;

	// create bitmap brush	
    hbitmap = LoadBitmap(hinst,MAKEINTRESOURCE(IDB_BACKGROUND));
	hbrush = CreatePatternBrush(hbitmap);
	DeleteBitmap(hbitmap);
	hDC = GetDC(hwnd);
	SelectBrush(hDC,hbrush);
	ReleaseDC(hwnd,hDC);
	SelectBrush(hDC,GetStockBrush(BLACK_BRUSH));

Hi, I have the above code right after i created a certain window. However, the window was not painted with the bitmap brush i created. Can someone explan why? I thought the new brush will takes effect for the rest of the program life if I use the style CS_OWNDC.

If I set the hbrBackground field to the bitmap brush during the window class registration, the window is painted properly. I find this very strange.

CS_OWNDC Just gives each window its own device context.

I have only made one window. It has its own DC and it is suppose to retain any changes in its DC attributes right? So if I change the brush after creating the window, it should be able to paint the window with the new bitmap brush or at least that's what I know.

Ah ha! It looks like you need to select the brush to the HDC before deleting the original bitmap.

I am quite sure i can delete the bitmap before i select the brush. Anyway i tried to select it in without deleting the bitmap. It still didnt work.

I didn't notice that he did that. Yeah that would be a major problem. There are some memory issues to consider when using CS_OWNDC depending on what you are doing too. CS_OWNDC is great for a window that serves as a canvas (i.e. a paint program), but in an app that is heavy on controls it tends to waste memory.

Removed all the ReleaseDC()s and EndPaint()...it still didnt work.
The strangest thing is that i checked the brush in the hDC using GetCurrentObject() and OBJ_BRUSH during every WM_PAINT msg. It has the right bitmap brush, but it just doesnt paint the window with that brush.

I can just fill the brush field with the bitmap brush before creating the window and make it work. But i really want to know what is wrong with the other method.

I managed to solve the problem by adding PatBlt while handling WM_PAINT msg.

Code:

void mainFrame::mainWindow_onPaint(HWND hwnd)
{
	PAINTSTRUCT ps;

	HDC hDC = BeginPaint(hwnd,&ps);
	PatBlt(hDC,0,0,512,512,PATCOPY);
	EndPaint(hwnd,&ps);
	
}

However, if i fill the hbrBackground field with the bitmap brush and do a PatBlt. I get a white screen again. Strange!

Hmm, i have encountered yet another problem, so i'm gonna post it here.

Code:

	// setup common controls
	icc.dwSize = sizeof(INITCOMMONCONTROLSEX);
	icc.dwICC = 0x00004000;//ICC_STANDARD_CLASSES
	InitCommonControlsEx(&icc);

Visual Studio .NET 2003 doesnt recognize ICC_STANDARD_CLASSES and complains it's a undeclared identifier. It is definitely found in <commctrl.h> and i have included that header file.

My edit control works without calling InitCommonControlsEx() or if i hardcode the value of dwICC. But Microsoft says i must call it to initialize controls and i dont want to expect any strange problem later.

Can someone help? Thanks alot!