moving graphics in a win32 c++ window

[Calin Negru]

I`m trying to animate things in a basic window. The code I have should get a rectangle (rc) move to the right however that does not happen, it`s all static.

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
static RECT rcBmp;
static HDC hdcCompat;
static HBITMAP hbmp;
static RECT rc;
static RECT rc2;
static RECT rc3;
static RECT rc4;
HBRUSH hbrWhite, hbrGray;
const COLORREF SomeColor = RGB(255,255,255);
const COLORREF SomeColor2 = RGB(0,0,1);
hbrWhite = CreateSolidBrush(SomeColor);
hbrGray = CreateSolidBrush(SomeColor2);

int y = 0;
HDC hdc = (HDC) wParam; 


switch (uMsg)
{
	case WM\_CREATE: 
	
	return 0L; 

case WM_ERASEBKGND:

GetClientRect(hwnd, &rc); 
SetMapMode(hdc, MM\_ANISOTROPIC); 
SetWindowExtEx(hdc, 100, 100, NULL); 
SetViewportExtEx(hdc, rc.right, rc.bottom, NULL); 
FillRect(hdc, &rc, hbrWhite); 


   
   
return 0;

case WM\_DESTROY:
    PostQuitMessage(0);
    return 0;

	
       
case WM\_PAINT:
    {
        PAINTSTRUCT ps;
		
        HDC hdc = BeginPaint(hwnd, &ps);

        

       
		 SetRect(&rc,x, 20, 40, 40); 
		FillRect(hdc, &rc, hbrGray); 
		SetRect(&rc2,60, 60, 80, 80); 
		FillRect(hdc, &rc2, hbrGray); 

        EndPaint(hwnd, &ps);
    }
    return 0;

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

}
void GameUpdate()
{

x = x +1;

}

[Edit] it looks like WM_PAINT isn`t triggered every frame, only if I minimize and then maximize the window a change takes place

[Lost User]

I think you need an "event"; like a timer tick; in order to create a "frame loop" (update and paint).

"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I

[Graham Breach]

Windows is event-driven, it doesn't have regular animation frame updates. You can use SetTimer() to get WM_TIMER messages as often as you want, then invalidate your window to get the WM_PAINT message and repaint. GDI performance is not very good though, so to reduce flicker you'll probably want to draw to an offscreen compatible device context and then BitBlt() that to the screen. Or use Direct2D - but then you'll have a new problem to think about.

[Lost User]

You need to call InvalidateRect function (winuser.h) - Win32 apps | Microsoft Docs[^] each time the object's position changes. The WM_PAINT message is only sent when Windows decides that the view needs repainting. Calling InvalidateRect tells it to do this.

[Calin Negru]

I had in mind switching my videogame from DirectX to GDI. After some attempts at getting a win app working the way I need it and failing I will probably give up on the idea. I should probably keep using DirectX. Thanks for your help Richard and everyone else. Sorry for taking your time, this GDI idea is just a dead end.

[Lost User]

I would suggest you remove that link from your message (and future ones), as the system assumes it is spam. And some people here will just flag the message which means it will not get published.