Thread: Centering a map, using GDI

Hi,

I'm having some problem trying to figure out a way how to center my rectangle inside my window. I'm trying to make the window ro stay centered even when the window is stretched or compressed. But I can't figure out a way how.


Here's my code:
-The DrawRect() function where I'm trying to center the rectangle
-The rest of the methods are just used to make the program run.

Code:

LRESULT CALLBACK HelloWndProc (HWND, UINT, WPARAM, LPARAM);
void DrawRect(HWND hwnd);

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, 
					PSTR szCMLine, int iCmdShow){
	static TCHAR szAppName[] = TEXT ("HelloApplication");
	static HWND	hwnd;
	MSG		msg;
	WNDCLASS wndclass;

	wndclass.style		= CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = HelloWndProc;
	wndclass.cbClsExtra	= 0;
	wndclass.cbWndExtra = sizeof(long)*2;
	wndclass.hInstance	= hInstance;
	wndclass.hIcon		= LoadIcon (NULL, IDI_APPLICATION);
	wndclass.hCursor	= LoadCursor (NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH);
	wndclass.lpszMenuName = NULL;
	wndclass.lpszClassName = szAppName;

	if (!RegisterClass (&wndclass)){
		MessageBox (NULL, TEXT ("This program requires Windows 95/98/NT"),
					szAppName, MB_ICONERROR);
		return 0;
	}
	hwnd = CreateWindow(szAppName,		
						TEXT("Quiz 2"), 
						WS_OVERLAPPEDWINDOW,	
						CW_USEDEFAULT,		
						CW_USEDEFAULT,		
						800,		
						600,		
						NULL,				
						NULL,				
						hInstance,			
						NULL);			
	SetWindowLong(hwnd,0,0);
	SetWindowLong(hwnd,4,0);
	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);
	
	while (TRUE){
		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			if (msg.message == WM_QUIT)
				break;
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
		else{
			DrawRect(hwnd);
			Sleep(500);
		}
	}
	return msg.wParam;
}

void DrawRect(HWND hwnd)
{
	HDC hdc;
	HBRUSH hBrush = CreateSolidBrush(RGB(0, 2, 255));
	HPEN hPen = CreatePen(PS_DASH, 1,(RGB(250, 5, 5)));

	static int  cxClient = 400;
	static int  cyClient = 300;
	static int EndX, EndY;
	long x, y;
	RECT rect;
	PAINTSTRUCT ps ;
	hdc = GetDC(hwnd);
	SelectObject(hdc, hBrush);
	SelectObject(hdc, hPen);
	x = GetWindowLong(hwnd,0);
	y = GetWindowLong(hwnd,4);

	BeginPaint(hwnd, &ps);
	SetMapMode(hdc, MM_ISOTROPIC);
	SetWindowExtEx(hdc, cxClient, -cyClient, NULL);
	SetViewportExtEx(hdc, 20, 40, NULL);
	SetViewportOrgEx(hdc, 400, 600, NULL);

	x *=2;
	y *=2;
	if ((x>= 6000) || (y>= 160000)){
		x = 200;
		y = 600;
	}
	if ((x==0) || (y==0)){
		x = 200;
		y = 600;
	}
	
	Rectangle(hdc,0,0,x,y);
	SetWindowLong(hwnd,0,x);
	SetWindowLong(hwnd,4,y);

	EndPaint (hwnd, &ps) ;
	
}

LRESULT CALLBACK HelloWndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){
	switch (message)
	{
		case WM_DESTROY:
			PostQuitMessage(0);
			return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}