Thread: Manipulating window from a dialog box

You need to use a "modeless" dialog box and handle the message loop yourself. Here's an example (not the best coding style, but you get the idea). Just make a dialog resource with an OK button (IDOK) and cancel button (IDCANCEL). Pushing the OK button toggles the window. Cancel closes the app.

Code:

#include <windows.h>

#define CLASS_NAME "AClass"

HWND      g_hwndWnd;
HWND      g_hwndDlg;
HINSTANCE g_hinst;

INT_PTR CALLBACK DialogProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam) {
	switch (uMsg) {
	case WM_INITDIALOG:
		return TRUE;
	case WM_COMMAND:
		switch (LOWORD(wParam)) {
		case IDOK:
			if (g_hwndWnd == 0) {
				g_hwndWnd = CreateWindowEx(
					0, CLASS_NAME, "Example",
					WS_OVERLAPPEDWINDOW,
					200, 0, 300, 300,
					NULL, NULL, g_hinst, NULL
					);
				if (g_hwndWnd == NULL) {
					MessageBox(0, "Can't create window", 0, 0);
					return TRUE;
				}
				ShowWindow(g_hwndWnd, SW_SHOW);
			}else{
				DestroyWindow(g_hwndWnd);
				g_hwndWnd = 0;
			}
			return TRUE;
		case IDCANCEL:
			DestroyWindow(g_hwndDlg);
			g_hwndDlg = 0;
			PostQuitMessage(0);
			return TRUE;
		}
	}
	return FALSE;
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
	switch (uMsg) {
	case WM_CLOSE:
		DestroyWindow(g_hwndWnd);
		g_hwndWnd = 0;
		return 0;
	}
	return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

int WinMain(HINSTANCE hinst, HINSTANCE unused, LPSTR cmd, int show) {
	WNDCLASS wc = { 0 };
	MSG msg;
	BOOL bRet;

	g_hinst = hinst;

	wc.style         = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc   = WindowProc;
	wc.hInstance     = hinst;
	wc.lpszClassName = CLASS_NAME;
	wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
	RegisterClass(&wc);

	g_hwndDlg = CreateDialog(hinst, MAKEINTRESOURCE(1001), 0, DialogProc);

	while ((bRet = GetMessage(&msg, NULL, 0, 0)) != 0) {
		if (bRet == -1) {
			MessageBox(0, "Error in GetMessage", 0, 0);
			return 0;
		}
		else if (!IsWindow(g_hwndDlg) || !IsDialogMessage(g_hwndDlg, &msg)) {
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}

    return 0;
}

You choose which window procedure will handle the timer by passing SetTimer the desired hwnd:

Code:

SetTimer(g_hwndWnd, 1, 200, 0);