win32_dvd_screensaver.c

#include <stdio.h>
#include <windows.h>

RECT gUsableAreaCoords = {0};
RECT gCurrentPos = {0};
INT gVelocityX = 5;
INT gVelocityY = 5;

DWORD gLast = 0;

#define WINDOW_X 320
#define WINDOW_Y 200

POINT gLastMousePos = {0};

LRESULT CALLBACK WindowProcessMessages(HWND hwnd, UINT msg, WPARAM param, LPARAM lparam) {
	DWORD now = GetTickCount();
	POINT currMousePos = {0};

	GetCursorPos(&currMousePos);
	if (currMousePos.x != gLastMousePos.x || currMousePos.y != gLastMousePos.y)
		PostQuitMessage(0);


	if ((now - gLast) > 10) {
		gLast = now;

		if (gCurrentPos.left <= 0 || gCurrentPos.left >= (gUsableAreaCoords.right - WINDOW_X)) { gVelocityX *= -1; }
		if (gCurrentPos.top <= 0 || gCurrentPos.top >= (gUsableAreaCoords.bottom - WINDOW_Y)) { gVelocityY *= -1; }

		GetWindowRect(hwnd, &gCurrentPos);

		gCurrentPos.left += gVelocityX;
		gCurrentPos.top += gVelocityY;

		SetWindowPos(hwnd, 0, gCurrentPos.left, gCurrentPos.top, WINDOW_X, WINDOW_Y, SWP_NOZORDER | SWP_NOSIZE | SWP_NOACTIVATE);
	}

	RECT rc = {0};
	GetClientRect(hwnd, &rc);
	InvalidateRect(hwnd, &rc, TRUE);

	switch (msg) {
		case WM_DESTROY:
			PostQuitMessage(0);
			return 0;
		default:
			return DefWindowProc(hwnd, msg, param, lparam);
	}
}


int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
	gLast = GetTickCount();
	GetCursorPos(&gLastMousePos);

	SystemParametersInfo(SPI_GETWORKAREA, 0, &gUsableAreaCoords, 0);

	WNDCLASS wc = {0};
	wc.hInstance = hInstance;
	wc.lpszClassName = "Something";
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
	wc.lpfnWndProc = WindowProcessMessages;
	RegisterClass(&wc);

	CreateWindowA("Something", "Fun", WS_SYSMENU | WS_VISIBLE, WINDOW_X, WINDOW_Y, WINDOW_X, WINDOW_Y, NULL, NULL, NULL, NULL);

	MSG msg = {0};
	while (GetMessage(&msg, NULL, 0, 0)) {
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}

	return 0;
}