Window Management & Input

ATOM WINAPI RegisterClassA(const WNDCLASSA* lpWndClass);

WNDCLASSA wc = {};                       // zero-init all fields
wc.lpfnWndProc   = MyWindowProc;        // required
wc.hInstance     = hInstance;
wc.lpszClassName = "GameWindow";        // required
wc.style         = CS_HREDRAW | CS_VREDRAW;

ATOM a = RegisterClass(&wc);
if (!a) {
    OutputDebugString("RegisterClass failed!");
    return -1;
}
      

HWND WINAPI CreateWindowExA(
    DWORD   dwExStyle,     // extended style, e.g. WS_EX_TOPMOST
    LPCSTR  lpClassName,   // class name from RegisterClassA
    LPCSTR  lpWindowName,  // title bar text
    DWORD   dwStyle,       // window style flags
    int     X, int Y,      // initial position
    int     nWidth, int nHeight, // initial size
    HWND    hWndParent,    // parent (ignored: child semantics not supported)
    HMENU   hMenu,         // NULL
    HINSTANCE hInstance,
    LPVOID  lpParam        // passed in WM_CREATE's CREATESTRUCT.lpCreateParams
);

// Convenience macro (no extended style):
HWND WINAPI CreateWindowA(lpClassName, lpWindowName, dwStyle,
                          X, Y, nWidth, nHeight,
                          hWndParent, hMenu, hInstance, lpParam);
      

// Full-screen-like popup window (no title bar)
HWND hwnd = CreateWindowEx(
    0,                   // no extended styles
    "GameWindow",        // class name registered above
    "Speedy Blupi",      // window title
    WS_POPUP | WS_VISIBLE,
    0, 0,                // top-left corner
    640, 480,            // resolution
    NULL, NULL, hInstance, NULL);

if (!hwnd) {
    OutputDebugString("CreateWindow failed");
    return -1;
}
      

// Pattern 1: PeekMessage loop (non-blocking, good for games that render every frame)
MSG msg = {};
while (msg.message != WM_QUIT) {
    if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    } else {
        GameUpdate();  // called every frame when no messages are pending
        GameRender();
    }
}

// Pattern 2: GetMessage loop (blocking, good for event-driven apps)
MSG msg;
while (GetMessage(&msg, NULL, 0, 0)) {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
}
return (int)msg.wParam;  // exit code from PostQuitMessage
      

case WM_MOUSEMOVE: {
    int x = LOWORD(lParam);                  // cursor X in client coords
    int y = HIWORD(lParam);                  // cursor Y in client coords
    BOOL lBtn = (wParam & MK_LBUTTON) != 0; // left button held?
    BOOL shift = (wParam & MK_SHIFT) != 0;
    OnMouseMove(x, y, lBtn, shift);
    return 0;
}

case WM_LBUTTONDOWN: {
    int x = LOWORD(lParam);
    int y = HIWORD(lParam);
    OnLeftClick(x, y);
    return 0;
}

case WM_LBUTTONUP:
    OnLeftRelease(LOWORD(lParam), HIWORD(lParam));
    return 0;

case WM_RBUTTONDOWN:
    OnRightClick(LOWORD(lParam), HIWORD(lParam));
    return 0;
      

POINT pt;
GetCursorPos(&pt);           // pt is in screen (global) coordinates
ScreenToClient(hwnd, &pt);   // convert to client-area coordinates

if (pt.x >= 0 && pt.y >= 0 && pt.x < 640 && pt.y < 480) {
    // cursor is inside the window client area
}
      

UINT_PTR WINAPI SetTimer(
    HWND     hWnd,       // window to receive WM_TIMER
    UINT_PTR nIDEvent,   // timer ID (0 = auto-assign unique ID)
    UINT     uElapse,    // interval in milliseconds
    void*    lpTimerFunc // ignored — always use NULL
);

BOOL WINAPI KillTimer(HWND hWnd, UINT_PTR uIDEvent);
      

#define TIMER_ANIMATION  1
#define TIMER_AUTOSAVE   2

// In WM_CREATE:
SetTimer(hWnd, TIMER_ANIMATION, 50, NULL);    // 20 Hz animation tick
SetTimer(hWnd, TIMER_AUTOSAVE,  30000, NULL); // auto-save every 30 s

// In WNDPROC:
case WM_TIMER:
    switch (wParam) {
    case TIMER_ANIMATION: AnimationStep(); break;
    case TIMER_AUTOSAVE:  AutoSave();      break;
    }
    return 0;

// In WM_DESTROY:
KillTimer(hWnd, TIMER_ANIMATION);
KillTimer(hWnd, TIMER_AUTOSAVE);
PostQuitMessage(0);
      

RECT r1, r2, result;
SetRect(&r1, 0, 0, 100, 100);
SetRect(&r2, 50, 50, 200, 200);

if (IntersectRect(&result, &r1, &r2)) {
    // result = {50, 50, 100, 100}
}

RECT bound;
UnionRect(&bound, &r1, &r2);
// bound = {0, 0, 200, 200}
      

int WINAPIV wsprintfA(LPSTR lpOut, LPCSTR lpFmt, ...);

// 1024-byte fixed internal buffer — do not use for long strings
char buf[64];
wsprintfA(buf, "Score: %d  Level: %d", score, level);