Win32 WM_SIZE message gives wrong dimensions-CodePudding

I am working on some OpenGL interface stuff and noticed that when I startup my application the WM_SIZE message gets send with width=1260 and height=677, even though I created the window with width=1280 and height=720.

Here is how I create the window:

MainWindow.handle = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW, windowClass.lpszClassName,
        "Some window", WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 1280, 720, 
        NULL, NULL, instance, NULL);

This is how I handle WM_SIZE:

case WM_SIZE: {
    Camera.width = LOWORD(lParam);
    Camera.height = HIWORD(lParam);
    MainWindow.width = LOWORD(lParam);
    MainWindow.height = HIWORD(lParam);
    glViewport(0, 0, LOWORD(lParam), HIWORD(lParam));
} break;

I suspect that those values (1260, 677) are wrong and not the actual window dimensions, since my interface 'hitboxes' are slightly off. If I resize the window manually, no matter how much, the correct WM_SIZE is send and the hitboxes are fine.

My question is why is this first WM_SIZE even send and why are those values slightly off? Can I maybe send an extra manual WM_SIZE to combat the initial WM_SIZE?

CodePudding user response：

Per the

Use GetWindowRect() to get the position and dimensions of the entire window.

Otherwise, if you want the client area to be a particular size, use AdjustWindowRect() or AdjustWindowRectEx() to calculate the necessary window size before calling CreateWindowEx(), eg:

RECT r;
r.left = 0;
r.top = 0;
r.right = 1280;
r.bottom = 720;
AdjustWindowRectEx(&r, WS_OVERLAPPEDWINDOW, FALSE, WS_EX_OVERLAPPEDWINDOW);

MainWindow.handle = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW, windowClass.lpszClassName,
        "Some window", WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, r.right-r.left, r.bottom-r.top, 
        NULL, NULL, instance, NULL);