fn on_nchittest()

in native/desktop-win32/src/win32/event_loop.rs [299:340]

• 42 lines of code
• 8 McCabe index (conditional complexity)

fn on_nchittest(event_loop: &EventLoop, window: &Window, wparam: WPARAM, lparam: LPARAM) -> Option<LRESULT> {
    if !window.has_custom_title_bar() || !window.is_resizable() {
        return None;
    }
    let hwnd = window.hwnd();
    let original_ht = {
        let mut dwm_result = LRESULT(0);
        if unsafe { DwmDefWindowProc(hwnd, WM_NCHITTEST, wparam, lparam, &raw mut dwm_result) }.as_bool() {
            dwm_result
        } else {
            unsafe { DefWindowProcW(hwnd, WM_NCHITTEST, wparam, lparam) }
        }
    };
    if original_ht != LRESULT(HTCLIENT as _) {
        return Some(original_ht);
    }
    let mouse_x = GET_X_LPARAM!(lparam.0);
    let mouse_y = GET_Y_LPARAM!(lparam.0);
    let event = NCHitTestEvent { mouse_x, mouse_y };
    let handled = event_loop.handle_event(window, event.into());
    if handled.is_some() {
        return Some(LRESULT(HTCLIENT as _));
    }
    let mut window_rect = RECT::default();
    let _ = unsafe { GetWindowRect(hwnd, &raw mut window_rect) };
    let current_dpi = unsafe { GetDpiForWindow(hwnd) };
    let resize_handle_height = unsafe {
        let current_dpi = GetDpiForWindow(hwnd);
        GetSystemMetricsForDpi(SM_CXPADDEDBORDER, current_dpi) + GetSystemMetricsForDpi(SM_CYSIZEFRAME, current_dpi)
    };
    let title_bar_height = resize_handle_height + unsafe { GetSystemMetricsForDpi(SM_CYSIZE, current_dpi) };
    let is_on_resize_border = mouse_y < (window_rect.top + resize_handle_height) as _;
    let is_within_title_bar = mouse_y < (window_rect.top + title_bar_height) as _;
    let hit_test_result = if is_on_resize_border {
        HTTOP
    } else if is_within_title_bar {
        HTCAPTION
    } else {
        HTCLIENT
    };
    Some(LRESULT(hit_test_result as _))
}