计时器消息会因为重绘消息停止？

不知道为什么拖动边框或者最大最小化会使定时器停止，求解释消息的机制，萌新求解释┭┮﹏┭┮

LRESULT CALLBACK wndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam)
{
PAINTSTRUCT paintStruct;

switch (message)
{
case WM_TIMER:              
    Game_Paint(hwnd);                
    return 0;
case WM_PAINT:
    g_hdc = BeginPaint(hwnd,&paintStruct);
    Game_Paint(hwnd);
    EndPaint(hwnd,&paintStruct);
    ValidateRect(hwnd,NULL);

    return 0;
case WM_KEYDOWN:
    if (wparam == VK_ADD)
    {
        DestroyWindow(hwnd);

    }return 0;
case WM_DESTROY:
    Game_Cleanup(hwnd);
    PostQuitMessage(0);
    return 0;
default:
    return DefWindowProc(hwnd,message,wparam,lparam);
}

}

找一下程式裡, KillTimer 有那些地方有被執行了......
wndProc 裡看不到有結束 Timer 的動作