pub enum PresentMode {
    /// The presentation engine does **not** wait for a vertical blanking period and 
    /// the request is presented immediately. This is a low-latency presentation mode,
    /// but visible tearing may be observed. Will fallback to `Fifo` if unavailable on the
    /// selected  platform and backend. Not optimal for mobile. 
    Immediate = 0,
    /// The presentation engine waits for the next vertical blanking period to update
    /// the current image, but frames may be submitted without delay. This is a low-latency 
    /// presentation mode and visible tearing will **not** be observed. Will fallback to `Fifo`
    /// if unavailable on the selected platform and backend. Not optimal for mobile.
    Mailbox = 1,
    /// The presentation engine waits for the next vertical blanking period to update 
    /// the current image. The framerate will be capped at the display refresh rate, 
    /// corresponding to the `VSync`. Tearing cannot be observed. Optimal for mobile.
    Fifo = 2,
}