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// Take a look at the license at the top of the repository in the LICENSE file.

use crate::FrameTimings;
use glib::translate::*;
use std::num::NonZeroU64;

impl FrameTimings {
    /// Gets the predicted time at which this frame will be displayed. Although
    /// no predicted time may be available, if one is available, it will
    /// be available while the frame is being generated, in contrast to
    /// [`presentation_time()`][Self::presentation_time()], which is only available
    /// after the frame has been presented. In general, if you are simply
    /// animating, you should use [`FrameClock::frame_time()`][crate::FrameClock::frame_time()] rather
    /// than this function, but this function is useful for applications
    /// that want exact control over latency. For example, a movie player
    /// may want this information for Audio/Video synchronization.
    ///
    /// # Returns
    ///
    /// The predicted time at which the frame will be presented,
    ///  in the timescale of `g_get_monotonic_time()`, or 0 if no predicted
    ///  presentation time is available.
    #[doc(alias = "gdk_frame_timings_get_predicted_presentation_time")]
    #[doc(alias = "get_predicted_presentation_time")]
    pub fn predicted_presentation_time(&self) -> Option<NonZeroU64> {
        let predicted_presentation_time = unsafe {
            ffi::gdk_frame_timings_get_predicted_presentation_time(self.to_glib_none().0)
        };
        // assuming presentation time is always positive
        assert!(predicted_presentation_time >= 0);
        // `0` means the value is not available
        NonZeroU64::new(predicted_presentation_time as u64)
    }

    /// Reurns the presentation time. This is the time at which the frame
    /// became visible to the user.
    ///
    /// # Returns
    ///
    /// the time the frame was displayed to the user, in the
    ///  timescale of `g_get_monotonic_time()`, or 0 if no presentation
    ///  time is available. See [`is_complete()`][Self::is_complete()]
    #[doc(alias = "gdk_frame_timings_get_presentation_time")]
    #[doc(alias = "get_presentation_time")]
    pub fn presentation_time(&self) -> Option<NonZeroU64> {
        let presentation_time =
            unsafe { ffi::gdk_frame_timings_get_presentation_time(self.to_glib_none().0) };
        // assuming presentation time is always positive
        assert!(presentation_time >= 0);
        // `0` means the value is not available
        NonZeroU64::new(presentation_time as u64)
    }

    /// Gets the natural interval between presentation times for
    /// the display that this frame was displayed on. Frame presentation
    /// usually happens during the “vertical blanking interval”.
    ///
    /// # Returns
    ///
    /// the refresh interval of the display, in microseconds,
    ///  or 0 if the refresh interval is not available.
    ///  See [`is_complete()`][Self::is_complete()].
    #[doc(alias = "gdk_frame_timings_get_refresh_interval")]
    #[doc(alias = "get_refresh_interval")]
    pub fn refresh_interval(&self) -> Option<NonZeroU64> {
        let refresh_interval =
            unsafe { ffi::gdk_frame_timings_get_refresh_interval(self.to_glib_none().0) };
        // assuming refresh interval is always positive
        assert!(refresh_interval >= 0);
        // `0` means the value is not available
        NonZeroU64::new(refresh_interval as u64)
    }
}