metal: make post_commit_margin configurable

jay-config/src/_private/client.rs

@@ -744,6 +744,10 @@ impl Client {
         self.send(&ClientMessage::SetDirectScanoutEnabled { device, enabled });
     }
 
+    pub fn set_flip_margin(&self, device: DrmDevice, margin: Duration) {
+        self.send(&ClientMessage::SetFlipMargin { device, margin });
+    }
+
     pub fn connector_connected(&self, connector: Connector) -> bool {
         let res = self.send_with_response(&ClientMessage::ConnectorConnected { connector });
         get_response!(res, false, ConnectorConnected { connected });

jay-config/src/_private/ipc.rs

@@ -513,6 +513,10 @@ pub enum ClientMessage<'a> {
         connector: Connector,
         format: Format,
     },
+    SetFlipMargin {
+        device: DrmDevice,
+        margin: Duration,
+    },
 }
 
 #[derive(Serialize, Deserialize, Debug)]

jay-config/src/video.rs

@@ -12,7 +12,7 @@ use {
         _private::WireMode,
     },
     serde::{Deserialize, Serialize},
-    std::str::FromStr,
+    std::{str::FromStr, time::Duration},
 };
 
 /// The mode of a connector.
@@ -504,6 +504,16 @@ impl DrmDevice {
     pub fn set_direct_scanout_enabled(self, enabled: bool) {
         get!().set_direct_scanout_enabled(Some(self), enabled);
     }
+
+    /// Sets the flip margin of this device.
+    ///
+    /// This is duration between the compositor initiating a page flip and the output's
+    /// vblank event. This determines the minimum input latency. The default is 1.5 ms.
+    ///
+    /// Note that if the margin is too small, the compositor will dynamically increase it.
+    pub fn set_flip_margin(self, margin: Duration) {
+        get!().set_flip_margin(self, margin);
+    }
 }
 
 /// A graphics API.