drm: Add vrr property helpers

src/backend/drm/compositor/mod.rs

@@ -172,7 +172,10 @@ use crate::{
     wayland::{shm, single_pixel_buffer},
 };
 
-use super::{error::AccessError, DrmDeviceFd, DrmSurface, Framebuffer, PlaneClaim, PlaneInfo, Planes};
+use super::{
+    error::AccessError, surface::VrrSupport, DrmDeviceFd, DrmSurface, Framebuffer, PlaneClaim, PlaneInfo,
+    Planes,
+};
 
 pub mod dumb;
 mod elements;
@@ -1582,6 +1585,7 @@ where
     primary_plane_damage_bag: DamageBag<i32, BufferCoords>,
     supports_fencing: bool,
     direct_scanout: bool,
+    vrr: bool,
     reset_pending: bool,
     signaled_fence: Option<Arc<OwnedFd>>,
 
@@ -1769,6 +1773,7 @@ where
                         primary_plane_damage_bag: DamageBag::new(4),
                         primary_is_opaque: is_opaque,
                         direct_scanout: true,
+                        vrr: false,
                         reset_pending: true,
                         signaled_fence,
                         current_frame,
@@ -2357,6 +2362,17 @@ where
             }
         }
 
+        // If we only have a cursor update and vrr is enabled,
+        // don't update to not artificially increase the framerate
+        if self.vrr
+            && cursor_plane_element.is_some()
+            && overlay_plane_elements.is_empty()
+            && primary_plane_scanout_element.is_none()
+            && primary_plane_elements.is_empty()
+        {
+            let _ = cursor_plane_element.take();
+        }
+
         // Cleanup old state (e.g. old dmabuffers)
         for element_state in element_states.values_mut() {
             element_state.fb_cache.cleanup();
@@ -2930,6 +2946,26 @@ where
         Ok(())
     }
 
+    /// Returns if Variable Refresh Rate is advertised as supported by the given connector.
+    ///
+    /// See [`DrmSurface::vrr_supported`] for more details.
+    pub fn vrr_supported(&self, conn: connector::Handle) -> FrameResult<VrrSupport, A, F> {
+        self.surface.vrr_supported(conn).map_err(FrameError::DrmError)
+    }
+
+    /// Tries to set variable refresh rate (VRR) for the next frame.
+    ///
+    /// Doing so might cause the next frame to trigger a modeset.
+    /// Check [`DrmCompositor::vrr_supported`], which indicates if VRR can be
+    /// used without a modeset on the attached connectors.
+    pub fn use_vrr(&mut self, vrr: bool) -> FrameResult<(), A, F> {
+        let res = self.surface.use_vrr(vrr).map_err(FrameError::DrmError);
+        if res.is_ok() {
+            self.vrr = vrr;
+        }
+        res
+    }
+
     /// Set the [`DebugFlags`] to use
     ///
     /// Note: This will reset the primary plane swapchain if

src/backend/drm/mod.rs

@@ -95,7 +95,7 @@ pub use error::Error as DrmError;
 use indexmap::IndexSet;
 #[cfg(feature = "backend_gbm")]
 pub use surface::gbm::{Error as GbmBufferedSurfaceError, GbmBufferedSurface};
-pub use surface::{DrmSurface, PlaneConfig, PlaneDamageClips, PlaneState};
+pub use surface::{DrmSurface, PlaneConfig, PlaneDamageClips, PlaneState, VrrSupport};
 
 use drm::{
     control::{crtc, framebuffer, plane, Device as ControlDevice, PlaneType},