drm: trigger vblank on commit

src/backend/drm/gbm/surface.rs

@@ -75,13 +75,16 @@ impl<D: RawDevice + 'static> GbmSurfaceInternal<D> {
 
         if self.recreated.get() {
             debug!(self.logger, "Commiting new state");
-            self.crtc.commit(fb).map_err(|_| SwapBuffersError::ContextLost)?;
+            if let Err(err) = self.crtc.commit(fb) {
+                error!(self.logger, "Error commiting crtc: {}", err);
+                return Err(SwapBuffersError::ContextLost);
+            }
             self.recreated.set(false);
+        } else {
+            trace!(self.logger, "Queueing Page flip");
+            RawSurface::page_flip(&self.crtc, fb)?;
         }
 
-        trace!(self.logger, "Queueing Page flip");
-        RawSurface::page_flip(&self.crtc, fb)?;
-
         self.current_frame_buffer.set(Some(fb));
 
         Ok(())

src/backend/drm/legacy/surface.rs

@@ -251,7 +251,18 @@ impl<A: AsRawFd + 'static> RawSurface for LegacyDrmSurfaceInternal<A> {
 
         *current = pending.clone();
 
-        Ok(())
+        ControlDevice::page_flip(
+            self,
+            self.crtc,
+            framebuffer,
+            &[PageFlipFlags::PageFlipEvent],
+            None,
+        )
+        .map_err(|source| Error::Access {
+            errmsg: "Failed to queue page flip",
+            dev: self.dev_path(),
+            source: source.compat(),
+        })
     }
 
     fn page_flip(&self, framebuffer: framebuffer::Handle) -> ::std::result::Result<(), SwapBuffersError> {

src/backend/drm/mod.rs

@@ -205,7 +205,10 @@ pub trait RawSurface: Surface + ControlDevice + BasicDevice {
     /// potentially causing some flickering. Check before performing this
     /// operation if a commit really is necessary using [`commit_pending`](RawSurface::commit_pending).
     ///
-    /// This operation is blocking until the crtc is in the desired state.
+    /// This operation is not necessarily blocking until the crtc is in the desired state,
+    /// but will trigger a `vblank` event once done.
+    /// Make sure to [set a `DeviceHandler`](Device::set_handler) and
+    /// [register the belonging `Device`](device_bind) before to receive the event in time.
     fn commit(&self, framebuffer: framebuffer::Handle) -> Result<(), <Self as Surface>::Error>;
     /// Page-flip the underlying [`crtc`](drm::control::crtc)
     /// to a new given [`framebuffer`].