cursor: allow cursor clearing on CursorBackend

src/backend/drm/atomic/surface.rs

@@ -646,6 +646,15 @@ impl<A: AsRawFd + 'static> CursorBackend for AtomicDrmSurfaceInternal<A> {
 
         Ok(())
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        let mut cursor = self.cursor.lock().unwrap();
+        if let Some(fb) = cursor.framebuffer.take() {
+            let _ = self.destroy_framebuffer(fb);
+        }
+
+        self.clear_plane(self.planes.cursor)
+    }
 }
 
 impl<A: AsRawFd + 'static> AtomicDrmSurfaceInternal<A> {
@@ -1022,6 +1031,10 @@ impl<A: AsRawFd + 'static> CursorBackend for AtomicDrmSurface<A> {
     ) -> Result<(), Error> {
         self.0.set_cursor_representation(buffer, hotspot)
     }
+    
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.0.clear_cursor_representation()
+    }
 }
 
 impl<A: AsRawFd + 'static> Surface for AtomicDrmSurface<A> {

src/backend/drm/common/fallback.rs

@@ -552,6 +552,7 @@ where
 
     fallback_surface_err_impl!(set_cursor_position, &Self, Result<(), EitherError<E3, E4>>, x: u32, y: u32);
     fallback_surface_err_impl!(set_cursor_representation, &Self, Result<(), EitherError<E3, E4>>, buffer: &Self::CursorFormat, hotspot: (u32, u32));
+    fallback_surface_err_impl!(clear_cursor_representation, &Self, Result<(), EitherError<E3, E4>>,);
 }
 
 #[cfg(feature = "renderer_gl")]

src/backend/drm/egl/surface.rs

@@ -92,6 +92,10 @@ where
     ) -> ::std::result::Result<(), Self::Error> {
         self.0.surface.set_cursor_representation(buffer, hotspot)
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.0.surface.clear_cursor_representation()
+    }
 }
 
 #[cfg(feature = "renderer_gl")]

src/backend/drm/eglstream/surface.rs

@@ -190,6 +190,17 @@ impl<S: RawSurface + 'static> CursorBackend for EglStreamSurfaceInternal<S> {
 
         Ok(())
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.crtc.set_cursor(self.crtc.crtc(), Option::<&DumbBuffer>::None)
+            .compat()
+            .map_err(|source| DrmError::Access {
+                errmsg: "Failed to clear cursor",
+                dev: self.crtc.dev_path(),
+                source,
+            })
+            .map_err(Error::Underlying)
+    }
 }
 
 /// egl stream surface for rendering
@@ -565,6 +576,10 @@ impl<S: RawSurface + 'static> CursorBackend for EglStreamSurface<S> {
     ) -> Result<(), Self::Error> {
         self.0.set_cursor_representation(buffer, hotspot)
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.0.clear_cursor_representation()
+    }
 }
 
 #[cfg(test)]

src/backend/drm/gbm/surface.rs

@@ -305,6 +305,22 @@ where
         *self.cursor.lock().unwrap() = (cursor, hotspot);
         Ok(())
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        *self.cursor.lock().unwrap() = (self.dev.lock()
+                .unwrap()
+                .create_buffer_object(
+                    1,
+                    1,
+                    GbmFormat::ARGB8888,
+                    BufferObjectFlags::CURSOR | BufferObjectFlags::WRITE,
+                )
+                .map_err(Error::BufferCreationFailed)?,
+            (0, 0)
+        );
+        self.crtc.clear_cursor_representation()
+            .map_err(Error::Underlying)
+    }
 }
 
 impl<S: RawSurface + 'static> Drop for GbmSurfaceInternal<S> {
@@ -415,6 +431,10 @@ where
     ) -> Result<(), Self::Error> {
         self.0.set_cursor_representation(buffer, hotspot)
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.0.clear_cursor_representation()
+    }
 }
 
 #[cfg(test)]

src/backend/drm/legacy/surface.rs

@@ -87,6 +87,16 @@ impl<A: AsRawFd + 'static> CursorBackend for LegacyDrmSurfaceInternal<A> {
 
         Ok(())
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Error> {
+        self.set_cursor(self.crtc, Option::<&DumbBuffer>::None)
+            .compat()    
+            .map_err(|source| Error::Access {
+                errmsg: "Failed to set cursor",
+                dev: self.dev_path(),
+                source,
+            })
+    }
 }
 
 impl<A: AsRawFd + 'static> Surface for LegacyDrmSurfaceInternal<A> {
@@ -498,6 +508,10 @@ impl<A: AsRawFd + 'static> CursorBackend for LegacyDrmSurface<A> {
     ) -> Result<(), Error> {
         self.0.set_cursor_representation(buffer, hotspot)
     }
+
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error> {
+        self.0.clear_cursor_representation()
+    }
 }
 
 impl<A: AsRawFd + 'static> Surface for LegacyDrmSurface<A> {

src/backend/graphics/cursor.rs

@@ -34,4 +34,7 @@ pub trait CursorBackend {
         cursor: &Self::CursorFormat,
         hotspot: (u32, u32),
     ) -> Result<(), Self::Error>;
+
+    /// Clear the current cursor image drawn on the [`CursorBackend`].
+    fn clear_cursor_representation(&self) -> Result<(), Self::Error>;
 }

src/backend/winit.rs

@@ -270,6 +270,12 @@ impl CursorBackend for WinitGraphicsBackend {
         // Cannot log this one, as `CursorFormat` is not `Debug` and should not be
         debug!(self.logger, "Changing cursor representation");
         self.window.window().set_cursor_icon(*cursor);
+        self.window.window().set_cursor_visible(true);
+        Ok(())
+    }
+
+    fn clear_cursor_representation(&self) -> ::std::result::Result<(), ()> {
+        self.window.window().set_cursor_visible(false);
         Ok(())
     }
 }