shm: Release buffer as soon as possible

anvil/src/drawing.rs

@@ -24,13 +24,15 @@ use smithay::{
 use crate::shell::{MyCompositorToken, MyWindowMap, SurfaceData};
 
 struct BufferTextures<T> {
-    buffer: wl_buffer::WlBuffer,
+    buffer: Option<wl_buffer::WlBuffer>,
     texture: T,
 }
 
 impl<T> Drop for BufferTextures<T> {
     fn drop(&mut self) {
-        self.buffer.release();
+        if let Some(buffer) = self.buffer.take() {
+            buffer.release();
+        }
     }
 }
 
@@ -86,6 +88,12 @@ where
                     if let Some(buffer) = data.current_state.buffer.take() {
                         match renderer.import_buffer(&buffer, Some(&attributes), egl_buffer_reader) {
                             Ok(m) => {
+                                let buffer = if smithay::wayland::shm::with_buffer_contents(&buffer, |_,_| ()).is_ok() {
+                                    buffer.release();
+                                    None
+                                } else {
+                                    Some(buffer)
+                                };
                                 data.texture = Some(Box::new(BufferTextures { buffer, texture: m })
                                     as Box<dyn std::any::Any + 'static>)
                             }

anvil/src/winit.rs

@@ -94,13 +94,6 @@ pub fn run_winit(
             break;
         }
 
-        // Send frame events so that client start drawing their next frame
-        state
-            .window_map
-            .borrow()
-            .send_frames(start_time.elapsed().as_millis() as u32);
-        display.borrow_mut().flush_clients(&mut state);
-
         // drawing logic
         {
             let mut renderer = renderer.borrow_mut();
@@ -174,6 +167,13 @@ pub fn run_winit(
             }
         }
 
+        // Send frame events so that client start drawing their next frame
+        state
+            .window_map
+            .borrow()
+            .send_frames(start_time.elapsed().as_millis() as u32);
+        display.borrow_mut().flush_clients(&mut state);
+
         if event_loop
             .dispatch(Some(Duration::from_millis(16)), &mut state)
             .is_err()