fix(wayland): buffer release proper timings

Author: technobaboo

src/wayland/core/buffer.rs

@@ -15,6 +15,13 @@ pub enum BufferBacking {
 	Dmabuf(DmabufBacking),
 }
 
+impl BufferBacking {
+	// Returns true if the buffer can be released immediately after texture update
+	pub fn can_release_after_update(&self) -> bool {
+		matches!(self, BufferBacking::Shm(_))
+	}
+}
+
 #[derive(Debug, Dispatcher)]
 pub struct Buffer {
 	pub id: ObjectId,
@@ -30,6 +37,10 @@ impl Buffer {
 		}
 	}
 
+	pub fn can_release_after_update(&self) -> bool {
+		self.backing.can_release_after_update()
+	}
+
 	pub fn size(&self) -> Vector2<usize> {
 		match &self.backing {
 			BufferBacking::Shm(backing) => backing.size(),

src/wayland/core/surface.rs

@@ -143,12 +143,16 @@ impl Surface {
 				.0
 				.get_all_param_info()
 				.set_texture("diffuse", new_tex);
+
+			// For SHM buffers, we can release immediately after copying to GPU
+			if buffer.can_release_after_update() {
+				let _ = self
+					.message_sink
+					.send(Message::ReleaseBuffer(buffer.clone()));
+			}
 		}
-		let _ = self
-			.message_sink
-			.send(Message::ReleaseBuffer(buffer.clone()));
-		self.apply_surface_materials();
 
+		self.apply_surface_materials();
 		let _ = state_lock.current().clean_lock.set(());
 	}
 
@@ -268,6 +272,20 @@ impl WlSurface for Surface {
 		{
 			let mut lock = self.state.lock();
 
+			// If we're getting a new buffer and the current one is DMA-BUF, release it
+			if let Some(new_buffer) = &lock.pending.buffer {
+				if let Some(current_buffer) = &lock.current().buffer {
+					// Don't release if it's the same buffer being reused
+					if !Arc::ptr_eq(new_buffer, current_buffer)
+						&& !current_buffer.can_release_after_update()
+					{
+						let _ = self
+							.message_sink
+							.send(Message::ReleaseBuffer(current_buffer.clone()));
+					}
+				}
+			}
+
 			let dirty = lock.current().clean_lock.get().is_none()
 				|| lock.pending.clean_lock.take().is_none();
 			lock.apply();