render: Reset buffers after non-space-tracked rendering

src/backend/kms/mod.rs

@@ -612,11 +612,23 @@ impl Surface {
             return Ok(());
         }
 
-        let nodes = state
+        if render::needs_buffer_reset(&self.output, state) {
+            self.surface.as_mut().unwrap().reset_buffers();
+        }
+
+        let workspace = state
             .shell
-            .active_space(&self.output)
-            .space
-            .windows()
+            .active_space(&self.output);
+        let nodes = workspace
+            .get_fullscreen(&self.output)
+            .map(|w| vec![w])
+            .unwrap_or_else(||
+                workspace
+                    .space
+                    .windows()
+                    .collect::<Vec<_>>()
+            )
+            .into_iter()
             .flat_map(|w| {
                 w.toplevel()
                     .get_surface()?

src/backend/render/mod.rs

@@ -104,6 +104,20 @@ impl AsGles2Renderer for GlMultiRenderer<'_> {
     }
 }
 
+pub fn needs_buffer_reset(output: &Output, state: &Common) -> bool {
+    use std::sync::atomic::{AtomicBool, Ordering};
+    struct DidCustomRendering(AtomicBool);
+
+    let will_render_custom = {
+        let workspace = state.shell.active_space(output);
+        workspace.get_fullscreen(output).is_some()
+    };
+
+    let userdata = output.user_data();
+    userdata.insert_if_missing(|| DidCustomRendering(AtomicBool::new(false)));
+    userdata.get::<DidCustomRendering>().unwrap().0.swap(will_render_custom, Ordering::AcqRel) != will_render_custom
+}
+
 pub fn render_output<R>(
     gpu: Option<&DrmNode>,
     renderer: &mut R,
@@ -128,7 +142,7 @@ where
     let workspace = state.shell.active_space(output);
     let maybe_fullscreen_window = workspace.get_fullscreen(output).cloned();
     let res = if let Some(window) = maybe_fullscreen_window {
-    #[cfg(not(feature = "debug"))]
+        #[cfg(not(feature = "debug"))]
         {
             render_fullscreen(gpu, renderer, window, state, output, hardware_cursor)
         }

src/backend/winit.rs

@@ -35,15 +35,25 @@ pub struct WinitState {
     backend: Rc<RefCell<WinitGraphicsBackend>>,
     //_global: GlobalDrop<WlOutput>,
     output: Output,
+    age_reset: u8,
     #[cfg(feature = "debug")]
     fps: Fps,
 }
 
 impl WinitState {
     pub fn render_output(&mut self, state: &mut Common) -> Result<()> {
+        if render::needs_buffer_reset(&self.output, state) {
+            self.reset_buffers();
+        }
+
         let backend = &mut *self.backend.borrow_mut();
         backend.bind().with_context(|| "Failed to bind buffer")?;
-        let age = backend.buffer_age().unwrap_or(0);
+        let age = if self.age_reset > 0 {
+            self.age_reset -= 1;
+            0
+        } else {
+            backend.buffer_age().unwrap_or(0)
+        };
 
         match render::render_output(
             None,
@@ -98,6 +108,10 @@ impl WinitState {
             Ok(())
         }
     }
+
+    pub fn reset_buffers(&mut self) {
+        self.age_reset = 3;
+    }
 }
 
 pub fn init_backend(event_loop: &mut EventLoop<State>, state: &mut State) -> Result<()> {
@@ -186,6 +200,7 @@ pub fn init_backend(event_loop: &mut EventLoop<State>, state: &mut State) -> Res
         output: output.clone(),
         #[cfg(feature = "debug")]
         fps: Fps::default(),
+        age_reset: 0,
     });
     state.common.output_conf.add_heads(std::iter::once(&output));
     state

src/backend/x11.rs

@@ -179,6 +179,10 @@ impl Surface {
         renderer: &mut Gles2Renderer,
         state: &mut Common,
     ) -> Result<()> {
+        if render::needs_buffer_reset(&self.output, state) {
+            self.surface.reset_buffers();
+        }
+
         let (buffer, age) = self
             .surface
             .buffer()