Add comments to functions that iterate over surfaces

These should be kept in sync with `render_input_order_internal`.

src/shell/focus/order.rs

@@ -77,6 +77,8 @@ fn render_input_order_internal<R: 'static>(
     element_filter: ElementFilter,
     mut callback: impl FnMut(Stage) -> ControlFlow<Result<R, OutputNoMode>, ()>,
 ) -> ControlFlow<Result<R, OutputNoMode>, ()> {
+    // NOTE: Keep in sync with other surface iteration functions
+
     if shell
         .zoom_state
         .as_ref()

src/shell/mod.rs

@@ -2046,6 +2046,8 @@ impl Shell {
     }
 
     pub fn visible_output_for_surface(&self, surface: &WlSurface) -> Option<&Output> {
+        // NOTE: Keep in sync with surface iteration in `render_input_order_internal`
+
         if let Some(session_lock) = &self.session_lock {
             return session_lock
                 .surfaces

src/state.rs

@@ -968,6 +968,8 @@ impl Common {
         output: &Output,
         render_element_states: &RenderElementStates,
     ) {
+        // NOTE: Keep in sync with surface iteration in `render_input_order_internal`
+
         let shell = self.shell.read();
         let processor = |namespace: Option<usize>| {
             move |surface: &WlSurface, states: &SurfaceData| {
@@ -1074,6 +1076,8 @@ impl Common {
         render_element_states: &RenderElementStates,
         mut dmabuf_feedback: impl FnMut(DrmNode) -> Option<SurfaceDmabufFeedback>,
     ) {
+        // NOTE: Keep in sync with surface iteration in `render_input_order_internal`
+
         let shell = self.shell.read();
 
         if let Some(session_lock) = shell.session_lock.as_ref()
@@ -1287,6 +1291,8 @@ impl Common {
 
     #[profiling::function]
     pub fn send_frames(&self, output: &Output, sequence: Option<usize>) {
+        // NOTE: Keep in sync with surface iteration in `render_input_order_internal`
+
         let time = self.clock.now();
         let should_send = |surface: &WlSurface, states: &SurfaceData| {
             // Do the standard primary scanout output check. For pointer surfaces it deduplicates