cea708overlay: clear more things on caption timeout

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1983>

video/closedcaption/src/cea608utils.rs

@@ -774,4 +774,13 @@ impl Cea608Renderer {
         self.rectangle = Some(rect.clone());
         Some(rect)
     }
+
+    pub fn clear(&mut self) {
+        self.state.reset();
+        let channel = self.channel();
+        self.frame.reset();
+        if let Some(channel) = channel {
+            self.set_channel(channel);
+        }
+    }
 }

video/closedcaption/src/cea708overlay/imp.rs

@@ -241,6 +241,7 @@ impl Cea708Overlay {
                 }
 
                 state.cea708_renderer.push_service(service);
+                self.reset_timeout(state, pts);
             }
         }
 
@@ -296,6 +297,7 @@ impl Cea708Overlay {
     }
 
     fn reset_timeout(&self, state: &mut State, pts: gst::ClockTime) {
+        gst::trace!(CAT, "resetting timeout to {pts:?}");
         state.last_cc_pts = Some(pts);
     }
 

video/closedcaption/src/cea708utils.rs

@@ -399,6 +399,10 @@ impl Cea708Renderer {
 
     pub fn clear_composition(&mut self) {
         self.composition.take();
+        if let Some(service) = self.service.as_mut() {
+            service.clear();
+        }
+        self.cea608.clear();
     }
 
     pub fn generate_composition(&mut self) -> Option<gst_video::VideoOverlayComposition> {
@@ -583,6 +587,14 @@ impl ServiceState {
         *self = Self::new();
     }
 
+    fn clear(&mut self) {
+        for window in self.windows.iter_mut() {
+            window.lines.clear();
+            window.pen_location = SetPenLocationArgs::default();
+            window.rectangle.take();
+        }
+    }
+
     fn handle_code(&mut self, code: &Code) {
         match code {
             Code::DefineWindow(args) => self.define_window(args),
@@ -1297,13 +1309,17 @@ impl Window {
             }
         };
 
-        let buffer = match render_buffer() {
+        let buffer = if width > 0 && height > 0 {
+            match render_buffer() {
                 Ok(buffer) => buffer,
                 Err(e) => {
                     self.dump();
                     gst::error!(CAT, "Failed to render buffer: \"{e}\"");
                     return None;
                 }
+            }
+        } else {
+            return None;
         };
         gst::trace!(
             CAT,