tty: Generalize DRM property helpers

This can cause a panic.

src/backend/tty.rs

@@ -38,6 +38,7 @@ use smithay::reexports::calloop::timer::{TimeoutAction, Timer};
 use smithay::reexports::calloop::{Dispatcher, LoopHandle, RegistrationToken};
 use smithay::reexports::drm::control::{
     self, connector, crtc, property, Device, Mode as DrmMode, ModeFlags, ModeTypeFlags,
+    ResourceHandle,
 };
 use smithay::reexports::gbm::Modifier;
 use smithay::reexports::input::Libinput;
@@ -1812,13 +1813,13 @@ fn surface_dmabuf_feedback(
 
 fn find_drm_property(
     drm: &DrmDevice,
-    crtc: crtc::Handle,
+    resource: impl ResourceHandle,
     name: &str,
 ) -> Option<(property::Handle, property::RawValue)> {
-    let props = match drm.get_properties(crtc) {
+    let props = match drm.get_properties(resource) {
         Ok(props) => props,
         Err(err) => {
-            warn!("error getting CRTC properties: {err:?}");
+            warn!("error getting properties: {err:?}");
             return None;
         }
     };
@@ -1833,13 +1834,13 @@ fn find_drm_property(
 
 fn get_drm_property(
     drm: &DrmDevice,
-    crtc: crtc::Handle,
+    resource: impl ResourceHandle,
     prop: property::Handle,
 ) -> Option<property::RawValue> {
-    let props = match drm.get_properties(crtc) {
+    let props = match drm.get_properties(resource) {
         Ok(props) => props,
         Err(err) => {
-            warn!("error getting CRTC properties: {err:?}");
+            warn!("error getting properties: {err:?}");
             return None;
         }
     };

src/dbus/mod.rs

@@ -67,7 +67,7 @@ impl DBusServers {
             dbus.conn_screen_shot = try_start(screenshot);
 
             #[cfg(feature = "xdp-gnome-screencast")]
-            {
+            if niri.pipewire.is_some() {
                 let (to_niri, from_screen_cast) = calloop::channel::channel();
                 niri.event_loop
                     .insert_source(from_screen_cast, {
@@ -82,6 +82,8 @@ impl DBusServers {
                     .unwrap();
                 let screen_cast = ScreenCast::new(backend.enabled_outputs(), to_niri);
                 dbus.conn_screen_cast = try_start(screen_cast);
+            } else {
+                warn!("disabling screencast support because we couldn't start PipeWire");
             }
         }
 

src/niri.rs

@@ -898,7 +898,11 @@ impl State {
                     }
                 };
 
-                let pw = self.niri.pipewire.as_ref().unwrap();
+                let Some(pw) = &self.niri.pipewire else {
+                    error!("screencasting must be disabled if PipeWire is missing");
+                    return;
+                };
+
                 match pw.start_cast(
                     to_niri.clone(),
                     gbm,