portal: include mapping_id in screencasts

src/ei/ei_ifs/ei_device.rs

@@ -15,8 +15,8 @@ use {
         wire_ei::{
             ei_device::{
                 ClientFrame, ClientStartEmulating, ClientStopEmulating, Destroyed, DeviceType,
-                Done, EiDeviceRequestHandler, Interface, Paused, Region, Release, Resumed,
+                Done, EiDeviceRequestHandler, Interface, Paused, Region, RegionMappingId, Release,
-                ServerFrame, ServerStartEmulating,
+                Resumed, ServerFrame, ServerStartEmulating,
             },
             EiDeviceId,
         },
@@ -100,6 +100,13 @@ impl EiDevice {
         });
     }
 
+    pub fn send_region_mapping_id(&self, mapping_id: &str) {
+        self.client.event(RegionMappingId {
+            self_id: self.id,
+            mapping_id,
+        });
+    }
+
     #[expect(dead_code)]
     pub fn send_paused(&self, serial: u32) {
         self.client.event(Paused {

src/ei/ei_ifs/ei_seat.rs

@@ -346,6 +346,7 @@ impl EiSeat {
         apply!(EI_CAP_KEYBOARD, create_keyboard);
         apply!(EI_CAP_TOUCHSCREEN, create_touchscreen);
         for output in self.client.state.root.outputs.lock().values() {
+            device.send_region_mapping_id(&output.global.connector.name);
             device.send_region(
                 output.node_absolute_position(),
                 output.global.persistent.scale.get(),

src/portal/ptl_remote_desktop.rs

@@ -90,7 +90,7 @@ impl UsrJayEiSessionOwner for StartingRemoteDesktop {
                 Some(self.dpy.clone()),
             );
         } else {
-            self.session.send_start_reply(None, None);
+            self.session.send_start_reply(None, None, None);
         }
     }
 

src/portal/ptl_screencast.rs

@@ -159,8 +159,19 @@ bitflags! {
 
 impl PwClientNodeOwner for StartingScreencast {
     fn bound_id(&self, node_id: u32) {
-        self.session
+        {
-            .send_start_reply(Some(node_id), create_restore_data(&self.dpy, &self.target));
+            let output = match &self.target {
+                ScreencastTarget::Output(o) => Some(o),
+                ScreencastTarget::Workspace(o, _, _) => Some(o),
+                ScreencastTarget::Toplevel(_) => None,
+            };
+            let mapping_id = output.and_then(|o| o.wl.name.borrow().clone());
+            self.session.send_start_reply(
+                Some(node_id),
+                create_restore_data(&self.dpy, &self.target),
+                mapping_id.as_deref(),
+            );
+        }
         let mut supported_formats = PwClientNodePortSupportedFormats {
             media_type: Some(SPA_MEDIA_TYPE_video),
             media_sub_type: Some(SPA_MEDIA_SUBTYPE_raw),

src/portal/ptl_session.rs

@@ -100,6 +100,7 @@ impl PortalSession {
         &self,
         pw_node_id: Option<u32>,
         restore_data: Option<Variant<'static>>,
+        mapping_id: Option<&str>,
     ) {
         let inner_type = DynamicType::DictEntry(
             Box::new(DynamicType::String),
@@ -133,6 +134,12 @@ impl PortalSession {
                 value: rd,
             });
         }
+        if let Some(mapping_id) = mapping_id {
+            variants.push(DictEntry {
+                key: "mapping_id".into(),
+                value: Variant::String(mapping_id.into()),
+            });
+        }
         if let Some(reply) = self.start_reply.take() {
             match reply {
                 PortalSessionReply::RemoteDesktop(reply) => {