protocols/workspace: Set ext workspace id for pinned workspace

The `id` is defined to be sent only once, on creation of the handle or
later. And only for workspaces that are "likely to be stable across
multiple sessions".

Set we add an `id` initially for pinned workspaces, and add one when the
workspace is pinned.

The `id` is not supposed to be human readable, so we just use a random
value.

src/wayland/protocols/workspace/ext.rs

@@ -51,6 +51,7 @@ pub struct WorkspaceDataInner {
     capabilities: Option<ext_workspace_handle_v1::WorkspaceCapabilities>,
     coordinates: Vec<u32>,
     states: Option<ext_workspace_handle_v1::State>,
+    ext_id: Option<String>,
     pub(super) cosmic_v2_handle: Option<Weak<ZcosmicWorkspaceHandleV2>>,
 }
 
@@ -404,9 +405,6 @@ where
                     },
                 ) {
                     mngr.workspace(&handle);
-                    if let Some(id) = workspace.ext_id.clone() {
-                        handle.id(id);
-                    }
                     workspace.ext_instances.push(handle);
                     workspace.ext_instances.last_mut().unwrap()
                 } else {
@@ -492,8 +490,12 @@ where
         handle_state.states = Some(states);
         changed = true;
     }
-    // TODO ext_workspace_handle_v1::id
-    // TODO send id if pinned
+
+    if handle_state.ext_id.is_none() {
+        if let Some(id) = workspace.ext_id.clone() {
+            instance.id(id);
+        }
+    }
 
     if let Some(cosmic_v2_handle) = handle_state
         .cosmic_v2_handle

src/wayland/protocols/workspace/mod.rs

@@ -356,7 +356,6 @@ where
         &mut self,
         group: &WorkspaceGroupHandle,
         tiling: zcosmic_workspace_handle_v2::TilingState,
-        // TODO way to add id to workspace that doesn't have it
         ext_id: Option<String>,
     ) -> Option<WorkspaceHandle> {
         if let Some(group) = self.0.groups.iter_mut().find(|g| g.id == group.id) {
@@ -597,6 +596,25 @@ where
             workspace.tiling = state;
         }
     }
+
+    pub fn set_id(
+        &mut self,
+        workspace: &WorkspaceHandle,
+        id: &str,
+    ) -> Result<(), WorkspaceIdAlreadySetError> {
+        if let Some(workspace) = self
+            .0
+            .groups
+            .iter_mut()
+            .find_map(|g| g.workspaces.iter_mut().find(|w| w.id == workspace.id))
+        {
+            if workspace.ext_id.is_some() {
+                return Err(WorkspaceIdAlreadySetError);
+            }
+            workspace.ext_id = Some(id.to_owned());
+        }
+        Ok(())
+    }
 }
 
 impl<'a, D> Drop for WorkspaceUpdateGuard<'a, D>
@@ -608,6 +626,9 @@ where
     }
 }
 
+#[derive(Clone, Copy, Debug)]
+pub struct WorkspaceIdAlreadySetError;
+
 macro_rules! delegate_workspace {
     ($(@<$( $lt:tt $( : $clt:tt $(+ $dlt:tt )* )? ),+>)? $ty: ty) => {
         smithay::reexports::wayland_server::delegate_global_dispatch!($(@< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)? $ty: [