fix: keep each workspace's windows apart when a workspace is removed

lib/extension/tree.js

@@ -709,9 +709,33 @@ export class Tree extends Node {
       global.window_group.remove_child(existingWsNode.actorBin);
 
     this.removeChild(existingWsNode);
+    // GNOME renumbered the workspaces after it: rename their nodes to match
+    this._renumberWorkspaces(wsIndex + 1);
     return true;
   }
 
+  /**
+   * Workspace and monitor nodes are named by workspace index (`ws{n}`, `mo{m}ws{n}`), and GNOME
+   * renumbers the workspaces after one that is removed. Rename the nodes of the workspaces from
+   * `fromIndex` on down by one, so that each keeps the windows of its workspace. Without this, a
+   * window was filed under the node of another workspace (#470). (GNOME only ever adds a workspace
+   * at the end; a window dropped between two in the overview goes to a new last workspace and the
+   * windows after it move one up, each through its own workspace change.)
+   */
+  _renumberWorkspaces(fromIndex) {
+    const indexOf = (node) => parseInt(String(node.nodeValue).slice(2), 10);
+    this.nodeWorkpaces
+      .filter((ws) => indexOf(ws) >= fromIndex)
+      .sort((a, b) => indexOf(a) - indexOf(b)) // lowest first: the new names are free already
+      .forEach((ws) => {
+        const index = indexOf(ws) - 1;
+        ws._data = `ws${index}`;
+        ws.getNodeByType(NODE_TYPES.MONITOR).forEach((monitor) => {
+          monitor._data = String(monitor.nodeValue).replace(/ws\d+$/, `ws${index}`);
+        });
+      });
+  }
+
   get nodeWorkpaces() {
     let nodeWorkspaces = this.getNodeByType(NODE_TYPES.WORKSPACE);
     return nodeWorkspaces;