tree: allow moving children between containers on different outputs

src/tree/container.rs

@@ -20,7 +20,8 @@ use {
             ContainingNode, Direction, FindTreeResult, FindTreeUsecase, FloatNode, FoundNode, Node,
             NodeId, NodeLayerLink, NodeLocation, OutputNode, TddType, TileDragDestination,
             ToplevelData, ToplevelNode, ToplevelNodeBase, ToplevelType, WorkspaceNode,
-            default_tile_drag_bounds, toplevel_set_floating, walker::NodeVisitor,
+            default_tile_drag_bounds, toplevel_set_floating, toplevel_set_workspace,
+            walker::NodeVisitor,
         },
         utils::{
             asyncevent::AsyncEvent,
@@ -1052,16 +1053,42 @@ impl ContainerNode {
 
     //
     pub fn move_child(self: Rc<Self>, child: Rc<dyn ToplevelNode>, direction: Direction) {
+        let move_to_neighboring_output = |child: Rc<dyn ToplevelNode>| {
+            let Some(output) = self.find_neighboring_output(direction) else {
+                return;
+            };
+            let ws = output.ensure_workspace();
+            let mut foci = SmallVec::new();
+            let move_foci = !ws.container_visible();
+            if move_foci {
+                collect_kb_foci2(child.clone(), &mut foci);
+            }
+            if let Some(c) = ws.container.get() {
+                self.clone().cnode_remove_child2(&*child, true);
+                c.insert_child(child, direction);
+            } else {
+                toplevel_set_workspace(&self.state, child, &ws);
+            }
+            if move_foci {
+                for seat in foci {
+                    ws.clone().node_do_focus(&seat, Direction::Unspecified);
+                }
+            }
+        };
+
         // CASE 1: This is the only child of the container. Replace the container by the child.
         if self.num_children.get() == 1 {
             if let Some(parent) = self.toplevel_data.parent.get()
                 && !self.toplevel_data.is_fullscreen.get()
-                && parent.cnode_accepts_child(&*child)
             {
-                parent.cnode_replace_child(self.deref(), child.clone());
+                if parent.cnode_accepts_child(&*child) {
-                self.toplevel_data.parent.take();
+                    parent.cnode_replace_child(self.deref(), child.clone());
-                self.child_nodes.borrow_mut().clear();
+                    self.toplevel_data.parent.take();
-                self.tl_destroy();
+                    self.child_nodes.borrow_mut().clear();
+                    self.tl_destroy();
+                } else {
+                    move_to_neighboring_output(child);
+                }
             }
             return;
         }
@@ -1112,7 +1139,10 @@ impl ContainerNode {
         }
         let parent = match parent_opt {
             Some(p) => p,
-            _ => return,
+            _ => {
+                move_to_neighboring_output(child);
+                return;
+            }
         };
         self.cnode_remove_child2(&*child, true);
         match prev {