Better handling of child windows

src/main.rs

@@ -1,3 +1,4 @@
+use std::collections::HashSet;
 use std::error::Error;
 
 use clap::Parser;
@@ -103,23 +104,30 @@ impl X11 {
             .copied()
             .unwrap_or(0);
 
-        // Try to get active window from _NET_ACTIVE_WINDOW
+        let client_ids = self.property_u32(self.root, self.atoms.net_client_list)?;
+        let client_set: HashSet<u32> = client_ids.iter().copied().collect();
+
+        // Try _NET_ACTIVE_WINDOW first, resolving the tree if the reported
+        // window is not a managed client (e.g. a transient helper window).
         let active_id = self
             .property_u32(self.root, self.atoms.net_active_window)?
             .first()
             .copied();
 
-        // Get the window with keyboard focus as a fallback
+        let resolved_active = match active_id {
-        let focused_window = self.get_focused_window().ok().flatten();
+            Some(0) | None => None,
-
+            Some(id) if client_set.contains(&id) => Some(id),
-        // Use the focused window if _NET_ACTIVE_WINDOW is 0 or invalid
+            Some(id) => self
-        let effective_active_id = if active_id == Some(0) || active_id.is_none() {
+                .resolve_to_client_window(x::Window::new(id))?
-            focused_window
+                .map(|w| w.resource_id())
-        } else {
+                .filter(|rid| client_set.contains(rid)),
-            active_id
         };
 
-        let client_ids = self.property_u32(self.root, self.atoms.net_client_list)?;
+        // Fall back to X11 keyboard focus.
+        let focused_window = self.get_focused_window().ok().flatten();
+
+        let effective_active_id =
+            resolved_active.or_else(|| focused_window.filter(|id| client_set.contains(id)));
 
         let mut workspaces: Vec<Workspace> = (0..workspace_count)
             .map(|id| Workspace {
@@ -169,13 +177,14 @@ impl X11 {
             workspace.windows.push(window);
         }
 
-        // If we still don't have an active window, try to find the focused window
+        // If we still don't have an active window, try to resolve the
-        if active_window.id == 0 {
+        // effective ID directly (it might not be in the client list we
-            if let Some(id) = effective_active_id {
+        // iterated above due to ordering).
-                if let Ok(window) = self.window_info(id) {
+        if active_window.id == 0
-                    active_window = window;
+            && let Some(id) = effective_active_id
-                }
+            && let Ok(window) = self.window_info(id)
-            }
+        {
+            active_window = window;
         }
 
         Ok(State {
@@ -188,7 +197,7 @@ impl X11 {
         let cookie = self.conn.send_request(&x::GetInputFocus {});
 
         let reply = self.conn.wait_for_reply(cookie)?;
-        let focus = reply.focus();
+        let mut focus = reply.focus();
 
         // If focus is the root window or PointerRoot, there's no focused window
         if focus == self.root {
@@ -198,30 +207,73 @@ impl X11 {
         // Check for PointerRoot (INPUTFOCUS_POINTER_ROOT is defined as Window with res_id 1)
         if focus.resource_id() == 1 {
             // Get the window under the pointer
-            let cookie = self.conn.send_request(&x::QueryPointer {
+            let cookie = self
-                window: self.root,
+                .conn
-            });
+                .send_request(&x::QueryPointer { window: self.root });
             let reply = self.conn.wait_for_reply(cookie)?;
             let child = reply.child();
 
             if child == x::Window::new(0) {
                 return Ok(None);
             }
-            return Ok(Some(child.resource_id()));
+            focus = child;
         }
 
         if focus == x::Window::new(0) {
             return Ok(None);
         }
 
-        Ok(Some(focus.resource_id()))
+        // Walk up the tree until we find a window with WM_CLASS set,
+        // which indicates it's a real managed client window.
+        let resolved = self.resolve_to_client_window(focus)?;
+
+        Ok(resolved.map(|w| w.resource_id()))
+    }
+
+    /// Walk up the X11 window tree starting at `window` until a window with
+    /// a `WM_CLASS` property is found. Returns `None` if no such ancestor
+    /// exists (e.g. because we hit the root window).
+    fn resolve_to_client_window(
+        &self,
+        mut window: x::Window,
+    ) -> Result<Option<x::Window>, Box<dyn Error>> {
+        // Limit hops to avoid infinite loops on malformed hierarchies.
+        for _ in 0..32 {
+            if window == self.root || window == x::Window::new(0) {
+                return Ok(None);
+            }
+
+            // If this window has a non-empty WM_CLASS, it's a managed client.
+            if let Ok(Some(bytes)) =
+                self.property_bytes_opt(window, self.atoms.wm_class, x::ATOM_STRING)
+                && !bytes.is_empty()
+            {
+                return Ok(Some(window));
+            }
+
+            // Move to parent.
+            let cookie = self.conn.send_request(&x::QueryTree { window });
+            let Ok(reply) = self.conn.wait_for_reply(cookie) else {
+                return Ok(None);
+            };
+
+            let parent = reply.parent();
+            if parent == window {
+                // Reached the top without finding a client window.
+                return Ok(None);
+            }
+            window = parent;
+        }
+
+        Ok(None)
     }
 
     fn is_dock_window(&self, id: u32) -> bool {
         let window = x::Window::new(id);
 
         // Check if it's a dock type window
-        if let Ok(Some(window_types)) = self.property_u32_opt(window, self.atoms.net_wm_window_type) {
+        if let Ok(Some(window_types)) = self.property_u32_opt(window, self.atoms.net_wm_window_type)
+        {
             let dock = self.atom_to_u32(self.atoms.net_wm_window_type_dock);
 
             for window_type in window_types {
@@ -341,7 +393,9 @@ impl X11 {
     fn watch(&self) -> Result<(), Box<dyn Error>> {
         self.select_events(
             self.root,
-            x::EventMask::PROPERTY_CHANGE | x::EventMask::SUBSTRUCTURE_NOTIFY | x::EventMask::FOCUS_CHANGE,
+            x::EventMask::PROPERTY_CHANGE
+                | x::EventMask::SUBSTRUCTURE_NOTIFY
+                | x::EventMask::FOCUS_CHANGE,
         );
 
         let client_ids = self.property_u32(self.root, self.atoms.net_client_list)?;
@@ -384,19 +438,15 @@ impl X11 {
                 }
 
                 xcb::Event::X(
-                    x::Event::DestroyNotify(_) | x::Event::MapNotify(_) | x::Event::UnmapNotify(_),
+                    x::Event::DestroyNotify(_)
+                    | x::Event::MapNotify(_)
+                    | x::Event::UnmapNotify(_)
+                    | x::Event::FocusIn(_)
+                    | x::Event::FocusOut(_),
                 ) => {
                     return Ok(());
                 }
 
-                xcb::Event::X(x::Event::FocusIn(_)) => {
-                    return Ok(());
-                }
-
-                xcb::Event::X(x::Event::FocusOut(_)) => {
-                    return Ok(());
-                }
-
                 _ => {}
             }
         }