Add honor-xdg-activation-with-invalid-serial debug flag

niri-config/src/lib.rs

@@ -2014,6 +2014,8 @@ pub struct DebugConfig {
     pub disable_monitor_names: bool,
     #[knuffel(child)]
     pub strict_new_window_focus_policy: bool,
+    #[knuffel(child)]
+    pub honor_xdg_activation_with_invalid_serial: bool,
 }
 
 #[derive(knuffel::DecodeScalar, Debug, Clone, Copy, PartialEq, Eq)]
@@ -4738,6 +4740,7 @@ mod tests {
                 keep_laptop_panel_on_when_lid_is_closed: false,
                 disable_monitor_names: false,
                 strict_new_window_focus_policy: false,
+                honor_xdg_activation_with_invalid_serial: false,
             },
             workspaces: [
                 Workspace {

src/handlers/mod.rs

@@ -709,14 +709,31 @@ impl XdgActivationHandler for State {
     }
 
     fn token_created(&mut self, _token: XdgActivationToken, data: XdgActivationTokenData) -> bool {
-        // Only tokens that were created while the application has keyboard focus are valid.
+        // Tokens without a serial are urgency-only. This is not specified, but it seems to be the
+        // common client behavior.
+        //
+        // We don't have urgency yet, so just ignore such tokens.
+        //
+        // See also: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/150
         let Some((serial, seat)) = data.serial else {
             return false;
         };
         let Some(seat) = Seat::<State>::from_resource(&seat) else {
             return false;
         };
 
+        // Widely-used clients such as Discord and Telegram make new tokens (with invalid serials)
+        // upon clicking on their tray icon or on their notification. This debug flag makes that
+        // work.
+        //
+        // Clicking on a notification sends clients a perfectly valid activation token from the
+        // notification daemon, but alas they ignore it. Maybe in the future the clients are fixed,
+        // and we can remove this debug flag.
+        let config = self.niri.config.borrow();
+        if config.debug.honor_xdg_activation_with_invalid_serial {
+            return true;
+        }
+
         // Check the serial against both a keyboard and a pointer, since layer-shell surfaces
         // with no keyboard interactivity won't have any keyboard focus.
         let kb_last_enter = seat.get_keyboard().unwrap().last_enter();

wiki/Configuration:-Debug-Options.md

@@ -27,6 +27,7 @@ debug {
     keep-laptop-panel-on-when-lid-is-closed
     disable-monitor-names
     strict-new-window-focus-policy
+    honor-xdg-activation-with-invalid-serial 
 }
 
 binds {
@@ -238,6 +239,25 @@ debug {
 }
 ```
 
+### `honor-xdg-activation-with-invalid-serial`
+
+<sup>Since: next release</sup>
+
+Widely-used clients such as Discord and Telegram make fresh xdg-activation tokens upon clicking on their tray icon or on their notification.
+Most of the time, these fresh tokens will have invalid serials, because the app needs to be focused to get a valid serial, and if the user clicks on a tray icon or a notification, it is usually because the app *isn't* focused, and the user wants to focus it.
+
+By default, niri ignores xdg-activation tokens with invalid serials, to prevent windows from randomly stealing focus.
+This debug flag makes niri honor such tokens, making the aforementioned widely-used apps get focus when clicking on their tray icon or notification.
+
+Amusingly, clicking on a notification sends the app a perfectly valid activation token from the notification daemon, but these apps seem to simply ignore it.
+Maybe in the future these apps/toolkits (Electron, Qt) are fixed, making this debug flag unnecessary.
+
+```kdl
+debug {
+    honor-xdg-activation-with-invalid-serial
+}
+```
+
 ### Key Bindings
 
 These are not debug options, but rather key bindings.