optimize out double rendering

src/Window.zig

@@ -174,15 +174,6 @@ pub fn applyRules(self: *Window) void {
     }
 }
 
-/// Whether this window currently has a tab drawn for it, i.e. it is tiled and
-/// visible on an output that is showing the tabbed layout.
-fn onTabBar(self: *Window) bool {
-    if (config.tabbar_height <= 0) return false;
-    if (!self.visible or self.floating or self.fullscreen or self.closed) return false;
-    const out = self.output orelse return false;
-    return out.state().layout == .tabbed;
-}
-
 /// Replace an owned string field, returning whether the value actually
 /// changed. Clients re-send strings that have not moved — a terminal animating
 /// a spinner in its title re-sets the same text several times a second — and
@@ -253,10 +244,11 @@ fn onEvent(_: *river.WindowV1, event: river.WindowV1.Event, self: *Window) void
             if (self.setString(&self.title, ev.title)) {
                 self.applyRules();
                 self.wm.ipcDirty();
-                // The tab bar has this title painted into it, so a window that
-                // is wearing a tab needs the strip redrawn. Terminals retitle
-                // themselves constantly, so ask only when it will show.
-                if (self.onTabBar()) self.wm.needsManage();
+                // No needsManage: river sent this event, so it already knows
+                // the title moved and starts a manage sequence of its own.
+                // Asking for one here bought a second, identical manage and
+                // render pass for every retitle — and terminals retitle
+                // themselves constantly.
             }
         },
 

src/Wm.zig

@@ -505,6 +505,12 @@ fn updateDefaultLayerOutput(self: *Wm) void {
     self.default_layer_output = out;
 }
 
+/// Ask river for a manage sequence.
+///
+/// Only needed for state changes river cannot see for itself: key bindings,
+/// pointer gestures and IPC commands. River already follows every batch of
+/// state events it sends us with a manage_start of its own, so calling this
+/// from an event handler asks for a second, redundant sequence.
 pub fn needsManage(self: *Wm) void {
     if (self.manage_requested) return;
     self.manage_requested = true;