logiguard fork: GPUI xdg-activation keyboard-focus serial fix

Single-commit orphan branch: full zed-industries/zed @ 8c74db0 source tree
with a 3-file patch applied (no upstream history).

Patch (crates/gpui_linux/src/linux/wayland/):
  - serial.rs: add SerialKind::KeyboardEnter
  - client.rs: store wl_keyboard.enter serial; add latest_serial_of()
  - window.rs: activate() uses keyboard-enter serial (Mutter focus gate)

Mutter honors window activation only when the token carries the keyboard-
focus serial from wl_keyboard.enter; GPUI used a stale mouse-press serial.
See docs/tray-window-focus-wayland.md in logiguard.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/gpui/examples/tab_stop.rs

@@ -0,0 +1,214 @@
+#![cfg_attr(target_family = "wasm", no_main)]
+
+use gpui::{
+    App, Bounds, Context, Div, ElementId, FocusHandle, KeyBinding, SharedString, Stateful, Window,
+    WindowBounds, WindowOptions, actions, div, prelude::*, px, size,
+};
+use gpui_platform::application;
+
+actions!(example, [Tab, TabPrev]);
+
+struct Example {
+    focus_handle: FocusHandle,
+    items: Vec<FocusHandle>,
+    message: SharedString,
+}
+
+impl Example {
+    fn new(window: &mut Window, cx: &mut Context<Self>) -> Self {
+        let items = vec![
+            cx.focus_handle().tab_index(1).tab_stop(true),
+            cx.focus_handle().tab_index(2).tab_stop(true),
+            cx.focus_handle().tab_index(3).tab_stop(true),
+            cx.focus_handle(),
+            cx.focus_handle().tab_index(2).tab_stop(true),
+        ];
+
+        let focus_handle = cx.focus_handle();
+        window.focus(&focus_handle, cx);
+
+        Self {
+            focus_handle,
+            items,
+            message: SharedString::from("Press `Tab`, `Shift-Tab` to switch focus."),
+        }
+    }
+
+    fn on_tab(&mut self, _: &Tab, window: &mut Window, cx: &mut Context<Self>) {
+        window.focus_next(cx);
+        self.message = SharedString::from("You have pressed `Tab`.");
+    }
+
+    fn on_tab_prev(&mut self, _: &TabPrev, window: &mut Window, cx: &mut Context<Self>) {
+        window.focus_prev(cx);
+        self.message = SharedString::from("You have pressed `Shift-Tab`.");
+    }
+}
+
+impl Render for Example {
+    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        fn tab_stop_style<T: Styled>(this: T) -> T {
+            this.border_3().border_color(gpui::blue())
+        }
+
+        fn button(id: impl Into<ElementId>) -> Stateful<Div> {
+            div()
+                .id(id)
+                .h_10()
+                .flex_1()
+                .flex()
+                .justify_center()
+                .items_center()
+                .border_1()
+                .border_color(gpui::black())
+                .bg(gpui::black())
+                .text_color(gpui::white())
+                .focus(tab_stop_style)
+                .shadow_sm()
+        }
+
+        div()
+            .id("app")
+            .track_focus(&self.focus_handle)
+            .on_action(cx.listener(Self::on_tab))
+            .on_action(cx.listener(Self::on_tab_prev))
+            .size_full()
+            .flex()
+            .flex_col()
+            .p_4()
+            .gap_3()
+            .bg(gpui::white())
+            .text_color(gpui::black())
+            .child(self.message.clone())
+            .children(
+                self.items
+                    .clone()
+                    .into_iter()
+                    .enumerate()
+                    .map(|(ix, item_handle)| {
+                        div()
+                            .id(("item", ix))
+                            .track_focus(&item_handle)
+                            .h_10()
+                            .w_full()
+                            .flex()
+                            .justify_center()
+                            .items_center()
+                            .border_1()
+                            .border_color(gpui::black())
+                            .when(
+                                item_handle.tab_stop && item_handle.is_focused(window),
+                                tab_stop_style,
+                            )
+                            .map(|this| match item_handle.tab_stop {
+                                true => this
+                                    .hover(|this| this.bg(gpui::black().opacity(0.1)))
+                                    .child(format!("tab_index: {}", item_handle.tab_index)),
+                                false => this.opacity(0.4).child("tab_stop: false"),
+                            })
+                    }),
+            )
+            .child(
+                div()
+                    .flex()
+                    .flex_row()
+                    .gap_3()
+                    .items_center()
+                    .child(
+                        button("el1")
+                            .tab_index(4)
+                            .child("Button 1")
+                            .on_click(cx.listener(|this, _, _, cx| {
+                                this.message = "You have clicked Button 1.".into();
+                                cx.notify();
+                            })),
+                    )
+                    .child(
+                        button("el2")
+                            .tab_index(5)
+                            .child("Button 2")
+                            .on_click(cx.listener(|this, _, _, cx| {
+                                this.message = "You have clicked Button 2.".into();
+                                cx.notify();
+                            })),
+                    ),
+            )
+            .child(
+                div()
+                    .id("group-1")
+                    .tab_index(6)
+                    .tab_group()
+                    .tab_stop(false)
+                    .child(
+                        button("group-1-button-1")
+                            .tab_index(1)
+                            .child("Tab index [6, 1]"),
+                    )
+                    .child(
+                        button("group-1-button-2")
+                            .tab_index(2)
+                            .child("Tab index [6, 2]"),
+                    )
+                    .child(
+                        button("group-1-button-3")
+                            .tab_index(3)
+                            .child("Tab index [6, 3]"),
+                    ),
+            )
+            .child(
+                div()
+                    .id("group-2")
+                    .tab_index(7)
+                    .tab_group()
+                    .tab_stop(false)
+                    .child(
+                        button("group-2-button-1")
+                            .tab_index(1)
+                            .child("Tab index [7, 1]"),
+                    )
+                    .child(
+                        button("group-2-button-2")
+                            .tab_index(2)
+                            .child("Tab index [7, 2]"),
+                    )
+                    .child(
+                        button("group-2-button-3")
+                            .tab_index(3)
+                            .child("Tab index [7, 3]"),
+                    ),
+            )
+    }
+}
+
+fn run_example() {
+    application().run(|cx: &mut App| {
+        cx.bind_keys([
+            KeyBinding::new("tab", Tab, None),
+            KeyBinding::new("shift-tab", TabPrev, None),
+        ]);
+
+        let bounds = Bounds::centered(None, size(px(800.), px(600.0)), cx);
+        cx.open_window(
+            WindowOptions {
+                window_bounds: Some(WindowBounds::Windowed(bounds)),
+                ..Default::default()
+            },
+            |window, cx| cx.new(|cx| Example::new(window, cx)),
+        )
+        .unwrap();
+
+        cx.activate(true);
+    });
+}
+
+#[cfg(not(target_family = "wasm"))]
+fn main() {
+    run_example();
+}
+
+#[cfg(target_family = "wasm")]
+#[wasm_bindgen::prelude::wasm_bindgen(start)]
+pub fn start() {
+    gpui_platform::web_init();
+    run_example();
+}