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/popover.rs

@@ -0,0 +1,191 @@
+#![cfg_attr(target_family = "wasm", no_main)]
+
+use gpui::{
+    Anchor, App, Context, Div, Hsla, Stateful, Window, WindowOptions, anchored, deferred, div,
+    prelude::*, px,
+};
+use gpui_platform::application;
+
+/// An example show use deferred to create a floating layers.
+struct HelloWorld {
+    open: bool,
+    secondary_open: bool,
+}
+
+fn button(id: &'static str) -> Stateful<Div> {
+    div()
+        .id(id)
+        .bg(gpui::black())
+        .text_color(gpui::white())
+        .px_3()
+        .py_1()
+}
+
+fn popover() -> Div {
+    div()
+        .flex()
+        .flex_col()
+        .items_center()
+        .justify_center()
+        .shadow_lg()
+        .p_3()
+        .rounded_md()
+        .bg(gpui::white())
+        .text_color(gpui::black())
+        .border_1()
+        .text_sm()
+        .border_color(gpui::black().opacity(0.1))
+}
+
+fn line(color: Hsla) -> Div {
+    div().w(px(480.)).h_2().bg(color.opacity(0.25))
+}
+
+impl HelloWorld {
+    fn render_secondary_popover(
+        &mut self,
+        _window: &mut Window,
+        cx: &mut Context<Self>,
+    ) -> impl IntoElement {
+        button("secondary-btn")
+            .mt_2()
+            .child("Child Popover")
+            .on_click(cx.listener(|this, _, _, cx| {
+                this.secondary_open = true;
+                cx.notify();
+            }))
+            .when(self.secondary_open, |this| {
+                this.child(
+                    // Now GPUI supports nested deferred!
+                    deferred(
+                        anchored()
+                            .anchor(Anchor::TopLeft)
+                            .snap_to_window_with_margin(px(8.))
+                            .child(
+                                popover()
+                                    .child("This is second level Popover with nested deferred!")
+                                    .bg(gpui::white())
+                                    .border_color(gpui::blue())
+                                    .on_mouse_down_out(cx.listener(|this, _, _, cx| {
+                                        this.secondary_open = false;
+                                        cx.notify();
+                                    })),
+                            ),
+                    )
+                    .priority(2),
+                )
+            })
+    }
+}
+
+impl Render for HelloWorld {
+    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        div()
+            .flex()
+            .flex_col()
+            .gap_3()
+            .size_full()
+            .bg(gpui::white())
+            .text_color(gpui::black())
+            .justify_center()
+            .items_center()
+            .child(
+                div()
+                    .flex()
+                    .flex_row()
+                    .gap_4()
+                    .child(
+                        button("popover0").child("Opened Popover").child(
+                            deferred(
+                                anchored()
+                                    .anchor(Anchor::TopLeft)
+                                    .snap_to_window_with_margin(px(8.))
+                                    .child(popover().w_96().gap_3().child(
+                                        "This is a default opened Popover, \
+                                        we can use deferred to render it \
+                                        in a floating layer.",
+                                    )),
+                            )
+                            .priority(0),
+                        ),
+                    )
+                    .child(
+                        button("popover1")
+                            .child("Open Popover")
+                            .on_click(cx.listener(|this, _, _, cx| {
+                                this.open = true;
+                                cx.notify();
+                            }))
+                            .when(self.open, |this| {
+                                this.child(
+                                    deferred(
+                                        anchored()
+                                            .anchor(Anchor::TopLeft)
+                                            .snap_to_window_with_margin(px(8.))
+                                            .child(
+                                                popover()
+                                                    .w_96()
+                                                    .gap_3()
+                                                    .child(
+                                                        "This is first level Popover, \
+                                                   we can use deferred to render it \
+                                                   in a floating layer.\n\
+                                                   Click outside to close.",
+                                                    )
+                                                    .when(!self.secondary_open, |this| {
+                                                        this.on_mouse_down_out(cx.listener(
+                                                            |this, _, _, cx| {
+                                                                this.open = false;
+                                                                cx.notify();
+                                                            },
+                                                        ))
+                                                    })
+                                                    // Here we need render popover after the content
+                                                    // to ensure it will be on top layer.
+                                                    .child(
+                                                        self.render_secondary_popover(window, cx),
+                                                    ),
+                                            ),
+                                    )
+                                    .priority(1),
+                                )
+                            }),
+                    ),
+            )
+            .child(
+                "Here is an example text rendered, \
+                to ensure the Popover will float above this contents.",
+            )
+            .children([
+                line(gpui::red()),
+                line(gpui::yellow()),
+                line(gpui::blue()),
+                line(gpui::green()),
+            ])
+    }
+}
+
+fn run_example() {
+    application().run(|cx: &mut App| {
+        cx.open_window(WindowOptions::default(), |_, cx| {
+            cx.new(|_| HelloWorld {
+                open: false,
+                secondary_open: false,
+            })
+        })
+        .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();
+}