T46: Ely peeks over the main window's top edge from behind it, as the owner asked after the 0.1.3 film: her head and fingers from the icon's paths in a transparent window of her own, kept on the edge as each platform allows, macOS's child window, Windows' owned popup, X11's popup moved and stacked above the frame, Wayland's anchored popup; ten faces follow the most pressing of the sessions' marks, with hops, a shake and a rise; a press winks; Settings, Terminal, Ely turns her off

src/pet/macos.rs

@@ -0,0 +1,78 @@
+//! Ely's window on macOS: a child of the main window at its level, so it moves with it and keeps its layer and Space.
+
+use anyhow::bail;
+use gpui::Window;
+use objc::{
+    msg_send,
+    runtime::{NO, Object},
+    sel, sel_impl,
+};
+use raw_window_handle::{HasWindowHandle, RawWindowHandle};
+
+use super::LEFT;
+
+/// AppKit's `NSWindowAbove`.
+const ABOVE: isize = 1;
+
+#[repr(C)]
+#[derive(Clone, Copy)]
+struct Point {
+    x: f64,
+    y: f64,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy)]
+struct Rect {
+    origin: Point,
+    width: f64,
+    height: f64,
+}
+
+/// Her NSWindow and the main one's.
+pub struct Glue {
+    pet: *mut Object,
+    main: *mut Object,
+}
+
+impl Glue {
+    /// Makes her window the main window's child, at its level and in its Spaces, with no shadow.
+    pub fn new(pet: &Window, main: &Window) -> anyhow::Result<Self> {
+        let (pet, main) = (native(pet)?, native(main)?);
+        unsafe {
+            let level: isize = msg_send![main, level];
+            let _: () = msg_send![pet, setLevel: level];
+            let spaces: usize = msg_send![main, collectionBehavior];
+            let _: () = msg_send![pet, setCollectionBehavior: spaces];
+            let _: () = msg_send![pet, setHasShadow: NO];
+            let _: () = msg_send![main, addChildWindow: pet ordered: ABOVE];
+        }
+        Ok(Self { pet, main })
+    }
+
+    /// Stands her on the main window's top edge, `LEFT` points in from its left.
+    pub fn place(&self, _: &Window) -> anyhow::Result<()> {
+        unsafe {
+            let frame: Rect = msg_send![self.main, frame];
+            let at = Point {
+                x: frame.origin.x + f64::from(LEFT),
+                y: frame.origin.y + frame.height,
+            };
+            let _: () = msg_send![self.pet, setFrameOrigin: at];
+        }
+        Ok(())
+    }
+}
+
+/// The NSWindow gpui made for `window`.
+fn native(window: &Window) -> anyhow::Result<*mut Object> {
+    let handle = HasWindowHandle::window_handle(window)
+        .map_err(|error| anyhow::anyhow!("pet: no native handle: {error:?}"))?;
+    let RawWindowHandle::AppKit(appkit) = handle.as_raw() else {
+        bail!("pet: not an AppKit window");
+    };
+    let view = appkit.ns_view.as_ptr() as *mut Object;
+    let native: *mut Object = unsafe { msg_send![view, window] };
+    anyhow::ensure!(!native.is_null(), "pet: the view is in no window");
+    Ok(native)
+}