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/windows.rs

@@ -0,0 +1,66 @@
+//! Ely's window on Windows: owned by the main window, so it stays above it and hides with it, and moved as it moves.
+
+use anyhow::bail;
+use gpui::Window;
+use raw_window_handle::{HasWindowHandle, RawWindowHandle};
+use windows_sys::Win32::{
+    Foundation::{HWND, RECT},
+    UI::WindowsAndMessaging::{
+        GWLP_HWNDPARENT, GetWindowRect, HWND_NOTOPMOST, SWP_NOACTIVATE, SWP_NOMOVE, SWP_NOSIZE,
+        SWP_NOZORDER, SetWindowLongPtrW, SetWindowPos,
+    },
+};
+
+use super::{HEAD, LEFT, ROOM};
+
+/// Her window and the main one.
+pub struct Glue {
+    pet: HWND,
+    main: HWND,
+}
+
+impl Glue {
+    /// Gives her window the main window as owner, and takes away the topmost place gpui gives a popup.
+    pub fn new(pet: &Window, main: &Window) -> anyhow::Result<Self> {
+        let (pet, main) = (native(pet)?, native(main)?);
+        unsafe {
+            SetWindowLongPtrW(pet, GWLP_HWNDPARENT, main as isize);
+            let flags = SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE;
+            anyhow::ensure!(
+                SetWindowPos(pet, HWND_NOTOPMOST, 0, 0, 0, 0, flags) != 0,
+                "pet: her window keeps the topmost place"
+            );
+        }
+        Ok(Self { pet, main })
+    }
+
+    /// Stands her on the main window's top edge, `LEFT` points in from its left.
+    pub fn place(&self, main: &Window) -> anyhow::Result<()> {
+        let scale = main.scale_factor();
+        let mut frame = RECT::default();
+        unsafe {
+            anyhow::ensure!(
+                GetWindowRect(self.main, &mut frame) != 0,
+                "pet: the main window's place does not read"
+            );
+            let x = frame.left + (LEFT * scale).round() as i32;
+            let y = frame.top - ((HEAD + ROOM) * scale).round() as i32;
+            let flags = SWP_NOSIZE | SWP_NOZORDER | SWP_NOACTIVATE;
+            anyhow::ensure!(
+                SetWindowPos(self.pet, std::ptr::null_mut(), x, y, 0, 0, flags) != 0,
+                "pet: her window does not move"
+            );
+        }
+        Ok(())
+    }
+}
+
+/// The HWND gpui made for `window`.
+fn native(window: &Window) -> anyhow::Result<HWND> {
+    let handle = HasWindowHandle::window_handle(window)
+        .map_err(|error| anyhow::anyhow!("pet: no native handle: {error:?}"))?;
+    let RawWindowHandle::Win32(win32) = handle.as_raw() else {
+        bail!("pet: not a Win32 window");
+    };
+    Ok(win32.hwnd.get() as HWND)
+}