feat(desktop): home app (system-only launch cap, LAUNCH_BADGE: apps+launch only), pm starts it with session (relaunch <=5); display keys F1/Alt+Tab next, F2 home, F4 close app (ROLE from launcher, terminal exempt), close returns to previous window; closed window -> app exits; shell 'name &'; launch by id; pm stack 8, storage 16 clients

crates/libkos/src/display.rs

@@ -37,6 +37,12 @@ pub fn set_accent(window: CapSlot, rgb: u32) -> bool {
     syscall::request(window, [w::ACCENT, rgb as usize, 0, 0]).is_ok_and(|r| r[0] == w::OK)
 }
 
+/// A launcher says what the window it opened is (`window::role`), before
+/// the app runs; whether the display took it.
+pub fn set_role(window: CapSlot, role: usize) -> bool {
+    syscall::request(window, [w::ROLE, role, 0, 0]).is_ok_and(|r| r[0] == w::OK)
+}
+
 /// Closes `window`: every copy of it, and its buffer, stop working.
 pub fn close(window: CapSlot) {
     let _ = syscall::request(window, [w::CLOSE, 0, 0, 0]);
@@ -62,15 +68,20 @@ pub enum Event {
     Input(crate::input::InputEvent),
     /// Ask for the theme again (`theme`).
     ThemeChanged,
+    /// The window is gone (the user closed it, or the display went):
+    /// the app is done.
+    Closed,
 }
 
 /// `window`'s next event, if one is waiting; ones not known here are
 /// skipped.
 pub fn poll(window: CapSlot) -> Option<Event> {
     loop {
-        let words = syscall::request(window, [w::POLL, 0, 0, 0]).ok()?;
+        let Ok(words) = syscall::request(window, [w::POLL, 0, 0, 0]) else { return Some(Event::Closed) };
         match words[0] {
             0 => return None,
+            // What the display answers through a window it has closed.
+            usize::MAX => return Some(Event::Closed),
             w::THEME_CHANGED => return Some(Event::ThemeChanged),
             _ => {
                 if let Some(e) = crate::input::decode(words) {
@@ -81,11 +92,14 @@ pub fn poll(window: CapSlot) -> Option<Event> {
     }
 }
 
-/// `window`'s next input event, if one is waiting.
+/// `window`'s next input event, if one is waiting. A program whose window
+/// is gone exits here.
 pub fn poll_input(window: CapSlot) -> Option<crate::input::InputEvent> {
     loop {
-        if let Event::Input(e) = poll(window)? {
-            return Some(e);
+        match poll(window)? {
+            Event::Input(e) => return Some(e),
+            Event::Closed => syscall::exit(),
+            Event::ThemeChanged => {}
         }
     }
 }