feat(display): input routed via display server to focused app; input Subscribe; uses caps badged + Delegate

crates/libkos/src/display.rs

@@ -50,3 +50,23 @@ pub fn draw_text(ep: CapSlot, x: ScreenCoord, y: ScreenCoord, fg: Color, bg: Col
 /// The display server's character cell, in pixels.
 pub const CELL_WIDTH: usize = 8;
 pub const CELL_HEIGHT: usize = 16;
+
+/// Takes input focus: returns a notification signalled whenever events
+/// arrive; read them with `poll_input`.
+pub fn subscribe_input(ep: CapSlot) -> Option<CapSlot> {
+    use types::badge::Badge;
+    use types::permission::{Permission, PermissionSet};
+    let notify = syscall::create_notification().ok()?;
+    // Signal only (Delegate just to send it; the transfer strips it).
+    let signal = PermissionSet::empty().with(Permission::Write).with(Permission::Delegate);
+    let copy = syscall::mint(notify, Badge::NONE, signal).ok()?;
+    let sent = syscall::call(ep, [types::display::input::SUBSCRIBE, 0, 0, 0], Some(copy));
+    syscall::drop_cap(copy);
+    (sent.ok()?.words()[0] == 0).then_some(notify)
+}
+
+/// The next input event, if this process has focus and one is waiting.
+pub fn poll_input(ep: CapSlot) -> Option<crate::input::InputEvent> {
+    let words = syscall::request(ep, [types::display::input::POLL, 0, 0, 0]).ok()?;
+    crate::input::decode(words)
+}

crates/libkos/src/input.rs

@@ -38,7 +38,11 @@ fn decode_key(kind: usize, extra: usize) -> Option<Key> {
 }
 
 pub fn poll_event(ep: CapSlot) -> Option<InputEvent> {
-    let [tag, kind, extra, _] = syscall::request(ep, [0; 4]).ok()?;
+    decode(syscall::request(ep, [0; 4]).ok()?)
+}
+
+/// An event as the input server words it.
+pub fn decode([tag, kind, extra, _]: [usize; 4]) -> Option<InputEvent> {
     match tag {
         0 => None,
         1 => decode_key(kind, extra).map(InputEvent::KeyDown),