feat(core): Add preliminary anim frame support

core/embed/rust/src/ui/component/base.rs

@@ -135,35 +135,42 @@ pub enum Event {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq)]
-pub struct TimerToken(usize);
+pub struct TimerToken(u32);
 
 impl TimerToken {
     /// Value of an invalid (or missing) token.
     pub const INVALID: TimerToken = TimerToken(0);
 
-    pub fn from_raw(raw: usize) -> Self {
+    pub const fn from_raw(raw: u32) -> Self {
         Self(raw)
     }
 
-    pub fn into_raw(self) -> usize {
+    pub const fn into_raw(self) -> u32 {
         self.0
     }
 }
 
 pub struct EventCtx {
     timers: Vec<(TimerToken, Duration), { Self::MAX_TIMERS }>,
-    next_token: usize,
+    next_token: u32,
     paint_requested: bool,
 }
 
 impl EventCtx {
+    /// Timer token dedicated for animation frames.
+    pub const ANIM_FRAME_TIMER: TimerToken = TimerToken(1);
+
+    // 0 == `TimerToken::INVALID`,
+    // 1 == `Self::ANIM_FRAME_TIMER`.
+    const STARTING_TIMER_TOKEN: u32 = 2;
+
     /// Maximum amount of timers requested in one event tick.
     const MAX_TIMERS: usize = 4;
 
     pub fn new() -> Self {
         Self {
             timers: Vec::new(),
-            next_token: 1,
+            next_token: Self::STARTING_TIMER_TOKEN,
             paint_requested: false,
         }
     }
@@ -182,21 +189,37 @@ impl EventCtx {
     /// Request a timer event to be delivered after `deadline` elapses.
     pub fn request_timer(&mut self, deadline: Duration) -> TimerToken {
         let token = self.next_timer_token();
-        if self.timers.push((token, deadline)).is_err() {
-            // The timer queue is full. Let's just ignore this request.
-            #[cfg(feature = "ui_debug")]
-            panic!("timer queue is full");
-        }
+        self.register_timer(token, deadline);
         token
     }
 
+    /// Request an animation frame timer to fire as soon as possible.
+    pub fn request_anim_frame(&mut self) {
+        self.register_timer(Self::ANIM_FRAME_TIMER, Duration::ZERO);
+    }
+
     pub fn pop_timer(&mut self) -> Option<(TimerToken, Duration)> {
         self.timers.pop()
     }
 
+    fn register_timer(&mut self, token: TimerToken, deadline: Duration) {
+        if self.timers.push((token, deadline)).is_err() {
+            // The timer queue is full, this would be a development error in the layout
+            // layer. Let's panic in the debug env.
+            #[cfg(feature = "ui_debug")]
+            panic!("timer queue is full");
+        }
+    }
+
     fn next_timer_token(&mut self) -> TimerToken {
         let token = TimerToken(self.next_token);
-        self.next_token += 1;
+        // We start again from the beginning if the token counter overflows. This would
+        // probably happen in case of a bug and a long-running session. Let's risk the
+        // collisions in such case.
+        self.next_token = self
+            .next_token
+            .checked_add(1)
+            .unwrap_or(Self::STARTING_TIMER_TOKEN);
         token
     }
 }

core/embed/rust/src/ui/layout/obj.rs

@@ -254,7 +254,7 @@ impl TryFrom<Obj> for TimerToken {
     type Error = Error;
 
     fn try_from(value: Obj) -> Result<Self, Self::Error> {
-        let raw: usize = value.try_into()?;
+        let raw: u32 = value.try_into()?;
         let this = Self::from_raw(raw);
         Ok(this)
     }

core/embed/rust/src/ui/model_tt/component/loader.rs

@@ -67,10 +67,14 @@ impl Loader {
     pub fn progress(&self, now: Instant) -> Option<u16> {
         match &self.state {
             State::Initial => None,
-            State::Growing(animation) | State::Shrinking(animation) => Some(animation.value(now)),
+            State::Growing(anim) | State::Shrinking(anim) => Some(anim.value(now)),
         }
     }
 
+    pub fn is_started(&self) -> bool {
+        matches!(self.state, State::Growing(_) | State::Shrinking(_))
+    }
+
     pub fn is_finished(&self, now: Instant) -> bool {
         self.progress(now) == Some(display::LOADER_MAX)
     }
@@ -79,7 +83,13 @@ impl Loader {
 impl Component for Loader {
     type Msg = Never;
 
-    fn event(&mut self, _ctx: &mut EventCtx, _event: Event) -> Option<Self::Msg> {
+    fn event(&mut self, ctx: &mut EventCtx, event: Event) -> Option<Self::Msg> {
+        if let Event::Timer(EventCtx::ANIM_FRAME_TIMER) = event {
+            if self.is_started() {
+                ctx.request_paint();
+                ctx.request_anim_frame();
+            }
+        }
         None
     }