refactor(core/rust/ui): emit event when component tree is initialized

[no changelog]

core/embed/rust/librust_qstr.h

@@ -23,7 +23,7 @@ static void _librust_qstrs(void) {
   MP_QSTR_request_bip39;
   MP_QSTR_request_slip39;
 
-  MP_QSTR_set_timer_fn;
+  MP_QSTR_attach_timer_fn;
   MP_QSTR_touch_event;
   MP_QSTR_button_event;
   MP_QSTR_timer;

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

@@ -226,6 +226,9 @@ pub enum Event {
     /// Previously requested timer was triggered. This invalidates the timer
     /// token (another timer has to be requested).
     Timer(TimerToken),
+    /// Component has been attached to component tree. This event is sent once
+    /// before any other events.
+    Attach,
     /// Internally-handled event to inform all `Child` wrappers in a sub-tree to
     /// get scheduled for painting.
     RequestPaint,

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

@@ -268,7 +268,7 @@ impl LayoutObj {
         static TYPE: Type = obj_type! {
             name: Qstr::MP_QSTR_Layout,
             locals: &obj_dict!(obj_map! {
-                Qstr::MP_QSTR_set_timer_fn => obj_fn_2!(ui_layout_set_timer_fn).as_obj(),
+                Qstr::MP_QSTR_attach_timer_fn => obj_fn_2!(ui_layout_attach_timer_fn).as_obj(),
                 Qstr::MP_QSTR_touch_event => obj_fn_var!(4, 4, ui_layout_touch_event).as_obj(),
                 Qstr::MP_QSTR_button_event => obj_fn_var!(3, 3, ui_layout_button_event).as_obj(),
                 Qstr::MP_QSTR_timer => obj_fn_2!(ui_layout_timer).as_obj(),
@@ -339,11 +339,13 @@ impl From<Never> for Obj {
     }
 }
 
-extern "C" fn ui_layout_set_timer_fn(this: Obj, timer_fn: Obj) -> Obj {
+extern "C" fn ui_layout_attach_timer_fn(this: Obj, timer_fn: Obj) -> Obj {
     let block = || {
         let this: Gc<LayoutObj> = this.try_into()?;
         this.obj_set_timer_fn(timer_fn);
-        Ok(Obj::const_true())
+        let msg = this.obj_event(Event::Attach)?;
+        assert!(msg == Obj::const_none());
+        Ok(Obj::const_none())
     };
     unsafe { util::try_or_raise(block) }
 }

core/src/trezor/ui/layouts/t1.py

@@ -18,17 +18,17 @@ class _RustLayout(ui.Layout):
     def __init__(self, layout: Any):
         self.layout = layout
         self.timer = loop.Timer()
-        self.layout.set_timer_fn(self.set_timer)
 
     def set_timer(self, token: int, deadline: int) -> None:
         self.timer.schedule(deadline, token)
 
     def create_tasks(self) -> tuple[loop.Task, ...]:
-        return self.handle_input_and_rendering(), self.handle_timers()
+        return self.handle_timers(), self.handle_input_and_rendering()
 
     def handle_input_and_rendering(self) -> loop.Task:  # type: ignore [awaitable-is-generator]
         button = loop.wait(io.BUTTON)
         ui.display.clear()
+        self.layout.attach_timer_fn(self.set_timer)
         self.layout.paint()
         while True:
             # Using `yield` instead of `await` to avoid allocations.

core/src/trezor/ui/layouts/tt_v2/__init__.py

@@ -19,7 +19,6 @@ class _RustLayout(ui.Layout):
     def __init__(self, layout: Any):
         self.layout = layout
         self.timer = loop.Timer()
-        self.layout.set_timer_fn(self.set_timer)
 
     def set_timer(self, token: int, deadline: int) -> None:
         self.timer.schedule(deadline, token)
@@ -30,8 +29,8 @@ class _RustLayout(ui.Layout):
             from apps.debug import confirm_signal, input_signal
 
             return (
-                self.handle_input_and_rendering(),
                 self.handle_timers(),
+                self.handle_input_and_rendering(),
                 confirm_signal(),
                 input_signal(),
             )
@@ -50,9 +49,13 @@ class _RustLayout(ui.Layout):
     else:
 
         def create_tasks(self) -> tuple[loop.AwaitableTask, ...]:
-            return self.handle_input_and_rendering(), self.handle_timers()
+            return self.handle_timers(), self.handle_input_and_rendering()
 
     def _before_render(self) -> None:
+        # Clear the screen of any leftovers.
+        ui.backlight_fade(ui.style.BACKLIGHT_DIM)
+        ui.display.clear()
+
         if __debug__ and self.should_notify_layout_change:
             from apps.debug import notify_layout_change
 
@@ -62,10 +65,13 @@ class _RustLayout(ui.Layout):
             self.should_notify_layout_change = False
             notify_layout_change(self)
 
+        # Turn the brightness on again.
+        ui.backlight_fade(self.BACKLIGHT_LEVEL)
+
     def handle_input_and_rendering(self) -> loop.Task:  # type: ignore [awaitable-is-generator]
         touch = loop.wait(io.TOUCH)
         self._before_render()
-        ui.display.clear()
+        self.layout.attach_timer_fn(self.set_timer)
         self.layout.paint()
         # self.layout.bounds()
         while True: