fix(core/rust/ui): expose method for completely repainting layout

[no changelog]

core/embed/rust/librust_qstr.h

@@ -47,6 +47,7 @@ static void _librust_qstrs(void) {
   MP_QSTR_button_event;
   MP_QSTR_timer;
   MP_QSTR_paint;
+  MP_QSTR_request_complete_repaint;
   MP_QSTR_trace;
   MP_QSTR_bounds;
   MP_QSTR_page_count;

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

@@ -282,6 +282,7 @@ impl LayoutObj {
                 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(),
                 Qstr::MP_QSTR_paint => obj_fn_1!(ui_layout_paint).as_obj(),
+                Qstr::MP_QSTR_request_complete_repaint => obj_fn_1!(ui_layout_request_complete_repaint).as_obj(),
                 Qstr::MP_QSTR_trace => obj_fn_2!(ui_layout_trace).as_obj(),
                 Qstr::MP_QSTR_bounds => obj_fn_1!(ui_layout_bounds).as_obj(),
                 Qstr::MP_QSTR_page_count => obj_fn_1!(ui_layout_page_count).as_obj(),
@@ -421,6 +422,22 @@ extern "C" fn ui_layout_paint(this: Obj) -> Obj {
     unsafe { util::try_or_raise(block) }
 }
 
+extern "C" fn ui_layout_request_complete_repaint(this: Obj) -> Obj {
+    let block = || {
+        let this: Gc<LayoutObj> = this.try_into()?;
+        let event = Event::RequestPaint;
+        let msg = this.obj_event(event)?;
+        if msg != Obj::const_none() {
+            // Messages raised during a `RequestPaint` dispatch are not propagated, let's
+            // make sure we don't do that.
+            #[cfg(feature = "ui_debug")]
+            panic!("cannot raise messages during RequestPaint");
+        };
+        Ok(Obj::const_none())
+    };
+    unsafe { util::try_or_raise(block) }
+}
+
 extern "C" fn ui_layout_page_count(this: Obj) -> Obj {
     let block = || {
         let this: Gc<LayoutObj> = this.try_into()?;

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

@@ -28,6 +28,10 @@ class _RustLayout(ui.Layout):
     def set_timer(self, token: int, deadline: int) -> None:
         self.timer.schedule(deadline, token)
 
+    def request_complete_repaint(self) -> None:
+        msg = self.layout.request_complete_repaint()
+        assert msg is None
+
     if __debug__:
 
         def create_tasks(self) -> tuple[loop.AwaitableTask, ...]:

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

@@ -185,6 +185,7 @@ async def _prompt_number(
                 )
             )
         )
+        num_input.request_complete_repaint()
 
 
 async def slip39_prompt_threshold(