chore(core): More style fixes in Rust UI

core/embed/rust/src/error.rs

@@ -1,4 +1,5 @@
 use core::convert::{Infallible, TryInto};
+
 use cstr_core::CStr;
 
 use crate::micropython::{ffi, obj::Obj, qstr::Qstr};

core/embed/rust/src/lib.rs

@@ -31,5 +31,5 @@ fn panic(_info: &core::panic::PanicInfo) -> ! {
 
     // TODO: Ideally we would take the file and line info out of
     // `PanicInfo::location()`.
-    trezorhal::common::fatal_error(&empty, &msg, &empty, 0, &empty);
+    trezorhal::common::fatal_error(empty, msg, empty, 0, empty);
 }

core/embed/rust/src/protobuf/error.rs

@@ -2,7 +2,7 @@ use cstr_core::CStr;
 
 use crate::{error::Error, micropython::qstr::Qstr};
 
-/* XXX const version of from_bytes_with_nul_unchecked is nightly-only */
+// XXX const version of `from_bytes_with_nul_unchecked` is nightly-only.
 
 pub fn experimental_not_enabled() -> Error {
     let msg =

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

@@ -5,8 +5,8 @@ use crate::ui::{
 
 use super::button::{Button, ButtonMsg::Clicked};
 
-pub enum DialogMsg<T: Component> {
-    Content(T::Msg),
+pub enum DialogMsg<T> {
+    Content(T),
     LeftClicked,
     RightClicked,
 }
@@ -40,7 +40,7 @@ impl<T: Component> Dialog<T> {
 }
 
 impl<T: Component> Component for Dialog<T> {
-    type Msg = DialogMsg<T>;
+    type Msg = DialogMsg<T::Msg>;
 
     fn event(&mut self, ctx: &mut EventCtx, event: Event) -> Option<Self::Msg> {
         if let Some(msg) = self.content.event(ctx, event) {

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

@@ -1,11 +1,12 @@
-use core::convert::TryInto;
+use core::convert::{TryFrom, TryInto};
 
 use crate::{
+    error::Error,
     micropython::{buffer::Buffer, obj::Obj},
     ui::{
         component::{
             model_tt::{theme, Button, Dialog, DialogMsg, Text},
-            Child, Component, Never,
+            Child, Never,
         },
         display,
     },
@@ -14,16 +15,18 @@ use crate::{
 
 use super::obj::LayoutObj;
 
-impl<T> From<DialogMsg<T>> for Obj
+impl<T> TryFrom<DialogMsg<T>> for Obj
 where
-    T: Component,
-    T::Msg: Into<Obj>,
+    Obj: TryFrom<T>,
+    Error: From<<T as TryInto<Obj>>::Error>,
 {
-    fn from(val: DialogMsg<T>) -> Self {
+    type Error = Error;
+
+    fn try_from(val: DialogMsg<T>) -> Result<Self, Self::Error> {
         match val {
-            DialogMsg::Content(c) => c.into(),
-            DialogMsg::LeftClicked => 1.try_into().unwrap(),
-            DialogMsg::RightClicked => 2.try_into().unwrap(),
+            DialogMsg::Content(c) => Ok(c.try_into()?),
+            DialogMsg::LeftClicked => 1.try_into(),
+            DialogMsg::RightClicked => 2.try_into(),
         }
     }
 }

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

@@ -26,18 +26,18 @@ use crate::{
 /// wrapping trait that is implemented for all components where `Component::Msg`
 /// can be converted to `Obj`.
 pub trait ObjComponent {
-    fn obj_event(&mut self, ctx: &mut EventCtx, event: Event) -> Obj;
+    fn obj_event(&mut self, ctx: &mut EventCtx, event: Event) -> Result<Obj, Error>;
     fn obj_paint(&mut self);
 }
 
 impl<T> ObjComponent for Child<T>
 where
     T: Component,
-    T::Msg: Into<Obj>,
+    T::Msg: TryInto<Obj, Error = Error>,
 {
-    fn obj_event(&mut self, ctx: &mut EventCtx, event: Event) -> Obj {
+    fn obj_event(&mut self, ctx: &mut EventCtx, event: Event) -> Result<Obj, Error> {
         self.event(ctx, event)
-            .map_or_else(Obj::const_none, Into::into)
+            .map_or_else(|| Ok(Obj::const_none()), TryInto::try_into)
     }
 
     fn obj_paint(&mut self) {
@@ -105,12 +105,15 @@ impl LayoutObj {
     fn obj_event(&self, event: Event) -> Result<Obj, Error> {
         let inner = &mut *self.inner.borrow_mut();
 
+        // Clear the upwards-propagating paint request flag from the last event pass.
+        inner.event_ctx.clear_paint_requests();
+
+        // Send the event down the component tree. Bail out in case of failure.
         // SAFETY: `inner.root` is unique because of the `inner.borrow_mut()`.
-        let msg = unsafe { Gc::as_mut(&mut inner.root) }.obj_event(&mut inner.event_ctx, event);
+        let msg = unsafe { Gc::as_mut(&mut inner.root) }.obj_event(&mut inner.event_ctx, event)?;
 
-        // Clear the upwards-propagating paint request flag, all concerning `Child`
-        // wrappers should have already marked themselves for painting.
-        inner.event_ctx.clear_paint_requests();
+        // All concerning `Child` wrappers should have already marked themselves for
+        // painting by now, and we're prepared for a paint pass.
 
         // Drain any pending timers into the callback.
         while let Some((token, deadline)) = inner.event_ctx.pop_timer() {