refactor(core): move and cleanup show_share_words

- model_t version was moved from using plain Paragraph to a dedicated
component `ShareWords` so that it's consistent with other models. This
allowed to move formatting to Rust and allowed the trait function to
have `words` parameter of type `Vec<TString, 33>`
- model_r ShareWords::render slightly refactored to be consistent with
the new model_t version
- mercury uses a unique version. The reason is that mercury SwipeFlow
contains also the initial screen with instructions and prompt screen at
the end.

core/embed/rust/librust_qstr.h

@@ -254,7 +254,6 @@ static void _librust_qstrs(void) {
   MP_QSTR_flow_confirm_summary;
   MP_QSTR_flow_get_address;
   MP_QSTR_flow_prompt_backup;
-  MP_QSTR_flow_show_share_words;
   MP_QSTR_flow_warning_hi_prio;
   MP_QSTR_get_language;
   MP_QSTR_get_transition_out;
@@ -291,6 +290,7 @@ static void _librust_qstrs(void) {
   MP_QSTR_inputs__return;
   MP_QSTR_inputs__show;
   MP_QSTR_inputs__space;
+  MP_QSTR_instructions;
   MP_QSTR_instructions__continue_holding;
   MP_QSTR_instructions__continue_in_app;
   MP_QSTR_instructions__enter_next_share;
@@ -641,7 +641,6 @@ static void _librust_qstrs(void) {
   MP_QSTR_set_brightness;
   MP_QSTR_setting__adjust;
   MP_QSTR_setting__apply;
-  MP_QSTR_share_words;
   MP_QSTR_share_words__words_in_order;
   MP_QSTR_share_words__wrote_down_all;
   MP_QSTR_show_address_details;
@@ -658,6 +657,7 @@ static void _librust_qstrs(void) {
   MP_QSTR_show_progress_coinjoin;
   MP_QSTR_show_remaining_shares;
   MP_QSTR_show_share_words;
+  MP_QSTR_show_share_words_mercury;
   MP_QSTR_show_simple;
   MP_QSTR_show_success;
   MP_QSTR_show_wait_text;
@@ -683,7 +683,6 @@ static void _librust_qstrs(void) {
   MP_QSTR_summary_title;
   MP_QSTR_text;
   MP_QSTR_text_confirm;
-  MP_QSTR_text_info;
   MP_QSTR_text_mono;
   MP_QSTR_time_ms;
   MP_QSTR_timer;

core/embed/rust/src/ui/api/firmware_upy.rs

@@ -2,6 +2,7 @@ use crate::{
     io::BinaryData,
     micropython::{
         gc::Gc,
+        iter::IterBuf,
         list::List,
         macros::{obj_fn_1, obj_fn_kw, obj_module},
         map::Map,
@@ -25,6 +26,7 @@ use crate::{
         ui_features_fw::UIFeaturesFirmware,
     },
 };
+use heapless::Vec;
 
 /// Dummy implementation so that we can use `Empty` in a return type of unimplemented trait
 /// function
@@ -478,6 +480,54 @@ extern "C" fn new_show_remaining_shares(n_args: usize, args: *const Obj, kwargs:
     unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
 }
 
+extern "C" fn new_show_share_words(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
+    let block = move |_args: &[Obj], kwargs: &Map| {
+        let words: Obj = kwargs.get(Qstr::MP_QSTR_words)?;
+        let title: Option<TString> = kwargs
+            .get(Qstr::MP_QSTR_title)
+            .and_then(Obj::try_into_option)
+            .unwrap_or(None);
+
+        let words: Vec<TString, 33> = util::iter_into_vec(words)?;
+
+        let layout = ModelUI::show_share_words(words, title)?;
+        Ok(LayoutObj::new_root(layout)?.into())
+    };
+    unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
+}
+
+extern "C" fn new_show_share_words_mercury(
+    n_args: usize,
+    args: *const Obj,
+    kwargs: *mut Map,
+) -> Obj {
+    let block = move |_args: &[Obj], kwargs: &Map| {
+        let words: Obj = kwargs.get(Qstr::MP_QSTR_words)?;
+        let subtitle: Option<TString> = kwargs
+            .get(Qstr::MP_QSTR_subtitle)
+            .and_then(Obj::try_into_option)
+            .unwrap_or(None);
+        let instructions: Obj = kwargs.get(Qstr::MP_QSTR_instructions)?;
+        let text_footer: Option<TString> = kwargs
+            .get(Qstr::MP_QSTR_description)
+            .and_then(Obj::try_into_option)
+            .unwrap_or(None);
+        let text_confirm: TString = kwargs.get(Qstr::MP_QSTR_text_confirm)?.try_into()?;
+
+        let words: Vec<TString, 33> = util::iter_into_vec(words)?;
+
+        let layout = ModelUI::show_share_words_mercury(
+            words,
+            subtitle,
+            instructions,
+            text_footer,
+            text_confirm,
+        )?;
+        Ok(LayoutObj::new_root(layout)?.into())
+    };
+    unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
+}
+
 extern "C" fn new_show_simple(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
         let text: TString = kwargs.get(Qstr::MP_QSTR_text)?.try_into()?;
@@ -923,6 +973,26 @@ pub static mp_module_trezorui_api: Module = obj_module! {
     ///     """Shows SLIP39 state after info button is pressed on `confirm_recovery`."""
     Qstr::MP_QSTR_show_remaining_shares => obj_fn_kw!(0, new_show_remaining_shares).as_obj(),
 
+    /// def show_share_words(
+    ///     *,
+    ///     words: Iterable[str],
+    ///     title: str | None = None,
+    /// ) -> LayoutObj[UiResult]:
+    ///     """Show mnemonic for backup."""
+    Qstr::MP_QSTR_show_share_words => obj_fn_kw!(0, new_show_share_words).as_obj(),
+
+    /// def show_share_words_mercury(
+    ///     *,
+    ///     words: Iterable[str],
+    ///     subtitle: str | None,
+    ///     instructions: Iterable[str],
+    ///     text_footer: str | None,
+    ///     text_confirm: str,
+    /// ) -> LayoutObj[UiResult]:
+    ///     """Show mnemonic for wallet backup preceded by an instruction screen and followed by a
+    ///     confirmation screen."""
+    Qstr::MP_QSTR_show_share_words_mercury => obj_fn_kw!(0, new_show_share_words_mercury).as_obj(),
+
     /// def show_simple(
     ///     *,
     ///     text: str,

core/embed/rust/src/ui/model_mercury/flow/show_share_words.rs

@@ -78,15 +78,15 @@ fn footer_updating_func(
 }
 
 pub fn new_show_share_words(
-    title: TString<'static>,
-    subtitle: TString<'static>,
     share_words_vec: Vec<TString<'static>, 33>,
-    description: Option<TString<'static>>,
+    subtitle: TString<'static>,
     instructions_paragraphs: ParagraphVecShort<'static>,
+    text_footer: Option<TString<'static>>,
     text_confirm: TString<'static>,
 ) -> Result<SwipeFlow, error::Error> {
     let nwords = share_words_vec.len();
     let paragraphs_spacing = 8;
+    let title = TR::reset__recovery_wallet_backup_title.into();
 
     let content_instruction = Frame::left_aligned(
         title,
@@ -97,7 +97,7 @@ pub fn new_show_share_words(
         ),
     )
     .with_subtitle(TR::words__instructions.into())
-    .with_footer(TR::instructions__swipe_up.into(), description)
+    .with_footer(TR::instructions__swipe_up.into(), text_footer)
     .with_swipe(Direction::Up, SwipeSettings::default())
     .map(|msg| matches!(msg, FrameMsg::Content(_)).then_some(FlowMsg::Confirmed))
     .one_button_request(ButtonRequestCode::ResetDevice.with_name("share_words"))

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

@@ -658,38 +658,6 @@ extern "C" fn new_confirm_total(n_args: usize, args: *const Obj, kwargs: *mut Ma
     unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
 }
 
-extern "C" fn new_show_share_words(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
-    let block = move |_args: &[Obj], kwargs: &Map| {
-        let title: TString = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
-        let subtitle: TString = kwargs.get(Qstr::MP_QSTR_subtitle)?.try_into()?;
-        let share_words_obj: Obj = kwargs.get(Qstr::MP_QSTR_words)?;
-        let share_words_vec: Vec<TString, 33> = util::iter_into_vec(share_words_obj)?;
-        let description: Option<TString> = kwargs
-            .get(Qstr::MP_QSTR_description)?
-            .try_into_option()?
-            .and_then(|desc: TString| if desc.is_empty() { None } else { Some(desc) });
-        let text_info: Obj = kwargs.get(Qstr::MP_QSTR_text_info)?;
-        let text_confirm: TString = kwargs.get(Qstr::MP_QSTR_text_confirm)?.try_into()?;
-
-        let mut instructions_paragraphs = ParagraphVecShort::new();
-        for item in IterBuf::new().try_iterate(text_info)? {
-            let text: TString = item.try_into()?;
-            instructions_paragraphs.add(Paragraph::new(&theme::TEXT_MAIN_GREY_LIGHT, text));
-        }
-
-        let flow = flow::show_share_words::new_show_share_words(
-            title,
-            subtitle,
-            share_words_vec,
-            description,
-            instructions_paragraphs,
-            text_confirm,
-        )?;
-        Ok(LayoutObj::new_root(flow)?.into())
-    };
-    unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
-}
-
 extern "C" fn new_confirm_with_info(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
         let title: TString = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
@@ -932,19 +900,6 @@ pub static mp_module_trezorui2: Module = obj_module! {
     ///     """Prompt a user to create backup with an option to skip."""
     Qstr::MP_QSTR_flow_prompt_backup => obj_fn_0!(new_prompt_backup).as_obj(),
 
-    /// def flow_show_share_words(
-    ///     *,
-    ///     title: str,
-    ///     subtitle: str,
-    ///     words: Iterable[str],
-    ///     description: str,
-    ///     text_info: Iterable[str],
-    ///     text_confirm: str,
-    /// ) -> LayoutObj[UiResult]:
-    ///     """Show wallet backup words preceded by an instruction screen and followed by
-    ///     confirmation."""
-    Qstr::MP_QSTR_flow_show_share_words => obj_fn_kw!(0, new_show_share_words).as_obj(),
-
     /// def flow_get_address(
     ///     *,
     ///     address: str | bytes,

core/embed/rust/src/ui/model_mercury/ui_features_fw.rs

@@ -537,6 +537,38 @@ impl UIFeaturesFirmware for ModelMercuryFeatures {
         Ok(obj)
     }
 
+    fn show_share_words(
+        words: heapless::Vec<TString<'static>, 33>,
+        _title: Option<TString<'static>>,
+    ) -> Result<impl LayoutMaybeTrace, Error> {
+        Err::<RootComponent<Empty, ModelMercuryFeatures>, Error>(Error::ValueError(
+            c"use flow_share_words instead",
+        ))
+    }
+
+    fn show_share_words_mercury(
+        words: heapless::Vec<TString<'static>, 33>,
+        subtitle: Option<TString<'static>>,
+        instructions: crate::micropython::obj::Obj,
+        text_footer: Option<TString<'static>>,
+        text_confirm: TString<'static>,
+    ) -> Result<impl LayoutMaybeTrace, Error> {
+        let mut instructions_paragraphs = ParagraphVecShort::new();
+        for item in crate::micropython::iter::IterBuf::new().try_iterate(instructions)? {
+            let text: TString = item.try_into()?;
+            instructions_paragraphs.add(Paragraph::new(&theme::TEXT_MAIN_GREY_LIGHT, text));
+        }
+
+        let flow = flow::show_share_words::new_show_share_words(
+            words,
+            subtitle.unwrap_or(TString::empty()),
+            instructions_paragraphs,
+            text_footer,
+            text_confirm,
+        )?;
+        Ok(flow)
+    }
+
     fn show_remaining_shares(
         pages_iterable: crate::micropython::obj::Obj, // TODO: replace Obj
     ) -> Result<impl LayoutMaybeTrace, Error> {

core/embed/rust/src/ui/model_tr/component/share_words.rs

@@ -92,23 +92,24 @@ impl<'a> ShareWords<'a> {
     fn render_words<'s>(&'s self, target: &mut impl Renderer<'s>) {
         let mut y_offset = 0;
         // Showing the word index and the words itself
-        for i in 0..WORDS_PER_PAGE {
+        for (word_idx, word) in self
+            .share_words
+            .iter()
+            .enumerate()
+            .skip(self.page_index * WORDS_PER_PAGE)
+            .take(WORDS_PER_PAGE)
+        {
+            let ordinal = word_idx + 1;
             y_offset += NUMBER_FONT.line_height() + EXTRA_LINE_HEIGHT;
-            let index = self.word_index() + i;
-            if index >= self.share_words.len() {
-                break;
-            }
-            let word = &self.share_words[index];
-            let baseline = self.area.top_left() + Offset::y(y_offset);
-            let ordinal = uformat!("{}.", index + 1);
+            let base = self.area.top_left() + Offset::y(y_offset);
 
-            shape::Text::new(baseline + Offset::x(NUMBER_X_OFFSET), &ordinal)
+            let ordinal_txt = uformat!("{}.", ordinal);
+            shape::Text::new(base + Offset::x(NUMBER_X_OFFSET), &ordinal_txt)
                 .with_font(NUMBER_FONT)
                 .with_fg(theme::FG)
                 .render(target);
-
             word.map(|w| {
-                shape::Text::new(baseline + Offset::x(WORD_X_OFFSET), w)
+                shape::Text::new(base + Offset::x(WORD_X_OFFSET), w)
                     .with_font(WORD_FONT)
                     .with_fg(theme::FG)
                     .render(target);
@@ -171,13 +172,15 @@ impl<'a> crate::trace::Trace for ShareWords<'a> {
             self.get_final_text()
         } else {
             let mut content = ShortString::new();
-            for i in 0..WORDS_PER_PAGE {
-                let index = self.word_index() + i;
-                if index >= self.share_words.len() {
-                    break;
-                }
-                self.share_words[index]
-                    .map(|word| unwrap!(uwrite!(content, "{}. {}\n", index + 1, word)));
+            for (word_idx, word) in self
+                .share_words
+                .iter()
+                .enumerate()
+                .skip(self.page_index * WORDS_PER_PAGE)
+                .take(WORDS_PER_PAGE)
+            {
+                let ordinal = word_idx + 1;
+                word.map(|w| unwrap!(uwrite!(content, "{}. {}\n", ordinal, w)));
             }
             content
         };

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

@@ -839,25 +839,6 @@ extern "C" fn new_confirm_more(n_args: usize, args: *const Obj, kwargs: *mut Map
     unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
 }
 
-extern "C" fn new_show_share_words(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
-    let block = |_args: &[Obj], kwargs: &Map| {
-        let share_words_obj: Obj = kwargs.get(Qstr::MP_QSTR_share_words)?;
-        let share_words: Vec<TString, 33> = util::iter_into_vec(share_words_obj)?;
-
-        let cancel_btn = Some(ButtonDetails::up_arrow_icon());
-        let confirm_btn =
-            Some(ButtonDetails::text(TR::buttons__hold_to_confirm.into()).with_default_duration());
-
-        let obj = LayoutObj::new(
-            ButtonPage::new(ShareWords::new(share_words), theme::BG)
-                .with_cancel_btn(cancel_btn)
-                .with_confirm_btn(confirm_btn),
-        )?;
-        Ok(obj.into())
-    };
-    unsafe { util::try_with_args_and_kwargs(n_args, args, kwargs, block) }
-}
-
 #[no_mangle]
 pub static mp_module_trezorui2: Module = obj_module! {
     /// from trezor import utils
@@ -1016,11 +997,4 @@ pub static mp_module_trezorui2: Module = obj_module! {
     ///     """Confirm long content with the possibility to go back from any page.
     ///     Meant to be used with confirm_with_info."""
     Qstr::MP_QSTR_confirm_more => obj_fn_kw!(0, new_confirm_more).as_obj(),
-
-    /// def show_share_words(
-    ///     *,
-    ///     share_words: Iterable[str],
-    /// ) -> LayoutObj[UiResult]:
-    ///     """Shows a backup seed."""
-    Qstr::MP_QSTR_show_share_words => obj_fn_kw!(0, new_show_share_words).as_obj(),
 };