From 32c3320f07a11e3f6011f5a34fa696e572ab2e8e Mon Sep 17 00:00:00 2001
From: matejcik <ja@matejcik.cz>
Date: Wed, 9 Feb 2022 15:20:39 +0100
Subject: [PATCH] refactor(core/rust): pass around &str instead of [u8] in most
 places

---
 core/embed/rust/src/trezorhal/display.rs      | 10 ++-
 core/embed/rust/src/ui/component/label.rs     |  4 +-
 core/embed/rust/src/ui/component/paginated.rs |  4 +-
 .../rust/src/ui/component/text/formatted.rs   | 77 ++++++++++---------
 core/embed/rust/src/ui/component/text/iter.rs |  2 +-
 .../rust/src/ui/component/text/layout.rs      | 38 ++++-----
 .../rust/src/ui/component/text/paragraphs.rs  | 16 ++--
 core/embed/rust/src/ui/display.rs             | 10 ++-
 .../rust/src/ui/model_t1/component/button.rs  |  6 +-
 .../rust/src/ui/model_t1/component/dialog.rs  |  6 +-
 .../rust/src/ui/model_t1/component/frame.rs   |  6 +-
 core/embed/rust/src/ui/model_t1/layout.rs     | 30 ++++----
 .../rust/src/ui/model_tt/component/button.rs  |  8 +-
 .../rust/src/ui/model_tt/component/frame.rs   |  6 +-
 .../ui/model_tt/component/keyboard/bip39.rs   |  8 +-
 .../ui/model_tt/component/keyboard/common.rs  | 15 ++--
 .../model_tt/component/keyboard/mnemonic.rs   | 13 ++--
 .../model_tt/component/keyboard/passphrase.rs |  2 +-
 .../src/ui/model_tt/component/keyboard/pin.rs | 18 ++---
 .../ui/model_tt/component/keyboard/slip39.rs  | 13 ++--
 .../rust/src/ui/model_tt/component/page.rs    |  2 +-
 core/embed/rust/src/ui/model_tt/layout.rs     | 36 ++++-----
 22 files changed, 169 insertions(+), 161 deletions(-)

diff --git a/core/embed/rust/src/trezorhal/display.rs b/core/embed/rust/src/trezorhal/display.rs
index bba6527b6..f470b531d 100644
--- a/core/embed/rust/src/trezorhal/display.rs
+++ b/core/embed/rust/src/trezorhal/display.rs
@@ -67,7 +67,7 @@ pub fn backlight(val: i32) -> i32 {
     unsafe { display_backlight(val) }
 }
 
-pub fn text(baseline_x: i32, baseline_y: i32, text: &[u8], font: i32, fgcolor: u16, bgcolor: u16) {
+pub fn text(baseline_x: i32, baseline_y: i32, text: &str, font: i32, fgcolor: u16, bgcolor: u16) {
     unsafe {
         display_text(
             baseline_x,
@@ -81,10 +81,16 @@ pub fn text(baseline_x: i32, baseline_y: i32, text: &[u8], font: i32, fgcolor: u
     }
 }
 
-pub fn text_width(text: &[u8], font: i32) -> i32 {
+pub fn text_width(text: &str, font: i32) -> i32 {
     unsafe { display_text_width(text.as_ptr() as _, text.len() as _, font) }
 }
 
+pub fn char_width(ch: char, font: i32) -> i32 {
+    let mut buf = [0u8; 4];
+    let encoding = ch.encode_utf8(&mut buf);
+    text_width(encoding, font)
+}
+
 pub fn text_height(font: i32) -> i32 {
     unsafe { display_text_height(font) }
 }
diff --git a/core/embed/rust/src/ui/component/label.rs b/core/embed/rust/src/ui/component/label.rs
index 68d31f56e..27ad2f1d1 100644
--- a/core/embed/rust/src/ui/component/label.rs
+++ b/core/embed/rust/src/ui/component/label.rs
@@ -21,7 +21,7 @@ pub struct Label<T> {
 
 impl<T> Label<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     pub fn new(text: T, align: Alignment, style: LabelStyle) -> Self {
         Self {
@@ -58,7 +58,7 @@ where
 
 impl<T> Component for Label<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     type Msg = Never;
 
diff --git a/core/embed/rust/src/ui/component/paginated.rs b/core/embed/rust/src/ui/component/paginated.rs
index 059b559fe..70f6ac17a 100644
--- a/core/embed/rust/src/ui/component/paginated.rs
+++ b/core/embed/rust/src/ui/component/paginated.rs
@@ -20,8 +20,8 @@ pub trait Paginate {
 
 impl<F, T> Paginate for FormattedText<F, T>
 where
-    F: AsRef<[u8]>,
-    T: AsRef<[u8]>,
+    F: AsRef<str>,
+    T: AsRef<str>,
 {
     fn page_count(&mut self) -> usize {
         let mut page_count = 1; // There's always at least one page.
diff --git a/core/embed/rust/src/ui/component/text/formatted.rs b/core/embed/rust/src/ui/component/text/formatted.rs
index 6944e8e30..f74486b7e 100644
--- a/core/embed/rust/src/ui/component/text/formatted.rs
+++ b/core/embed/rust/src/ui/component/text/formatted.rs
@@ -21,7 +21,7 @@ pub const MAX_ARGUMENTS: usize = 6;
 pub struct FormattedText<F, T> {
     layout: TextLayout,
     format: F,
-    args: LinearMap<&'static [u8], T, MAX_ARGUMENTS>,
+    args: LinearMap<&'static str, T, MAX_ARGUMENTS>,
     char_offset: usize,
 }
 
@@ -35,7 +35,7 @@ impl<F, T> FormattedText<F, T> {
         }
     }
 
-    pub fn with(mut self, key: &'static [u8], value: T) -> Self {
+    pub fn with(mut self, key: &'static str, value: T) -> Self {
         if self.args.insert(key, value).is_err() {
             #[cfg(feature = "ui_debug")]
             panic!("text args map is full");
@@ -83,18 +83,18 @@ impl<F, T> FormattedText<F, T> {
 
 impl<F, T> FormattedText<F, T>
 where
-    F: AsRef<[u8]>,
-    T: AsRef<[u8]>,
+    F: AsRef<str>,
+    T: AsRef<str>,
 {
     pub fn layout_content(&self, sink: &mut dyn LayoutSink) -> LayoutFit {
         let mut cursor = self.layout.initial_cursor();
         let mut ops = Op::skip_n_text_bytes(
             Tokenizer::new(self.format.as_ref()).flat_map(|arg| match arg {
                 Token::Literal(literal) => Some(Op::Text(literal)),
-                Token::Argument(b"mono") => Some(Op::Font(self.layout.mono_font)),
-                Token::Argument(b"bold") => Some(Op::Font(self.layout.bold_font)),
-                Token::Argument(b"normal") => Some(Op::Font(self.layout.normal_font)),
-                Token::Argument(b"medium") => Some(Op::Font(self.layout.medium_font)),
+                Token::Argument("mono") => Some(Op::Font(self.layout.mono_font)),
+                Token::Argument("bold") => Some(Op::Font(self.layout.bold_font)),
+                Token::Argument("normal") => Some(Op::Font(self.layout.normal_font)),
+                Token::Argument("medium") => Some(Op::Font(self.layout.medium_font)),
                 Token::Argument(argument) => self
                     .args
                     .get(argument)
@@ -108,8 +108,8 @@ where
 
 impl<F, T> Component for FormattedText<F, T>
 where
-    F: AsRef<[u8]>,
-    T: AsRef<[u8]>,
+    F: AsRef<str>,
+    T: AsRef<str>,
 {
     type Msg = Never;
 
@@ -141,8 +141,8 @@ pub mod trace {
 
     impl<'a, F, T> crate::trace::Trace for TraceText<'a, F, T>
     where
-        F: AsRef<[u8]>,
-        T: AsRef<[u8]>,
+        F: AsRef<str>,
+        T: AsRef<str>,
     {
         fn trace(&self, d: &mut dyn crate::trace::Tracer) {
             self.0.layout_content(&mut TraceSink(d));
@@ -153,8 +153,8 @@ pub mod trace {
 #[cfg(feature = "ui_debug")]
 impl<F, T> crate::trace::Trace for FormattedText<F, T>
 where
-    F: AsRef<[u8]>,
-    T: AsRef<[u8]>,
+    F: AsRef<str>,
+    T: AsRef<str>,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Text");
@@ -166,9 +166,9 @@ where
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Token<'a> {
     /// Process literal text content.
-    Literal(&'a [u8]),
+    Literal(&'a str),
     /// Process argument with specified descriptor.
-    Argument(&'a [u8]),
+    Argument(&'a str),
 }
 
 /// Processes a format string into an iterator of `Token`s.
@@ -182,17 +182,18 @@ pub enum Token<'a> {
 /// assert!(matches!(parser.next(), Some(Token::Literal(", where you been?"))));
 /// ```
 pub struct Tokenizer<'a> {
-    input: &'a [u8],
+    input: &'a str,
     inner: Peekable<Enumerate<slice::Iter<'a, u8>>>,
 }
 
 impl<'a> Tokenizer<'a> {
     /// Create a new tokenizer for bytes of a formatting string `input`,
     /// returning an iterator.
-    pub fn new(input: &'a [u8]) -> Self {
+    pub fn new(input: &'a str) -> Self {
+        assert!(input.is_ascii());
         Self {
             input,
-            inner: input.iter().enumerate().peekable(),
+            inner: input.as_bytes().iter().enumerate().peekable(),
         }
     }
 }
@@ -246,26 +247,26 @@ mod tests {
 
     #[test]
     fn tokenizer_yields_expected_tokens() {
-        assert!(Tokenizer::new(b"").eq([]));
-        assert!(Tokenizer::new(b"x").eq([Token::Literal(b"x")]));
-        assert!(Tokenizer::new(b"x\0y").eq([Token::Literal("x\0y".as_bytes())]));
-        assert!(Tokenizer::new(b"{").eq([]));
-        assert!(Tokenizer::new(b"x{").eq([Token::Literal(b"x")]));
-        assert!(Tokenizer::new(b"x{y").eq([Token::Literal(b"x")]));
-        assert!(Tokenizer::new(b"{}").eq([Token::Argument(b"")]));
-        assert!(Tokenizer::new(b"x{}y{").eq([
-            Token::Literal(b"x"),
-            Token::Argument(b""),
-            Token::Literal(b"y"),
+        assert!(Tokenizer::new("").eq([]));
+        assert!(Tokenizer::new("x").eq([Token::Literal("x")]));
+        assert!(Tokenizer::new("x\0y").eq([Token::Literal("x\0y")]));
+        assert!(Tokenizer::new("{").eq([]));
+        assert!(Tokenizer::new("x{").eq([Token::Literal("x")]));
+        assert!(Tokenizer::new("x{y").eq([Token::Literal("x")]));
+        assert!(Tokenizer::new("{}").eq([Token::Argument("")]));
+        assert!(Tokenizer::new("x{}y{").eq([
+            Token::Literal("x"),
+            Token::Argument(""),
+            Token::Literal("y"),
         ]));
-        assert!(Tokenizer::new(b"{\0}").eq([Token::Argument("\0".as_bytes()),]));
-        assert!(Tokenizer::new(b"{{y}").eq([Token::Argument(b"{y"),]));
-        assert!(Tokenizer::new(b"{{{{xyz").eq([]));
-        assert!(Tokenizer::new(b"x{}{{}}}}").eq([
-            Token::Literal(b"x"),
-            Token::Argument(b""),
-            Token::Argument(b"{"),
-            Token::Literal(b"}}}"),
+        assert!(Tokenizer::new("{\0}").eq([Token::Argument("\0"),]));
+        assert!(Tokenizer::new("{{y}").eq([Token::Argument("{y"),]));
+        assert!(Tokenizer::new("{{{{xyz").eq([]));
+        assert!(Tokenizer::new("x{}{{}}}}").eq([
+            Token::Literal("x"),
+            Token::Argument(""),
+            Token::Argument("{"),
+            Token::Literal("}}}"),
         ]));
     }
 }
diff --git a/core/embed/rust/src/ui/component/text/iter.rs b/core/embed/rust/src/ui/component/text/iter.rs
index fd99c5c79..5d148b899 100644
--- a/core/embed/rust/src/ui/component/text/iter.rs
+++ b/core/embed/rust/src/ui/component/text/iter.rs
@@ -169,7 +169,7 @@ trait GlyphMetrics {
 
 impl GlyphMetrics for Font {
     fn char_width(&self, ch: char) -> i32 {
-        self.text_width(&[ch as u8])
+        Font::char_width(*self, ch)
     }
 
     fn line_height(&self) -> i32 {
diff --git a/core/embed/rust/src/ui/component/text/layout.rs b/core/embed/rust/src/ui/component/text/layout.rs
index 5e8a60009..38aa93fff 100644
--- a/core/embed/rust/src/ui/component/text/layout.rs
+++ b/core/embed/rust/src/ui/component/text/layout.rs
@@ -114,11 +114,11 @@ impl TextLayout {
         self.bounds.top_left() + Offset::y(self.text_font.text_height() + self.padding_top)
     }
 
-    pub fn fit_text(&self, text: &[u8]) -> LayoutFit {
+    pub fn fit_text(&self, text: &str) -> LayoutFit {
         self.layout_text(text, &mut self.initial_cursor(), &mut TextNoOp)
     }
 
-    pub fn render_text(&self, text: &[u8]) {
+    pub fn render_text(&self, text: &str) {
         self.layout_text(text, &mut self.initial_cursor(), &mut TextRenderer);
     }
 
@@ -167,7 +167,7 @@ impl TextLayout {
 
     pub fn layout_text(
         &self,
-        text: &[u8],
+        text: &str,
         cursor: &mut Point,
         sink: &mut dyn LayoutSink,
     ) -> LayoutFit {
@@ -276,7 +276,7 @@ impl LayoutFit {
 
 /// Visitor for text segment operations.
 pub trait LayoutSink {
-    fn text(&mut self, _cursor: Point, _layout: &TextLayout, _text: &[u8]) {}
+    fn text(&mut self, _cursor: Point, _layout: &TextLayout, _text: &str) {}
     fn hyphen(&mut self, _cursor: Point, _layout: &TextLayout) {}
     fn ellipsis(&mut self, _cursor: Point, _layout: &TextLayout) {}
     fn line_break(&mut self, _cursor: Point) {}
@@ -290,7 +290,7 @@ impl LayoutSink for TextNoOp {}
 pub struct TextRenderer;
 
 impl LayoutSink for TextRenderer {
-    fn text(&mut self, cursor: Point, layout: &TextLayout, text: &[u8]) {
+    fn text(&mut self, cursor: Point, layout: &TextLayout, text: &str) {
         display::text(
             cursor,
             text,
@@ -303,7 +303,7 @@ impl LayoutSink for TextRenderer {
     fn hyphen(&mut self, cursor: Point, layout: &TextLayout) {
         display::text(
             cursor,
-            b"-",
+            "-",
             layout.hyphen_font,
             layout.hyphen_color,
             layout.background_color,
@@ -313,7 +313,7 @@ impl LayoutSink for TextRenderer {
     fn ellipsis(&mut self, cursor: Point, layout: &TextLayout) {
         display::text(
             cursor,
-            b"...",
+            "...",
             layout.ellipsis_font,
             layout.ellipsis_color,
             layout.background_color,
@@ -330,8 +330,8 @@ pub mod trace {
     pub struct TraceSink<'a>(pub &'a mut dyn crate::trace::Tracer);
 
     impl<'a> LayoutSink for TraceSink<'a> {
-        fn text(&mut self, _cursor: Point, _layout: &TextLayout, text: &[u8]) {
-            self.0.bytes(text);
+        fn text(&mut self, _cursor: Point, _layout: &TextLayout, text: &str) {
+            self.0.string(text);
         }
 
         fn hyphen(&mut self, _cursor: Point, _layout: &TextLayout) {
@@ -351,7 +351,7 @@ pub mod trace {
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Op<'a> {
     /// Render text with current color and font.
-    Text(&'a [u8]),
+    Text(&'a str),
     /// Set current text color.
     Color(Color),
     /// Set currently used font.
@@ -396,22 +396,22 @@ struct Span {
 
 impl Span {
     fn fit_horizontally(
-        text: &[u8],
+        text: &str,
         max_width: i32,
         text_font: Font,
         hyphen_font: Font,
         breaking: LineBreaking,
     ) -> Self {
-        const ASCII_LF: u8 = b'\n';
-        const ASCII_CR: u8 = b'\r';
-        const ASCII_SPACE: u8 = b' ';
-        const ASCII_HYPHEN: u8 = b'-';
+        const ASCII_LF: char = '\n';
+        const ASCII_CR: char = '\r';
+        const ASCII_SPACE: char = ' ';
+        const ASCII_HYPHEN: char = '-';
 
-        fn is_whitespace(ch: u8) -> bool {
+        fn is_whitespace(ch: char) -> bool {
             ch == ASCII_SPACE || ch == ASCII_LF || ch == ASCII_CR
         }
 
-        let hyphen_width = hyphen_font.text_width(&[ASCII_HYPHEN]);
+        let hyphen_width = hyphen_font.char_width(ASCII_HYPHEN);
 
         // The span we return in case the line has to break. We mutate it in the
         // possible break points, and its initial value is returned in case no text
@@ -427,8 +427,8 @@ impl Span {
         let mut span_width = 0;
         let mut found_any_whitespace = false;
 
-        for (i, &ch) in text.iter().enumerate() {
-            let char_width = text_font.text_width(&[ch]);
+        for (i, ch) in text.char_indices() {
+            let char_width = text_font.char_width(ch);
 
             // Consider if we could be breaking the line at this position.
             if is_whitespace(ch) {
diff --git a/core/embed/rust/src/ui/component/text/paragraphs.rs b/core/embed/rust/src/ui/component/text/paragraphs.rs
index dffacf27c..d45c945bb 100644
--- a/core/embed/rust/src/ui/component/text/paragraphs.rs
+++ b/core/embed/rust/src/ui/component/text/paragraphs.rs
@@ -29,7 +29,7 @@ pub struct Paragraphs<T> {
 
 impl<T> Paragraphs<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     pub fn new() -> Self {
         Self {
@@ -114,7 +114,7 @@ where
 
 impl<T> Component for Paragraphs<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     type Msg = Never;
 
@@ -146,7 +146,7 @@ where
 
 impl<T> Paginate for Paragraphs<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     fn page_count(&mut self) -> usize {
         // There's always at least one page.
@@ -175,7 +175,7 @@ pub mod trace {
 
     impl<T> crate::trace::Trace for Paragraphs<T>
     where
-        T: AsRef<[u8]>,
+        T: AsRef<str>,
     {
         fn trace(&self, t: &mut dyn crate::trace::Tracer) {
             t.open("Paragraphs");
@@ -201,20 +201,20 @@ pub struct Paragraph<T> {
 
 impl<T> Paragraph<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     pub fn new(content: T, layout: TextLayout) -> Self {
         Self { content, layout }
     }
 
-    pub fn content(&self, char_offset: usize) -> &[u8] {
+    pub fn content(&self, char_offset: usize) -> &str {
         &self.content.as_ref()[char_offset..]
     }
 }
 
 impl<T> Dimensions for Paragraph<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     fn fit(&mut self, area: Rect) {
         self.layout.bounds = area;
@@ -246,7 +246,7 @@ struct PageBreakIterator<'a, T> {
 /// `PageOffset { 0, 0 }` even if the paragraph vector is empty.
 impl<'a, T> Iterator for PageBreakIterator<'a, T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     /// `PageOffset` denotes the first paragraph that is rendered and a
     /// character offset in that paragraph.
diff --git a/core/embed/rust/src/ui/display.rs b/core/embed/rust/src/ui/display.rs
index b6874cd0a..e128a492a 100644
--- a/core/embed/rust/src/ui/display.rs
+++ b/core/embed/rust/src/ui/display.rs
@@ -152,7 +152,7 @@ pub fn loader_indeterminate(
     );
 }
 
-pub fn text(baseline: Point, text: &[u8], font: Font, fg_color: Color, bg_color: Color) {
+pub fn text(baseline: Point, text: &str, font: Font, fg_color: Color, bg_color: Color) {
     display::text(
         baseline.x,
         baseline.y,
@@ -163,7 +163,7 @@ pub fn text(baseline: Point, text: &[u8], font: Font, fg_color: Color, bg_color:
     );
 }
 
-pub fn text_center(baseline: Point, text: &[u8], font: Font, fg_color: Color, bg_color: Color) {
+pub fn text_center(baseline: Point, text: &str, font: Font, fg_color: Color, bg_color: Color) {
     let w = font.text_width(text);
     display::text(
         baseline.x - w / 2,
@@ -183,10 +183,14 @@ impl Font {
         Self(id)
     }
 
-    pub fn text_width(self, text: &[u8]) -> i32 {
+    pub fn text_width(self, text: &str) -> i32 {
         display::text_width(text, self.0)
     }
 
+    pub fn char_width(self, ch: char) -> i32 {
+        display::char_width(ch, self.0)
+    }
+
     pub fn text_height(self) -> i32 {
         display::text_height(self.0)
     }
diff --git a/core/embed/rust/src/ui/model_t1/component/button.rs b/core/embed/rust/src/ui/model_t1/component/button.rs
index 6d2b523db..3febad2ef 100644
--- a/core/embed/rust/src/ui/model_t1/component/button.rs
+++ b/core/embed/rust/src/ui/model_t1/component/button.rs
@@ -37,7 +37,7 @@ pub struct Button<T> {
     state: State,
 }
 
-impl<T: AsRef<[u8]>> Button<T> {
+impl<T: AsRef<str>> Button<T> {
     pub fn new(pos: ButtonPos, content: ButtonContent<T>, styles: ButtonStyleSheet) -> Self {
         Self {
             pos,
@@ -100,7 +100,7 @@ impl<T: AsRef<[u8]>> Button<T> {
 
 impl<T> Component for Button<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     type Msg = ButtonMsg;
 
@@ -157,7 +157,7 @@ where
 #[cfg(feature = "ui_debug")]
 impl<T> crate::trace::Trace for Button<T>
 where
-    T: AsRef<[u8]> + crate::trace::Trace,
+    T: AsRef<str> + crate::trace::Trace,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Button");
diff --git a/core/embed/rust/src/ui/model_t1/component/dialog.rs b/core/embed/rust/src/ui/model_t1/component/dialog.rs
index 3e39bca6e..5f1dd5a3c 100644
--- a/core/embed/rust/src/ui/model_t1/component/dialog.rs
+++ b/core/embed/rust/src/ui/model_t1/component/dialog.rs
@@ -22,7 +22,7 @@ pub struct Dialog<T, U> {
 impl<T, U> Dialog<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     pub fn new(content: T, left: Option<Button<U>>, right: Option<Button<U>>) -> Self {
         Self {
@@ -40,7 +40,7 @@ where
 impl<T, U> Component for Dialog<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     type Msg = DialogMsg<T::Msg>;
 
@@ -80,7 +80,7 @@ where
 impl<T, U> crate::trace::Trace for Dialog<T, U>
 where
     T: crate::trace::Trace,
-    U: crate::trace::Trace + AsRef<[u8]>,
+    U: crate::trace::Trace + AsRef<str>,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Dialog");
diff --git a/core/embed/rust/src/ui/model_t1/component/frame.rs b/core/embed/rust/src/ui/model_t1/component/frame.rs
index 0ea55f538..f26447526 100644
--- a/core/embed/rust/src/ui/model_t1/component/frame.rs
+++ b/core/embed/rust/src/ui/model_t1/component/frame.rs
@@ -14,7 +14,7 @@ pub struct Frame<T, U> {
 impl<T, U> Frame<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     pub fn new(title: U, content: T) -> Self {
         Self {
@@ -32,7 +32,7 @@ where
 impl<T, U> Component for Frame<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     type Msg = T::Msg;
 
@@ -68,7 +68,7 @@ where
 impl<T, U> crate::trace::Trace for Frame<T, U>
 where
     T: crate::trace::Trace,
-    U: crate::trace::Trace + AsRef<[u8]>,
+    U: crate::trace::Trace + AsRef<str>,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Frame");
diff --git a/core/embed/rust/src/ui/model_t1/layout.rs b/core/embed/rust/src/ui/model_t1/layout.rs
index 99e1cbafe..e4758bb08 100644
--- a/core/embed/rust/src/ui/model_t1/layout.rs
+++ b/core/embed/rust/src/ui/model_t1/layout.rs
@@ -2,7 +2,7 @@ use core::convert::TryInto;
 
 use crate::{
     error::Error,
-    micropython::{buffer::Buffer, map::Map, module::Module, obj::Obj, qstr::Qstr},
+    micropython::{buffer::StrBuffer, map::Map, module::Module, obj::Obj, qstr::Qstr},
     ui::{
         component::{
             base::Component,
@@ -39,7 +39,7 @@ where
 impl<T, U> ComponentMsgObj for Frame<T, U>
 where
     T: ComponentMsgObj,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
         self.inner().msg_try_into_obj(msg)
@@ -48,12 +48,12 @@ where
 
 extern "C" fn new_confirm_action(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = |_args: &[Obj], kwargs: &Map| {
-        let title: Buffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
-        let action: Option<Buffer> = kwargs.get(Qstr::MP_QSTR_action)?.try_into_option()?;
-        let description: Option<Buffer> =
+        let title: StrBuffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
+        let action: Option<StrBuffer> = kwargs.get(Qstr::MP_QSTR_action)?.try_into_option()?;
+        let description: Option<StrBuffer> =
             kwargs.get(Qstr::MP_QSTR_description)?.try_into_option()?;
-        let verb: Option<Buffer> = kwargs.get(Qstr::MP_QSTR_verb)?.try_into_option()?;
-        let verb_cancel: Option<Buffer> =
+        let verb: Option<StrBuffer> = kwargs.get(Qstr::MP_QSTR_verb)?.try_into_option()?;
+        let verb_cancel: Option<StrBuffer> =
             kwargs.get(Qstr::MP_QSTR_verb_cancel)?.try_into_option()?;
         let reverse: bool = kwargs.get(Qstr::MP_QSTR_reverse)?.try_into()?;
 
@@ -74,8 +74,8 @@ extern "C" fn new_confirm_action(n_args: usize, args: *const Obj, kwargs: *mut M
             title,
             ButtonPage::new(
                 FormattedText::new::<theme::T1DefaultText>(format)
-                    .with(b"action", action.unwrap_or_default())
-                    .with(b"description", description.unwrap_or_default()),
+                    .with("action", action.unwrap_or_default())
+                    .with("description", description.unwrap_or_default()),
                 theme::BG,
             ),
         ))?;
@@ -86,9 +86,9 @@ extern "C" fn new_confirm_action(n_args: usize, args: *const Obj, kwargs: *mut M
 
 extern "C" fn new_confirm_text(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = |_args: &[Obj], kwargs: &Map| {
-        let title: Buffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
-        let data: Buffer = kwargs.get(Qstr::MP_QSTR_data)?.try_into()?;
-        let description: Option<Buffer> =
+        let title: StrBuffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
+        let data: StrBuffer = kwargs.get(Qstr::MP_QSTR_data)?.try_into()?;
+        let description: Option<StrBuffer> =
             kwargs.get(Qstr::MP_QSTR_description)?.try_into_option()?;
 
         let obj = LayoutObj::new(Frame::new(
@@ -165,7 +165,7 @@ mod tests {
     impl<T, U> ComponentMsgObj for Dialog<T, U>
     where
         T: ComponentMsgObj,
-        U: AsRef<[u8]>,
+        U: AsRef<str>,
     {
         fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
             match msg {
@@ -182,7 +182,7 @@ mod tests {
             FormattedText::new::<theme::T1DefaultText>(
                 "Testing text layout, with some text, and some more text. And {param}",
             )
-            .with(b"param", b"parameters!"),
+            .with("param", "parameters!"),
             Some(Button::with_text(
                 ButtonPos::Left,
                 "Left",
@@ -212,7 +212,7 @@ arameters! > left:<Button text:Left > right:<Button text:Right > >"#
                 FormattedText::new::<theme::T1DefaultText>(
                     "Testing text layout, with some text, and some more text. And {param}",
                 )
-                .with(b"param", b"parameters!"),
+                .with("param", "parameters!"),
                 Some(Button::with_text(
                     ButtonPos::Left,
                     "Left",
diff --git a/core/embed/rust/src/ui/model_tt/component/button.rs b/core/embed/rust/src/ui/model_tt/component/button.rs
index f3650fd93..0cfb79e95 100644
--- a/core/embed/rust/src/ui/model_tt/component/button.rs
+++ b/core/embed/rust/src/ui/model_tt/component/button.rs
@@ -156,7 +156,7 @@ impl<T> Button<T> {
 
     pub fn paint_content(&self, style: &ButtonStyle)
     where
-        T: AsRef<[u8]>,
+        T: AsRef<str>,
     {
         match &self.content {
             ButtonContent::Empty => {}
@@ -189,7 +189,7 @@ impl<T> Button<T> {
 
 impl<T> Component for Button<T>
 where
-    T: AsRef<[u8]>,
+    T: AsRef<str>,
 {
     type Msg = ButtonMsg;
 
@@ -266,7 +266,7 @@ where
 #[cfg(feature = "ui_debug")]
 impl<T> crate::trace::Trace for Button<T>
 where
-    T: AsRef<[u8]> + crate::trace::Trace,
+    T: AsRef<str> + crate::trace::Trace,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Button");
@@ -322,7 +322,7 @@ impl<T> Button<T> {
     where
         F0: Fn(ButtonMsg) -> Option<R>,
         F1: Fn(ButtonMsg) -> Option<R>,
-        T: AsRef<[u8]>,
+        T: AsRef<str>,
     {
         const BUTTON_SPACING: i32 = 6;
         (
diff --git a/core/embed/rust/src/ui/model_tt/component/frame.rs b/core/embed/rust/src/ui/model_tt/component/frame.rs
index ff8a41ee3..86bcac91d 100644
--- a/core/embed/rust/src/ui/model_tt/component/frame.rs
+++ b/core/embed/rust/src/ui/model_tt/component/frame.rs
@@ -14,7 +14,7 @@ pub struct Frame<T, U> {
 impl<T, U> Frame<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     pub fn new(title: U, content: T) -> Self {
         Self {
@@ -32,7 +32,7 @@ where
 impl<T, U> Component for Frame<T, U>
 where
     T: Component,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     type Msg = T::Msg;
 
@@ -76,7 +76,7 @@ where
 impl<T, U> crate::trace::Trace for Frame<T, U>
 where
     T: crate::trace::Trace,
-    U: crate::trace::Trace + AsRef<[u8]>,
+    U: crate::trace::Trace + AsRef<str>,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("Frame");
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/bip39.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/bip39.rs
index 4b79d087c..fc19e97e2 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/bip39.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/bip39.rs
@@ -20,7 +20,7 @@ use crate::{
 const MAX_LENGTH: usize = 8;
 
 pub struct Bip39Input {
-    button: Button<&'static [u8]>,
+    button: Button<&'static str>,
     textbox: TextBox<MAX_LENGTH>,
     multi_tap: MultiTapKeyboard,
     suggested_word: Option<&'static str>,
@@ -95,7 +95,7 @@ impl Component for Bip39Input {
         self.button.paint_background(&style);
 
         // Paint the entered content (the prefix of the suggested word).
-        let text = self.textbox.content().as_bytes();
+        let text = self.textbox.content();
         let width = style.font.text_width(text);
         // Content starts in the left-center point, offset by 16px to the right and 8px
         // to the bottom.
@@ -113,7 +113,7 @@ impl Component for Bip39Input {
             let word_baseline = text_baseline + Offset::new(width, 0);
             display::text(
                 word_baseline,
-                word.as_bytes(),
+                word,
                 style.font,
                 theme::GREY_LIGHT,
                 style.button_color,
@@ -211,7 +211,7 @@ impl Bip39Input {
             // Disabled button.
             self.button.disable(ctx);
             self.button.set_stylesheet(ctx, theme::button_default());
-            self.button.set_content(ctx, ButtonContent::Text(b""));
+            self.button.set_content(ctx, ButtonContent::Text(""));
         }
     }
 }
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/common.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/common.rs
index 87b325750..f23eeb333 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/common.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/common.rs
@@ -79,9 +79,6 @@ impl MultiTapKeyboard {
     /// the pending state. Caller is required to handle the timer event and
     /// call `Self::clear_pending_state` when the timer hits.
     pub fn click_key(&mut self, ctx: &mut EventCtx, key: usize, key_text: &str) -> TextEdit {
-        // To simplify things, we assume the key text is ASCII-only.
-        let ascii_text = key_text.as_bytes();
-
         let (is_pending, press) = match &self.pending {
             Some(pending) if pending.key == key => {
                 // This key is pending. Cycle the last inserted character through the
@@ -102,7 +99,7 @@ impl MultiTapKeyboard {
         // progress into a pending state (to display the pending marker), but such
         // transition only happens as a result of an append op, so the painting should
         // be requested by handling the `TextEdit`.
-        self.pending = if ascii_text.len() > 1 {
+        self.pending = if key_text.len() > 1 {
             Some(Pending {
                 key,
                 press,
@@ -112,7 +109,9 @@ impl MultiTapKeyboard {
             None
         };
 
-        let ch = ascii_text[press % ascii_text.len()] as char;
+        assert!(!key_text.is_empty());
+        // Now we can be sure that a looped iterator will return a value
+        let ch = key_text.chars().cycle().nth(press).unwrap();
         if is_pending {
             TextEdit::ReplaceLast(ch)
         } else {
@@ -208,11 +207,11 @@ impl<const L: usize> TextBox<L> {
     }
 }
 
-pub fn paint_pending_marker(text_baseline: Point, text: &[u8], font: Font, color: Color) {
+pub fn paint_pending_marker(text_baseline: Point, text: &str, font: Font, color: Color) {
     // Measure the width of the last character of input.
-    if let Some(last) = text.last().copied() {
+    if let Some(last) = text.chars().last() {
         let width = font.text_width(text);
-        let last_width = font.text_width(&[last]);
+        let last_width = font.char_width(last);
         // Draw the marker 2px under the start of the baseline of the last character.
         let marker_origin = text_baseline + Offset::new(width - last_width, 2);
         // Draw the marker 1px longer than the last character, and 3px thick.
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/mnemonic.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/mnemonic.rs
index 8e60e4248..1ba286c2e 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/mnemonic.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/mnemonic.rs
@@ -19,17 +19,17 @@ pub struct MnemonicKeyboard<T, U> {
     /// Initial prompt, displayed on empty input.
     prompt: Child<Maybe<Label<U>>>,
     /// Backspace button.
-    back: Child<Maybe<Button<&'static [u8]>>>,
+    back: Child<Maybe<Button<&'static str>>>,
     /// Input area, acting as the auto-complete and confirm button.
     input: Child<Maybe<T>>,
     /// Key buttons.
-    keys: [Child<Button<&'static [u8]>>; MNEMONIC_KEY_COUNT],
+    keys: [Child<Button<&'static str>>; MNEMONIC_KEY_COUNT],
 }
 
 impl<T, U> MnemonicKeyboard<T, U>
 where
     T: MnemonicInput,
-    U: Deref<Target = [u8]>,
+    U: Deref<Target = str>,
 {
     pub fn new(input: T, prompt: U) -> Self {
         Self {
@@ -42,10 +42,7 @@ where
                 Button::with_icon(theme::ICON_BACK).styled(theme::button_clear()),
             )),
             input: Child::new(Maybe::hidden(theme::BG, input)),
-            keys: T::keys()
-                .map(str::as_bytes)
-                .map(Button::with_text)
-                .map(Child::new),
+            keys: T::keys().map(Button::with_text).map(Child::new),
         }
     }
 
@@ -87,7 +84,7 @@ where
 impl<T, U> Component for MnemonicKeyboard<T, U>
 where
     T: MnemonicInput,
-    U: Deref<Target = [u8]>,
+    U: Deref<Target = str>,
 {
     type Msg = MnemonicKeyboardMsg;
 
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/passphrase.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/passphrase.rs
index 6e2f4de73..e91000929 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/passphrase.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/passphrase.rs
@@ -250,7 +250,7 @@ impl Component for Input {
 
         let style = theme::label_default();
         let text_baseline = self.area.bottom_left() - TEXT_OFFSET;
-        let text = self.textbox.content().as_bytes();
+        let text = self.textbox.content();
 
         // Possible optimization is to redraw the background only when pending character
         // is replaced, or only draw rectangle over the pending character and
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/pin.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/pin.rs
index d244562c7..88289353e 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/pin.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/pin.rs
@@ -1,5 +1,5 @@
 use core::ops::Deref;
-use heapless::Vec;
+use heapless::String;
 
 use crate::{
     trezorhal::random,
@@ -26,7 +26,7 @@ const MAX_LENGTH: usize = 9;
 const DIGIT_COUNT: usize = 10; // 0..10
 
 pub struct PinKeyboard<T> {
-    digits: Vec<u8, MAX_LENGTH>,
+    digits: String<MAX_LENGTH>,
     allow_cancel: bool,
     major_prompt: Label<T>,
     minor_prompt: Label<T>,
@@ -40,7 +40,7 @@ pub struct PinKeyboard<T> {
 
 impl<T> PinKeyboard<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     const HEADER_HEIGHT: i32 = 25;
     const HEADER_PADDING_SIDE: i32 = 5;
@@ -56,7 +56,7 @@ where
         major_warning: Option<T>,
         allow_cancel: bool,
     ) -> Self {
-        let digits = Vec::new();
+        let digits = String::new();
 
         // Control buttons.
         let reset_btn = Button::with_icon(theme::ICON_BACK)
@@ -97,7 +97,7 @@ where
     }
 
     fn pin_modified(&mut self, ctx: &mut EventCtx) {
-        let is_full = self.digits.is_full();
+        let is_full = self.digits.len() == self.digits.capacity();
         for btn in &mut self.digit_btns {
             btn.mutate(ctx, |ctx, btn| btn.enable_if(ctx, !is_full));
         }
@@ -118,14 +118,14 @@ where
             .mutate(ctx, |ctx, dots| dots.update(ctx, digit_count));
     }
 
-    pub fn pin(&self) -> &[u8] {
+    pub fn pin(&self) -> &str {
         &self.digits
     }
 }
 
 impl<T> Component for PinKeyboard<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     type Msg = PinKeyboardMsg;
 
@@ -188,7 +188,7 @@ where
         for btn in &mut self.digit_btns {
             if let Some(Clicked) = btn.event(ctx, event) {
                 if let ButtonContent::Text(text) = btn.inner().content() {
-                    if self.digits.extend_from_slice(text.as_ref()).is_err() {
+                    if self.digits.push_str(text).is_err() {
                         // `self.pin` is full and wasn't able to accept all of
                         // `text`. Should not happen.
                     }
@@ -309,7 +309,7 @@ impl Component for PinDots {
 #[cfg(feature = "ui_debug")]
 impl<T> crate::trace::Trace for PinKeyboard<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     fn trace(&self, t: &mut dyn crate::trace::Tracer) {
         t.open("PinKeyboard");
diff --git a/core/embed/rust/src/ui/model_tt/component/keyboard/slip39.rs b/core/embed/rust/src/ui/model_tt/component/keyboard/slip39.rs
index fe6a8831e..b4f008d07 100644
--- a/core/embed/rust/src/ui/model_tt/component/keyboard/slip39.rs
+++ b/core/embed/rust/src/ui/model_tt/component/keyboard/slip39.rs
@@ -25,7 +25,7 @@ use crate::{
 const MAX_LENGTH: usize = 8;
 
 pub struct Slip39Input {
-    button: Button<&'static [u8]>,
+    button: Button<&'static str>,
     textbox: TextBox<MAX_LENGTH>,
     multi_tap: MultiTapKeyboard,
     final_word: Option<&'static str>,
@@ -139,8 +139,9 @@ impl Component for Slip39Input {
             if let (Some(key), Some(press)) =
                 (self.multi_tap.pending_key(), self.multi_tap.pending_press())
             {
-                let ascii_text = Self::keys()[key].as_bytes();
-                let ch = ascii_text[press % ascii_text.len()] as char;
+                assert!(!Self::keys()[key].is_empty());
+                // Now we can be sure that the looped iterator will return a value.
+                let ch = Self::keys()[key].chars().cycle().nth(press).unwrap();
                 text.pop();
                 text.push(ch)
                     .assert_if_debugging_ui("Text buffer is too small");
@@ -148,7 +149,7 @@ impl Component for Slip39Input {
         }
         display::text(
             text_baseline,
-            text.as_bytes(),
+            text.as_str(),
             style.font,
             style.text_color,
             style.button_color,
@@ -156,7 +157,7 @@ impl Component for Slip39Input {
 
         // Paint the pending marker.
         if self.multi_tap.pending_key().is_some() && self.final_word.is_none() {
-            paint_pending_marker(text_baseline, text.as_bytes(), style.font, style.text_color);
+            paint_pending_marker(text_baseline, text.as_str(), style.font, style.text_color);
         }
 
         // Paint the icon.
@@ -221,7 +222,7 @@ impl Slip39Input {
             // Disabled button.
             self.button.disable(ctx);
             self.button.set_stylesheet(ctx, theme::button_default());
-            self.button.set_content(ctx, ButtonContent::Text(b""));
+            self.button.set_content(ctx, ButtonContent::Text(""));
         }
     }
 
diff --git a/core/embed/rust/src/ui/model_tt/component/page.rs b/core/embed/rust/src/ui/model_tt/component/page.rs
index 7115e5bdf..a8fd4fe60 100644
--- a/core/embed/rust/src/ui/model_tt/component/page.rs
+++ b/core/embed/rust/src/ui/model_tt/component/page.rs
@@ -57,7 +57,7 @@ where
     fn paint_hint(&mut self) {
         display::text_center(
             self.pad.area.bottom_center() - Offset::y(3),
-            b"SWIPE TO CONTINUE",
+            "SWIPE TO CONTINUE",
             theme::FONT_BOLD, // FIXME: Figma has this as 14px but bold is 16px
             theme::GREY_LIGHT,
             theme::BG,
diff --git a/core/embed/rust/src/ui/model_tt/layout.rs b/core/embed/rust/src/ui/model_tt/layout.rs
index c1b9d10e9..d8759e739 100644
--- a/core/embed/rust/src/ui/model_tt/layout.rs
+++ b/core/embed/rust/src/ui/model_tt/layout.rs
@@ -2,7 +2,7 @@ use core::{convert::TryInto, ops::Deref};
 
 use crate::{
     error::Error,
-    micropython::{buffer::Buffer, map::Map, module::Module, obj::Obj, qstr::Qstr},
+    micropython::{buffer::StrBuffer, map::Map, module::Module, obj::Obj, qstr::Qstr},
     ui::{
         component::{
             base::ComponentExt,
@@ -30,7 +30,7 @@ use super::{
 impl<T, U> ComponentMsgObj for Dialog<T, Button<U>, Button<U>>
 where
     T: ComponentMsgObj,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
         match msg {
@@ -57,7 +57,7 @@ where
 
 impl<T> ComponentMsgObj for PinKeyboard<T>
 where
-    T: Deref<Target = [u8]>,
+    T: Deref<Target = str>,
 {
     fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
         match msg {
@@ -79,7 +79,7 @@ impl ComponentMsgObj for PassphraseKeyboard {
 impl<T, U> ComponentMsgObj for MnemonicKeyboard<T, U>
 where
     T: MnemonicInput,
-    U: Deref<Target = [u8]>,
+    U: Deref<Target = str>,
 {
     fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
         match msg {
@@ -97,7 +97,7 @@ where
 impl<T, U> ComponentMsgObj for Frame<T, U>
 where
     T: ComponentMsgObj,
-    U: AsRef<[u8]>,
+    U: AsRef<str>,
 {
     fn msg_try_into_obj(&self, msg: Self::Msg) -> Result<Obj, Error> {
         self.inner().msg_try_into_obj(msg)
@@ -120,11 +120,11 @@ where
 
 extern "C" fn new_confirm_action(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
-        let title: Buffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
-        let action: Option<Buffer> = kwargs.get(Qstr::MP_QSTR_action)?.try_into_option()?;
-        let description: Option<Buffer> =
+        let title: StrBuffer = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
+        let action: Option<StrBuffer> = kwargs.get(Qstr::MP_QSTR_action)?.try_into_option()?;
+        let description: Option<StrBuffer> =
             kwargs.get(Qstr::MP_QSTR_description)?.try_into_option()?;
-        let verb: Option<Buffer> = kwargs.get(Qstr::MP_QSTR_verb)?.try_into_option()?;
+        let verb: Option<StrBuffer> = kwargs.get(Qstr::MP_QSTR_verb)?.try_into_option()?;
         let reverse: bool = kwargs.get(Qstr::MP_QSTR_reverse)?.try_into()?;
 
         let paragraphs = {
@@ -161,11 +161,11 @@ extern "C" fn new_confirm_action(n_args: usize, args: *const Obj, kwargs: *mut M
 
 extern "C" fn new_request_pin(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
-        let prompt: Buffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
-        let subprompt: Buffer = kwargs.get(Qstr::MP_QSTR_subprompt)?.try_into()?;
+        let prompt: StrBuffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
+        let subprompt: StrBuffer = kwargs.get(Qstr::MP_QSTR_subprompt)?.try_into()?;
         let allow_cancel: Option<bool> =
             kwargs.get(Qstr::MP_QSTR_allow_cancel)?.try_into_option()?;
-        let warning: Option<Buffer> = kwargs.get(Qstr::MP_QSTR_warning)?.try_into_option()?;
+        let warning: Option<StrBuffer> = kwargs.get(Qstr::MP_QSTR_warning)?.try_into_option()?;
         let obj = LayoutObj::new(
             PinKeyboard::new(prompt, subprompt, warning, allow_cancel.unwrap_or(true)).into_child(),
         )?;
@@ -176,7 +176,7 @@ extern "C" fn new_request_pin(n_args: usize, args: *const Obj, kwargs: *mut Map)
 
 extern "C" fn new_request_passphrase(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
-        let _prompt: Buffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
+        let _prompt: StrBuffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
         let _max_len: u32 = kwargs.get(Qstr::MP_QSTR_max_len)?.try_into()?;
         let obj = LayoutObj::new(PassphraseKeyboard::new().into_child())?;
         Ok(obj.into())
@@ -186,7 +186,7 @@ extern "C" fn new_request_passphrase(n_args: usize, args: *const Obj, kwargs: *m
 
 extern "C" fn new_request_bip39(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
-        let prompt: Buffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
+        let prompt: StrBuffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
         let obj = LayoutObj::new(MnemonicKeyboard::new(Bip39Input::new(), prompt).into_child())?;
         Ok(obj.into())
     };
@@ -195,7 +195,7 @@ extern "C" fn new_request_bip39(n_args: usize, args: *const Obj, kwargs: *mut Ma
 
 extern "C" fn new_request_slip39(n_args: usize, args: *const Obj, kwargs: *mut Map) -> Obj {
     let block = move |_args: &[Obj], kwargs: &Map| {
-        let prompt: Buffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
+        let prompt: StrBuffer = kwargs.get(Qstr::MP_QSTR_prompt)?.try_into()?;
         let obj = LayoutObj::new(MnemonicKeyboard::new(Slip39Input::new(), prompt).into_child())?;
         Ok(obj.into())
     };
@@ -288,9 +288,9 @@ mod tests {
             FormattedText::new::<theme::TTDefaultText>(
                 "Testing text layout, with some text, and some more text. And {param}",
             )
-            .with(b"param", b"parameters!"),
-            Button::with_text(b"Left"),
-            Button::with_text(b"Right"),
+            .with("param", "parameters!"),
+            Button::with_text("Left"),
+            Button::with_text("Right"),
         );
         layout.place(SCREEN);
         assert_eq!(