feat(core): T3T1 Instructions component

core/embed/rust/src/ui/display/font.rs

@@ -293,6 +293,16 @@ impl Font {
 
         text.len() // it fits in its entirety
     }
+
+    pub fn visible_text_height_ex(&self, text: &str) -> (i16, i16) {
+        let (mut ascent, mut descent) = (0, 0);
+        for c in text.chars() {
+            let glyph = self.get_glyph(c);
+            ascent = ascent.max(glyph.bearing_y);
+            descent = descent.max(glyph.height - glyph.bearing_y);
+        }
+        (ascent, descent)
+    }
 }
 
 pub trait GlyphMetrics {

core/embed/rust/src/ui/model_mercury/component/instructions.rs

@@ -0,0 +1,129 @@
+use crate::{
+    strutil::TString,
+    ui::{
+        component::{text::TextStyle, Component, Event, EventCtx, Never},
+        constant::WIDTH,
+        geometry::{Alignment, Offset, Rect},
+        model_mercury::theme,
+        shape::{Renderer, Text},
+    },
+};
+
+/// Component showing a task instruction (e.g. "Swipe up") and optionally task
+/// description (e.g. "Confirm transaction") to a user. The component
+/// is typically placed at the bottom of the screen. The height of the provided
+/// area must be 18px (only instruction) or 37px (both description and
+/// instruction). The content and style of both description and instruction is
+/// configurable separatedly.
+pub struct Instructions<'a> {
+    area: Rect,
+    text_instruction: TString<'a>,
+    text_description: Option<TString<'a>>,
+    style_instruction: &'static TextStyle,
+    style_description: &'static TextStyle,
+}
+
+impl<'a> Instructions<'a> {
+    /// height for component with only instruction [px]
+    pub const HEIGHT_SIMPLE: i16 = 18;
+    /// height for component with both description and instruction [px]
+    pub const HEIGHT_DEFAULT: i16 = 37;
+
+    pub fn new<T: Into<TString<'a>>>(instruction: T) -> Self {
+        Self {
+            area: Rect::zero(),
+            text_instruction: instruction.into(),
+            text_description: None,
+            style_instruction: &theme::TEXT_SUB,
+            style_description: &theme::TEXT_SUB,
+        }
+    }
+
+    pub fn with_description<T: Into<TString<'a>>>(self, description: T) -> Self {
+        Self {
+            text_description: Some(description.into()),
+            ..self
+        }
+    }
+
+    pub fn update_instruction<T: Into<TString<'a>>>(&mut self, ctx: &mut EventCtx, s: T) {
+        self.text_instruction = s.into();
+        ctx.request_paint();
+    }
+
+    pub fn update_description<T: Into<TString<'a>>>(&mut self, ctx: &mut EventCtx, s: T) {
+        self.text_description = Some(s.into());
+        ctx.request_paint();
+    }
+
+    pub fn update_instruction_style(&mut self, ctx: &mut EventCtx, style: &'static TextStyle) {
+        self.style_instruction = style;
+        ctx.request_paint();
+    }
+
+    pub fn update_description_style(&mut self, ctx: &mut EventCtx, style: &'static TextStyle) {
+        self.style_description = style;
+        ctx.request_paint();
+    }
+}
+
+impl<'a> Component for Instructions<'a> {
+    type Msg = Never;
+
+    fn place(&mut self, bounds: Rect) -> Rect {
+        let h = bounds.height();
+        assert!(h == Instructions::HEIGHT_SIMPLE || h == Instructions::HEIGHT_DEFAULT);
+        assert!(bounds.width() == WIDTH);
+        self.area = bounds;
+        bounds
+    }
+
+    fn event(&mut self, _ctx: &mut EventCtx, _event: Event) -> Option<Self::Msg> {
+        None
+    }
+
+    fn paint(&mut self) {
+        // TODO: remove when ui-t3t1 done
+        todo!()
+    }
+
+    fn render<'s>(&'s self, target: &mut impl Renderer<'s>) {
+        // show description only if there is space for it
+        if self.area.height() == Instructions::HEIGHT_DEFAULT {
+            if let Some(description) = self.text_description {
+                let area_description = self.area.split_top(Instructions::HEIGHT_SIMPLE).0;
+                let text_description_font_descent = self
+                    .style_description
+                    .text_font
+                    .visible_text_height_ex("Ay")
+                    .1;
+                let text_description_baseline =
+                    area_description.bottom_center() - Offset::y(text_description_font_descent);
+
+                description.map(|t| {
+                    Text::new(text_description_baseline, t)
+                        .with_font(self.style_description.text_font)
+                        .with_fg(self.style_description.text_color)
+                        .with_align(Alignment::Center)
+                        .render(target);
+                });
+            }
+        }
+
+        let area_instruction = self.area.split_bottom(Instructions::HEIGHT_SIMPLE).1;
+        let text_instruction_font_descent = self
+            .style_instruction
+            .text_font
+            .visible_text_height_ex("Ay")
+            .1;
+        let text_instruction_baseline =
+            area_instruction.bottom_center() - Offset::y(text_instruction_font_descent);
+        self.text_instruction.map(|t| {
+            Text::new(text_instruction_baseline, t)
+                .with_font(self.style_instruction.text_font)
+                .with_fg(self.style_instruction.text_color)
+                .with_align(Alignment::Center)
+                .render(target);
+        });
+    }
+}

core/embed/rust/src/ui/model_mercury/component/mod.rs

@@ -6,6 +6,7 @@ mod button;
 mod coinjoin_progress;
 mod dialog;
 mod fido;
+mod instructions;
 mod vertical_menu;
 #[rustfmt::skip]
 mod fido_icons;
@@ -40,6 +41,7 @@ pub use fido::{FidoConfirm, FidoMsg};
 pub use frame::{Frame, FrameMsg};
 #[cfg(feature = "micropython")]
 pub use homescreen::{check_homescreen_format, Homescreen, HomescreenMsg, Lockscreen};
+pub use instructions::Instructions;
 pub use keyboard::{
     bip39::Bip39Input,
     mnemonic::{MnemonicInput, MnemonicKeyboard, MnemonicKeyboardMsg},

core/embed/rust/src/ui/shape/text.rs

@@ -120,15 +120,3 @@ impl<'a, 's> ShapeClone<'s> for Text<'a> {
         Some(clone.uninit.init(Text { text, ..self }))
     }
 }
-
-impl Font {
-    fn visible_text_height_ex(&self, text: &str) -> (i16, i16) {
-        let (mut ascent, mut descent) = (0, 0);
-        for c in text.chars() {
-            let glyph = self.get_glyph(c);
-            ascent = ascent.max(glyph.bearing_y);
-            descent = descent.max(glyph.height - glyph.bearing_y);
-        }
-        (ascent, descent)
-    }
-}