feat(core/rust): cleaner backlight functions

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

@@ -31,30 +31,31 @@ pub use crate::ui::display::toif::Icon;
 #[cfg(any(feature = "model_tt", feature = "model_tr"))]
 pub use loader::{loader, loader_indeterminate, LOADER_MAX, LOADER_MIN};
 
-pub fn backlight() -> i32 {
-    display::backlight(-1)
+pub fn backlight() -> u16 {
+    display::backlight(-1) as u16
 }
 
-pub fn set_backlight(val: i32) {
-    display::backlight(val);
+pub fn set_backlight(val: u16) {
+    display::backlight(val as i32);
 }
 
-pub fn fade_backlight(target: i32) {
-    const BACKLIGHT_DELAY: Duration = Duration::from_millis(14);
-    const BACKLIGHT_STEP: usize = 15;
+pub fn fade_backlight(target: u16) {
+    const FADE_DURATION_MS: u32 = 50;
+    fade_backlight_duration(target, FADE_DURATION_MS);
+}
 
-    let current = backlight();
-    if current < target {
-        for val in (current..target).step_by(BACKLIGHT_STEP) {
-            set_backlight(val);
-            time::sleep(BACKLIGHT_DELAY);
-        }
-    } else {
-        for val in (target..current).rev().step_by(BACKLIGHT_STEP) {
-            set_backlight(val);
-            time::sleep(BACKLIGHT_DELAY);
-        }
+pub fn fade_backlight_duration(target: u16, duration_ms: u32) {
+    let target = target as i32;
+    let duration_ms = duration_ms as i32;
+    let current = backlight() as i32;
+
+    for i in 0..duration_ms {
+        let val = i32::lerp(current, target, i as f32 / duration_ms as f32);
+        set_backlight(val as u16);
+        time::sleep(Duration::from_millis(1));
     }
+    //account for imprecise rounding
+    set_backlight(target as u16);
 }
 
 pub fn rect_fill(r: Rect, fg_color: Color) {
@@ -1094,6 +1095,10 @@ impl Color {
         Self(r | g | b)
     }
 
+    pub const fn alpha(bg: Color, alpha: u16) -> Self {
+        Self::rgba(bg, 0xFF, 0xFF, 0xFF, alpha)
+    }
+
     pub const fn r(self) -> u8 {
         (self.0 >> 8) as u8 & 0xF8
     }

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

@@ -21,7 +21,7 @@ pub struct SwipePage<T, U> {
     scrollbar: ScrollBar,
     hint: Label<&'static str>,
     button_back: Option<Button<&'static str>>,
-    fade: Option<i32>,
+    fade: Option<u16>,
 }
 
 impl<T, U> SwipePage<T, U>

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

@@ -20,8 +20,8 @@ pub struct Swipe {
     pub allow_down: bool,
     pub allow_left: bool,
     pub allow_right: bool,
-    backlight_start: i32,
-    backlight_end: i32,
+    backlight_start: u16,
+    backlight_end: u16,
     origin: Option<Point>,
 }
 
@@ -82,7 +82,7 @@ impl Swipe {
         let start = self.backlight_start as f32;
         let end = self.backlight_end as f32;
         let value = start + ratio * (end - start);
-        display::set_backlight(value as i32);
+        display::set_backlight(value as u16);
     }
 }
 

core/embed/rust/src/ui/model_tt/theme.rs

@@ -17,11 +17,11 @@ use num_traits::FromPrimitive;
 pub const ERASE_HOLD_DURATION: Duration = Duration::from_millis(1500);
 
 // Typical backlight values.
-pub const BACKLIGHT_NORMAL: i32 = 150;
-pub const BACKLIGHT_LOW: i32 = 45;
-pub const BACKLIGHT_DIM: i32 = 5;
-pub const BACKLIGHT_NONE: i32 = 2;
-pub const BACKLIGHT_MAX: i32 = 255;
+pub const BACKLIGHT_NORMAL: u16 = 150;
+pub const BACKLIGHT_LOW: u16 = 45;
+pub const BACKLIGHT_DIM: u16 = 5;
+pub const BACKLIGHT_NONE: u16 = 2;
+pub const BACKLIGHT_MAX: u16 = 255;
 
 // Color palette.
 pub const WHITE: Color = Color::rgb(0xFF, 0xFF, 0xFF);