trezor.ui imports backlight_fade symbol so changes to this file are not needed

(also we generally don't import trezorfoo modules directly in app code)

fixed 1c7bde1

trezor.ui imports backlight_fade symbol so changes to this file are not needed

fixed 1c7bde1

wondering if there's any point in keeping this testcase around? it's just a smoke test for existence of the function, we're not verifying any result here 🤷‍♀️

Probably not, we should either make something useful of it or remove it. I'd say its out of scope here though

unwrap! please

here's a slightly tidier version of this function though:

#[cfg(feature = "backlight")]
pub fn fade_backlight_duration(target: u8, duration_ms: u32) {
    let target = target as i32;
    let current = backlight() as i32;
    let duration = Duration::from_millis(duration_ms);

    if animation_disabled() {
        set_backlight(target as u8);
        return;
    }

    let mut now = Instant::now();
    let start = now;
    let end = unwrap!(start.checked_add(duration));

    while now < end {
        let elapsed = unwrap!(now.checked_duration_since(start));
        let val = i32::lerp(current, target, elapsed / duration);
        set_backlight(val as u8);
        time::sleep(Duration::from_millis(1));
        now = Instant::now();
    }
    //account for imprecise rounding
    set_backlight(target as u8);
}

see below

There’s a small chance that the app might crash when the timer wraps from its maximum value to 0. How about using StopWatch instead of the timer here? It could slightly simplify the code and resolve this minor issue:

    let timer = Stopwatch::new_started();

    while timer.elapsed() < Duration::from_millis(duration_ms as _) {
        let elapsed = timer.elapsed().to_millis();
        let val = i32::lerp(current, target, elapsed as f32 / duration_ms as f32);
        set_backlight(val as u8);
        time::sleep(Duration::from_millis(1));
    }

yeah, I suspected there's an existing code that could help here.

(also note that Durations support division and the result is a f32, see my suggested version of this function)

while you're touching this, please also convert this unwrap() to unwrap!

changed to the combo of your suggestions: 1c7bde1

i replaced that unwrap(), but note that there are unwrap()s in bunch of other places in our rust codebase, so probably some larger cleanup should take place. (would there be a way to automatically check for this?)