libsurfer/

viewport.rs

use std::ops::RangeInclusive;

use derive_more::{Add, AddAssign, Div, Mul, Neg, Sub, SubAssign};
use num::{BigInt, BigRational, FromPrimitive, ToPrimitive};
use serde::{Deserialize, Serialize};

#[derive(
    Debug,
    Clone,
    Copy,
    Serialize,
    Deserialize,
    Add,
    Sub,
    Mul,
    Neg,
    AddAssign,
    SubAssign,
    PartialOrd,
    PartialEq,
)]
pub struct Relative(pub f64);

impl Relative {
    #[must_use]
    pub fn absolute(&self, max_timestamp: &BigInt, time_offset: &BigInt) -> Absolute {
        Absolute(
            time_offset.to_f64().unwrap()
                + self.0
                    * (max_timestamp - time_offset)
                        .to_f64()
                        .expect("Failed to convert timestamp to f64"),
        )
    }

    #[must_use]
    pub fn inner(&self) -> f64 {
        self.0
    }

    #[must_use]
    pub fn min(&self, other: &Relative) -> Self {
        Self(self.0.min(other.0))
    }

    #[must_use]
    pub fn max(&self, other: &Relative) -> Self {
        Self(self.0.max(other.0))
    }
}

impl std::ops::Div for Relative {
    type Output = Relative;

    fn div(self, rhs: Self) -> Self::Output {
        Self(self.0 / rhs.0)
    }
}

#[derive(
    Debug, Clone, Copy, Serialize, Deserialize, Add, Sub, Mul, Neg, Div, PartialOrd, PartialEq,
)]
pub struct Absolute(pub f64);

impl Absolute {
    #[must_use]
    pub fn relative(&self, max_timestamp: &BigInt, time_offset: &BigInt) -> Relative {
        Relative(
            (self.0 - time_offset.to_f64().unwrap())
                / (max_timestamp - time_offset)
                    .to_f64()
                    .expect("Failed to convert timestamp to f64"),
        )
    }

    #[must_use]
    pub fn inner(&self) -> f64 {
        self.0
    }
}

impl std::ops::Div for Absolute {
    type Output = Absolute;

    fn div(self, rhs: Self) -> Self::Output {
        Self(self.0 / rhs.0)
    }
}

impl From<&BigInt> for Absolute {
    fn from(value: &BigInt) -> Self {
        Self(value.to_f64().expect("Failed to convert timestamp to f64"))
    }
}

fn default_edge_space() -> f64 {
    0.2
}

fn default_min_width() -> Absolute {
    Absolute(0.5)
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub struct Viewport {
    pub curr_left: Relative,
    pub curr_right: Relative,

    target_left: Relative,
    target_right: Relative,

    move_start_left: Relative,
    move_start_right: Relative,

    // Number of seconds since the the last time a movement happened
    move_duration: Option<f32>,
    pub move_strategy: ViewportStrategy,
    #[serde(skip, default = "default_edge_space")]
    edge_space: f64,

    #[serde(skip, default = "default_min_width")]
    min_width: Absolute,
}

impl Default for Viewport {
    fn default() -> Self {
        Self {
            curr_left: Relative(0.0),
            curr_right: Relative(1.0),
            target_left: Relative(0.0),
            target_right: Relative(1.0),
            move_start_left: Relative(0.0),
            move_start_right: Relative(1.0),
            move_duration: None,
            move_strategy: ViewportStrategy::Instant,
            edge_space: default_edge_space(),
            min_width: default_min_width(),
        }
    }
}

impl Viewport {
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }
    #[must_use]
    pub fn left_edge_time(self, max_timestamp: &BigInt, time_offset: &BigInt) -> BigInt {
        BigInt::from(self.curr_left.absolute(max_timestamp, time_offset).0 as i64)
    }
    #[must_use]
    pub fn right_edge_time(self, max_timestamp: &BigInt, time_offset: &BigInt) -> BigInt {
        BigInt::from(self.curr_right.absolute(max_timestamp, time_offset).0 as i64)
    }

    /// Converts x-pixel position to absolute time with time offset support
    #[must_use]
    pub fn as_absolute_time(
        &self,
        x: f64,
        view_width: f32,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> Absolute {
        let time_spacing = self.width_absolute(max_timestamp, time_offset) / f64::from(view_width);
        self.curr_left.absolute(max_timestamp, time_offset) + time_spacing * x
    }

    #[must_use]
    pub fn as_time_bigint(
        &self,
        x: f32,
        view_width: f32,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> BigInt {
        let Viewport {
            curr_left: left,
            curr_right: right,
            ..
        } = &self;

        let big_right = BigRational::from_f64(right.absolute(max_timestamp, time_offset).0)
            .unwrap_or_else(|| BigRational::from_u8(1).unwrap());
        let big_left = BigRational::from_f64(left.absolute(max_timestamp, time_offset).0)
            .unwrap_or_else(|| BigRational::from_u8(1).unwrap());
        let big_width =
            BigRational::from_f32(view_width).unwrap_or_else(|| BigRational::from_u8(1).unwrap());
        let big_x = BigRational::from_f32(x).unwrap_or_else(|| BigRational::from_u8(1).unwrap());

        let time = big_left.clone() + (big_right - big_left) / big_width * big_x;
        time.round().to_integer()
    }

    /// Computes which x-pixel corresponds to the specified time assuming the viewport is rendered
    /// into a viewport of `view_width`
    #[must_use]
    pub fn pixel_from_time(
        &self,
        time: &BigInt,
        view_width: f32,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> f32 {
        let distance_from_left =
            Absolute(time.to_f64().unwrap()) - self.curr_left.absolute(max_timestamp, time_offset);
        let width = self.width_absolute(max_timestamp, time_offset);

        (((distance_from_left / width).0) * f64::from(view_width)) as f32
    }

    /// Computes which x-pixel corresponds to the specified absolute time with time offset support
    #[must_use]
    pub fn pixel_from_absolute_time(
        &self,
        time: Absolute,
        view_width: f32,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> f32 {
        let distance_from_left = time - self.curr_left.absolute(max_timestamp, time_offset);
        let width = self.width_absolute(max_timestamp, time_offset);

        (((distance_from_left / width).0) * f64::from(view_width)) as f32
    }

    /// Return new viewport for a different file length.
    ///
    /// Tries to keep the current zoom level and position. If zoom is not possible it
    /// will zoom in as much as needed to keep border margins. If the new waveform is
    /// too short, the viewport will be moved to the left as much as needed for the zoom level.
    #[must_use]
    pub fn clip_to(
        &self,
        old_max_timestamp: &BigInt,
        new_max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> Viewport {
        let left_timestamp = self.curr_left.absolute(old_max_timestamp, time_offset);
        let right_timestamp = self.curr_right.absolute(old_max_timestamp, time_offset);
        let absolute_width = right_timestamp - left_timestamp;

        let new_absolute_width = new_max_timestamp
            .to_f64()
            .expect("Failed to convert timestamp to f64")
            * (2.0 * self.edge_space);
        let (left, right) = if absolute_width.0 > new_absolute_width {
            // is the new waveform so short that we can't keep the current zoom level?
            (Relative(-self.edge_space), Relative(1.0 + self.edge_space))
        } else {
            // our zoom level is achievable but we don't know the waveform is long enough
            let new_num_ts_f64 = new_max_timestamp
                .to_f64()
                .expect("Failed to convert timestamp to f64");
            let unmoved_left = Relative(left_timestamp.0 / new_num_ts_f64);
            let unmoved_right = Relative((left_timestamp + absolute_width).0 / new_num_ts_f64);
            if unmoved_right <= Relative(1.0 + self.edge_space) {
                // waveform is long enough, keep current view as-is
                (unmoved_left, unmoved_right)
            } else {
                // waveform is too short, clip end to the right edge (including empty space)
                // since we checked above for zoom level, we know that there must be enough
                // waveform to the left to keep the current zoom level
                let relative_width = absolute_width.0 / new_num_ts_f64;
                (
                    Relative(1.0 + self.edge_space - relative_width),
                    Relative(1.0 + self.edge_space),
                )
            }
        };

        Viewport {
            curr_left: left,
            curr_right: right,
            target_left: left,
            target_right: right,
            move_start_left: left,
            move_start_right: right,
            move_duration: None,
            move_strategy: self.move_strategy,
            edge_space: self.edge_space,
            min_width: self.min_width,
        }
    }

    #[inline]
    fn width(&self) -> Relative {
        self.curr_right - self.curr_left
    }

    #[inline]
    pub(crate) fn width_absolute(&self, max_timestamp: &BigInt, time_offset: &BigInt) -> Absolute {
        self.curr_right.absolute(max_timestamp, time_offset)
            - self.curr_left.absolute(max_timestamp, time_offset)
    }

    pub fn go_to_time(&mut self, center: &BigInt, max_timestamp: &BigInt, time_offset: &BigInt) {
        let center_point: Absolute = center.into();
        let half_width = self.half_width_absolute(max_timestamp, time_offset);

        let target_left = (center_point - half_width).relative(max_timestamp, time_offset);
        let target_right = (center_point + half_width).relative(max_timestamp, time_offset);
        self.set_viewport_to_clipped(target_left, target_right, max_timestamp, time_offset);
    }

    pub fn zoom_to_fit(&mut self) {
        self.set_target_left(Relative(0.0));
        self.set_target_right(Relative(1.0));
    }

    pub fn go_to_start(&mut self) {
        let old_width = self.width();
        self.set_target_left(Relative(0.0));
        self.set_target_right(old_width);
    }

    pub fn go_to_end(&mut self) {
        self.set_target_left(Relative(1.0) - self.width());
        self.set_target_right(Relative(1.0));
    }

    pub fn zoom_to_time(
        &mut self,
        center: &BigInt,
        delta: f64,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) {
        let center = Absolute::from(center);
        let half_width = (self.curr_right.absolute(max_timestamp, time_offset)
            - self.curr_left.absolute(max_timestamp, time_offset))
            * delta
            * 0.5;

        self.set_viewport_to_clipped(
            (center - half_width).relative(max_timestamp, time_offset),
            (center + half_width).relative(max_timestamp, time_offset),
            max_timestamp,
            time_offset,
        );
    }

    pub fn handle_canvas_zoom(
        &mut self,
        mouse_ptr_timestamp: Option<BigInt>,
        delta: f64,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) {
        // Zoom or scroll
        let Viewport {
            curr_left: left,
            curr_right: right,
            ..
        } = &self;

        let (target_left, target_right) = if let Some(mouse_location) =
            mouse_ptr_timestamp.map(|t| Absolute::from(&t).relative(max_timestamp, time_offset))
        {
            (
                (*left - mouse_location) / Relative(delta) + mouse_location,
                (*right - mouse_location) / Relative(delta) + mouse_location,
            )
        } else {
            let mid_point = self.midpoint();
            let offset = self.half_width() * delta;

            (mid_point - offset, mid_point + offset)
        };

        self.set_viewport_to_clipped(target_left, target_right, max_timestamp, time_offset);
    }

    pub fn handle_canvas_scroll(&mut self, deltay: f64) {
        // Scroll 5% of the viewport per scroll event.
        // One scroll event yields 50
        let scroll_step = -self.width() / Relative(50. * 20.);
        let scaled_deltay = scroll_step * deltay;
        self.set_viewport_to_clipped_no_width_check(
            self.curr_left + scaled_deltay,
            self.curr_right + scaled_deltay,
        );
    }

    fn set_viewport_to_clipped(
        &mut self,
        target_left: Relative,
        target_right: Relative,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) {
        let rel_min_width = self.min_width.relative(max_timestamp, time_offset);

        if (target_right - target_left) <= rel_min_width + Relative(f64::EPSILON) {
            let center = (target_left + target_right) * 0.5;
            self.set_viewport_to_clipped_no_width_check(
                center - rel_min_width,
                center + rel_min_width,
            );
        } else {
            self.set_viewport_to_clipped_no_width_check(target_left, target_right);
        }
    }

    fn set_viewport_to_clipped_no_width_check(
        &mut self,
        target_left: Relative,
        target_right: Relative,
    ) {
        let width = target_right - target_left;

        let abs_min = Relative(-self.edge_space);
        let abs_max = Relative(1.0 + self.edge_space);

        let max_right = Relative(1.0) + width * self.edge_space;
        let min_left = -width * self.edge_space;
        if width > (abs_max - abs_min) {
            self.set_target_left(abs_min);
            self.set_target_right(abs_max);
        } else if target_left < min_left {
            self.set_target_left(min_left);
            self.set_target_right(min_left + width);
        } else if target_right > max_right {
            self.set_target_left(max_right - width);
            self.set_target_right(max_right);
        } else {
            self.set_target_left(target_left);
            self.set_target_right(target_right);
        }
    }

    #[inline]
    fn midpoint(&self) -> Relative {
        (self.curr_right + self.curr_left) * 0.5
    }

    #[inline]
    fn half_width(&self) -> Relative {
        self.width() * 0.5
    }

    #[inline]
    fn half_width_absolute(&self, max_timestamp: &BigInt, time_offset: &BigInt) -> Absolute {
        (self.width() * 0.5).absolute(max_timestamp, time_offset)
    }

    pub fn zoom_to_range(
        &mut self,
        left: &BigInt,
        right: &BigInt,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) {
        self.set_viewport_to_clipped(
            Absolute::from(left).relative(max_timestamp, time_offset),
            Absolute::from(right).relative(max_timestamp, time_offset),
            max_timestamp,
            time_offset,
        );
    }

    pub fn go_to_cursor_if_not_in_view(
        &mut self,
        cursor: &BigInt,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) -> bool {
        let fcursor = cursor.into();
        if fcursor <= self.curr_left.absolute(max_timestamp, time_offset)
            || fcursor >= self.curr_right.absolute(max_timestamp, time_offset)
        {
            self.go_to_time_f64(fcursor, max_timestamp, time_offset);
            true
        } else {
            false
        }
    }

    pub fn go_to_time_f64(
        &mut self,
        center: Absolute,
        max_timestamp: &BigInt,
        time_offset: &BigInt,
    ) {
        let half_width = (self.curr_right.absolute(max_timestamp, time_offset)
            - self.curr_left.absolute(max_timestamp, time_offset))
            / 2.;

        self.set_viewport_to_clipped(
            (center - half_width).relative(max_timestamp, time_offset),
            (center + half_width).relative(max_timestamp, time_offset),
            max_timestamp,
            time_offset,
        );
    }

    fn set_target_left(&mut self, target_left: Relative) {
        if let ViewportStrategy::Instant = self.move_strategy {
            self.curr_left = target_left;
        } else {
            self.target_left = target_left;
            self.move_start_left = self.curr_left;
            self.move_duration = Some(0.);
        }
    }
    fn set_target_right(&mut self, target_right: Relative) {
        if let ViewportStrategy::Instant = self.move_strategy {
            self.curr_right = target_right;
        } else {
            self.target_right = target_right;
            self.move_start_right = self.curr_right;
            self.move_duration = Some(0.);
        }
    }

    pub fn move_viewport(&mut self, frame_time: f32) {
        match &self.move_strategy {
            ViewportStrategy::Instant => {
                self.curr_left = self.target_left;
                self.curr_right = self.target_right;
                self.move_duration = None;
            }
            ViewportStrategy::EaseInOut { duration } => {
                if let Some(move_duration) = &mut self.move_duration {
                    if *move_duration + frame_time >= *duration {
                        self.move_duration = None;
                        self.curr_left = self.target_left;
                        self.curr_right = self.target_right;
                    } else {
                        *move_duration += frame_time;

                        self.curr_left = Relative(ease_in_out_size(
                            self.move_start_left.0..=self.target_left.0,
                            f64::from(*move_duration) / f64::from(*duration),
                        ));
                        self.curr_right = Relative(ease_in_out_size(
                            self.move_start_right.0..=self.target_right.0,
                            f64::from(*move_duration) / f64::from(*duration),
                        ));
                    }
                }
            }
        }
    }

    #[must_use]
    pub fn is_moving(&self) -> bool {
        self.move_duration.is_some()
    }
}

#[must_use]
fn ease_in_out_size(r: RangeInclusive<f64>, t: f64) -> f64 {
    r.start() + ((r.end() - r.start()) * -((std::f64::consts::PI * t).cos() - 1.) * 0.5)
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum ViewportStrategy {
    Instant,
    EaseInOut { duration: f32 },
}

#[cfg(test)]
mod tests {
    use super::*;
    use num::BigInt;

    fn bi(n: i64) -> BigInt {
        BigInt::from(n)
    }

    #[test]
    fn ease_in_out_endpoints_and_mid() {
        let r = 0.0..=10.0;
        let s0 = ease_in_out_size(r.clone(), 0.0);
        let s05 = ease_in_out_size(r.clone(), 0.5);
        let s1 = ease_in_out_size(r.clone(), 1.0);
        assert!((s0 - 0.0).abs() < 1e-12);
        assert!((s05 - 5.0).abs() < 1e-12);
        assert!((s1 - 10.0).abs() < 1e-12);
    }

    #[test]
    fn relative_absolute_roundtrip() {
        // Test with zero offset
        let n = bi(1000);
        let offset = bi(0);
        let r = Relative(0.25);
        let abs = r.absolute(&n, &offset);
        // 0.25 * 1000 = 250.0
        assert!((abs.0 - 250.0).abs() < 1e-9);
        let back = abs.relative(&n, &offset);
        assert!((back.0 - r.0).abs() < 1e-9);

        let offset = bi(500);
        let r = Relative(0.25);
        let abs = r.absolute(&n, &offset);
        // 500 + 0.25 * (1000 - 500) = 500 + 125 = 625.0
        assert!((abs.0 - 625.0).abs() < 1e-9);
        let back = abs.relative(&n, &offset);
        assert!((back.0 - r.0).abs() < 1e-9);
    }

    #[test]
    fn pixel_from_time_consistency() {
        let vp = Viewport::default();
        let n = bi(1000);
        let view_w = 1000.0_f32;

        let time_offset = bi(0);
        let time_abs = Absolute(250.0);
        let x1 = vp.pixel_from_absolute_time(time_abs, view_w, &n, &time_offset);
        let x2 = vp.pixel_from_time(&bi(250), view_w, &n, &time_offset);
        assert!((x1 - 250.0).abs() < 1e-6);
        assert!((x2 - 250.0).abs() < 1e-6);

        let time_offset = bi(500);
        let time_abs = Absolute(750.0); // 250 + 500 offset
        let x1 = vp.pixel_from_absolute_time(time_abs, view_w, &n, &time_offset);
        let x2 = vp.pixel_from_time(&bi(750), view_w, &n, &time_offset);
        assert!((x1 - 500.0).abs() < 1e-6);
        assert!((x2 - 500.0).abs() < 1e-6);
    }

    #[test]
    fn set_viewport_min_width_enforced() {
        let mut vp = Viewport::default();
        let n = bi(1000);
        let offset = bi(0);
        // Try to set zero-width viewport at center
        let center = Relative(0.5);
        vp.set_viewport_to_clipped(center, center, &n, &offset);
        // width must be at least min_width.relative_with_offset(n, offset)
        let rel_min = vp.min_width.relative(&n, &offset).0;
        let width = (vp.curr_right - vp.curr_left).0;
        assert!(
            width + f64::EPSILON >= rel_min,
            "width {width} < min {rel_min}"
        );
    }

    #[test]
    fn go_to_start_and_end_preserve_width() {
        let mut vp = Viewport::default();
        let w0 = (vp.curr_right - vp.curr_left).0;
        vp.go_to_end();
        let w1 = (vp.curr_right - vp.curr_left).0;
        assert!((w0 - w1).abs() < 1e-12);
        assert!((vp.curr_right.0 - 1.0).abs() < 1e-12);
        vp.go_to_start();
        let w2 = (vp.curr_right - vp.curr_left).0;
        assert!((w0 - w2).abs() < 1e-12);
        assert!((vp.curr_left.0 - 0.0).abs() < 1e-12);
    }

    #[test]
    fn move_viewport_ease_in_out_reaches_target() {
        let mut vp = Viewport {
            move_strategy: ViewportStrategy::EaseInOut { duration: 0.3 },
            ..Default::default()
        };
        let n = bi(1000);
        let offset = bi(0);
        // request a move
        vp.set_viewport_to_clipped(Relative(0.1), Relative(0.3), &n, &offset);
        let mut t = 0.0;
        // step in a few frames
        while vp.is_moving() && t < 1.0 {
            vp.move_viewport(0.05);
            t += 0.05;
        }
        assert!(!vp.is_moving());
        assert!((vp.curr_left.0 - 0.1).abs() < 1e-6);
        assert!((vp.curr_right.0 - 0.3).abs() < 1e-6);
    }

    #[test]
    fn clip_to_does_not_invert_viewport() {
        // Regression test: when clipping viewport to a file with different max_timestamp,
        // the viewport should never become inverted (left > right).
        // This reproduces the exact scenario from the bug report.
        let mut vp = Viewport::default();
        vp.curr_left = Relative(0.9027133537478365);
        vp.curr_right = Relative(0.9455180041784441);
        vp.target_left = vp.curr_left;
        vp.target_right = vp.curr_right;

        let old_max_timestamp = bi(122055);
        let new_max_timestamp = bi(131445);
        let time_offset = bi(0);

        let clipped = vp.clip_to(&old_max_timestamp, &new_max_timestamp, &time_offset);

        assert!(
            clipped.curr_left.0 < clipped.curr_right.0,
            "Viewport inverted after clip_to: left={} >= right={}",
            clipped.curr_left.0,
            clipped.curr_right.0
        );
    }

    #[test]
    fn clip_to_preserves_valid_viewport_on_file_growth() {
        // When file grows, viewport should still be valid and maintain approximate position
        let mut vp = Viewport::default();
        vp.curr_left = Relative(0.8);
        vp.curr_right = Relative(0.9);
        vp.target_left = vp.curr_left;
        vp.target_right = vp.curr_right;

        let old_max_timestamp = bi(1000);
        let new_max_timestamp = bi(2000); // file doubled in size
        let time_offset = bi(0);

        let clipped = vp.clip_to(&old_max_timestamp, &new_max_timestamp, &time_offset);

        // Must not be inverted
        assert!(
            clipped.curr_left.0 < clipped.curr_right.0,
            "Viewport inverted: left={} >= right={}",
            clipped.curr_left.0,
            clipped.curr_right.0
        );

        // Width should be preserved (in absolute terms, so halved in relative terms)
        let old_width = 0.1; // 0.9 - 0.8
        let expected_relative_width = old_width * 1000.0 / 2000.0; // 0.05
        let actual_width = clipped.curr_right.0 - clipped.curr_left.0;
        assert!(
            (actual_width - expected_relative_width).abs() < 1e-9,
            "Width not preserved: expected={}, actual={}",
            expected_relative_width,
            actual_width
        );
    }

    #[test]
    fn clip_to_handles_file_shrink_with_viewport_overshoot() {
        // When file shrinks and viewport would overshoot the new file boundary,
        // clip_to must correctly reposition the viewport to stay within bounds.
        let mut vp = Viewport::default();
        // Viewing timestamps 950-1000 in a 1000-timestamp file (relative 0.95-1.0)
        vp.curr_left = Relative(0.95);
        vp.curr_right = Relative(1.0);
        vp.target_left = vp.curr_left;
        vp.target_right = vp.curr_right;

        let old_max_timestamp = bi(1000);
        let new_max_timestamp = bi(500); // file shrinks
        let time_offset = bi(0);

        let clipped = vp.clip_to(&old_max_timestamp, &new_max_timestamp, &time_offset);

        // Must not be inverted
        assert!(
            clipped.curr_left.0 < clipped.curr_right.0,
            "Viewport inverted: left={} >= right={}",
            clipped.curr_left.0,
            clipped.curr_right.0
        );

        // Left edge must be valid (>= -edge_space)
        assert!(
            clipped.curr_left.0 >= -vp.edge_space,
            "Left edge out of bounds: {}",
            clipped.curr_left.0
        );

        // Width should be preserved in absolute terms (50 timestamps = 0.1 relative in new file)
        let expected_relative_width = 50.0 / 500.0; // 0.1
        let actual_width = clipped.curr_right.0 - clipped.curr_left.0;
        assert!(
            (actual_width - expected_relative_width).abs() < 1e-9,
            "Width not preserved: expected={}, actual={}",
            expected_relative_width,
            actual_width
        );
    }
}