gpui-component 0.7.1

use gpui::{
    App, Bounds, ContentMask, Entity, IntoElement, ParentElement as _, Path, PathBuilder, Pixels,
    RenderOnce, StyleRefinement, Styled, Window, canvas, div, point, px, size,
};

use crate::{ActiveTheme as _, Sizable, Size, StyledExt as _};

use instant::Instant;

use super::SpeechState;

/// The width of a waveform the caller does not size.
const DEFAULT_WIDTH: Pixels = px(96.);

/// The space between bars, relative to their width.
const GAP_RATIO: f32 = 2.5;

/// A live waveform of a [`SpeechState`]'s input levels.
///
/// Each level is a bar that grows up and down from the midline; silence is a
/// dot. The newest level enters at the trailing edge and older ones scroll
/// toward the leading edge at a steady pace, redrawn every frame while audio is
/// captured, so the trail grows from the trailing edge until it fills the
/// width. Before any audio, nothing is drawn. With reduced motion the bars
/// still show each level but do not scroll between them.
///
/// Size the waveform like any element, e.g. `.w_full()` to span a row; it is
/// 96 px wide by default, and its height follows [`Sizable`].
#[derive(IntoElement)]
pub struct SpeechWaveform {
    state: Entity<SpeechState>,
    size: Size,
    style: StyleRefinement,
}

impl SpeechWaveform {
    /// A waveform for `state`.
    pub fn new(state: &Entity<SpeechState>) -> Self {
        Self {
            state: state.clone(),
            size: Size::default(),
            style: StyleRefinement::default(),
        }
    }

    fn height(&self) -> Pixels {
        match self.size {
            Size::Size(height) => height,
            Size::XSmall => px(12.),
            Size::Small => px(16.),
            Size::Medium => px(20.),
            Size::Large => px(24.),
        }
    }
}

impl Sizable for SpeechWaveform {
    fn with_size(mut self, size: impl Into<Size>) -> Self {
        self.size = size.into();
        self
    }
}

impl Styled for SpeechWaveform {
    fn style(&mut self) -> &mut StyleRefinement {
        &mut self.style
    }
}

impl RenderOnce for SpeechWaveform {
    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
        let height = self.height();
        // Bars thicken with the waveform so a tall one does not read as hairlines,
        // and stand apart so a run of silence reads as a row of dots.
        let bar = (height * 0.125).round().clamp(px(2.), px(4.));
        let gap = (bar * GAP_RATIO).round();
        let state = self.state.read(cx);
        let capturing = state.status().is_capturing();
        let levels: Vec<f32> = state.levels().collect();
        let animate = capturing && !cx.reduce_motion();
        // The bars follow an even clock rather than the arrival of each level,
        // which comes in uneven bursts: the newest bar slides in from just past
        // the trailing edge, so the waveform scrolls without stepping or
        // stalling. Without animation the newest bar sits at the edge.
        let scroll = state
            .level_lead_at(Instant::now())
            .filter(|_| animate)
            .map_or(0., |lead| -lead);
        if animate {
            window.request_animation_frame();
        }
        let color = if capturing {
            cx.theme().primary
        } else {
            cx.theme().muted_foreground
        };

        div()
            .h(height)
            .w(DEFAULT_WIDTH)
            .flex_shrink_0()
            .refine_style(&self.style)
            .child(
                canvas(
                    |_, _, _| {},
                    move |bounds, _, window, _| {
                        // A bar sliding in is cut at the trailing edge, not drawn past it.
                        // Bars are anti-aliased paths, not quads: quads snap to whole
                        // device pixels, so a bar moving a fraction of a pixel per
                        // frame would step instead of glide.
                        window.with_content_mask(Some(ContentMask { bounds }), |window| {
                            for rect in bar_rects(bounds, &levels, scroll, bar, gap) {
                                if let Some(path) = capsule(rect) {
                                    window.paint_path(path, color);
                                }
                            }
                        });
                    },
                )
                .size_full(),
            )
    }
}

/// A capsule filling `rect`: round caps on its short ends, a dot when square.
fn capsule(rect: Bounds<Pixels>) -> Option<Path<Pixels>> {
    let radius = rect.size.width.min(rect.size.height) / 2.;
    let radii = point(radius, radius);
    let (left, right) = (rect.left(), rect.right());
    let (top, bottom) = (rect.top() + radius, rect.bottom() - radius);
    let mut path = PathBuilder::fill();
    path.move_to(point(left, top));
    path.arc_to(radii, px(0.), false, true, point(right, top));
    path.line_to(point(right, bottom));
    path.arc_to(radii, px(0.), false, true, point(left, bottom));
    path.close();
    path.build().ok()
}

/// The bars for `levels` (oldest first) in `bounds`: the newest at the trailing
/// edge, `scroll` of a step further toward the leading edge (negative past the
/// trailing edge, where a bar is cut off or left out), each centered on
/// the midline and at least as tall as it is wide. Only levels that exist are
/// drawn, so a short history leaves the leading part empty.
fn bar_rects(
    bounds: Bounds<Pixels>,
    levels: &[f32],
    scroll: f32,
    bar: Pixels,
    gap: Pixels,
) -> Vec<Bounds<Pixels>> {
    let pitch = bar + gap;
    let height = bounds.size.height;
    let middle = bounds.origin.y + height / 2.;
    // Enough bars to reach the leading edge from wherever the newest one sits.
    let count = ((bounds.size.width + gap) / pitch - scroll.min(0.))
        .ceil()
        .max(0.) as usize
        + 1;
    (0..count)
        .filter_map(|from_end| {
            let right = bounds.right() - pitch * (from_end as f32 + scroll);
            let left = right - bar;
            if left < bounds.left() - px(0.5) || left >= bounds.right() {
                return None;
            }
            let level = levels[levels.len().checked_sub(from_end + 1)?];
            let bar_height = (height * level.clamp(0., 1.)).max(bar);
            Some(Bounds::new(
                point(left, middle - bar_height / 2.),
                size(bar, bar_height),
            ))
        })
        .collect()
}

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

    fn bounds(width: f32, height: f32) -> Bounds<Pixels> {
        Bounds::new(point(px(10.), px(20.)), size(px(width), px(height)))
    }

    #[test]
    fn a_short_history_grows_from_the_trailing_edge() {
        let bounds = bounds(98., 20.);
        let rects = bar_rects(bounds, &[0.2, 0.9], 0., px(2.), px(5.));
        assert_eq!(rects.len(), 2);
        assert_eq!(rects[0].right(), bounds.right());
        assert_eq!(rects[0].size.height, px(18.));
        assert_eq!(rects[1].right(), bounds.right() - px(7.));
        assert_eq!(rects[1].size.height, px(4.));
    }

    #[test]
    fn a_long_history_fills_the_width() {
        let bounds = bounds(96., 20.);
        let rects = bar_rects(bounds, &[0.; 64], 0., px(2.), px(5.));
        // 96 px at a 7 px pitch fits 14 bars; the oldest sit off the leading edge.
        assert_eq!(rects.len(), 14);
        assert!(
            rects
                .iter()
                .all(|rect| rect.left() >= bounds.left() - px(0.5))
        );
    }

    #[test]
    fn nothing_is_drawn_before_any_audio() {
        assert!(bar_rects(bounds(96., 20.), &[], 0., px(2.), px(5.)).is_empty());
    }

    #[test]
    fn bars_grow_from_the_midline_and_silence_is_a_dot() {
        let bounds = bounds(40., 20.);
        for rect in bar_rects(bounds, &[0.5, 0.], 0., px(2.), px(5.)) {
            let middle = rect.origin.y + rect.size.height / 2.;
            assert_eq!(middle, px(30.));
            assert!(rect.size.height >= px(2.));
        }
    }

    #[test]
    fn scrolling_moves_bars_toward_the_leading_edge() {
        let bounds = bounds(40., 20.);
        let still = bar_rects(bounds, &[1.; 8], 0., px(2.), px(5.));
        let moving = bar_rects(bounds, &[1.; 8], 0.5, px(2.), px(5.));
        assert_eq!(still[0].left() - moving[0].left(), px(3.5));
        assert!(
            moving
                .iter()
                .all(|rect| rect.left() >= bounds.left() - px(0.5))
        );
    }

    #[test]
    fn a_bar_past_the_trailing_edge_is_left_out_until_it_slides_in() {
        let bounds = bounds(40., 20.);
        // The newest bar sits a whole pitch past the edge: not drawn yet.
        let out = bar_rects(bounds, &[1., 0.5], -1., px(2.), px(5.));
        assert_eq!(out.len(), 1);
        assert_eq!(out[0].right(), bounds.right());
        // A fifth of a pitch out (1.4 px): drawn across the edge, cut by the
        // content mask.
        let entering = bar_rects(bounds, &[1., 0.5], -0.2, px(2.), px(5.));
        assert_eq!(entering.len(), 2);
        assert!(entering[0].left() < bounds.right());
    }
}