feat: preview thumbnail surface and pixels

src/main.rs

@@ -16,6 +16,7 @@ mod region;
 mod render;
 mod selection;
 mod stack;
+mod thumbnail;
 mod wayland;
 
 use std::path::PathBuf;

src/thumbnail.rs

@@ -0,0 +1,447 @@
+//! One preview thumbnail: its layer surface, pixels, animation and gestures.
+
+use std::path::PathBuf;
+use std::time::Instant;
+
+use anyhow::{Context, Result};
+use image::{RgbaImage, imageops};
+use smithay_client_toolkit::{
+    compositor::{CompositorState, FrameCallbackData, Region},
+    shell::{
+        WaylandSurface,
+        wlr_layer::{Anchor, KeyboardInteractivity, Layer, LayerShell, LayerSurface},
+    },
+    shm::{
+        Shm,
+        slot::{Buffer, SlotPool},
+    },
+};
+use wayland_client::{QueueHandle, protocol::wl_shm};
+use wayland_protocols::wp::viewporter::client::{
+    wp_viewport::WpViewport, wp_viewporter::WpViewporter,
+};
+
+use crate::stack::{self, Anim, EDGE_MARGIN, Release};
+use crate::wayland::{Output, State};
+
+pub const NAMESPACE: &str = "valw-preview";
+
+/// Premultiplied BGRA of the 1 px border: #e0e0e0 at 80% opacity.
+const BORDER: [u8; 4] = [179, 179, 179, 204];
+
+/// The thumbnail image for `img` on an output with `scale` physical pixels
+/// per logical pixel: returns the physical-size image and its logical size.
+pub fn downscale(img: &RgbaImage, scale: f64) -> (RgbaImage, (u32, u32)) {
+    let logical = stack::thumb_size(img.width(), img.height());
+    let physical = (
+        ((logical.0 as f64 * scale).round() as u32).max(1),
+        ((logical.1 as f64 * scale).round() as u32).max(1),
+    );
+    let small = if physical == img.dimensions() {
+        img.clone()
+    } else {
+        imageops::resize(
+            img,
+            physical.0,
+            physical.1,
+            imageops::FilterType::CatmullRom,
+        )
+    };
+    (small, logical)
+}
+
+/// Paints `small` into a transparent ARGB8888 `canvas` that is `canvas_width`
+/// px wide and as tall as `small`, starting at column `x0` and clipped to the
+/// canvas, with a 1 px border on the image's edges.
+pub fn paint(canvas: &mut [u8], canvas_width: u32, small: &RgbaImage, x0: i64) {
+    canvas.fill(0);
+    let (w, h) = small.dimensions();
+    for y in 0..h {
+        for x in 0..w {
+            let cx = x0 + x as i64;
+            if cx < 0 || cx >= canvas_width as i64 {
+                continue;
+            }
+            let edge = x == 0 || y == 0 || x == w - 1 || y == h - 1;
+            let px = if edge {
+                BORDER
+            } else {
+                let [r, g, b, _] = small.get_pixel(x, y).0;
+                [b, g, r, 255]
+            };
+            let i = ((y * canvas_width) as usize + cx as usize) * 4;
+            canvas[i..i + 4].copy_from_slice(&px);
+        }
+    }
+}
+
+/// What the host should do after a pointer release.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Action {
+    OpenEditor,
+}
+
+pub struct Thumbnail {
+    pub id: u64,
+    pub output: String,
+    pub path: PathBuf,
+    layer: LayerSurface,
+    viewport: WpViewport,
+    pool: SlotPool,
+    buffer: Option<Buffer>,
+    small: RgbaImage,
+    /// Logical size of the image (not the surface, which has padding).
+    pub size: (u32, u32),
+    scale: f64,
+    /// How far right of its resting place the image is drawn, logical px.
+    offset: f64,
+    anim: Option<(Anim, Instant)>,
+    drag: Option<(f64, f64)>,
+    margin: u32,
+    /// Input region while visible (the image) and while hidden (nothing).
+    input: Region,
+    no_input: Region,
+    /// Hidden for a capture: drawn fully transparent, clicks pass through.
+    hidden: bool,
+    configured: bool,
+    frame_pending: bool,
+    started: bool,
+    closing: bool,
+    expired: bool,
+}
+
+/// The Wayland objects a new thumbnail needs.
+pub struct Parts<'a> {
+    pub compositor: &'a CompositorState,
+    pub layer_shell: &'a LayerShell,
+    pub viewporter: &'a WpViewporter,
+    pub shm: &'a Shm,
+}
+
+impl Thumbnail {
+    pub fn new(
+        id: u64,
+        path: PathBuf,
+        image: &RgbaImage,
+        output: &Output,
+        parts: &Parts,
+        qh: &QueueHandle<State>,
+    ) -> Result<Thumbnail> {
+        let (small, size) = downscale(image, output.scale);
+        let surface = parts.compositor.create_surface(qh);
+        let layer = parts.layer_shell.create_layer_surface(
+            qh,
+            surface,
+            Layer::Overlay,
+            Some(NAMESPACE),
+            Some(&output.wl),
+        );
+        layer.set_anchor(Anchor::BOTTOM | Anchor::RIGHT);
+        // Never take keyboard focus away from what the user is typing in.
+        layer.set_keyboard_interactivity(KeyboardInteractivity::None);
+        layer.set_size(size.0 + EDGE_MARGIN, size.1);
+        layer.set_margin(0, 0, EDGE_MARGIN as i32, 0);
+        // Clicks on the transparent padding go through to what's below.
+        let input = Region::new(parts.compositor).context("could not create an input region")?;
+        input.add(0, 0, size.0 as i32, size.1 as i32);
+        let no_input = Region::new(parts.compositor).context("could not create an input region")?;
+        layer.wl_surface().set_input_region(Some(input.wl_region()));
+        let viewport = parts.viewporter.get_viewport(layer.wl_surface(), qh, ());
+        viewport.set_destination((size.0 + EDGE_MARGIN) as i32, size.1 as i32);
+        // The first commit has no buffer; the compositor answers with a
+        // configure, and the first draw starts the slide-in.
+        layer.commit();
+
+        let buffer_len = (small.height() * canvas_width(size.0, output.scale) * 4) as usize;
+        Ok(Thumbnail {
+            id,
+            output: output.geom.name.clone(),
+            path,
+            layer,
+            viewport,
+            pool: SlotPool::new(buffer_len * 2, parts.shm).context("could not create shm pool")?,
+            buffer: None,
+            small,
+            size,
+            scale: output.scale,
+            offset: travel(size.0),
+            anim: None,
+            drag: None,
+            margin: EDGE_MARGIN,
+            input,
+            no_input,
+            hidden: false,
+            configured: false,
+            frame_pending: false,
+            started: false,
+            closing: false,
+            expired: false,
+        })
+    }
+
+    pub fn is(&self, surface: &wayland_client::protocol::wl_surface::WlSurface) -> bool {
+        self.layer.wl_surface() == surface
+    }
+
+    pub fn is_layer(&self, layer: &LayerSurface) -> bool {
+        self.layer.wl_surface() == layer.wl_surface()
+    }
+
+    pub fn is_closing(&self) -> bool {
+        self.closing
+    }
+
+    /// The slide-out has finished (or is invisible anyway).
+    pub fn is_finished(&self) -> bool {
+        self.closing && (self.anim.is_none() || self.hidden)
+    }
+
+    /// Makes the thumbnail invisible and click-through. The surface stays
+    /// mapped: remapping would need a configure that niri doesn't send.
+    pub fn hide(&mut self, qh: &QueueHandle<State>) {
+        if self.hidden {
+            return;
+        }
+        self.hidden = true;
+        self.layer
+            .wl_surface()
+            .set_input_region(Some(self.no_input.wl_region()));
+        self.draw(qh, true);
+    }
+
+    pub fn show(&mut self, qh: &QueueHandle<State>) {
+        if !self.hidden {
+            return;
+        }
+        self.hidden = false;
+        self.layer
+            .wl_surface()
+            .set_input_region(Some(self.input.wl_region()));
+        self.draw(qh, true);
+    }
+
+    pub fn set_margin(&mut self, margin: u32) {
+        if margin == self.margin {
+            return;
+        }
+        self.margin = margin;
+        self.layer.set_margin(0, 0, margin as i32, 0);
+        self.layer.commit();
+    }
+
+    pub fn configure(&mut self, qh: &QueueHandle<State>) {
+        self.configured = true;
+        if !self.started {
+            self.started = true;
+            self.anim = Some((Anim::slide_in(travel(self.size.0)), Instant::now()));
+        }
+        self.draw(qh, false);
+    }
+
+    pub fn frame_done(&mut self, qh: &QueueHandle<State>) {
+        self.frame_pending = false;
+        if self.anim.is_some() || self.drag.is_some() {
+            self.draw(qh, false);
+        }
+    }
+
+    /// The timeout fired: slide out, unless the user is dragging it.
+    pub fn expire(&mut self, qh: &QueueHandle<State>) {
+        self.expired = true;
+        if self.drag.is_none() {
+            self.slide_out(qh);
+        }
+    }
+
+    pub fn slide_out(&mut self, qh: &QueueHandle<State>) {
+        if self.closing {
+            return;
+        }
+        self.closing = true;
+        self.anim = Some((
+            Anim::slide_out(self.offset, travel(self.size.0)),
+            Instant::now(),
+        ));
+        self.draw(qh, false);
+    }
+
+    pub fn press(&mut self, x: f64, y: f64) {
+        if !self.closing {
+            self.anim = None;
+            self.drag = Some((x, y));
+        }
+    }
+
+    pub fn motion(&mut self, x: f64, qh: &QueueHandle<State>) {
+        if let Some((x0, _)) = self.drag {
+            self.offset = stack::drag_offset(x - x0);
+            self.draw(qh, false);
+        }
+    }
+
+    pub fn release(&mut self, x: f64, y: f64, qh: &QueueHandle<State>) -> Option<Action> {
+        let (x0, y0) = self.drag.take()?;
+        match stack::release(x - x0, y - y0, self.size.0 as f64) {
+            Release::Click => {
+                self.slide_out(qh);
+                Some(Action::OpenEditor)
+            }
+            Release::Dismiss => {
+                self.slide_out(qh);
+                None
+            }
+            Release::SnapBack if self.expired => {
+                self.slide_out(qh);
+                None
+            }
+            Release::SnapBack => {
+                self.anim = Some((Anim::snap_back(self.offset), Instant::now()));
+                self.draw(qh, false);
+                None
+            }
+        }
+    }
+
+    fn draw(&mut self, qh: &QueueHandle<State>, force: bool) {
+        if let Some((anim, start)) = self.anim {
+            let (offset, done) = anim.at(start.elapsed().as_secs_f64() * 1000.0);
+            self.offset = offset;
+            if done {
+                self.anim = None;
+            }
+        }
+        // Hide and show must reach the screen now, even mid-animation.
+        if !self.configured || (self.frame_pending && !force) {
+            return;
+        }
+        let width = canvas_width(self.size.0, self.scale);
+        let height = self.small.height();
+        let Ok((buffer, canvas)) = self.pool.create_buffer(
+            width as i32,
+            height as i32,
+            width as i32 * 4,
+            wl_shm::Format::Argb8888,
+        ) else {
+            tracing::warn!("could not allocate a thumbnail buffer");
+            return;
+        };
+        if self.hidden {
+            canvas.fill(0);
+        } else {
+            paint(
+                canvas,
+                width,
+                &self.small,
+                (self.offset * self.scale).round() as i64,
+            );
+        }
+        let surface = self.layer.wl_surface();
+        surface.damage_buffer(0, 0, width as i32, height as i32);
+        // Keep drawing while something moves; motion that arrives while a
+        // frame is pending is picked up by the next frame callback.
+        if self.anim.is_some() || self.drag.is_some() {
+            surface.frame(qh, FrameCallbackData(surface.clone()));
+            self.frame_pending = true;
+        }
+        if buffer.attach_to(surface).is_err() {
+            tracing::warn!("could not attach a thumbnail buffer");
+            return;
+        }
+        self.layer.commit();
+        self.buffer = Some(buffer);
+    }
+}
+
+impl Drop for Thumbnail {
+    fn drop(&mut self) {
+        self.viewport.destroy();
+    }
+}
+
+/// How far right the image moves to be fully off-screen.
+fn travel(image_width: u32) -> f64 {
+    (image_width + EDGE_MARGIN) as f64
+}
+
+/// Physical width of the surface: the image plus the edge padding.
+fn canvas_width(image_width: u32, scale: f64) -> u32 {
+    (((image_width + EDGE_MARGIN) as f64 * scale).round() as u32).max(1)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn downscale_fits_long_edge_at_scale_one() {
+        let img = RgbaImage::new(1920, 1080);
+        let (small, logical) = downscale(&img, 1.0);
+        assert_eq!(logical, (220, 124));
+        assert_eq!(small.dimensions(), (220, 124));
+    }
+
+    #[test]
+    fn downscale_renders_physical_pixels_at_fractional_scale() {
+        let img = RgbaImage::new(1920, 1080);
+        let (small, logical) = downscale(&img, 1.25);
+        assert_eq!(logical, (220, 124));
+        assert_eq!(small.dimensions(), (275, 155));
+    }
+
+    #[test]
+    fn downscale_leaves_small_images_alone() {
+        let img = RgbaImage::from_pixel(100, 50, image::Rgba([1, 2, 3, 255]));
+        let (small, logical) = downscale(&img, 1.0);
+        assert_eq!(logical, (100, 50));
+        assert_eq!(small, img);
+    }
+
+    fn pixel(canvas: &[u8], width: u32, x: u32, y: u32) -> [u8; 4] {
+        let i = ((y * width + x) * 4) as usize;
+        canvas[i..i + 4].try_into().unwrap()
+    }
+
+    /// 4x3 red image, so the inner pixels are (1,1) and (2,1).
+    fn red() -> RgbaImage {
+        RgbaImage::from_pixel(4, 3, image::Rgba([255, 0, 0, 255]))
+    }
+
+    #[test]
+    fn paint_at_rest_has_border_image_and_transparent_padding() {
+        let mut canvas = vec![9u8; 6 * 3 * 4];
+        paint(&mut canvas, 6, &red(), 0);
+        assert_eq!(pixel(&canvas, 6, 0, 0), BORDER);
+        assert_eq!(pixel(&canvas, 6, 1, 1), [0, 0, 255, 255], "BGRA red");
+        assert_eq!(pixel(&canvas, 6, 3, 1), BORDER);
+        assert_eq!(pixel(&canvas, 6, 4, 1), [0; 4], "padding is transparent");
+        assert_eq!(pixel(&canvas, 6, 5, 2), [0; 4]);
+    }
+
+    #[test]
+    fn paint_with_offset_shifts_and_clips() {
+        let mut canvas = vec![0u8; 6 * 3 * 4];
+        paint(&mut canvas, 6, &red(), 3);
+        assert_eq!(pixel(&canvas, 6, 2, 1), [0; 4], "left of the image");
+        assert_eq!(pixel(&canvas, 6, 3, 1), BORDER);
+        assert_eq!(pixel(&canvas, 6, 4, 1), [0, 0, 255, 255]);
+        assert_eq!(
+            pixel(&canvas, 6, 5, 1),
+            [0, 0, 255, 255],
+            "clipped at the edge"
+        );
+    }
+
+    #[test]
+    fn paint_fully_off_screen_is_empty() {
+        let mut canvas = vec![7u8; 6 * 3 * 4];
+        paint(&mut canvas, 6, &red(), 6);
+        assert!(canvas.iter().all(|&b| b == 0));
+    }
+
+    #[test]
+    fn canvas_includes_padding() {
+        assert_eq!(canvas_width(220, 1.0), 236);
+        assert_eq!(canvas_width(220, 1.25), 295);
+        assert_eq!(travel(220), 236.0);
+    }
+}

src/wayland.rs

@@ -38,6 +38,8 @@ pub struct Output {
     pub wl: wl_output::WlOutput,
     pub geom: OutputGeom,
     pub transform: wl_output::Transform,
+    /// Physical pixels per logical pixel, e.g. 1.25.
+    pub scale: f64,
 }
 
 pub struct Wayland {
@@ -112,29 +114,7 @@ impl Wayland {
 
     /// All outputs with a known name and logical geometry.
     pub fn outputs(&self) -> Vec<Output> {
-        self.state
-            .outputs
-            .outputs()
-            .filter_map(|wl| {
-                let info = self.state.outputs.info(&wl)?;
-                let (x, y) = info.logical_position?;
-                let (width, height) = info.logical_size?;
-                Some(Output {
-                    geom: OutputGeom {
-                        name: info
-                            .name
-                            .clone()
-                            .unwrap_or_else(|| format!("output-{}", info.id)),
-                        x,
-                        y,
-                        width,
-                        height,
-                    },
-                    transform: info.transform,
-                    wl,
-                })
-            })
-            .collect()
+        self.state.output_list()
     }
 
     /// `(interface, version)` of every global, sorted.
@@ -218,6 +198,57 @@ impl Wayland {
     }
 }
 
+impl State {
+    /// All outputs with a known name and logical geometry.
+    pub fn output_list(&self) -> Vec<Output> {
+        self.outputs
+            .outputs()
+            .filter_map(|wl| {
+                let info = self.outputs.info(&wl)?;
+                let (x, y) = info.logical_position?;
+                let (width, height) = info.logical_size?;
+                Some(Output {
+                    scale: output_scale(&info, width),
+                    geom: OutputGeom {
+                        name: info
+                            .name
+                            .clone()
+                            .unwrap_or_else(|| format!("output-{}", info.id)),
+                        x,
+                        y,
+                        width,
+                        height,
+                    },
+                    transform: info.transform,
+                    wl,
+                })
+            })
+            .collect()
+    }
+}
+
+/// Physical pixels per logical pixel: the current mode's width (turned to
+/// match the logical orientation) over the logical width.
+fn output_scale(info: &smithay_client_toolkit::output::OutputInfo, logical_width: i32) -> f64 {
+    let Some(mode) = info.modes.iter().find(|m| m.current) else {
+        return info.scale_factor as f64;
+    };
+    let (w, h) = mode.dimensions;
+    let rotated = matches!(
+        info.transform,
+        wl_output::Transform::_90
+            | wl_output::Transform::_270
+            | wl_output::Transform::Flipped90
+            | wl_output::Transform::Flipped270
+    );
+    let physical_width = if rotated { h } else { w };
+    if logical_width > 0 {
+        physical_width as f64 / logical_width as f64
+    } else {
+        1.0
+    }
+}
+
 impl CompositorHandler for State {
     fn scale_factor_changed(
         &mut self,