feat: frozen-frame region selection overlay

src/main.rs

@@ -1,6 +1,3 @@
-// Modules land before the CLI uses them; Task 11 removes this.
-#![allow(dead_code)]
-
 mod capture;
 mod config;
 mod detach;
@@ -11,6 +8,7 @@ mod lock;
 mod log;
 mod niri;
 mod output;
+mod region;
 mod render;
 mod selection;
 mod wayland;
@@ -48,6 +46,11 @@ enum Command {
         #[command(flatten)]
         common: Common,
     },
+    /// Drag to select a region (Cmd+Shift+4).
+    Region {
+        #[command(flatten)]
+        common: Common,
+    },
     /// Report what the compositor and system support.
     Doctor,
 }
@@ -76,6 +79,7 @@ fn parse_delay(s: &str) -> Result<Duration, String> {
 
 enum Mode {
     Screen { all: bool },
+    Region,
 }
 
 fn main() -> ExitCode {
@@ -106,6 +110,7 @@ fn run(cli: Cli) -> Result<()> {
     match cli.command {
         Command::Doctor => doctor::run(),
         Command::Screen { all, common } => capture(Mode::Screen { all }, common),
+        Command::Region { common } => capture(Mode::Region, common),
     }
 }
 
@@ -139,6 +144,11 @@ fn capture(mode: Mode, common: Common) -> Result<()> {
                 (vec![(frame.to_rgba(frame.full()), None)], 0)
             }
         }
+        Mode::Region => {
+            let frames = wl.capture(&outputs, cursor)?;
+            let (i, r) = region::select(&mut wl, &outputs, &frames)?;
+            (vec![(frames[i].to_rgba(r), None)], 0)
+        }
     };
     drop(wl);
 
@@ -224,10 +234,10 @@ mod tests {
     fn flag_conflicts() {
         assert!(parses(&["screen", "--all"]));
         assert!(parses(&["screen", "-o", "-"]));
-        assert!(parses(&["screen", "--clipboard-only", "--cursor"]));
+        assert!(parses(&["region", "--clipboard-only", "--cursor"]));
         assert!(!parses(&["screen", "--all", "-o", "-"]));
         assert!(!parses(&["screen", "--all", "--clipboard-only"]));
-        assert!(!parses(&["screen", "--clipboard-only", "-o", "a.png"]));
+        assert!(!parses(&["region", "--clipboard-only", "-o", "a.png"]));
     }
 
     #[test]

src/region.rs

@@ -0,0 +1,279 @@
+use std::sync::Arc;
+
+use anyhow::{Context, Result};
+use smithay_client_toolkit::{
+    compositor::FrameCallbackData,
+    seat::pointer::{BTN_LEFT, BTN_RIGHT, PointerEvent, PointerEventKind},
+    shell::{
+        WaylandSurface,
+        wlr_layer::{Anchor, KeyboardInteractivity, Layer, LayerSurface},
+    },
+    shm::{
+        Shm,
+        slot::{Buffer, SlotPool},
+    },
+};
+use wayland_client::{
+    QueueHandle,
+    protocol::{wl_shm, wl_surface::WlSurface},
+};
+use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::{
+    Shape, WpCursorShapeDeviceV1,
+};
+use wayland_protocols::wp::viewporter::client::wp_viewport::WpViewport;
+
+use crate::error::{Cancelled, HintExt};
+use crate::frame::{Bgrx, Frame, OutputGeom, PixelRect};
+use crate::render;
+use crate::selection::{self, Point, Selection};
+use crate::wayland::{Output, State, Wayland};
+
+pub const NAMESPACE: &str = "valw-overlay";
+
+/// What the user picked: an output index and a rectangle in its frame.
+pub type Picked = (usize, PixelRect);
+
+/// One full-screen layer surface per output, showing the frozen frame.
+pub struct Overlay {
+    surfaces: Vec<Surface>,
+    selection: Selection,
+    /// Output where the current drag started; the capture is clipped to it.
+    anchor: Option<usize>,
+    outcome: Option<Option<Picked>>,
+}
+
+struct Surface {
+    layer: LayerSurface,
+    viewport: WpViewport,
+    geom: OutputGeom,
+    width: u32,
+    height: u32,
+    dark: Vec<u8>,
+    bright: Arc<Bgrx>,
+    pool: SlotPool,
+    buffer: Option<Buffer>,
+    configured: bool,
+    frame_pending: bool,
+    dirty: bool,
+}
+
+/// Shows the overlay on every output and waits for a selection.
+/// Returns `Cancelled` if the user presses Esc or right-clicks.
+pub fn select(wl: &mut Wayland, outputs: &[Output], frames: &[Frame]) -> Result<Picked> {
+    let qh = wl.queue.handle();
+    let s = &wl.state;
+    let layer_shell = s
+        .layer_shell
+        .as_ref()
+        .context("compositor does not support wlr-layer-shell")
+        .hint("run `valw doctor` to see what the compositor supports")?;
+    let viewporter = s
+        .viewporter
+        .as_ref()
+        .context("compositor does not support wp-viewporter")
+        .hint("run `valw doctor` to see what the compositor supports")?;
+
+    let mut surfaces = Vec::new();
+    for (output, frame) in outputs.iter().zip(frames) {
+        let surface = s.compositor.create_surface(&qh);
+        let layer = layer_shell.create_layer_surface(
+            &qh,
+            surface,
+            Layer::Overlay,
+            Some(NAMESPACE),
+            Some(&output.wl),
+        );
+        layer.set_anchor(Anchor::all());
+        layer.set_exclusive_zone(-1);
+        layer.set_keyboard_interactivity(KeyboardInteractivity::Exclusive);
+        layer.commit();
+        let viewport = viewporter.get_viewport(layer.wl_surface(), &qh, ());
+        surfaces.push(Surface::new(layer, viewport, frame, &s.shm)?);
+    }
+
+    tracing::debug!(
+        "overlay buffers ready {:?} after start",
+        crate::log::since_start()
+    );
+    wl.state.overlay = Some(Overlay {
+        surfaces,
+        selection: Selection::default(),
+        anchor: None,
+        outcome: None,
+    });
+    let result = wl.dispatch_blocking(|s| s.overlay.as_ref().is_some_and(|o| o.outcome.is_some()));
+    let outcome = wl.state.overlay.take().and_then(|o| o.outcome);
+    // Dropping the overlay destroys the surfaces; make that visible right away.
+    let _ = wl.conn.flush();
+    result?;
+    outcome.flatten().ok_or_else(|| Cancelled.into())
+}
+
+impl Surface {
+    fn new(layer: LayerSurface, viewport: WpViewport, frame: &Frame, shm: &Shm) -> Result<Surface> {
+        let (width, height) = frame.pixels.dimensions();
+        let len = (width * height * 4) as usize;
+        Ok(Surface {
+            layer,
+            viewport,
+            geom: frame.output.clone(),
+            width,
+            height,
+            dark: render::dim(frame.pixels.as_raw(), render::DIM),
+            bright: Arc::clone(&frame.pixels),
+            // Room for two buffers so one can be on screen while we draw the next.
+            pool: SlotPool::new(len * 2, shm).context("could not create shm pool")?,
+            buffer: None,
+            configured: false,
+            frame_pending: false,
+            dirty: true,
+        })
+    }
+
+    fn draw(&mut self, sel: Option<PixelRect>, qh: &QueueHandle<State>) {
+        let stride = self.width as i32 * 4;
+        let Ok((buffer, canvas)) = self.pool.create_buffer(
+            self.width as i32,
+            self.height as i32,
+            stride,
+            wl_shm::Format::Xrgb8888,
+        ) else {
+            tracing::warn!("could not allocate an overlay buffer");
+            return;
+        };
+        render::compose(canvas, &self.dark, self.bright.as_raw(), self.width, sel);
+
+        let surface = self.layer.wl_surface();
+        surface.damage_buffer(0, 0, self.width as i32, self.height as i32);
+        surface.frame(qh, FrameCallbackData(surface.clone()));
+        if buffer.attach_to(surface).is_err() {
+            tracing::warn!("could not attach the overlay buffer");
+            return;
+        }
+        self.layer.commit();
+        self.buffer = Some(buffer);
+        self.frame_pending = true;
+        self.dirty = false;
+    }
+}
+
+impl Overlay {
+    pub fn cancel(&mut self) {
+        self.outcome.get_or_insert(None);
+    }
+
+    fn index_of(&self, surface: &WlSurface) -> Option<usize> {
+        self.surfaces
+            .iter()
+            .position(|s| s.layer.wl_surface() == surface)
+    }
+
+    /// The selection as drawn on surface `i`: only the anchor output shows it.
+    fn selection_on(&self, i: usize) -> Option<PixelRect> {
+        let Selection::Dragging { start, end } = self.selection else {
+            return None;
+        };
+        let s = &self.surfaces[i];
+        (self.anchor == Some(i))
+            .then(|| selection::clip(start, end, &s.geom, s.width, s.height))
+            .flatten()
+    }
+
+    fn redraw(&mut self, i: usize, qh: &QueueHandle<State>) {
+        let sel = self.selection_on(i);
+        let s = &mut self.surfaces[i];
+        s.dirty = true;
+        if s.configured && !s.frame_pending {
+            s.draw(sel, qh);
+        }
+    }
+
+    pub fn configure(&mut self, layer: &LayerSurface, (w, h): (u32, u32), qh: &QueueHandle<State>) {
+        let Some(i) = self.index_of(layer.wl_surface()) else {
+            return;
+        };
+        let s = &mut self.surfaces[i];
+        // Show the physical-size buffer 1:1 on the logical-size surface.
+        s.viewport.set_destination(w as i32, h as i32);
+        if !s.configured {
+            s.configured = true;
+            let name = s.geom.name.clone();
+            self.redraw(i, qh);
+            tracing::info!(
+                "overlay on {name} committed {:?} after start",
+                crate::log::since_start()
+            );
+        }
+    }
+
+    pub fn frame_done(&mut self, surface: &WlSurface, qh: &QueueHandle<State>) {
+        let Some(i) = self.index_of(surface) else {
+            return;
+        };
+        self.surfaces[i].frame_pending = false;
+        if self.surfaces[i].dirty {
+            self.redraw(i, qh);
+        }
+    }
+
+    pub fn pointer(
+        &mut self,
+        events: &[PointerEvent],
+        cursor: Option<&WpCursorShapeDeviceV1>,
+        qh: &QueueHandle<State>,
+    ) {
+        for event in events {
+            let Some(i) = self.index_of(&event.surface) else {
+                continue;
+            };
+            let g = &self.surfaces[i].geom;
+            let p = Point {
+                x: g.x as f64 + event.position.0,
+                y: g.y as f64 + event.position.1,
+            };
+            match event.kind {
+                PointerEventKind::Enter { serial } => {
+                    if let Some(cursor) = cursor {
+                        cursor.set_shape(serial, Shape::Crosshair);
+                    }
+                }
+                PointerEventKind::Press {
+                    button: BTN_LEFT, ..
+                } => {
+                    self.selection.press(p);
+                    self.anchor = Some(i);
+                }
+                PointerEventKind::Press {
+                    button: BTN_RIGHT, ..
+                } => self.cancel(),
+                PointerEventKind::Motion { .. } => {
+                    self.selection.motion(p);
+                    if let Some(a) = self.anchor {
+                        self.redraw(a, qh);
+                    }
+                }
+                PointerEventKind::Release {
+                    button: BTN_LEFT, ..
+                } => {
+                    let (Some((start, end)), Some(a)) = (self.selection.release(p), self.anchor)
+                    else {
+                        continue;
+                    };
+                    let s = &self.surfaces[a];
+                    match selection::resolve(start, end, &s.geom, s.width, s.height) {
+                        Some(rect) => {
+                            tracing::info!(
+                                "selected {rect:?} on {} (logical {start:?} to {end:?})",
+                                s.geom.name
+                            );
+                            self.outcome = Some(Some((a, rect)));
+                        }
+                        // A click, not a drag: clear it and keep waiting.
+                        None => self.redraw(a, qh),
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}

src/wayland.rs

@@ -30,6 +30,7 @@ use wayland_protocols_wlr::screencopy::v1::client::zwlr_screencopy_manager_v1::Z
 use crate::capture::Pending;
 use crate::error::HintExt;
 use crate::frame::OutputGeom;
+use crate::region::Overlay;
 
 /// An output as valw sees it.
 #[derive(Debug, Clone)]
@@ -61,6 +62,8 @@ pub struct State {
     pub pointer: Option<wl_pointer::WlPointer>,
     /// Screencopy requests in flight.
     pub captures: Vec<Pending>,
+    /// The region selection overlay, while it is open.
+    pub overlay: Option<Overlay>,
 }
 
 impl Wayland {
@@ -87,6 +90,7 @@ impl Wayland {
             keyboard: None,
             pointer: None,
             captures: Vec::new(),
+            overlay: None,
         };
         // Two round trips: one for wl_output, one for the xdg-output details.
         queue
@@ -233,7 +237,17 @@ impl CompositorHandler for State {
     ) {
     }
 
-    fn frame(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &wl_surface::WlSurface, _: u32) {}
+    fn frame(
+        &mut self,
+        _: &Connection,
+        qh: &QueueHandle<Self>,
+        surface: &wl_surface::WlSurface,
+        _: u32,
+    ) {
+        if let Some(overlay) = &mut self.overlay {
+            overlay.frame_done(surface, qh);
+        }
+    }
 
     fn surface_enter(
         &mut self,
@@ -267,16 +281,23 @@ impl OutputHandler for State {
 }
 
 impl LayerShellHandler for State {
-    fn closed(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &LayerSurface) {}
+    fn closed(&mut self, _: &Connection, _: &QueueHandle<Self>, _: &LayerSurface) {
+        if let Some(overlay) = &mut self.overlay {
+            overlay.cancel();
+        }
+    }
 
     fn configure(
         &mut self,
         _: &Connection,
-        _: &QueueHandle<Self>,
+        qh: &QueueHandle<Self>,
-        _: &LayerSurface,
+        layer: &LayerSurface,
-        _: LayerSurfaceConfigure,
+        configure: LayerSurfaceConfigure,
         _: u32,
     ) {
+        if let Some(overlay) = &mut self.overlay {
+            overlay.configure(layer, configure.new_size, qh);
+        }
     }
 }
 
@@ -363,8 +384,13 @@ impl KeyboardHandler for State {
         _: &QueueHandle<Self>,
         _: &wl_keyboard::WlKeyboard,
         _: u32,
-        _: KeyEvent,
+        event: KeyEvent,
     ) {
+        if event.keysym == Keysym::Escape
+            && let Some(overlay) = &mut self.overlay
+        {
+            overlay.cancel();
+        }
     }
 
     fn repeat_key(
@@ -404,10 +430,13 @@ impl PointerHandler for State {
     fn pointer_frame(
         &mut self,
         _: &Connection,
-        _: &QueueHandle<Self>,
+        qh: &QueueHandle<Self>,
         _: &wl_pointer::WlPointer,
-        _: &[PointerEvent],
+        events: &[PointerEvent],
     ) {
+        if let Some(overlay) = &mut self.overlay {
+            overlay.pointer(events, self.cursor_device.as_ref(), qh);
+        }
     }
 }