Milad Alizadeh
c607fc9a1c
Running wl-pick twice left the second instance hung with no window at all and no way to end it but kill. The hang was in the capture phase, not the overlay. sway answers a capture request for a toplevel that another client is already capturing with silence: no frame, no failed, no stopped. captures_settled() waits for every tile to reach one of those three, so it waited forever, holding its buffers, having never created a layer surface. Any concurrent capture client will do this, not just a second wl-pick. So the phases before the overlay is interactive now have a deadline. pump_for polls the connection with one, and a tile that never arrives is drawn as a bare label, exactly as an outright capture failure already was. report_unsettled names those tiles on stderr, which is the diagnostic whose absence made this hard to find. The first instance had a second problem: sway hands the keyboard to the new overlay and sends the old one wl_keyboard.leave, but the dispatcher only handled Key, so the loser sat on screen holding a grab it no longer had, deaf to every key. That is the process that stays around. Losing the grab for good now ends the run, so a second wl-pick started from the same keybinding replaces the first rather than stranding it. For good, because sway also sends leave followed immediately by enter on the same surface -- microseconds apart -- as a focus refresh when the pointer crosses the overlay. Treating a bare leave as terminal made a lone instance quit itself after less than a second. Focus is tracked in the dispatcher and the main loop only gives up once it has failed to come back. pump had no callers left after that: every wait is now either budgeted or focus-aware.
462 lines
17 KiB
Rust
462 lines
17 KiB
Rust
//! Capturing windows and displays.
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//!
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//! One session per tile, all opened before a single roundtrip so their buffer
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//! constraints arrive together, and every first frame put in flight at once: the
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//! compositor is bandwidth-bound reading pixels back, so serialising the
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//! captures only adds latency.
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//!
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//! The pixels are never mapped into this process. A capture buffer goes straight
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//! to a subsurface for display, so the compositor writes those pages and samples
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//! them again itself.
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use std::error::Error;
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use std::os::fd::AsFd;
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use std::time::{Duration, Instant};
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use wayland_client::protocol::{
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wl_buffer::{self, WlBuffer},
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wl_callback, wl_output, wl_shm,
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wl_subsurface::WlSubsurface,
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wl_surface::WlSurface,
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};
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use wayland_client::{Connection, Dispatch, QueueHandle, WEnum};
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use wayland_protocols::ext::image_capture_source::v1::client::ext_image_capture_source_v1::ExtImageCaptureSourceV1;
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use wayland_protocols::ext::image_copy_capture::v1::client::{
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ext_image_copy_capture_frame_v1::{self, ExtImageCopyCaptureFrameV1},
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ext_image_copy_capture_manager_v1,
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ext_image_copy_capture_session_v1::{self, ExtImageCopyCaptureSessionV1},
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};
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use wayland_protocols::wp::viewporter::client::wp_viewport::WpViewport;
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use crate::app::App;
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use crate::shm;
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use crate::target::{Kind, Target};
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/// Which tiles keep updating after the first frame.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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pub enum Live {
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/// Every tile.
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All,
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/// Only the selected tile: much cheaper, and still reads as alive.
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Current,
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/// Nothing: one snapshot each, a picker rather than an expose.
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None,
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}
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impl Live {
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pub fn parse(s: &str) -> Result<Self, String> {
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match s.trim() {
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"all" => Ok(Live::All),
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"current" => Ok(Live::Current),
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"none" => Ok(Live::None),
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other => Err(format!("{other:?} is not all, current or none")),
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}
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}
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}
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/// One capture buffer. `busy` means the compositor still holds it — either it is
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/// on screen or a capture is writing into it — so we must not scribble over it.
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pub struct Slot {
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pub(crate) buffer: WlBuffer,
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pub(crate) busy: bool,
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}
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pub struct Tile {
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pub(crate) target: Target,
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pub(crate) session: Option<ExtImageCopyCaptureSessionV1>,
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/// A capture in flight, and which slot it is filling.
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pub(crate) frame: Option<ExtImageCopyCaptureFrameV1>,
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pub(crate) filling: Option<usize>,
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pub(crate) slots: Vec<Slot>,
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/// The slot currently attached to the subsurface.
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pub(crate) showing: Option<usize>,
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pub(crate) formats: Vec<wl_shm::Format>,
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pub(crate) format: Option<wl_shm::Format>,
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/// Buffer size the session requires: the window's full resolution.
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pub(crate) size: (u32, u32),
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pub(crate) transform: wl_output::Transform,
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pub(crate) session_done: bool,
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pub(crate) ready: bool,
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pub(crate) settled: bool,
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/// When the last capture was asked for, for rate limiting, and how many
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/// frames this tile has produced.
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pub(crate) asked: Option<Instant>,
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pub(crate) frames: u32,
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pub(crate) surface: Option<WlSurface>,
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pub(crate) subsurface: Option<WlSubsurface>,
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pub(crate) viewport: Option<WpViewport>,
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}
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impl Tile {
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pub fn new(target: Target) -> Self {
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Self {
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target,
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session: None,
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frame: None,
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filling: None,
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slots: Vec::new(),
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showing: None,
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formats: Vec::new(),
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format: None,
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size: (0, 0),
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transform: wl_output::Transform::Normal,
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session_done: false,
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ready: false,
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settled: false,
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asked: None,
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frames: 0,
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surface: None,
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subsurface: None,
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viewport: None,
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}
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}
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pub fn bytes(&self) -> usize {
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self.size.0 as usize * 4 * self.size.1 as usize
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}
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/// Whether the buffer's contents are turned on their side relative to the
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/// window, which flips the aspect ratio we have to fit.
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pub fn rotated(&self) -> bool {
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use wl_output::Transform;
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matches!(
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self.transform,
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Transform::_90 | Transform::_270 | Transform::Flipped90 | Transform::Flipped270
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)
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}
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}
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impl App {
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/// Open one capture session per window whose toplevel we recognise. They are
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/// all opened before a single roundtrip, so every session's buffer
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/// constraints arrive together instead of costing a round trip each.
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pub fn open_sessions(&mut self, qh: &QueueHandle<Self>) {
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for (i, tile) in self.tiles.iter_mut().enumerate() {
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// A window's source comes from its toplevel handle, a display's from
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// its wl_output; everything after that is identical.
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let source: Option<ExtImageCaptureSourceV1> = match tile.target.kind {
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Kind::Window => self
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.toplevels
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.iter()
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.find(|(_, id)| !id.is_empty() && *id == tile.target.ft_id)
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.map(|(handle, _)| self.src_mgr.create_source(handle, qh, ())),
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Kind::Output => self
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.outputs
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.iter()
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.find(|(_, n)| *n == tile.target.id)
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.and_then(|(output, _)| {
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self.output_src_mgr
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.as_ref()
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.map(|mgr| mgr.create_source(output, qh, ()))
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}),
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};
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let Some(source) = source else {
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// Nothing to capture from: the tile stays label-only, and must
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// not be waited on.
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tile.settled = true;
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continue;
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};
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tile.session = Some(self.copy_mgr.create_session(
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&source,
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ext_image_copy_capture_manager_v1::Options::empty(),
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qh,
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i,
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));
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source.destroy();
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}
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}
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/// Allocate the capture buffers in one pool and put every first frame in
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/// flight at once: the compositor is bandwidth-bound reading pixels back, so
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/// serialising the captures only adds latency.
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///
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/// Live mode gets two buffers per window. A capture may not write into the
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/// buffer the compositor is currently displaying, so the two alternate:
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/// fill B while A is on screen, swap, and wait for A's release before
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/// touching it again.
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pub fn start_captures(&mut self, qh: &QueueHandle<Self>) -> Result<(), Box<dyn Error>> {
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const PAGE: usize = 4096;
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let mut total = 0usize;
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let mut offsets: Vec<Vec<usize>> = Vec::with_capacity(self.tiles.len());
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for tile in &mut self.tiles {
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offsets.push(Vec::new());
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if tile.session.is_none() {
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continue;
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}
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if !tile.session_done || tile.size.0 == 0 || tile.size.1 == 0 {
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tile.settled = true;
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continue;
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}
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// Any 32-bit format will do: we never read these pixels, we hand the
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// buffer straight back for display, so byte order stays the
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// compositor's business on both ends.
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tile.format = tile
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.formats
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.iter()
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.copied()
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.find(|f| matches!(f, wl_shm::Format::Xrgb8888 | wl_shm::Format::Argb8888))
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.or_else(|| tile.formats.first().copied());
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if tile.format.is_none() {
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tile.settled = true;
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continue;
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}
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// Only a tile that will be re-captured needs a second buffer, and a
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// display's is the size of the whole screen.
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let slots = if self.live == Live::None || tile.target.kind == Kind::Output {
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1
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} else {
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2
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};
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let last = offsets.last_mut().expect("just pushed");
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for _ in 0..slots {
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last.push(total);
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total += tile.bytes().div_ceil(PAGE) * PAGE;
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}
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}
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if total == 0 {
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return Ok(());
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}
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self.stats.pool_bytes = total;
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// Note: no mmap. The compositor writes these pages and samples them
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// again for display; mapping them here would only cost us the faults.
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let file = shm::memfd("wl-pick-capture", total)?;
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let pool = self.shm.create_pool(file.as_fd(), total as i32, qh, ());
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for (i, slot_offsets) in offsets.iter().enumerate() {
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let (w, h, format) = {
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let t = &self.tiles[i];
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if t.settled || t.session.is_none() || t.format.is_none() {
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continue;
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}
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(t.size.0 as i32, t.size.1 as i32, t.format.unwrap())
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};
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for &offset in slot_offsets {
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let slot = self.tiles[i].slots.len();
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let buffer = pool.create_buffer(offset as i32, w, h, w * 4, format, qh, (i, slot));
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self.tiles[i].slots.push(Slot {
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buffer,
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busy: false,
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});
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}
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self.request_capture(i, qh);
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}
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pool.destroy(); // the buffers keep the mapping alive
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Ok(())
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}
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/// Ask the compositor for one frame of window `i`, into a free slot.
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///
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/// After a session's first frame the compositor only answers once the window
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/// content changes, so a request left outstanding on an idle window costs
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/// nothing: this is damage-driven, and the rate limit only bites on windows
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/// that really are animating.
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fn request_capture(&mut self, i: usize, qh: &QueueHandle<Self>) -> bool {
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let t = &mut self.tiles[i];
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if t.frame.is_some() || t.session.is_none() {
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return false; // already waiting on one
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}
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let Some(slot) = t.slots.iter().position(|s| !s.busy) else {
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self.stats.starved += 1;
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return false; // both buffers still held by the compositor
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};
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let (w, h) = (t.size.0 as i32, t.size.1 as i32);
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let frame = t
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.session
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.as_ref()
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.expect("checked above")
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.create_frame(qh, i);
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frame.attach_buffer(&t.slots[slot].buffer);
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frame.damage_buffer(0, 0, w, h);
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frame.capture();
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t.frame = Some(frame);
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t.filling = Some(slot);
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t.asked = Some(Instant::now());
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true
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}
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/// A capture landed: show it, and let go of the slot it replaced.
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fn frame_ready(&mut self, i: usize) {
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let t = &mut self.tiles[i];
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let Some(slot) = t.filling.take() else { return };
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t.frames += 1;
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t.ready = true;
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t.settled = true;
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t.slots[slot].busy = true; // the compositor reads it until it releases it
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let previous = t.showing.replace(slot);
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// Before the overlay is mapped there is nothing to attach to yet;
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// place_tiles picks up `showing` instead.
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if let Some(surface) = t.surface.clone() {
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let (w, h) = (t.size.0 as i32, t.size.1 as i32);
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surface.attach(Some(&t.slots[slot].buffer), 0, 0);
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surface.damage_buffer(0, 0, w, h);
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surface.commit();
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} else if let Some(prev) = previous {
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// Not on screen yet, so the old slot was never actually read.
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t.slots[prev].busy = false;
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}
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}
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/// Ask for the next frame callback. A commit is needed for the compositor to
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/// schedule one, and an empty commit is enough.
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pub fn arm_frame_callback(&mut self, qh: &QueueHandle<Self>) {
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if self.live == Live::None {
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return;
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}
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if let Some(surface) = self.surface.clone() {
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surface.frame(qh, ());
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surface.commit();
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}
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}
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/// Re-capture whatever is due. Driven by frame callbacks, so it stops when
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/// the overlay is not being presented.
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pub fn tick(&mut self, qh: &QueueHandle<Self>) {
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self.stats.ticks += 1;
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if self.live == Live::None {
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return;
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}
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let interval = Duration::from_secs_f64(1.0 / self.fps.max(1) as f64);
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let now = Instant::now();
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for i in 0..self.tiles.len() {
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if self.live == Live::Current && i != self.sel {
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continue;
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}
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// A display tile shows this overlay, which shows the display tile:
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// refreshing it never settles and costs a whole screen per frame.
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if self.tiles[i].target.kind == Kind::Output {
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continue;
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}
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// Nor is there any point refreshing a tile that is scrolled out of
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// sight — that is a readback for pixels nobody sees.
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if self.layout.tile(i as i32, self.scroll).is_none() {
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continue;
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}
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let t = &self.tiles[i];
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if t.slots.is_empty() || t.frame.is_some() {
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continue;
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}
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if t.asked.is_some_and(|a| now.duration_since(a) < interval) {
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continue;
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}
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self.request_capture(i, qh);
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}
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}
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}
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// --- event plumbing -------------------------------------------------------
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impl Dispatch<ExtImageCopyCaptureSessionV1, usize> for App {
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fn event(
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app: &mut Self,
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_: &ExtImageCopyCaptureSessionV1,
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event: ext_image_copy_capture_session_v1::Event,
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&i: &usize,
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_: &Connection,
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_: &QueueHandle<Self>,
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) {
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let Some(tile) = app.tiles.get_mut(i) else {
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return;
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};
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match event {
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ext_image_copy_capture_session_v1::Event::BufferSize { width, height } => {
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tile.size = (width, height)
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}
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ext_image_copy_capture_session_v1::Event::ShmFormat {
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format: WEnum::Value(f),
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} => tile.formats.push(f),
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ext_image_copy_capture_session_v1::Event::Done => tile.session_done = true,
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ext_image_copy_capture_session_v1::Event::Stopped => tile.settled = true,
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_ => {}
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}
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}
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}
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impl Dispatch<ExtImageCopyCaptureFrameV1, usize> for App {
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fn event(
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app: &mut Self,
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_: &ExtImageCopyCaptureFrameV1,
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event: ext_image_copy_capture_frame_v1::Event,
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&i: &usize,
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_: &Connection,
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_: &QueueHandle<Self>,
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) {
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let Some(tile) = app.tiles.get_mut(i) else {
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return;
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};
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match event {
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ext_image_copy_capture_frame_v1::Event::Transform {
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transform: WEnum::Value(t),
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} => tile.transform = t,
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ext_image_copy_capture_frame_v1::Event::Ready => {
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// The protocol wants the frame destroyed once ready; the buffer
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// stays ours to display.
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if let Some(frame) = tile.frame.take() {
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frame.destroy();
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}
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app.frame_ready(i);
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}
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ext_image_copy_capture_frame_v1::Event::Failed { reason } => {
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// Live mode retries on the next tick; only a failure with no
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// frame yet leaves the tile without a thumbnail.
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if tile.frames == 0 {
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eprintln!(
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"wl-pick: capture failed for {:?} ({reason:?})",
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tile.target.title
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);
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}
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tile.settled = true;
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if let Some(slot) = tile.filling.take() {
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tile.slots[slot].busy = false;
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}
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if let Some(frame) = tile.frame.take() {
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frame.destroy();
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}
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}
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_ => {}
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}
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}
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}
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/// A released capture buffer is a slot we may capture into again.
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///
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/// Release is the whole contract: with wl_shm the compositor copies the pixels
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/// out at commit and hands the buffer straight back, so the slot currently on
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/// screen is usually free too. (Waiting for it to stop being the displayed slot
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/// instead would deadlock — that release never comes twice.)
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impl Dispatch<WlBuffer, (usize, usize)> for App {
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fn event(
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app: &mut Self,
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_: &WlBuffer,
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event: wl_buffer::Event,
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&(tile, slot): &(usize, usize),
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_: &Connection,
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_: &QueueHandle<Self>,
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) {
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if let wl_buffer::Event::Release = event
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&& let Some(t) = app.tiles.get_mut(tile)
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{
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t.slots[slot].busy = false;
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}
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}
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}
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|
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/// Frame callbacks are the clock for live updates: they arrive as the compositor
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/// presents the overlay, so re-captures stop when it is not being shown.
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impl Dispatch<wl_callback::WlCallback, ()> for App {
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fn event(
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app: &mut Self,
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_: &wl_callback::WlCallback,
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event: wl_callback::Event,
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_: &(),
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_: &Connection,
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qh: &QueueHandle<Self>,
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) {
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if let wl_callback::Event::Done { .. } = event {
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app.tick(qh);
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app.arm_frame_callback(qh);
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}
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}
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}
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