1 files changed, 78 insertions, 0 deletions
diff --git a/crates/core/src/manager/capture.rs b/crates/core/src/manager/capture.rs
new file mode 100644
index 0000000..41fe0cd
--- /dev/null
+++ b/crates/core/src/manager/capture.rs
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+//! Requesting an off-screen render of a workspace's window tree to a file.
+//! Split out the same way `lock.rs` is - see `super` (`mod.rs`) for
+//! `WindowManager`'s field definitions.
+
+use super::*;
+
+/// One queued `srd capture workspace <id> <path> [WxH]` request. Core has
+/// no renderer of its own (that's backend-owned, same boundary
+/// `request_lock`/`request_output_position` already cross) - this is
+/// just the request's data, drained and acted on by whichever backend is
+/// actually running.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CaptureRequest {
+    pub workspace: WorkspaceId,
+    pub path: String,
+    /// `None` renders at the workspace's own monitor resolution.
+    pub size: Option<(u32, u32)>,
+}
+
+impl WindowManager {
+    /// Queues an off-screen capture of `workspace`'s window tree, written
+    /// to `path` as a PPM image once the backend's next poll drains it.
+    /// Exists for exactly one reason: a workspace switcher (AGS's Overview)
+    /// wanting a thumbnail of a workspace that is not the one currently on
+    /// screen. `wlr-screencopy` (what `grim`, and this compositor's own
+    /// `screencopy.rs`, use) can only ever see what an output is actually
+    /// presenting - it has no way to see a workspace that is not the
+    /// active one, which is exactly the case a workspace-switcher preview
+    /// needs most. This is not a re-implementation of screencopy; it is
+    /// the one thing screencopy structurally cannot do, requested the same
+    /// cross-boundary way `request_lock` is.
+    ///
+    /// Multiple requests for the same workspace queue independently (unlike
+    /// `request_lock`'s single flag) - a caller asking for two different
+    /// sizes, or overwriting a previous request for the same workspace
+    /// before the backend gets to it, are both legitimate.
+    pub fn request_capture_workspace(&mut self, workspace: WorkspaceId, path: String, size: Option<(u32, u32)>) {
+        self.capture_requests.push(CaptureRequest { workspace, path, size });
+    }
+
+    /// Takes every currently-queued capture request, leaving none pending.
+    /// The backend calls this once per poll, same as
+    /// `drain_output_position_requests`.
+    pub fn drain_capture_requests(&mut self) -> Vec<CaptureRequest> {
+        std::mem::take(&mut self.capture_requests)
+    }
+
+    /// Front-to-back window ids for an arbitrary (not necessarily current)
+    /// workspace - the same "topmost first" convention
+    /// `visible_windows_front_to_back` already gives the current one, but
+    /// that method is hardcoded to `self.current_workspace`, and a capture
+    /// request's whole reason for existing is targeting a workspace that
+    /// usually is *not* the current one. `order` is back-to-front (see its
+    /// own field doc comment), hence the same `.rev()` that method uses.
+    pub fn window_ids_on_workspace_front_to_back(&self, workspace: WorkspaceId) -> Vec<WindowId> {
+        self.order.iter().rev().filter(|&&id| self.windows.get(&id).is_some_and(|w| w.workspace == workspace && !w.minimized)).copied().collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn capture_requests_drain_in_arrival_order() {
+        let mut wm = WindowManager::new();
+        wm.request_capture_workspace(0, "/tmp/a.ppm".into(), None);
+        wm.request_capture_workspace(1, "/tmp/b.ppm".into(), Some((100, 100)));
+        assert_eq!(
+            wm.drain_capture_requests(),
+            vec![
+                CaptureRequest { workspace: 0, path: "/tmp/a.ppm".into(), size: None },
+                CaptureRequest { workspace: 1, path: "/tmp/b.ppm".into(), size: Some((100, 100)) },
+            ]
+        );
+        assert!(wm.drain_capture_requests().is_empty(), "must not report the same requests twice");
+    }
+}