feat: valw window

src/window.rs

@@ -0,0 +1,70 @@
+//! Window mode: niri picks the window and renders it; valw reads the result.
+
+use std::path::PathBuf;
+use std::time::Duration;
+
+use anyhow::Result;
+use image::RgbaImage;
+
+use crate::error::Cancelled;
+use crate::niri;
+
+/// How long niri gets to render and write the window.
+const TIMEOUT: Duration = Duration::from_secs(5);
+
+/// Lets the user click a window. Returns its pixels and the output it is
+/// on, if niri knows. Esc during the pick is `Cancelled`.
+pub fn capture(cursor: bool) -> Result<(RgbaImage, Option<String>)> {
+    let window = niri::pick_window()?.ok_or(Cancelled)?;
+    tracing::info!("picked window {} ({:?})", window.id, window.app_id);
+    let tmp = TempFile(temp_path());
+    niri::screenshot_window(window.id, &tmp.0, cursor, TIMEOUT)?;
+    let image = crate::thumbnail::load(&tmp.0)?;
+    let workspaces = niri::workspaces().unwrap_or_else(|e| {
+        tracing::warn!("no workspace list: {e:#}");
+        Vec::new()
+    });
+    Ok((image, niri::output_of(window.workspace_id, &workspaces)))
+}
+
+/// Where niri writes the window: next to the capture lock, one per process.
+fn temp_path() -> PathBuf {
+    crate::lock::default_path().with_file_name(format!("valw-window-{}.png", std::process::id()))
+}
+
+/// Removes the temporary screenshot however `capture` ends.
+struct TempFile(PathBuf);
+
+impl Drop for TempFile {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_file(&self.0);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn temp_file_is_removed_on_drop() {
+        let dir = std::env::temp_dir().join(format!("valw-window-test-{}", std::process::id()));
+        std::fs::create_dir_all(&dir).unwrap();
+        let path = dir.join("shot.png");
+        std::fs::write(&path, b"png").unwrap();
+        drop(TempFile(path.clone()));
+        assert!(!path.exists());
+        // A file niri never wrote is fine too.
+        drop(TempFile(dir.join("missing.png")));
+        std::fs::remove_dir(&dir).unwrap();
+    }
+
+    #[test]
+    fn temp_path_is_absolute_and_per_process() {
+        let p = temp_path();
+        assert!(p.is_absolute(), "niri rejects relative paths: {p:?}");
+        assert!(
+            p.to_string_lossy()
+                .contains(&std::process::id().to_string())
+        );
+    }
+}