wallpaper: unset removes a per-output override

lmtt/src/main.rs

@@ -117,6 +117,14 @@ enum WallpaperCommand {
         #[arg(long)]
         no_publish: bool,
     },
+    /// Remove the current user's per-output wallpaper override
+    Unset {
+        #[arg(long)]
+        output: String,
+        /// Do not refresh the greeter-readable snapshot
+        #[arg(long)]
+        no_publish: bool,
+    },
     /// Resolve the effective wallpaper for an output
     Resolve {
         #[arg(long, default_value = "default")]
@@ -248,6 +256,21 @@ fn cmd_wallpaper(command: WallpaperCommand) -> Result<()> {
                 publish_current(&profile)?;
             }
         }
+        WallpaperCommand::Unset { output, no_publish } => {
+            let profile_path = appearance_profiles::user_profile_path()
+                .ok_or_else(|| anyhow::anyhow!("cannot determine the user config directory"))?;
+            let mut profile = Profile::load(&profile_path)?.unwrap_or_default();
+            if profile.output.remove(&output).is_none() {
+                // Idempotent: nothing to write or republish.
+                println!("No wallpaper override for {output}");
+            } else {
+                write_profile(&profile_path, &profile)?;
+                println!("Removed the wallpaper override for {output}");
+                if !no_publish {
+                    publish_current(&profile)?;
+                }
+            }
+        }
         WallpaperCommand::Resolve {
             output,
             description,

lmtt/tests/wallpaper_unset.rs

@@ -0,0 +1,108 @@
+//! `lmtt wallpaper unset` against a throwaway XDG tree, publish skipped.
+use std::path::{Path, PathBuf};
+use std::process::{Command, Output};
+
+fn sandbox() -> PathBuf {
+    let dir = std::env::temp_dir().join(format!("lmtt-unset-{}", std::process::id()));
+    std::fs::remove_dir_all(&dir).ok();
+    std::fs::create_dir_all(dir.join("config")).unwrap();
+    std::fs::create_dir_all(dir.join("cache")).unwrap();
+    dir
+}
+
+fn lmtt(sandbox: &Path, args: &[&str]) -> Output {
+    Command::new(env!("CARGO_BIN_EXE_lmtt"))
+        .args(args)
+        .env("HOME", sandbox)
+        .env("XDG_CONFIG_HOME", sandbox.join("config"))
+        .env("XDG_CACHE_HOME", sandbox.join("cache"))
+        .env("XDG_DATA_HOME", sandbox.join("data"))
+        .env_remove("WAYLAND_DISPLAY")
+        .output()
+        .expect("run lmtt")
+}
+
+fn ok(out: &Output) -> String {
+    assert!(
+        out.status.success(),
+        "lmtt failed ({}): {}",
+        out.status,
+        String::from_utf8_lossy(&out.stderr)
+    );
+    String::from_utf8_lossy(&out.stdout).into_owned()
+}
+
+#[test]
+fn unset_removes_only_that_override_and_is_idempotent() {
+    let sb = sandbox();
+    let image = sb.join("wall.png");
+    std::fs::write(&image, b"set only canonicalizes; publish is skipped").unwrap();
+    let image = image.to_str().unwrap();
+    let profile = sb.join("config/appearance-profiles/default.toml");
+
+    ok(&lmtt(&sb, &["wallpaper", "set", image, "--no-publish"]));
+    ok(&lmtt(
+        &sb,
+        &[
+            "wallpaper",
+            "set",
+            image,
+            "--output",
+            "desc:Test Monitor",
+            "--no-publish",
+        ],
+    ));
+    ok(&lmtt(
+        &sb,
+        &[
+            "wallpaper",
+            "set",
+            image,
+            "--output",
+            "DP-9",
+            "--no-publish",
+        ],
+    ));
+    let text = std::fs::read_to_string(&profile).unwrap();
+    assert!(text.contains("desc:Test Monitor"), "{text}");
+    assert!(text.contains("DP-9"), "{text}");
+
+    let out = ok(&lmtt(
+        &sb,
+        &[
+            "wallpaper",
+            "unset",
+            "--output",
+            "desc:Test Monitor",
+            "--no-publish",
+        ],
+    ));
+    assert!(out.contains("Removed"), "{out}");
+    let text = std::fs::read_to_string(&profile).unwrap();
+    assert!(!text.contains("desc:Test Monitor"), "{text}");
+    assert!(text.contains("DP-9"), "other overrides survive: {text}");
+    assert!(
+        text.contains("[background]"),
+        "the global rule survives: {text}"
+    );
+
+    // Idempotent: exit 0, nothing rewritten.
+    let before = std::fs::metadata(&profile).unwrap().modified().unwrap();
+    let out = ok(&lmtt(
+        &sb,
+        &[
+            "wallpaper",
+            "unset",
+            "--output",
+            "desc:Test Monitor",
+            "--no-publish",
+        ],
+    ));
+    assert!(out.contains("No wallpaper override"), "{out}");
+    assert_eq!(
+        std::fs::metadata(&profile).unwrap().modified().unwrap(),
+        before
+    );
+
+    std::fs::remove_dir_all(&sb).ok();
+}