Decode portal wallpapers by content and simplify status bar

Detect wallpaper image formats from their contents so extensionless portal copies render on the desktop and lock screen. Preserve decode limits and cover extensionless files with regression tests.

Remove the Bluetooth icon from the status bar.

compositor/src/wallpaper.rs

@@ -83,11 +83,20 @@ impl WallpaperState {
             let wakeup = wakeup.clone();
             std::thread::spawn(move || {
                 let load = || -> Result<image::RgbaImage, String> {
-                    let (width, height) = image::image_dimensions(&path).map_err(|e| e.to_string())?;
+                    use image::ImageDecoder;
+                    let mut reader = image::ImageReader::open(&path)
+                        .map_err(|e| e.to_string())?
+                        .with_guessed_format()
+                        .map_err(|e| e.to_string())?;
+                    let mut limits = image::Limits::default();
+                    limits.max_alloc = Some(256 * 1024 * 1024);
+                    reader.limits(limits);
+                    let decoder = reader.into_decoder().map_err(|e| e.to_string())?;
+                    let (width, height) = decoder.dimensions();
                     if u64::from(width) * u64::from(height) * 4 > 256 * 1024 * 1024 {
                         return Err("wallpaper exceeds the 256 MiB decode limit".into());
                     }
-                    image::open(path)
+                    image::DynamicImage::from_decoder(decoder)
                         .map(|image| image.into_rgba8())
                         .map_err(|e| e.to_string())
                 };
@@ -329,6 +338,28 @@ fn image_geometry(
 mod tests {
     use super::*;
 
+    #[test]
+    fn portal_wallpaper_decodes_without_a_filename_extension() {
+        let directory = tempfile::tempdir().unwrap();
+        let expected = image::RgbaImage::from_pixel(3, 2, image::Rgba([32, 80, 160, 255]));
+        for name in ["wallpaper-portal", "wallpaper.jpg"] {
+            let path = directory.path().join(name);
+            expected.save_with_format(&path, image::ImageFormat::Png).unwrap();
+            let mut state = WallpaperState::new(WallpaperConfig {
+                path: Some(path),
+                mode: WallpaperMode::Fill,
+            });
+            let decoded = state
+                .receiver
+                .take()
+                .unwrap()
+                .recv_timeout(Duration::from_secs(5))
+                .unwrap()
+                .unwrap();
+            assert_eq!(decoded, expected);
+        }
+    }
+
     #[test]
     fn failed_upload_retry_wakes_idle_loop_and_does_not_spin_when_output_is_inactive() {
         use smithay::backend::renderer::ContextId;