improve vaapi init failure error message

src/avhw.rs

@@ -15,7 +15,7 @@ pub struct AvHwDevCtx {
 }
 
 impl AvHwDevCtx {
-    pub fn new_libva(dri_device: &str) -> Self {
+    pub fn new_libva(dri_device: &str) -> Result<Self, ffmpeg::Error> {
         unsafe {
             let mut hw_device_ctx = null_mut();
 
@@ -31,9 +31,12 @@ impl AvHwDevCtx {
                 opts.as_mut_ptr(),
                 0,
             );
-            assert_eq!(sts, 0, "failed to open {dri_device}");
 
-            Self { ptr: hw_device_ctx }
+            if sts != 0 {
+                Err(ffmpeg::Error::from(sts))
+            } else {
+                Ok(Self { ptr: hw_device_ctx })
+            }
         }
     }
 

src/main.rs

@@ -1226,7 +1226,10 @@ impl EncState {
 
         eprintln!("Opening libva device from DRM device {dri_device}");
 
-        let mut hw_device_ctx = AvHwDevCtx::new_libva(dri_device);
+        let mut hw_device_ctx = match AvHwDevCtx::new_libva(dri_device) {
+            Ok(hdc) => hdc,
+            Err(e) => bail!("Failed to load vaapi device: {e}\nThis is likely *not* a bug in wl-screenrec, but an issue with your vaapi installation. Follow your distribution's instructions. If you're pretty sure you've done this correctly, create a new issue with the output of `vainfo` and if `wf-recorder -c h264_vaapi -d /dev/dri/card0` works."),
+        };
         let mut frames_rgb = hw_device_ctx
             .create_frame_ctx(capture_pixfmt, capture_w, capture_h)
             .unwrap();