Fix regressed wl_shm format choosing, delay it until formats are available

src/main.rs

@@ -59,7 +59,7 @@ pub struct State {
     pub layer_shell: LayerShell,
     pub viewporter: WpViewporter,
     pub wallpaper_dir: PathBuf,
-    pub shm_format: wl_shm::Format,
+    pub shm_format: Option<wl_shm::Format>,
     pub background_layers: Vec<BackgroundLayer>,
     pub compositor_connection_task: ConnectionTask,
     pub color_transform: ColorTransform,
@@ -67,6 +67,21 @@ pub struct State {
     pub gpu: Option<Gpu>,
 }
 
+impl State {
+    fn shm_format(&mut self) -> wl_shm::Format {
+        *self.shm_format.get_or_insert_with(|| {
+            let mut format = wl_shm::Format::Xrgb8888;
+            // Consume less gpu memory by using Bgr888 if available,
+            // fall back to the always supported Xrgb8888 otherwise
+            if self.shm.formats().contains(&wl_shm::Format::Bgr888) {
+                format = wl_shm::Format::Bgr888
+            }
+            debug!("Using shm format: {format:?}");
+            format
+        })
+    }
+}
+
 fn main() -> Result<(), ()> {
     run().map_err(|e| { error!("{e:#}"); })
 }
@@ -104,15 +119,12 @@ fn run() -> anyhow::Result<()> {
     let compositor_state = CompositorState::bind(&globals, &qh).unwrap();
     let layer_shell = LayerShell::bind(&globals, &qh).unwrap();
     let shm = Shm::bind(&globals, &qh).unwrap();
-    let mut shm_format = wl_shm::Format::Xrgb8888;
-    if cli.pixelformat != Some(PixelFormat::Baseline) {
-        // Consume less gpu memory by using Bgr888 if available,
-        // fall back to the always supported Xrgb8888 otherwise
-        if shm.formats().contains(&wl_shm::Format::Bgr888) {
-            shm_format = wl_shm::Format::Bgr888;
-        }
-    }
-    debug!("Using shm format: {shm_format:?}");
+    let shm_format = if cli.pixelformat == Some(PixelFormat::Baseline) {
+        debug!("Using shm format: {:?}", wl_shm::Format::Xrgb8888);
+        Some(wl_shm::Format::Xrgb8888)
+    } else {
+        None
+    };
 
     let registry_state = RegistryState::new(&globals);
 

src/wayland.rs

@@ -923,7 +923,8 @@ fn load_wallpapers(
             return
         }
     };
-    let shm_stride = match state.shm_format {
+    let shm_format = state.shm_format();
+    let shm_stride = match shm_format {
         wl_shm::Format::Xrgb8888 => width as usize * 4,
         wl_shm::Format::Bgr888 => {
             // Align buffer stride to both 4 and pixel format
@@ -1044,7 +1045,7 @@ fn load_wallpapers(
             width as u32,
             height as u32,
             shm_stride,
-            state.shm_format,
+            shm_format,
             state.color_transform,
             &mut resizer,
         ) {
@@ -1057,7 +1058,7 @@ fn load_wallpapers(
             width,
             height,
             shm_stride.try_into().unwrap(),
-            state.shm_format,
+            shm_format,
             (),
             qh,
         );