Linux: default to XWayland for file drag-and-drop on Wayland desktops

Cargo.lock

@@ -2989,6 +2989,7 @@ dependencies = [
  "muda",
  "rfd",
  "serde_json",
+ "winit",
  "winresource",
 ]
 

apps/lightcraft/Cargo.toml

@@ -32,6 +32,9 @@ log = { workspace = true }
 # Icon + VERSIONINFO for lightcraft.exe; build.rs only uses it when targeting Windows.
 winresource = "0.1"
 
+[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
+winit = { version = "0.30", default-features = false, features = ["x11"] }
+
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 rfd = { workspace = true }
 

apps/lightcraft/src/main.rs

@@ -754,6 +754,18 @@ fn main() -> eframe::Result {
     };
     // the app's copy: `log_file` is still named in the message of a start that fails
     let app_log_file = log_file.clone();
+    #[cfg(all(unix, not(target_os = "macos")))]
+    let mut options = options;
+    // winit has no file drag-and-drop on Wayland (only on X11), so dropping files from the file
+    // manager showed a "no" cursor. Run through XWayland when it's there; LIGHTCRAFT_WAYLAND=1
+    // keeps the native Wayland backend.
+    #[cfg(all(unix, not(target_os = "macos")))]
+    if std::env::var_os("DISPLAY").is_some() && std::env::var_os("LIGHTCRAFT_WAYLAND").is_none() {
+        options.event_loop_builder = Some(Box::new(|b| {
+            use winit::platform::x11::EventLoopBuilderExtX11;
+            b.with_x11();
+        }));
+    }
     let started = eframe::run_native(
         "LightCraft",
         options,