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

Cargo.lock

@@ -3068,6 +3068,7 @@ dependencies = [
  "serde_json",
  "solvecraft-engine",
  "solvecraft-ui-egui",
+ "winit",
 ]
 
 [[package]]

apps/solvecraft/Cargo.toml

@@ -18,3 +18,6 @@ egui = { workspace = true }
 serde_json = { workspace = true }
 log = { workspace = true }
 rfd = { workspace = true }
+
+[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
+winit = { version = "0.30", default-features = false, features = ["x11"] }

apps/solvecraft/src/main.rs

@@ -132,6 +132,17 @@ fn main() -> eframe::Result {
         multisampling: samples,
         ..Default::default()
     };
+    let mut options = options;
+    #[cfg(all(unix, not(target_os = "macos")))]
+    // 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; SOLVECRAFT_WAYLAND=1
+    // keeps the native Wayland backend.
+    if std::env::var_os("DISPLAY").is_some() && std::env::var_os("SOLVECRAFT_WAYLAND").is_none() {
+        options.event_loop_builder = Some(Box::new(|b| {
+            use winit::platform::x11::EventLoopBuilderExtX11;
+            b.with_x11();
+        }));
+    }
     eframe::run_native(
         "SolveCraft",
         options,