fix(macos): open files double-clicked in Finder (#1031)

macOS hands files opened from Finder, the Dock or open -a to the application delegate's application:openURLs:, which winit's delegate lacks, so AppKit showed "SolidCraft cannot open files in the SolidCraft design format". open_documents adds that method to the delegate's class before launch finishes and queues the paths for the UI, which opens them like files named on the command line.

This is the one place SolidCraft's own code uses unsafe: the app crate denies unsafe_code instead of forbidding it, and only the two macOS-only functions in open_documents.rs allow it, with the reason documented there and in AGENTS.md. Adapted from VectorCraft (see ATTRIBUTION.md).

Closes #997.

apps/solidcraft/src/main.rs

@@ -10,12 +10,14 @@
 //! See `solidcraft_ui_egui::control` and docs/control-protocol.md.
 #![cfg_attr(all(target_os = "windows", not(debug_assertions)), windows_subsystem = "windows")]
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
-#![forbid(unsafe_code)]
+#![deny(unsafe_code)]
 
 #[cfg(not(target_os = "macos"))]
 #[path = "../../../assets/icons/app/shared/source/app_icon.rs"]
 mod app_icon;
 mod control_server;
+#[cfg(target_os = "macos")]
+mod open_documents;
 #[cfg(any(target_os = "windows", target_os = "linux"))]
 mod space_mouse;
 
@@ -38,6 +40,10 @@ impl eframe::App for App {
             ctx.send_viewport_cmd(egui::ViewportCommand::CancelClose);
             solidcraft_ui_egui::documents::request_quit(&mut self.solve);
         }
+        #[cfg(target_os = "macos")]
+        for f in open_documents::take() {
+            self.solve.open_path_async(&f);
+        }
         self.solve.logic(ctx);
         #[cfg(any(target_os = "windows", target_os = "linux"))]
         self.space_mouse.tick(&mut self.solve, ctx);
@@ -286,6 +292,9 @@ fn main() -> eframe::Result {
             b.with_x11();
         }));
     }
+    // Files opened from Finder and the Dock arrive as events, not arguments.
+    #[cfg(target_os = "macos")]
+    open_documents::install();
     let result = eframe::run_native(
         "SolidCraft",
         options,
@@ -320,6 +329,12 @@ fn main() -> eframe::Result {
                 app.session.mark_saved();
                 app.session.undo.clear();
             }
+            // A launch from Finder: its files arrived before the window.
+            #[cfg(target_os = "macos")]
+            let files = {
+                open_documents::set_ui(&cc.egui_ctx);
+                [files, open_documents::take()].concat()
+            };
             for f in &files {
                 app.open_path_async(f);
             }