Workaround resource manager RwLock deadlock (#78). Closes https://github.com/iceiix/steven/issues/75

game.resource_manager, an Arc<RwLock<resources::Manager>>, sometimes hangs on write(), apparently a deadlock. Switch to using try_write() and continue the main game loop iteration if it fails, using the previous resource version and allow main loop tick if can't obtain a write lock. No warning is logged since this error is recoverable and seemingly intermittent. May not be the best fix, but unblocking iterative development.

src/main.rs

@@ -240,6 +240,7 @@ fn main() {
     };
     game.renderer.camera.pos = cgmath::Point3::new(0.5, 13.2, 0.5);
 
+    let mut last_resource_version = 0;
     while !game.should_close {
 
         let now = Instant::now();
@@ -250,10 +251,18 @@ fn main() {
         let (physical_width, physical_height) = window.get_inner_size().unwrap().to_physical(game.dpi_factor).into();
 
         let version = {
-            let mut res = game.resource_manager.write().unwrap();
-            res.tick(&mut resui, &mut ui_container, delta);
-            res.version()
+            let try_res = game.resource_manager.try_write();
+            if try_res.is_ok() {
+                let mut res = try_res.unwrap();
+                res.tick(&mut resui, &mut ui_container, delta);
+                res.version()
+            } else {
+                // TODO: why does game.resource_manager.write() sometimes deadlock?
+                //warn!("Failed to obtain mutable reference to resource manager!");
+                last_resource_version
+            }
         };
+        last_resource_version = version;
 
         let vsync_changed = *game.vars.get(settings::R_VSYNC);
         if vsync != vsync_changed {