Merge pull request #1312 from sdroege/gio-async-no-send

Don't require `Send` closures for GIO-style async functions
gtk-rs · Jan 24, 2022 · e0d8d8d · e0d8d8d
2 parents c174cf7 + 8be43af
commit e0d8d8d
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Showing 2 changed files with 33 additions and 7 deletions.
diff --git a/src/analysis/bounds.rs b/src/analysis/bounds.rs
@@ -133,10 +133,8 @@ impl Bounds {
                         }
                         let parameters = format_out_parameters(&out_parameters);
                         let error_type = find_error_type(env, function);
-                        type_string = format!(
-                            "FnOnce(Result<{}, {}>) + Send + 'static",
-                            parameters, error_type
-                        );
+                        type_string =
+                            format!("FnOnce(Result<{}, {}>) + 'static", parameters, error_type);
                         let bound_name = *self.unused.front().unwrap();
                         callback_info = Some(CallbackInfo {
                             callback_type: type_string.clone(),

diff --git a/src/codegen/function_body_chunk.rs b/src/codegen/function_body_chunk.rs
@@ -716,12 +716,30 @@ impl Builder {
         chunks: &mut Vec<Chunk>,
         trampoline: &AsyncTrampoline,
     ) {
+        chunks.push(Chunk::Custom(String::from(
+            r###"
+                let main_context = glib::MainContext::ref_thread_default();
+                let is_main_context_owner = main_context.is_owner();
+                let has_acquired_main_context = (!is_main_context_owner)
+                    .then(|| main_context.acquire().ok())
+                    .flatten();
+                assert!(
+                    is_main_context_owner || has_acquired_main_context.is_some(),
+                    "Async operations only allowed if the thread is owning the MainContext"
+                );
+        "###,
+        )));
+
         chunks.push(Chunk::Let {
             name: "user_data".to_string(),
             is_mut: false,
-            value: Box::new(Chunk::Custom("Box_::new(callback)".into())),
+            value: Box::new(Chunk::Custom(format!(
+                "Box_::new({}::new(callback))",
+                use_glib_type(env, "thread_guard::ThreadGuard")
+            ))),
             type_: Some(Box::new(Chunk::Custom(format!(
-                "Box_<{}>",
+                "Box_<{}<{}>>",
+                use_glib_type(env, "thread_guard::ThreadGuard"),
                 trampoline.bound_name
             )))),
         });
@@ -874,7 +892,17 @@ impl Builder {
             is_mut: false,
             value: Box::new(Chunk::Custom("Box_::from_raw(user_data as *mut _)".into())),
             type_: Some(Box::new(Chunk::Custom(format!(
-                "Box_<{}>",
+                "Box_<{}<{}>>",
+                use_glib_type(env, "thread_guard::ThreadGuard"),
+                trampoline.bound_name
+            )))),
+        });
+        body.push(Chunk::Let {
+            name: "callback".to_string(),
+            is_mut: false,
+            value: Box::new(Chunk::Custom("callback.into_inner()".into())),
+            type_: Some(Box::new(Chunk::Custom(format!(
+                "{}",
                 trampoline.bound_name
             )))),
         });