💥 Redo all higher order template functions

This does what we did for a few functions in the last few commits for
every function. We now use either the `std::invocable` concept or our
own `invocable_returning` concept wherever possible to make sure we pass
function types to these template functions, since constraint errors are
a lot more readable than template deduction errors. And instead of
having to specify the return type as a template argument, we now just
use `std::invoke_result_t<F>` instead. The VST3 message handling
functions are still using the good old `typename F` since those are
overloaded polymorphic functions. This was also a good moment to modify
`AdHocSocketHandler::send()` to allow functions returning void (this got
rid of an old fixme where we had to return some dummy value from a
function instead of just not returning anything).

src/wine-host/bridges/vst3.cpp

@@ -226,7 +226,7 @@ void Vst3Bridge::run() {
                 // as well do the same thing with `setState()`. See below.
                 // NOTE: We also try to handle mutual recursion here, in case
                 //       this happens during a resize
-                return do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                return do_mutual_recursion_on_gui_thread([&]() -> tresult {
                     // This same function is defined in both `IComponent` and
                     // `IEditController`, so the host is calling one or the
                     // other
@@ -246,7 +246,7 @@ void Vst3Bridge::run() {
                 // NOTE: This also requires mutual recursion because REAPER will
                 //       call `getState()` while opening a popup menu
                 const tresult result =
-                    do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                    do_mutual_recursion_on_gui_thread([&]() -> tresult {
                         // This same function is defined in both `IComponent`
                         // and `IEditController`, so the host is calling one or
                         // the other
@@ -350,7 +350,7 @@ void Vst3Bridge::run() {
                 //       much slower in Ardour, but there's no other non-hacky
                 //       solution for this (and bypassing Ardour's connection
                 //       proxies sort of goes against the idea behind yabridge)
-                return do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                return do_mutual_recursion_on_gui_thread([&]() -> tresult {
                     return object_instances[request.instance_id]
                         .connection_point->notify(
                             request.message_ptr.get_original());
@@ -435,7 +435,7 @@ void Vst3Bridge::run() {
                 //       mutually recursive because the host will immediately
                 //       relay the parameter change the plugin has just
                 //       announced.
-                return do_mutual_recursion_on_off_thread<tresult>([&]() {
+                return do_mutual_recursion_on_off_thread([&]() -> tresult {
                     return object_instances[request.instance_id]
                         .edit_controller->setParamNormalized(request.id,
                                                              request.value);
@@ -782,7 +782,7 @@ void Vst3Bridge::run() {
                 // not run from the GUI thread
                 Steinberg::ViewRect size{};
                 const tresult result =
-                    do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                    do_mutual_recursion_on_gui_thread([&]() -> tresult {
                         return object_instances[request.owner_instance_id]
                             .plug_view_instance->plug_view->getSize(&size);
                     });
@@ -800,7 +800,7 @@ void Vst3Bridge::run() {
                 //       code on the same thread that's currently waiting for a
                 //       response to the message it sent. See the docstring of
                 //       this function for more information on how this works.
-                return do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                return do_mutual_recursion_on_gui_thread([&]() -> tresult {
                     return object_instances[request.owner_instance_id]
                         .plug_view_instance->plug_view->onSize(
                             &request.new_size);
@@ -847,7 +847,7 @@ void Vst3Bridge::run() {
                 -> YaPlugView::CanResize::Response {
                 // To prevent weird behaviour we'll perform all size related
                 // functions from the GUI thread, including this one
-                return do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                return do_mutual_recursion_on_gui_thread([&]() -> tresult {
                     return object_instances[request.owner_instance_id]
                         .plug_view_instance->plug_view->canResize();
                 });
@@ -855,7 +855,7 @@ void Vst3Bridge::run() {
             [&](YaPlugView::CheckSizeConstraint& request)
                 -> YaPlugView::CheckSizeConstraint::Response {
                 const tresult result =
-                    do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                    do_mutual_recursion_on_gui_thread([&]() -> tresult {
                         return object_instances[request.owner_instance_id]
                             .plug_view_instance->plug_view->checkSizeConstraint(
                                 &request.rect);
@@ -1032,7 +1032,7 @@ void Vst3Bridge::run() {
                 //       plugins (like TEOTE) require this to be called from the
                 //       same thread when that happens.
                 const tresult result =
-                    do_mutual_recursion_on_off_thread<tresult>([&]() {
+                    do_mutual_recursion_on_off_thread([&]() -> tresult {
                         return object_instances[request.instance_id]
                             .unit_info->getProgramName(
                                 request.list_id, request.program_index, name);
@@ -1325,8 +1325,8 @@ size_t Vst3Bridge::register_object_instance(
                         //       handled from the same thread to prevent
                         //       deadlocks caused by mutually recursive function
                         //       calls.
-                        return do_mutual_recursion_on_off_thread<tresult>(
-                            [&]() {
+                        return do_mutual_recursion_on_off_thread(
+                            [&]() -> tresult {
                                 return object_instances[request.instance_id]
                                     .component->setActive(request.state);
                             });

src/wine-host/bridges/vst3.h

@@ -294,12 +294,9 @@ class Vst3Bridge : public HostBridge {
      * run on the UI thread through `main_context` as usual.
      *
      * @see Vst3Bridge::send_mutually_recursive_message
-     *
-     * TODO: Refactor these two functions, `run_gui_task()`, and
-     *       `main_context.run_in_context` to use `std::invocation_result_t`
      */
-    template <typename T, typename F>
-    T do_mutual_recursion_on_gui_thread(F&& fn) {
+    template <std::invocable F>
+    std::invoke_result_t<F> do_mutual_recursion_on_gui_thread(F&& fn) {
         // If the above function is currently being called from some thread,
         // then we'll call `fn` from that same thread. Otherwise we'll just
         // submit it to the main IO context.
@@ -317,8 +314,8 @@ class Vst3Bridge : public HostBridge {
      *
      * @see Vst3Bridge::do_mutual_recursion_on_gui_thread
      */
-    template <typename T, typename F>
-    T do_mutual_recursion_on_off_thread(F&& fn) {
+    template <std::invocable F>
+    std::invoke_result_t<F> do_mutual_recursion_on_off_thread(F&& fn) {
         return mutual_recursion.handle(std::forward<F>(fn));
     }