Continue work to separate idle and uiIdle

source/backend/CarlaBackend.h

@@ -164,9 +164,9 @@ static const uint PLUGIN_CAN_PANNING = 0x080;
 static const uint PLUGIN_NEEDS_FIXED_BUFFERS = 0x100;
 
 /*!
- * Plugin needs all UI events in a single/main thread.
+ * Plugin needs to receive all UI events in the main thread.
  */
-static const uint PLUGIN_NEEDS_SINGLE_THREAD = 0x200;
+static const uint PLUGIN_NEEDS_UI_MAIN_THREAD = 0x200;
 
 /** @} */
 

source/backend/CarlaPlugin.hpp

@@ -665,7 +665,7 @@ public:
 
     /*!
      * Idle function (non-UI), called at regular intervals.
-     * This function is called from the main thread only if PLUGIN_USES_SINGLE_THREAD is set.
+     * @note: This function is NOT called from the main thread.
      */
     virtual void idle();
 
@@ -729,15 +729,6 @@ public:
     void sendMidiAllNotesOffToCallback();
 #endif
 
-    // -------------------------------------------------------------------
-    // Post-poned events
-
-    /*!
-     * Process all the post-poned events.
-     * This function is called from the main thread if PLUGIN_USES_SINGLE_THREAD is set.
-     */
-    void postRtEventsRun();
-
     // -------------------------------------------------------------------
     // UI Stuff
 
@@ -749,33 +740,38 @@ public:
 
     /*!
      * UI idle function, called at regular intervals.
-     * This function is called from the main thread only if PLUGIN_USES_SINGLE_THREAD is set.
+     * This function is only called from the main thread if PLUGIN_NEEDS_UI_MAIN_THREAD is set.
      * @note This function may sometimes be called even if the UI is not visible yet.
      */
     virtual void uiIdle();
 
     /*!
      * Tell the UI a parameter has changed.
+     * @see uiIdle
      */
     virtual void uiParameterChange(const uint32_t index, const float value) noexcept;
 
     /*!
      * Tell the UI the current program has changed.
+     * @see uiIdle
      */
     virtual void uiProgramChange(const uint32_t index) noexcept;
 
     /*!
      * Tell the UI the current midi program has changed.
+     * @see uiIdle
      */
     virtual void uiMidiProgramChange(const uint32_t index) noexcept;
 
     /*!
      * Tell the UI a note has been pressed.
+     * @see uiIdle
      */
     virtual void uiNoteOn(const uint8_t channel, const uint8_t note, const uint8_t velo) noexcept;
 
     /*!
      * Tell the UI a note has been released.
+     * @see uiIdle
      */
     virtual void uiNoteOff(const uint8_t channel, const uint8_t note) noexcept;
 

source/backend/CarlaUtils.cpp

@@ -431,7 +431,7 @@ const CarlaCachedPluginInfo* carla_get_cached_plugin_info(CB::PluginType ptype,
         if (desc->hints & NATIVE_PLUGIN_NEEDS_FIXED_BUFFERS)
             info.hints |= CB::PLUGIN_NEEDS_FIXED_BUFFERS;
         if (desc->hints & NATIVE_PLUGIN_NEEDS_SINGLE_THREAD)
-            info.hints |= CB::PLUGIN_NEEDS_SINGLE_THREAD;
+            info.hints |= CB::PLUGIN_NEEDS_UI_MAIN_THREAD;
 
         info.audioIns      = desc->audioIns;
         info.audioOuts     = desc->audioOuts;
@@ -460,10 +460,8 @@ const CarlaCachedPluginInfo* carla_get_cached_plugin_info(CB::PluginType ptype,
         // features
         info.hints = 0x0;
 
-#if 0
-        if (lilvPlugin.get_uis().size() > 0 || lilvPlugin.get_modgui_resources_directory().as_uri() != nullptr)
+        if (lilvPlugin.get_uis().size() > 0 /*|| lilvPlugin.get_modgui_resources_directory().as_uri() != nullptr*/)
             info.hints |= CB::PLUGIN_HAS_CUSTOM_UI;
-#endif
 
         {
             Lilv::Nodes lilvFeatureNodes(lilvPlugin.get_supported_features());

source/backend/engine/CarlaEngine.cpp

@@ -294,18 +294,11 @@ void CarlaEngine::idle() noexcept
         {
             const uint hints(plugin->getHints());
 
-            if (hints & PLUGIN_NEEDS_SINGLE_THREAD)
+            if ((hints & PLUGIN_HAS_CUSTOM_UI) != 0 && (hints & PLUGIN_NEEDS_UI_MAIN_THREAD) != 0)
             {
                 try {
-                    plugin->idle();
-                } CARLA_SAFE_EXCEPTION_CONTINUE("Plugin idle");
-
-                if (hints & PLUGIN_HAS_CUSTOM_UI)
-                {
-                    try {
-                        plugin->uiIdle();
-                    } CARLA_SAFE_EXCEPTION_CONTINUE("Plugin uiIdle");
-                }
+                    plugin->uiIdle();
+                } CARLA_SAFE_EXCEPTION_CONTINUE("Plugin uiIdle");
             }
         }
     }

source/backend/engine/CarlaEngineThread.cpp

@@ -47,17 +47,16 @@ void CarlaEngineThread::run() noexcept
 #endif
     carla_debug("CarlaEngineThread::run()");
 
-    bool needsSingleThread, needsUiUpdates, oscRegisted;
     float value;
-#ifdef BUILD_BRIDGE
-    oscRegisted = false;
 
+#ifdef BUILD_BRIDGE
     for (; /*kEngine->isRunning() &&*/ ! shouldThreadExit();)
     {
+        const bool oscRegisted = false;
 #else
     for (; kEngine->isRunning() && ! shouldThreadExit();)
     {
-        oscRegisted = kEngine->isOscControlRegistered();
+        const bool oscRegisted = kEngine->isOscControlRegistered();
 #endif
 
         for (uint i=0, count = kEngine->getCurrentPluginCount(); i < count; ++i)
@@ -67,20 +66,20 @@ void CarlaEngineThread::run() noexcept
             CARLA_SAFE_ASSERT_CONTINUE(plugin != nullptr && plugin->isEnabled());
             CARLA_SAFE_ASSERT_UINT2(i == plugin->getId(), i, plugin->getId());
 
-            needsSingleThread = (plugin->getHints() & PLUGIN_NEEDS_SINGLE_THREAD);
-            needsUiUpdates    = (plugin->getHints() & PLUGIN_HAS_CUSTOM_UI) && ! needsSingleThread;
+            const uint hints(plugin->getHints());
+            const bool updateUI((hints & PLUGIN_HAS_CUSTOM_UI) != 0 && (hints & PLUGIN_NEEDS_UI_MAIN_THREAD) == 0);
 
             // -----------------------------------------------------------
-            // Process postponed events
+            // DSP Idle
 
-            if (! needsSingleThread)
-            {
-                try {
-                    plugin->idle();
-                } CARLA_SAFE_EXCEPTION("idle()")
-            }
+            try {
+                plugin->idle();
+            } CARLA_SAFE_EXCEPTION("idle()")
+
+            // -----------------------------------------------------------
+            // Post-poned events
 
-            if (oscRegisted || needsUiUpdates)
+            if (oscRegisted || updateUI)
             {
                 // -------------------------------------------------------
                 // Update parameter outputs
@@ -98,11 +97,11 @@ void CarlaEngineThread::run() noexcept
                         kEngine->oscSend_control_set_parameter_value(i, static_cast<int32_t>(j), value);
 #endif
                     // Update UI
-                    if (needsUiUpdates)
+                    if (updateUI)
                         plugin->uiParameterChange(j, value);
                 }
 
-                if (needsUiUpdates)
+                if (updateUI)
                 {
                     try {
                         plugin->uiIdle();

source/backend/plugin/CarlaPlugin.cpp

@@ -1363,7 +1363,181 @@ void CarlaPlugin::idle()
     if (! pData->enabled)
         return;
 
-    postRtEventsRun();
+    const bool hasUI(pData->hints & PLUGIN_HAS_CUSTOM_UI);
+    const bool needsUiMainThread(pData->hints & PLUGIN_NEEDS_UI_MAIN_THREAD);
+#ifndef BUILD_BRIDGE
+    const bool sendOsc(pData->engine->isOscControlRegistered());
+#endif
+
+    const CarlaMutexLocker sl(pData->postRtEvents.mutex);
+
+    for (RtLinkedList<PluginPostRtEvent>::Itenerator it = pData->postRtEvents.data.begin(); it.valid(); it.next())
+    {
+        const PluginPostRtEvent& event(it.getValue(kPluginPostRtEventFallback));
+        CARLA_SAFE_ASSERT_CONTINUE(event.type != kPluginPostRtEventNull);
+
+        switch (event.type)
+        {
+        case kPluginPostRtEventNull: {
+        } break;
+
+        case kPluginPostRtEventDebug: {
+            pData->engine->callback(ENGINE_CALLBACK_DEBUG, pData->id, event.value1, event.value2, event.value3, nullptr);
+        } break;
+
+        case kPluginPostRtEventParameterChange: {
+            // Update UI
+            if (event.value1 >= 0 && hasUI)
+            {
+                if (needsUiMainThread)
+                    pData->postUiEvents.append(event);
+                else
+                    uiParameterChange(static_cast<uint32_t>(event.value1), event.value3);
+            }
+
+            if (event.value2 != 1)
+            {
+#ifndef BUILD_BRIDGE
+                // Update OSC control client
+                if (sendOsc)
+                    pData->engine->oscSend_control_set_parameter_value(pData->id, event.value1, event.value3);
+#endif
+                // Update Host
+                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, event.value1, 0, event.value3, nullptr);
+            }
+        } break;
+
+        case kPluginPostRtEventProgramChange: {
+            // Update UI
+            if (event.value1 >= 0 && hasUI)
+            {
+                if (needsUiMainThread)
+                    pData->postUiEvents.append(event);
+                else
+                    uiProgramChange(static_cast<uint32_t>(event.value1));
+            }
+
+            // Update param values
+            for (uint32_t j=0; j < pData->param.count; ++j)
+            {
+                const float paramDefault(pData->param.ranges[j].def);
+                const float paramValue(getParameterValue(j));
+
+#ifndef BUILD_BRIDGE
+                if (sendOsc)
+                {
+                    pData->engine->oscSend_control_set_parameter_value(pData->id, static_cast<int32_t>(j), paramValue);
+                    pData->engine->oscSend_control_set_default_value(pData->id, j, paramDefault);
+                }
+#endif
+                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, static_cast<int>(j), 0, paramValue, nullptr);
+                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_DEFAULT_CHANGED, pData->id, static_cast<int>(j), 0, paramDefault, nullptr);
+            }
+
+#ifndef BUILD_BRIDGE
+            // Update OSC control client
+            if (sendOsc)
+                pData->engine->oscSend_control_set_current_program(pData->id, event.value1);
+#endif
+            // Update Host
+            pData->engine->callback(ENGINE_CALLBACK_PROGRAM_CHANGED, pData->id, event.value1, 0, 0.0f, nullptr);
+
+        } break;
+
+        case kPluginPostRtEventMidiProgramChange: {
+            // Update UI
+            if (event.value1 >= 0 && hasUI)
+            {
+                if (needsUiMainThread)
+                    pData->postUiEvents.append(event);
+                else
+                    uiMidiProgramChange(static_cast<uint32_t>(event.value1));
+            }
+
+            // Update param values
+            for (uint32_t j=0; j < pData->param.count; ++j)
+            {
+                const float paramDefault(pData->param.ranges[j].def);
+                const float paramValue(getParameterValue(j));
+
+#ifndef BUILD_BRIDGE
+                if (sendOsc)
+                {
+                    pData->engine->oscSend_control_set_parameter_value(pData->id, static_cast<int32_t>(j), paramValue);
+                    pData->engine->oscSend_control_set_default_value(pData->id, j, paramDefault);
+                }
+#endif
+                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, static_cast<int>(j), 0, paramValue, nullptr);
+                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_DEFAULT_CHANGED, pData->id, static_cast<int>(j), 0, paramDefault, nullptr);
+            }
+
+#ifndef BUILD_BRIDGE
+            // Update OSC control client
+            if (sendOsc)
+                pData->engine->oscSend_control_set_current_midi_program(pData->id, event.value1);
+#endif
+            // Update Host
+            pData->engine->callback(ENGINE_CALLBACK_MIDI_PROGRAM_CHANGED, pData->id, event.value1, 0, 0.0f, nullptr);
+
+        } break;
+
+        case kPluginPostRtEventNoteOn: {
+            CARLA_SAFE_ASSERT_BREAK(event.value1 >= 0 && event.value1 < MAX_MIDI_CHANNELS);
+            CARLA_SAFE_ASSERT_BREAK(event.value2 >= 0 && event.value2 < MAX_MIDI_NOTE);
+            CARLA_SAFE_ASSERT_BREAK(event.value3 >= 0 && event.value3 < MAX_MIDI_VALUE);
+
+            const uint8_t channel  = static_cast<uint8_t>(event.value1);
+            const uint8_t note     = static_cast<uint8_t>(event.value2);
+            const uint8_t velocity = uint8_t(event.value3);
+
+            // Update UI
+            if (hasUI)
+            {
+                if (needsUiMainThread)
+                    pData->postUiEvents.append(event);
+                else
+                    uiNoteOn(channel, note, velocity);
+            }
+
+#ifndef BUILD_BRIDGE
+            // Update OSC control client
+            if (sendOsc)
+                pData->engine->oscSend_control_note_on(pData->id, channel, note, velocity);
+#endif
+            // Update Host
+            pData->engine->callback(ENGINE_CALLBACK_NOTE_ON, pData->id, event.value1, event.value2, event.value3, nullptr);
+
+        } break;
+
+        case kPluginPostRtEventNoteOff: {
+            CARLA_SAFE_ASSERT_BREAK(event.value1 >= 0 && event.value1 < MAX_MIDI_CHANNELS);
+            CARLA_SAFE_ASSERT_BREAK(event.value2 >= 0 && event.value2 < MAX_MIDI_NOTE);
+
+            const uint8_t channel = static_cast<uint8_t>(event.value1);
+            const uint8_t note    = static_cast<uint8_t>(event.value2);
+
+            // Update UI
+            if (hasUI)
+            {
+                if (needsUiMainThread)
+                    pData->postUiEvents.append(event);
+                else
+                    uiNoteOff(channel, note);
+            }
+
+#ifndef BUILD_BRIDGE
+            // Update OSC control client
+            if (sendOsc)
+                pData->engine->oscSend_control_note_off(pData->id, channel, note);
+#endif
+            // Update Host
+            pData->engine->callback(ENGINE_CALLBACK_NOTE_OFF, pData->id, event.value1, event.value2, 0.0f, nullptr);
+
+        } break;
+        }
+    }
+
+    pData->postRtEvents.data.clear();
 }
 
 bool CarlaPlugin::tryLock(const bool forcedOffline) noexcept
@@ -1575,174 +1749,60 @@ void CarlaPlugin::sendMidiAllNotesOffToCallback()
 #endif
 
 // -------------------------------------------------------------------
-// Post-poned events
+// UI Stuff
 
-void CarlaPlugin::postRtEventsRun()
+void CarlaPlugin::showCustomUI(const bool)
 {
-    const CarlaMutexLocker sl(pData->postRtEvents.mutex);
-#ifndef BUILD_BRIDGE
-    const bool sendOsc(pData->engine->isOscControlRegistered());
-#endif
+    CARLA_SAFE_ASSERT(false);
+}
 
-    for (RtLinkedList<PluginPostRtEvent>::Itenerator it = pData->postRtEvents.data.begin(); it.valid(); it.next())
+void CarlaPlugin::uiIdle()
+{
+    if (pData->hints & PLUGIN_NEEDS_UI_MAIN_THREAD)
     {
-        const PluginPostRtEvent& event(it.getValue(kPluginPostRtEventFallback));
-        CARLA_SAFE_ASSERT_CONTINUE(event.type != kPluginPostRtEventNull);
-
-        switch (event.type)
+        // Update parameter outputs
+        for (uint32_t i=0; i < pData->param.count; ++i)
         {
-        case kPluginPostRtEventNull: {
-        } break;
-
-        case kPluginPostRtEventDebug: {
-            pData->engine->callback(ENGINE_CALLBACK_DEBUG, pData->id, event.value1, event.value2, event.value3, nullptr);
-        } break;
-
-        case kPluginPostRtEventParameterChange: {
-            // Update UI
-            if (event.value1 >= 0 && (pData->hints & PLUGIN_HAS_CUSTOM_UI) != 0)
-                uiParameterChange(static_cast<uint32_t>(event.value1), event.value3);
+            if (pData->param.data[i].type == PARAMETER_OUTPUT)
+                uiParameterChange(i, getParameterValue(i));
+        }
 
-            if (event.value2 != 1)
-            {
-#ifndef BUILD_BRIDGE
-                // Update OSC control client
-                if (sendOsc)
-                    pData->engine->oscSend_control_set_parameter_value(pData->id, event.value1, event.value3);
-#endif
-                // Update Host
-                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, event.value1, 0, event.value3, nullptr);
-            }
-        } break;
+        const CarlaMutexLocker sl(pData->postUiEvents.mutex);
 
-        case kPluginPostRtEventProgramChange: {
-            // Update UI
-            if (event.value1 >= 0 && (pData->hints & PLUGIN_HAS_CUSTOM_UI) != 0)
-                uiProgramChange(static_cast<uint32_t>(event.value1));
+        for (LinkedList<PluginPostRtEvent>::Itenerator it = pData->postUiEvents.data.begin(); it.valid(); it.next())
+        {
+            const PluginPostRtEvent& event(it.getValue(kPluginPostRtEventFallback));
+            CARLA_SAFE_ASSERT_CONTINUE(event.type != kPluginPostRtEventNull);
 
-            // Update param values
-            for (uint32_t j=0; j < pData->param.count; ++j)
+            switch (event.type)
             {
-                const float paramDefault(pData->param.ranges[j].def);
-                const float paramValue(getParameterValue(j));
-
-#ifndef BUILD_BRIDGE
-                if (sendOsc)
-                {
-                    pData->engine->oscSend_control_set_parameter_value(pData->id, static_cast<int32_t>(j), paramValue);
-                    pData->engine->oscSend_control_set_default_value(pData->id, j, paramDefault);
-                }
-#endif
-                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, static_cast<int>(j), 0, paramValue, nullptr);
-                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_DEFAULT_CHANGED, pData->id, static_cast<int>(j), 0, paramDefault, nullptr);
-            }
+            case kPluginPostRtEventNull:
+            case kPluginPostRtEventDebug:
+                break;
 
-#ifndef BUILD_BRIDGE
-            // Update OSC control client
-            if (sendOsc)
-                pData->engine->oscSend_control_set_current_program(pData->id, event.value1);
-#endif
-            // Update Host
-            pData->engine->callback(ENGINE_CALLBACK_PROGRAM_CHANGED, pData->id, event.value1, 0, 0.0f, nullptr);
+            case kPluginPostRtEventParameterChange:
+                uiParameterChange(static_cast<uint32_t>(event.value1), event.value3);
+                break;
 
-        } break;
+            case kPluginPostRtEventProgramChange:
+                uiProgramChange(static_cast<uint32_t>(event.value1));
+                break;
 
-        case kPluginPostRtEventMidiProgramChange: {
-            // Update UI
-            if (event.value1 >= 0 && (pData->hints & PLUGIN_HAS_CUSTOM_UI) != 0)
+            case kPluginPostRtEventMidiProgramChange:
                 uiMidiProgramChange(static_cast<uint32_t>(event.value1));
+                break;
 
-            // Update param values
-            for (uint32_t j=0; j < pData->param.count; ++j)
-            {
-                const float paramDefault(pData->param.ranges[j].def);
-                const float paramValue(getParameterValue(j));
+            case kPluginPostRtEventNoteOn:
+                uiNoteOn(static_cast<uint8_t>(event.value1), static_cast<uint8_t>(event.value2), uint8_t(event.value3));
+                break;
 
-#ifndef BUILD_BRIDGE
-                if (sendOsc)
-                {
-                    pData->engine->oscSend_control_set_parameter_value(pData->id, static_cast<int32_t>(j), paramValue);
-                    pData->engine->oscSend_control_set_default_value(pData->id, j, paramDefault);
-                }
-#endif
-                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_VALUE_CHANGED, pData->id, static_cast<int>(j), 0, paramValue, nullptr);
-                pData->engine->callback(ENGINE_CALLBACK_PARAMETER_DEFAULT_CHANGED, pData->id, static_cast<int>(j), 0, paramDefault, nullptr);
+            case kPluginPostRtEventNoteOff:
+                uiNoteOff(static_cast<uint8_t>(event.value1), static_cast<uint8_t>(event.value2));
+                break;
             }
-
-#ifndef BUILD_BRIDGE
-            // Update OSC control client
-            if (sendOsc)
-                pData->engine->oscSend_control_set_current_midi_program(pData->id, event.value1);
-#endif
-            // Update Host
-            pData->engine->callback(ENGINE_CALLBACK_MIDI_PROGRAM_CHANGED, pData->id, event.value1, 0, 0.0f, nullptr);
-
-        } break;
-
-        case kPluginPostRtEventNoteOn: {
-            CARLA_SAFE_ASSERT_BREAK(event.value1 >= 0 && event.value1 < MAX_MIDI_CHANNELS);
-            CARLA_SAFE_ASSERT_BREAK(event.value2 >= 0 && event.value2 < MAX_MIDI_NOTE);
-            CARLA_SAFE_ASSERT_BREAK(event.value3 >= 0 && event.value3 < MAX_MIDI_VALUE);
-
-            const uint8_t channel  = static_cast<uint8_t>(event.value1);
-            const uint8_t note     = static_cast<uint8_t>(event.value2);
-            const uint8_t velocity = uint8_t(event.value3);
-
-            // Update UI
-            if (pData->hints & PLUGIN_HAS_CUSTOM_UI)
-                uiNoteOn(channel, note, velocity);
-
-#ifndef BUILD_BRIDGE
-            // Update OSC control client
-            if (sendOsc)
-                pData->engine->oscSend_control_note_on(pData->id, channel, note, velocity);
-#endif
-            // Update Host
-            pData->engine->callback(ENGINE_CALLBACK_NOTE_ON, pData->id, event.value1, event.value2, event.value3, nullptr);
-
-        } break;
-
-        case kPluginPostRtEventNoteOff: {
-            CARLA_SAFE_ASSERT_BREAK(event.value1 >= 0 && event.value1 < MAX_MIDI_CHANNELS);
-            CARLA_SAFE_ASSERT_BREAK(event.value2 >= 0 && event.value2 < MAX_MIDI_NOTE);
-
-            const uint8_t channel = static_cast<uint8_t>(event.value1);
-            const uint8_t note    = static_cast<uint8_t>(event.value2);
-
-            // Update UI
-            if (pData->hints & PLUGIN_HAS_CUSTOM_UI)
-                uiNoteOff(channel, note);
-
-#ifndef BUILD_BRIDGE
-            // Update OSC control client
-            if (sendOsc)
-                pData->engine->oscSend_control_note_off(pData->id, channel, note);
-#endif
-            // Update Host
-            pData->engine->callback(ENGINE_CALLBACK_NOTE_OFF, pData->id, event.value1, event.value2, 0.0f, nullptr);
-
-        } break;
         }
-    }
-
-    pData->postRtEvents.data.clear();
-}
-
-// -------------------------------------------------------------------
-// UI Stuff
 
-void CarlaPlugin::showCustomUI(const bool)
-{
-    CARLA_SAFE_ASSERT(false);
-}
-
-void CarlaPlugin::uiIdle()
-{
-    // Update parameter outputs if needed
-    for (uint32_t i=0; i < pData->param.count; ++i)
-    {
-        if (pData->param.data[i].type == PARAMETER_OUTPUT)
-            uiParameterChange(i, getParameterValue(i));
+        pData->postUiEvents.data.clear();
     }
 
     if (pData->transientTryCounter == 0)

source/backend/plugin/CarlaPluginInternal.cpp

@@ -421,6 +421,32 @@ void CarlaPlugin::ProtectedData::PostRtEvents::clear() noexcept
     mutex.unlock();
 }
 
+// -----------------------------------------------------------------------
+// ProtectedData::PostUiEvents
+
+CarlaPlugin::ProtectedData::PostUiEvents::PostUiEvents() noexcept
+    : mutex(),
+      data() {}
+
+CarlaPlugin::ProtectedData::PostUiEvents::~PostUiEvents() noexcept
+{
+    clear();
+}
+
+void CarlaPlugin::ProtectedData::PostUiEvents::append(const PluginPostRtEvent& e) noexcept
+{
+    mutex.lock();
+    data.append(e);
+    mutex.unlock();
+}
+
+void CarlaPlugin::ProtectedData::PostUiEvents::clear() noexcept
+{
+    mutex.lock();
+    data.clear();
+    mutex.unlock();
+}
+
 #ifndef BUILD_BRIDGE
 // -----------------------------------------------------------------------
 // ProtectedData::PostProc
@@ -471,6 +497,7 @@ CarlaPlugin::ProtectedData::ProtectedData(CarlaEngine* const eng, const uint idx
       stateSave(),
       extNotes(),
       postRtEvents(),
+      postUiEvents(),
 #ifndef BUILD_BRIDGE
       postProc(),
 #endif

source/backend/plugin/CarlaPluginInternal.hpp

@@ -283,6 +283,19 @@ struct CarlaPlugin::ProtectedData {
 
     } postRtEvents;
 
+    struct PostUiEvents {
+        CarlaMutex mutex;
+        LinkedList<PluginPostRtEvent> data;
+
+        PostUiEvents() noexcept;
+        ~PostUiEvents() noexcept;
+        void append(const PluginPostRtEvent& event) noexcept;
+        void clear() noexcept;
+
+        CARLA_DECLARE_NON_COPY_STRUCT(PostUiEvents)
+
+    } postUiEvents;
+
 #ifndef BUILD_BRIDGE
     struct PostProc {
         float dryWet;

source/backend/plugin/CarlaPluginJuce.cpp

@@ -532,7 +532,7 @@ public:
         if (fInstance->hasEditor())
         {
             pData->hints |= PLUGIN_HAS_CUSTOM_UI;
-            pData->hints |= PLUGIN_NEEDS_SINGLE_THREAD;
+            pData->hints |= PLUGIN_NEEDS_UI_MAIN_THREAD;
         }
 
         if (aOuts > 0 && (aIns == aOuts || aIns == 1))

source/backend/plugin/CarlaPluginLV2.cpp

@@ -2305,8 +2305,8 @@ public:
         {
             pData->hints |= PLUGIN_HAS_CUSTOM_UI;
 
-            if (fUI.type == UI::TYPE_EMBED)
-                pData->hints |= PLUGIN_NEEDS_SINGLE_THREAD;
+            if (fUI.type == UI::TYPE_EMBED || fUI.type == UI::TYPE_EXTERNAL)
+                pData->hints |= PLUGIN_NEEDS_UI_MAIN_THREAD;
         }
 
         if (LV2_IS_GENERATOR(fRdfDescriptor->Type[0], fRdfDescriptor->Type[1]))

source/backend/plugin/CarlaPluginNative.cpp

@@ -1155,10 +1155,10 @@ public:
             pData->hints |= PLUGIN_IS_SYNTH;
         if (fDescriptor->hints & NATIVE_PLUGIN_HAS_UI)
             pData->hints |= PLUGIN_HAS_CUSTOM_UI;
-        if (fDescriptor->hints & NATIVE_PLUGIN_NEEDS_SINGLE_THREAD)
-            pData->hints |= PLUGIN_NEEDS_SINGLE_THREAD;
         if (fDescriptor->hints & NATIVE_PLUGIN_NEEDS_FIXED_BUFFERS)
             pData->hints |= PLUGIN_NEEDS_FIXED_BUFFERS;
+        if (fDescriptor->hints & NATIVE_PLUGIN_NEEDS_SINGLE_THREAD)
+            pData->hints |= PLUGIN_NEEDS_UI_MAIN_THREAD;
 
         // extra plugin hints
         pData->extraHints = 0x0;

source/backend/plugin/CarlaPluginVST2.cpp

@@ -809,7 +809,7 @@ public:
         if (fEffect->flags & effFlagsHasEditor)
         {
             pData->hints |= PLUGIN_HAS_CUSTOM_UI;
-            pData->hints |= PLUGIN_NEEDS_SINGLE_THREAD;
+            pData->hints |= PLUGIN_NEEDS_UI_MAIN_THREAD;
         }
 
         if (dispatcher(effGetVstVersion, 0, 0, nullptr, 0.0f) < kVstVersion)

source/carla_backend.py

@@ -209,8 +209,8 @@ PLUGIN_CAN_PANNING = 0x080
 # Plugin needs a constant, fixed-size audio buffer.
 PLUGIN_NEEDS_FIXED_BUFFERS = 0x100
 
-# Plugin needs all UI events in a single/main thread.
-PLUGIN_NEEDS_SINGLE_THREAD = 0x200
+# Plugin needs to receive all UI events in the main thread.
+PLUGIN_NEEDS_UI_MAIN_THREAD = 0x200
 
 # ------------------------------------------------------------------------------------------------------------
 # Plugin Options