Fix bridged LV2 UIs sometimes not initializing properly

source/bridges-ui/CarlaBridgeClient.cpp

@@ -110,9 +110,12 @@ void CarlaBridgeClient::oscInit(const char* const url)
     fOsc.init(url);
 }
 
-bool CarlaBridgeClient::oscIdle() const
+bool CarlaBridgeClient::oscIdle(const bool onlyOnce) const
 {
-    fOsc.idle();
+    if (onlyOnce)
+        fOsc.idleOnce();
+    else
+        fOsc.idle();
 
     return ! fUI.quit;
 }

source/bridges-ui/CarlaBridgeClient.hpp

@@ -66,7 +66,7 @@ public:
     // osc stuff
 
     void oscInit(const char* const url);
-    bool oscIdle() const;
+    bool oscIdle(const bool onlyOnce = false) const;
     void oscClose();
 
     bool isOscControlRegistered() const noexcept;

source/bridges-ui/CarlaBridgeOsc.cpp

@@ -88,6 +88,14 @@ void CarlaBridgeOsc::idle() const
     for (; lo_server_recv_noblock(fServer, 0) != 0;) {}
 }
 
+void CarlaBridgeOsc::idleOnce() const
+{
+    if (fServer == nullptr)
+        return;
+
+    lo_server_recv_noblock(fServer, 0);
+}
+
 void CarlaBridgeOsc::close()
 {
     CARLA_ASSERT(fControlData.source == nullptr); // must never be used

source/bridges-ui/CarlaBridgeOsc.hpp

@@ -59,6 +59,7 @@ public:
 
     void init(const char* const url);
     void idle() const;
+    void idleOnce() const;
     void close();
 
     // -------------------------------------------------------------------

source/bridges-ui/CarlaBridgeUI-LV2.cpp

@@ -567,7 +567,7 @@ public:
 
         for (;;)
         {
-            if (fIsReady || ! oscIdle())
+            if (fIsReady || ! oscIdle(true))
                 return;
         }
     }