Added OpenGL locking for OSX.

modules/juce_opengl/native/juce_OpenGL_android.h

@@ -129,6 +129,8 @@ public:
         return nullptr;
     }
 
+    struct Locker { Locker (NativeContext&) {} };
+
     Component& component;
 
 private:

modules/juce_opengl/native/juce_OpenGL_ios.h

@@ -154,6 +154,8 @@ public:
 
     int getSwapInterval() const noexcept    { return swapFrames; }
 
+    struct Locker { Locker (NativeContext&) {} };
+
 private:
     JuceGLView* view;
     CAEAGLLayer* glLayer;

modules/juce_opengl/native/juce_OpenGL_linux.h

@@ -169,6 +169,8 @@ public:
     void* getRawContext() const noexcept        { return renderContext; }
     GLuint getFrameBufferID() const noexcept    { return 0; }
 
+    struct Locker { Locker (NativeContext&) {} };
+
 private:
     GLXContext renderContext;
     Window embeddedWindow;

modules/juce_opengl/native/juce_OpenGL_osx.h

@@ -185,6 +185,22 @@ public:
         return [NSOpenGLContext currentContext] == renderContext;
     }
 
+    struct Locker
+    {
+        Locker (NativeContext& nc) : cglContext ((CGLContextObj) [nc.renderContext CGLContextObj])
+        {
+            CGLLockContext (cglContext);
+        }
+
+        ~Locker()
+        {
+            CGLUnlockContext (cglContext);
+        }
+
+    private:
+        CGLContextObj cglContext;
+    };
+
     void swapBuffers()
     {
         [renderContext flushBuffer];

modules/juce_opengl/native/juce_OpenGL_win32.h

@@ -112,6 +112,8 @@ public:
     void* getRawContext() const noexcept            { return renderContext; }
     unsigned int getFrameBufferID() const noexcept  { return 0; }
 
+    struct Locker { Locker (NativeContext&) {} };
+
 private:
     Component dummyComponent;
     ScopedPointer<ComponentPeer> nativeWindow;

modules/juce_opengl/opengl/juce_OpenGLContext.cpp

@@ -143,6 +143,8 @@ public:
         if (! context.makeActive())
             return false;
 
+        NativeContext::Locker locker (*nativeContext);
+
         JUCE_CHECK_OPENGL_ERROR
         glViewport (0, 0, component.getWidth(), component.getHeight());