GHOST: Add new interface to manage offscreen contexts.

Offscreen contexts are not attached to a window and can only be used for rendering to frambuffer objects.

CGL implementation : Brecht Van Lommel (brecht)
GLX implementation : Clément Foucault (fclem)
WGL implementation : Germano Cavalcante (mano-wii)

Other implementation are just place holder for now.

25 files changed, 686 insertions, 70 deletions

diff --git a/intern/ghost/CMakeLists.txt b/intern/ghost/CMakeLists.txt
index 5a97da28d17..7771af93d4f 100644
--- a/intern/ghost/CMakeLists.txt
+++ b/intern/ghost/CMakeLists.txt
@@ -54,6 +54,7 @@ set(SRC
 	intern/GHOST_WindowManager.cpp
 
 	GHOST_C-api.h
+	GHOST_IContext.h
 	GHOST_IEvent.h
 	GHOST_IEventConsumer.h
 	GHOST_ISystem.h
diff --git a/intern/ghost/GHOST_C-api.h b/intern/ghost/GHOST_C-api.h
index 967d3f58143..d5d8be7db8e 100644
--- a/intern/ghost/GHOST_C-api.h
+++ b/intern/ghost/GHOST_C-api.h
@@ -52,6 +52,7 @@ GHOST_DECLARE_HANDLE(GHOST_WindowHandle);
 GHOST_DECLARE_HANDLE(GHOST_EventHandle);
 GHOST_DECLARE_HANDLE(GHOST_RectangleHandle);
 GHOST_DECLARE_HANDLE(GHOST_EventConsumerHandle);
+GHOST_DECLARE_HANDLE(GHOST_ContextHandle);
 
 
 /**
@@ -189,6 +190,23 @@ extern GHOST_WindowHandle GHOST_CreateWindow(
         GHOST_GLSettings glSettings);
 
 /**
+ * Create a new offscreen context.
+ * Never explicitly delete the context, use disposeContext() instead.
+ * \param systemhandle The handle to the system
+ * \return A handle to the new context ( == NULL if creation failed).
+ */
+extern GHOST_ContextHandle GHOST_CreateOpenGLContext(GHOST_SystemHandle systemhandle);
+
+/**
+ * Dispose of a context.
+ * \param systemhandle The handle to the system
+ * \param contexthandle Handle to the context to be disposed.
+ * \return Indication of success.
+ */
+extern GHOST_TSuccess GHOST_DisposeOpenGLContext(GHOST_SystemHandle systemhandle,
+                                                    GHOST_ContextHandle contexthandle);
+
+/**
  * Returns the window user data.
  * \param windowhandle The handle to the window
  * \return The window user data.
@@ -711,6 +729,20 @@ extern GHOST_TSuccess GHOST_ActivateWindowDrawingContext(GHOST_WindowHandle wind
 extern GHOST_TSuccess GHOST_InvalidateWindow(GHOST_WindowHandle windowhandle);
 
 /**
+ * Activates the drawing context of this context.
+ * \param contexthandle The handle to the context
+ * \return A success indicator.
+ */
+extern GHOST_TSuccess GHOST_ActivateOpenGLContext(GHOST_ContextHandle contexthandle);
+
+/**
+ * Release the drawing context bound to this thread.
+ * \param contexthandle The handle to the context
+ * \return A success indicator.
+ */
+extern GHOST_TSuccess GHOST_ReleaseOpenGLContext(GHOST_ContextHandle contexthandle);
+
+/**
  * Returns the status of the tablet
  * \param windowhandle The handle to the window
  * \return Status of tablet
diff --git a/intern/ghost/GHOST_IContext.h b/intern/ghost/GHOST_IContext.h
new file mode 100644
index 00000000000..5b027a614ab
--- /dev/null
+++ b/intern/ghost/GHOST_IContext.h
@@ -0,0 +1,78 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
+ * All rights reserved.
+ *
+ * The Original Code is: all of this file.
+ *
+ * Contributor(s): none yet.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file ghost/GHOST_IContext.h
+ *  \ingroup GHOST
+ * Declaration of GHOST_IContext interface class.
+ */
+
+#ifndef __GHOST_IContext_H__
+#define __GHOST_IContext_H__
+
+#include "STR_String.h"
+#include "GHOST_Types.h"
+
+
+/**
+ * Interface for GHOST context.
+ *
+ * You can create a offscreen context (windowless) with the system's
+ * GHOST_ISystem::createOffscreenContext method.
+ * \see GHOST_ISystem#createOffscreenContext
+ *
+ * \author  Clément Foucault
+ * \date    Feb 9, 2018
+ */
+class GHOST_IContext
+{
+public:
+	/**
+	 * Destructor.
+	 */
+	virtual ~GHOST_IContext()
+	{
+	}
+
+	/**
+	 * Activates the drawing context.
+	 * \return  A boolean success indicator.
+	 */
+	virtual GHOST_TSuccess activateDrawingContext() = 0;
+
+	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	virtual GHOST_TSuccess releaseDrawingContext() = 0;
+
+#ifdef WITH_CXX_GUARDEDALLOC
+	MEM_CXX_CLASS_ALLOC_FUNCS("GHOST:GHOST_IContext")
+#endif
+};
+
+#endif // __GHOST_IContext_H__
+
diff --git a/intern/ghost/GHOST_ISystem.h b/intern/ghost/GHOST_ISystem.h
index 03193d6e1da..5c5590ef069 100644
--- a/intern/ghost/GHOST_ISystem.h
+++ b/intern/ghost/GHOST_ISystem.h
@@ -36,6 +36,7 @@
 #define __GHOST_ISYSTEM_H__
 
 #include "GHOST_Types.h"
+#include "GHOST_IContext.h"
 #include "GHOST_ITimerTask.h"
 #include "GHOST_IWindow.h"
 
@@ -262,6 +263,20 @@ public:
 	virtual GHOST_TSuccess disposeWindow(GHOST_IWindow *window) = 0;
 
 	/**
+	 * Create a new offscreen context.
+	 * Never explicitly delete the context, use disposeContext() instead.
+	 * \return  The new context (or 0 if creation failed).
+	 */
+	virtual GHOST_IContext *createOffscreenContext() = 0;
+
+	/**
+	 * Dispose of a context.
+	 * \param   context Pointer to the context to be disposed.
+	 * \return  Indication of success.
+	 */
+	virtual GHOST_TSuccess disposeContext(GHOST_IContext *context) = 0;
+
+	/**
 	 * Returns whether a window is valid.
 	 * \param   window Pointer to the window to be checked.
 	 * \return  Indication of validity.
diff --git a/intern/ghost/intern/GHOST_C-api.cpp b/intern/ghost/intern/GHOST_C-api.cpp
index ce653188760..2fe94171cf8 100644
--- a/intern/ghost/intern/GHOST_C-api.cpp
+++ b/intern/ghost/intern/GHOST_C-api.cpp
@@ -132,6 +132,22 @@ void GHOST_GetAllDisplayDimensions(GHOST_SystemHandle systemhandle,
 	system->getAllDisplayDimensions(*width, *height);
 }
 
+GHOST_ContextHandle GHOST_CreateOpenGLContext(GHOST_SystemHandle systemhandle)
+{
+	GHOST_ISystem *system = (GHOST_ISystem *) systemhandle;
+
+	return (GHOST_ContextHandle) system->createOffscreenContext();
+}
+
+GHOST_TSuccess GHOST_DisposeOpenGLContext(GHOST_SystemHandle systemhandle,
+                                             GHOST_ContextHandle contexthandle)
+{
+	GHOST_ISystem *system = (GHOST_ISystem *) systemhandle;
+	GHOST_IContext *context = (GHOST_IContext *) contexthandle;
+
+	return system->disposeContext(context);
+}
+
 GHOST_WindowHandle GHOST_CreateWindow(GHOST_SystemHandle systemhandle,
                                       const char *title,
                                       GHOST_TInt32 left,
@@ -713,7 +729,19 @@ GHOST_TSuccess GHOST_ActivateWindowDrawingContext(GHOST_WindowHandle windowhandl
 	return window->activateDrawingContext();
 }
 
+GHOST_TSuccess GHOST_ActivateOpenGLContext(GHOST_ContextHandle contexthandle)
+{
+	GHOST_IContext *context = (GHOST_IContext *) contexthandle;
+
+	return context->activateDrawingContext();
+}
+
+GHOST_TSuccess GHOST_ReleaseOpenGLContext(GHOST_ContextHandle contexthandle)
+{
+	GHOST_IContext *context = (GHOST_IContext *) contexthandle;
 
+	return context->releaseDrawingContext();
+}
 
 GHOST_TSuccess GHOST_InvalidateWindow(GHOST_WindowHandle windowhandle)
 {
diff --git a/intern/ghost/intern/GHOST_Context.h b/intern/ghost/intern/GHOST_Context.h
index 8776fa4764f..670b86d456f 100644
--- a/intern/ghost/intern/GHOST_Context.h
+++ b/intern/ghost/intern/GHOST_Context.h
@@ -33,6 +33,7 @@
 #ifndef __GHOST_CONTEXT_H__
 #define __GHOST_CONTEXT_H__
 
+#include "GHOST_IContext.h"
 #include "GHOST_Types.h"
 
 #include "glew-mx.h"
@@ -40,7 +41,7 @@
 #include <cstdlib> // for NULL
 
 
-class GHOST_Context
+class GHOST_Context : public GHOST_IContext
 {
 public:
 	/**
@@ -72,6 +73,12 @@ public:
 	virtual GHOST_TSuccess activateDrawingContext() = 0;
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	virtual GHOST_TSuccess releaseDrawingContext()= 0;
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
diff --git a/intern/ghost/intern/GHOST_ContextCGL.h b/intern/ghost/intern/GHOST_ContextCGL.h
index 6dcc4da0f0a..ea6eb485ce2 100644
--- a/intern/ghost/intern/GHOST_ContextCGL.h
+++ b/intern/ghost/intern/GHOST_ContextCGL.h
@@ -83,6 +83,12 @@ public:
 	GHOST_TSuccess activateDrawingContext();
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
diff --git a/intern/ghost/intern/GHOST_ContextCGL.mm b/intern/ghost/intern/GHOST_ContextCGL.mm
index 03af3cc497e..46993a1cd1d 100644
--- a/intern/ghost/intern/GHOST_ContextCGL.mm
+++ b/intern/ghost/intern/GHOST_ContextCGL.mm
@@ -35,6 +35,8 @@
 
 #include <Cocoa/Cocoa.h>
 
+//#define GHOST_MULTITHREADED_OPENGL
+
 #ifdef GHOST_MULTITHREADED_OPENGL
 #include <OpenGL/OpenGL.h>
 #endif
@@ -62,8 +64,6 @@ GHOST_ContextCGL::GHOST_ContextCGL(
       m_openGLContext(nil),
       m_debug(contextFlags)
 {
-	assert(openGLView != nil);
-
 	// for now be very strict about OpenGL version requested
 	switch (contextMajorVersion) {
 		case 2:
@@ -73,7 +73,7 @@ GHOST_ContextCGL::GHOST_ContextCGL(
 			break;
 		case 3:
 			// Apple didn't implement 3.0 or 3.1
-			assert(contextMinorVersion == 2);
+			assert(contextMinorVersion == 3);
 			assert(contextProfileMask == GL_CONTEXT_CORE_PROFILE_BIT);
 			m_coreProfile = true;
 			break;
@@ -88,7 +88,10 @@ GHOST_ContextCGL::~GHOST_ContextCGL()
 	if (m_openGLContext != nil) {
 		if (m_openGLContext == [NSOpenGLContext currentContext]) {
 			[NSOpenGLContext clearCurrentContext];
-			[m_openGLView clearGLContext];
+
+			if(m_openGLView) {
+				[m_openGLView clearGLContext];
+			}
 		}
 
 		if (m_openGLContext != s_sharedOpenGLContext || s_sharedCount == 1) {
@@ -167,6 +170,18 @@ GHOST_TSuccess GHOST_ContextCGL::activateDrawingContext()
 	}
 }
 
+GHOST_TSuccess GHOST_ContextCGL::releaseDrawingContext()
+{
+	if (m_openGLContext != nil) {
+		NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+		[NSOpenGLContext clearCurrentContext];
+		[pool drain];
+		return GHOST_kSuccess;
+	}
+	else {
+		return GHOST_kFailure;
+	}
+}
 
 GHOST_TSuccess GHOST_ContextCGL::updateDrawingContext()
 {
@@ -258,7 +273,7 @@ GHOST_TSuccess GHOST_ContextCGL::initializeDrawingContext()
 	std::vector<NSOpenGLPixelFormatAttribute> attribs;
 	attribs.reserve(40);
 
-	NSOpenGLContext *prev_openGLContext = [m_openGLView openGLContext];
+	NSOpenGLContext *prev_openGLContext = (m_openGLView) ? [m_openGLView openGLContext] : NULL;
 
 #ifdef GHOST_OPENGL_ALPHA
 	static const bool needAlpha   = true;
@@ -346,8 +361,7 @@ GHOST_TSuccess GHOST_ContextCGL::initializeDrawingContext()
 
 #ifdef GHOST_MULTITHREADED_OPENGL
 	//Switch openGL to multhreaded mode
-	CGLContextObj cglCtx = (CGLContextObj)[tmpOpenGLContext CGLContextObj];
-	if (CGLEnable(cglCtx, kCGLCEMPEngine) == kCGLNoError)
+	if (CGLEnable(CGLGetCurrentContext(), kCGLCEMPEngine) == kCGLNoError)
 		if (m_debug)
 			fprintf(stderr, "\nSwitched OpenGL to multithreaded mode\n");
 #endif
@@ -362,8 +376,10 @@ GHOST_TSuccess GHOST_ContextCGL::initializeDrawingContext()
 
 	initContextGLEW();
 
-	[m_openGLView setOpenGLContext:m_openGLContext];
-	[m_openGLContext setView:m_openGLView];
+	if (m_openGLView) {
+		[m_openGLView setOpenGLContext:m_openGLContext];
+		[m_openGLContext setView:m_openGLView];
+	}
 
 	if (s_sharedCount == 0)
 		s_sharedOpenGLContext = m_openGLContext;
@@ -380,7 +396,10 @@ GHOST_TSuccess GHOST_ContextCGL::initializeDrawingContext()
 
 error:
 
-	[m_openGLView setOpenGLContext:prev_openGLContext];
+	if (m_openGLView) {
+		[m_openGLView setOpenGLContext:prev_openGLContext];
+	}
+
 	[pixelFormat release];
 
 	[pool drain];
diff --git a/intern/ghost/intern/GHOST_ContextEGL.cpp b/intern/ghost/intern/GHOST_ContextEGL.cpp
index a591d9b7583..56962d24939 100644
--- a/intern/ghost/intern/GHOST_ContextEGL.cpp
+++ b/intern/ghost/intern/GHOST_ContextEGL.cpp
@@ -312,6 +312,17 @@ GHOST_TSuccess GHOST_ContextEGL::activateDrawingContext()
 	}
 }
 
+GHOST_TSuccess GHOST_ContextEGL::releaseDrawingContext()
+{
+	if (m_display) {
+		bindAPI(m_api);
+
+		return EGL_CHK(::eglMakeCurrent(m_display, None, None, NULL)) ? GHOST_kSuccess : GHOST_kFailure;
+	}
+	else {
+		return GHOST_kFailure;
+	}
+}
 
 void GHOST_ContextEGL::initContextEGLEW()
 {
diff --git a/intern/ghost/intern/GHOST_ContextEGL.h b/intern/ghost/intern/GHOST_ContextEGL.h
index 6dfb177f26d..83415f6be54 100644
--- a/intern/ghost/intern/GHOST_ContextEGL.h
+++ b/intern/ghost/intern/GHOST_ContextEGL.h
@@ -81,6 +81,12 @@ public:
 	GHOST_TSuccess activateDrawingContext();
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
diff --git a/intern/ghost/intern/GHOST_ContextGLX.cpp b/intern/ghost/intern/GHOST_ContextGLX.cpp
index 061ac29945b..fb7fa4ee762 100644
--- a/intern/ghost/intern/GHOST_ContextGLX.cpp
+++ b/intern/ghost/intern/GHOST_ContextGLX.cpp
@@ -74,7 +74,6 @@ GHOST_ContextGLX::GHOST_ContextGLX(
       m_contextResetNotificationStrategy(contextResetNotificationStrategy),
       m_context(None)
 {
-	assert(m_window  != 0);
 	assert(m_display != NULL);
 }
 
@@ -119,6 +118,16 @@ GHOST_TSuccess GHOST_ContextGLX::activateDrawingContext()
 	}
 }
 
+GHOST_TSuccess GHOST_ContextGLX::releaseDrawingContext()
+{
+	if (m_display) {
+		return ::glXMakeCurrent(m_display, None, NULL) ? GHOST_kSuccess : GHOST_kFailure;
+	}
+	else {
+		return GHOST_kFailure;
+	}
+}
+
 void GHOST_ContextGLX::initContextGLXEW()
 {
 	initContextGLEW();
@@ -246,9 +255,22 @@ const bool GLXEW_ARB_create_context_robustness =
 		}
 		attribs[i++] = 0;
 
+		/* Some drivers don't like having a true offscreen context.
+		 * Create a pixel buffer instead of a window to render to.
+		 * even if it will never be used for drawing. */
+		int pbuffer_attribs[] = {
+			GLX_PBUFFER_WIDTH, 1,
+			GLX_PBUFFER_HEIGHT, 1,
+			None
+		};
+
 		/* Create a GL 3.x context */
 		if (m_fbconfig) {
 			m_context = glXCreateContextAttribsARB(m_display, m_fbconfig, s_sharedContext, true, attribs);
+
+			if (!m_window) {
+				m_window = (Window)glXCreatePbuffer(m_display, m_fbconfig, pbuffer_attribs);
+			}
 		}
 		else {
 			GLXFBConfig *framebuffer_config = NULL;
@@ -263,6 +285,11 @@ const bool GLXEW_ARB_create_context_robustness =
 
 			if (framebuffer_config) {
 				m_context = glXCreateContextAttribsARB(m_display, framebuffer_config[0], s_sharedContext, True, attribs);
+
+				if (!m_window) {
+					m_window = (Window)glXCreatePbuffer(m_display, framebuffer_config[0], pbuffer_attribs);
+				}
+
 				XFree(framebuffer_config);
 			}
 		}
@@ -288,8 +315,10 @@ const bool GLXEW_ARB_create_context_robustness =
 		// which means we cannot use glX extensions until after we create a context
 		initContextGLXEW();
 
-		initClearGL();
-		::glXSwapBuffers(m_display, m_window);
+		if (m_window) {
+			initClearGL();
+			::glXSwapBuffers(m_display, m_window);
+		}
 
 		/* re initialize to get the extensions properly */
 		initContextGLXEW();
diff --git a/intern/ghost/intern/GHOST_ContextGLX.h b/intern/ghost/intern/GHOST_ContextGLX.h
index 51fb1dd57dc..ded1b293659 100644
--- a/intern/ghost/intern/GHOST_ContextGLX.h
+++ b/intern/ghost/intern/GHOST_ContextGLX.h
@@ -82,6 +82,12 @@ public:
 	GHOST_TSuccess activateDrawingContext();
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
diff --git a/intern/ghost/intern/GHOST_ContextNone.cpp b/intern/ghost/intern/GHOST_ContextNone.cpp
index 380ab532f7a..89bdf6b89fa 100644
--- a/intern/ghost/intern/GHOST_ContextNone.cpp
+++ b/intern/ghost/intern/GHOST_ContextNone.cpp
@@ -46,6 +46,12 @@ GHOST_TSuccess GHOST_ContextNone::activateDrawingContext()
 }
 
 
+GHOST_TSuccess GHOST_ContextNone::releaseDrawingContext()
+{
+	return GHOST_kSuccess;
+}
+
+
 GHOST_TSuccess GHOST_ContextNone::updateDrawingContext()
 {
 	return GHOST_kSuccess;
diff --git a/intern/ghost/intern/GHOST_ContextNone.h b/intern/ghost/intern/GHOST_ContextNone.h
index 80cce76190d..9f2af4ae235 100644
--- a/intern/ghost/intern/GHOST_ContextNone.h
+++ b/intern/ghost/intern/GHOST_ContextNone.h
@@ -61,6 +61,12 @@ public:
 
 	/**
 	 * Dummy function
+	 * \return  Always succeeds
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
+	 * Dummy function
 	 * \return Always succeeds
 	 */
 	GHOST_TSuccess updateDrawingContext();
diff --git a/intern/ghost/intern/GHOST_ContextSDL.cpp b/intern/ghost/intern/GHOST_ContextSDL.cpp
index 7a02e9743c3..1ba591bd0b2 100644
--- a/intern/ghost/intern/GHOST_ContextSDL.cpp
+++ b/intern/ghost/intern/GHOST_ContextSDL.cpp
@@ -105,6 +105,18 @@ GHOST_TSuccess GHOST_ContextSDL::activateDrawingContext()
 }
 
 
+GHOST_TSuccess GHOST_ContextSDL::releaseDrawingContext()
+{
+	if (m_context) {
+		/* Untested, may not work */
+		return SDL_GL_MakeCurrent(NULL, NULL) ? GHOST_kSuccess : GHOST_kFailure;
+	}
+	else {
+		return GHOST_kFailure;
+	}
+}
+
+
 GHOST_TSuccess GHOST_ContextSDL::initializeDrawingContext()
 {
 #ifdef GHOST_OPENGL_ALPHA
diff --git a/intern/ghost/intern/GHOST_ContextSDL.h b/intern/ghost/intern/GHOST_ContextSDL.h
index 61f339c1bc2..681d24bb7c6 100644
--- a/intern/ghost/intern/GHOST_ContextSDL.h
+++ b/intern/ghost/intern/GHOST_ContextSDL.h
@@ -86,6 +86,12 @@ public:
 	GHOST_TSuccess activateDrawingContext();
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
diff --git a/intern/ghost/intern/GHOST_ContextWGL.cpp b/intern/ghost/intern/GHOST_ContextWGL.cpp
index 7b5e30247a8..a23c0b0b26c 100644
--- a/intern/ghost/intern/GHOST_ContextWGL.cpp
+++ b/intern/ghost/intern/GHOST_ContextWGL.cpp
@@ -43,14 +43,7 @@
 HGLRC GHOST_ContextWGL::s_sharedHGLRC = NULL;
 int   GHOST_ContextWGL::s_sharedCount = 0;
 
-bool GHOST_ContextWGL::s_singleContextMode = false;
-
-
-/* Intel video-cards don't work fine with multiple contexts and
- * have to share the same context for all windows.
- * But if we just share context for all windows it could work incorrect
- * with multiple videocards configuration. Suppose, that Intel videocards
- * can't be in multiple-devices configuration. */
+/* Some third-generation Intel video-cards are constantly bring problems */
 static bool is_crappy_intel_card()
 {
 	return strstr((const char *)glGetString(GL_VENDOR), "Intel") != NULL;
@@ -69,6 +62,7 @@ GHOST_ContextWGL::GHOST_ContextWGL(
         int contextFlags,
         int contextResetNotificationStrategy)
     : GHOST_Context(stereoVisual, numOfAASamples),
+      m_dummyPbuffer(NULL),
       m_hWnd(hWnd),
       m_hDC(hDC),
       m_contextProfileMask(contextProfileMask),
@@ -85,8 +79,6 @@ GHOST_ContextWGL::GHOST_ContextWGL(
       m_dummyVersion(NULL)
 #endif
 {
-	assert(m_hWnd);
-	assert(m_hDC);
 }
 
 
@@ -106,12 +98,20 @@ GHOST_ContextWGL::~GHOST_ContextWGL()
 
 			WIN32_CHK(::wglDeleteContext(m_hGLRC));
 		}
+		if (m_dummyPbuffer) {
+			if (m_hDC != NULL)
+				WIN32_CHK(::wglReleasePbufferDCARB(m_dummyPbuffer, m_hDC));
+
+			WIN32_CHK(::wglDestroyPbufferARB(m_dummyPbuffer));
+		}
 	}
 
 #ifndef NDEBUG
-	free((void*)m_dummyRenderer);
-	free((void*)m_dummyVendor);
-	free((void*)m_dummyVersion);
+	if (m_dummyRenderer) {
+		free((void*)m_dummyRenderer);
+		free((void*)m_dummyVendor);
+		free((void*)m_dummyVersion);
+	}
 #endif
 }
 
@@ -154,6 +154,16 @@ GHOST_TSuccess GHOST_ContextWGL::activateDrawingContext()
 }
 
 
+GHOST_TSuccess GHOST_ContextWGL::releaseDrawingContext()
+{
+	if (WIN32_CHK(::wglMakeCurrent(NULL, NULL))) {
+		return GHOST_kSuccess;
+	}
+	else {
+		return GHOST_kFailure;
+	}
+}
+
 /* Ron Fosner's code for weighting pixel formats and forcing software.
  * See http://www.opengl.org/resources/faq/technical/weight.cpp
  */
@@ -317,6 +327,8 @@ static HWND clone_window(HWND hWnd, LPVOID lpParam)
 void GHOST_ContextWGL::initContextWGLEW(PIXELFORMATDESCRIPTOR &preferredPFD)
 {
 	HWND  dummyHWND  = NULL;
+	HPBUFFERARB dummyhBuffer = NULL;
+
 	HDC   dummyHDC   = NULL;
 	HGLRC dummyHGLRC = NULL;
 
@@ -333,23 +345,29 @@ void GHOST_ContextWGL::initContextWGLEW(PIXELFORMATDESCRIPTOR &preferredPFD)
 	prevHGLRC = ::wglGetCurrentContext();
 	WIN32_CHK(GetLastError() == NO_ERROR);
 
-	dummyHWND = clone_window(m_hWnd, NULL);
+	iPixelFormat = choose_pixel_format_legacy(m_hDC, preferredPFD);
 
-	if (dummyHWND == NULL)
+	if (iPixelFormat == 0)
 		goto finalize;
 
-	dummyHDC = GetDC(dummyHWND);
-
-	if (!WIN32_CHK(dummyHDC != NULL))
+	PIXELFORMATDESCRIPTOR chosenPFD;
+	if (!WIN32_CHK(::DescribePixelFormat(m_hDC, iPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &chosenPFD)))
 		goto finalize;
 
-	iPixelFormat = choose_pixel_format_legacy(dummyHDC, preferredPFD);
+	if (m_hWnd) {
+		dummyHWND = clone_window(m_hWnd, NULL);
 
-	if (iPixelFormat == 0)
-		goto finalize;
+		if (dummyHWND == NULL)
+			goto finalize;
 
-	PIXELFORMATDESCRIPTOR chosenPFD;
-	if (!WIN32_CHK(::DescribePixelFormat(dummyHDC, iPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &chosenPFD)))
+		dummyHDC = GetDC(dummyHWND);
+	}
+	else {
+		dummyhBuffer = wglCreatePbufferARB(m_hDC, iPixelFormat, 1, 1, 0);
+		dummyHDC = wglGetPbufferDCARB(dummyhBuffer);
+	}
+
+	if (!WIN32_CHK(dummyHDC != NULL))
 		goto finalize;
 
 	if (!WIN32_CHK(::SetPixelFormat(dummyHDC, iPixelFormat, &chosenPFD)))
@@ -378,8 +396,6 @@ void GHOST_ContextWGL::initContextWGLEW(PIXELFORMATDESCRIPTOR &preferredPFD)
 	m_dummyVersion  = _strdup(reinterpret_cast<const char *>(glGetString(GL_VERSION)));
 #endif
 
-	s_singleContextMode = is_crappy_intel_card();
-
 finalize:
 	WIN32_CHK(::wglMakeCurrent(prevHDC, prevHGLRC));
 
@@ -392,6 +408,12 @@ finalize:
 
 		WIN32_CHK(::DestroyWindow(dummyHWND));
 	}
+	else if (dummyhBuffer != NULL) {
+		if (dummyHDC != NULL)
+			WIN32_CHK(::wglReleasePbufferDCARB(dummyhBuffer, dummyHDC));
+
+		WIN32_CHK(::wglDestroyPbufferARB(dummyhBuffer));
+	}
 }
 
 
@@ -753,7 +775,9 @@ GHOST_TSuccess GHOST_ContextWGL::initializeDrawingContext()
 	HDC prevHDC = ::wglGetCurrentDC();
 	WIN32_CHK(GetLastError() == NO_ERROR);
 
-	if (!WGLEW_ARB_create_context || ::GetPixelFormat(m_hDC) == 0) {
+	const bool create_hDC = m_hDC == NULL;
+
+	if (!WGLEW_ARB_create_context || create_hDC || ::GetPixelFormat(m_hDC) == 0) {
 		const bool needAlpha = m_alphaBackground;
 
 #ifdef GHOST_OPENGL_STENCIL
@@ -770,20 +794,32 @@ GHOST_TSuccess GHOST_ContextWGL::initializeDrawingContext()
 		int iPixelFormat;
 		int lastPFD;
 
+		if (create_hDC) {
+			/* get a handle to a device context with graphics accelerator enabled */
+			m_hDC = wglGetCurrentDC();
+			if (m_hDC == NULL) {
+				m_hDC = GetDC(NULL);
+			}
+		}
+
 		PIXELFORMATDESCRIPTOR chosenPFD;
 
 		iPixelFormat = choose_pixel_format(m_stereoVisual, m_numOfAASamples, needAlpha, needStencil, sRGB);
 
 		if (iPixelFormat == 0) {
-			::wglMakeCurrent(prevHDC, prevHGLRC);
-			return GHOST_kFailure;
+			goto error;
+		}
+
+		if (create_hDC) {
+			/* create an off-screen pixel buffer (Pbuffer) */
+			m_dummyPbuffer = wglCreatePbufferARB(m_hDC, iPixelFormat, 1, 1, 0);
+			m_hDC = wglGetPbufferDCARB(m_dummyPbuffer);
 		}
 
 		lastPFD = ::DescribePixelFormat(m_hDC, iPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &chosenPFD);
 
 		if (!WIN32_CHK(lastPFD != 0)) {
-			::wglMakeCurrent(prevHDC, prevHGLRC);
-			return GHOST_kFailure;
+			goto error;
 		}
 
 		if (needAlpha && chosenPFD.cAlphaBits == 0)
@@ -793,8 +829,7 @@ GHOST_TSuccess GHOST_ContextWGL::initializeDrawingContext()
 			fprintf(stderr, "Warning! Unable to find a pixel format with a stencil buffer.\n");
 
 		if (!WIN32_CHK(::SetPixelFormat(m_hDC, iPixelFormat, &chosenPFD))) {
-			::wglMakeCurrent(prevHDC, prevHGLRC);
-			return GHOST_kFailure;
+			goto error;
 		}
 	}
 
@@ -870,30 +905,24 @@ GHOST_TSuccess GHOST_ContextWGL::initializeDrawingContext()
 
 		iAttributes.push_back(0);
 
-		if (!s_singleContextMode || s_sharedHGLRC == NULL)
-			m_hGLRC = ::wglCreateContextAttribsARB(m_hDC, NULL, &(iAttributes[0]));
-		else
-			m_hGLRC = s_sharedHGLRC;
+		m_hGLRC = ::wglCreateContextAttribsARB(m_hDC, NULL, &(iAttributes[0]));
 	}
 
 	if (!WIN32_CHK(m_hGLRC != NULL)) {
-		::wglMakeCurrent(prevHDC, prevHGLRC);
-		return GHOST_kFailure;
+		goto error;
 	}
 
-	if (s_sharedHGLRC == NULL)
-		s_sharedHGLRC = m_hGLRC;
-
 	s_sharedCount++;
 
-	if (!s_singleContextMode && s_sharedHGLRC != m_hGLRC && !WIN32_CHK(::wglShareLists(s_sharedHGLRC, m_hGLRC))) {
-		::wglMakeCurrent(prevHDC, prevHGLRC);
-		return GHOST_kFailure;
+	if (s_sharedHGLRC == NULL) {
+		s_sharedHGLRC = m_hGLRC;
+	}
+	else if (!WIN32_CHK(::wglShareLists(s_sharedHGLRC, m_hGLRC))) {
+		goto error;
 	}
 
 	if (!WIN32_CHK(::wglMakeCurrent(m_hDC, m_hGLRC))) {
-		::wglMakeCurrent(prevHDC, prevHGLRC);
-		return GHOST_kFailure;
+		goto error;
 	}
 
 	initContextGLEW();
@@ -923,6 +952,16 @@ GHOST_TSuccess GHOST_ContextWGL::initializeDrawingContext()
 #endif
 
 	return GHOST_kSuccess;
+error:
+	if (m_dummyPbuffer) {
+		if (m_hDC != NULL)
+			WIN32_CHK(::wglReleasePbufferDCARB(m_dummyPbuffer, m_hDC));
+
+		WIN32_CHK(::wglDestroyPbufferARB(m_dummyPbuffer));
+	}
+	::wglMakeCurrent(prevHDC, prevHGLRC);
+	return GHOST_kFailure;
+
 }
 
 
diff --git a/intern/ghost/intern/GHOST_ContextWGL.h b/intern/ghost/intern/GHOST_ContextWGL.h
index a07cc1b6301..b3b66c5f6e2 100644
--- a/intern/ghost/intern/GHOST_ContextWGL.h
+++ b/intern/ghost/intern/GHOST_ContextWGL.h
@@ -79,6 +79,12 @@ public:
 	GHOST_TSuccess activateDrawingContext();
 
 	/**
+	 * Release the drawing context of the calling thread.
+	 * \return  A boolean success indicator.
+	 */
+	GHOST_TSuccess releaseDrawingContext();
+
+	/**
 	 * Call immediately after new to initialize.  If this fails then immediately delete the object.
 	 * \return Indication as to whether initialization has succeeded.
 	 */
@@ -137,6 +143,10 @@ private:
 
 	void initContextWGLEW(PIXELFORMATDESCRIPTOR &preferredPFD);
 
+	/* offscreen buffer with size of 1x1 pixel,
+	 * kept here to release the device constext when closing the program. */
+	HPBUFFERARB m_dummyPbuffer;
+
 	HWND m_hWnd;
 	HDC  m_hDC;
 
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.h b/intern/ghost/intern/GHOST_SystemCocoa.h
index 6802ad42c7b..62d9774d81d 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.h
+++ b/intern/ghost/intern/GHOST_SystemCocoa.h
@@ -123,6 +123,25 @@ public:
 	    const GHOST_TEmbedderWindowID parentWindow = 0
 	    );
 	
+	/**
+	 * Create a new offscreen context.
+	 * Never explicitly delete the context, use disposeContext() instead.
+	 * \return  The new context (or 0 if creation failed).
+	 */
+	GHOST_IContext *
+	createOffscreenContext(
+	    );
+
+	/**
+	 * Dispose of a context.
+	 * \param   context Pointer to the context to be disposed.
+	 * \return  Indication of success.
+	 */
+	GHOST_TSuccess
+	disposeContext(
+	    GHOST_IContext *context
+	    );
+
 	/***************************************************************************************
 	 * Event management functionality
 	 ***************************************************************************************/
diff --git a/intern/ghost/intern/GHOST_SystemCocoa.mm b/intern/ghost/intern/GHOST_SystemCocoa.mm
index e9fffb6f60b..011719ea946 100644
--- a/intern/ghost/intern/GHOST_SystemCocoa.mm
+++ b/intern/ghost/intern/GHOST_SystemCocoa.mm
@@ -27,15 +27,6 @@
  * ***** END GPL LICENSE BLOCK *****
  */
 
-#import <Cocoa/Cocoa.h>
-
-/*For the currently not ported to Cocoa keyboard layout functions (64bit & 10.6 compatible)*/
-#include <Carbon/Carbon.h>
-
-#include <sys/time.h>
-#include <sys/types.h>
-#include <sys/sysctl.h>
-
 #include "GHOST_SystemCocoa.h"
 
 #include "GHOST_DisplayManagerCocoa.h"
@@ -51,12 +42,26 @@
 #include "GHOST_WindowManager.h"
 #include "GHOST_WindowCocoa.h"
 
+#if defined(WITH_GL_EGL)
+#  include "GHOST_ContextEGL.h"
+#else
+#  include "GHOST_ContextCGL.h"
+#endif
+
 #ifdef WITH_INPUT_NDOF
   #include "GHOST_NDOFManagerCocoa.h"
 #endif
 
 #include "AssertMacros.h"
 
+#import <Cocoa/Cocoa.h>
+
+/* For the currently not ported to Cocoa keyboard layout functions (64bit & 10.6 compatible) */
+#include <Carbon/Carbon.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/sysctl.h>
 
 #pragma mark KeyMap, mouse converters
 
@@ -581,6 +586,53 @@ GHOST_IWindow* GHOST_SystemCocoa::createWindow(
 }
 
 /**
+ * Create a new offscreen context.
+ * Never explicitly delete the context, use disposeContext() instead.
+ * \return  The new context (or 0 if creation failed).
+ */
+GHOST_IContext *
+GHOST_SystemCocoa::
+createOffscreenContext()
+{
+	GHOST_Context *context = new GHOST_ContextCGL(
+		false,
+		0,
+		NULL,
+		NULL,
+
+#if defined(WITH_GL_PROFILE_CORE)
+		GL_CONTEXT_CORE_PROFILE_BIT,
+		3, 3,
+#else
+		0, // no profile bit
+		2, 1,
+#endif
+		GHOST_OPENGL_CGL_CONTEXT_FLAGS,
+		GHOST_OPENGL_CGL_RESET_NOTIFICATION_STRATEGY);
+
+	if (context->initializeDrawingContext())
+		return context;
+	else
+		delete context;
+
+	return NULL;
+}
+
+/**
+ * Dispose of a context.
+ * \param   context Pointer to the context to be disposed.
+ * \return  Indication of success.
+ */
+GHOST_TSuccess
+GHOST_SystemCocoa::
+disposeContext(GHOST_IContext *context)
+{
+	delete context;
+
+	return GHOST_kSuccess;
+}
+
+/**
  * \note : returns coordinates in Cocoa screen coordinates
  */
 GHOST_TSuccess GHOST_SystemCocoa::getCursorPosition(GHOST_TInt32& x, GHOST_TInt32& y) const
diff --git a/intern/ghost/intern/GHOST_SystemWin32.cpp b/intern/ghost/intern/GHOST_SystemWin32.cpp
index b0dae432643..056b5536ab0 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.cpp
+++ b/intern/ghost/intern/GHOST_SystemWin32.cpp
@@ -56,6 +56,12 @@
 #include "GHOST_WindowManager.h"
 #include "GHOST_WindowWin32.h"
 
+#if defined(WITH_GL_EGL)
+#  include "GHOST_ContextEGL.h"
+#else
+#  include "GHOST_ContextWGL.h"
+#endif
+
 #ifdef WITH_INPUT_NDOF
   #include "GHOST_NDOFManagerWin32.h"
 #endif
@@ -299,6 +305,94 @@ GHOST_IWindow *GHOST_SystemWin32::createWindow(
 }
 
 
+/**
+ * Create a new offscreen context.
+ * Never explicitly delete the window, use disposeContext() instead.
+ * \return  The new context (or 0 if creation failed).
+ */
+GHOST_IContext *GHOST_SystemWin32::createOffscreenContext()
+{
+	bool debug_context = false; /* TODO: inform as a parameter */
+
+	GHOST_Context *context;
+
+#if defined(WITH_GL_PROFILE_CORE)
+	for (int minor = 5; minor >= 0; --minor) {
+			context = new GHOST_ContextWGL(
+			    false, true, 0,
+			    NULL, NULL,
+			    WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
+			    4, minor,
+			    (debug_context ? WGL_CONTEXT_DEBUG_BIT_ARB : 0),
+			    GHOST_OPENGL_WGL_RESET_NOTIFICATION_STRATEGY);
+
+			if (context->initializeDrawingContext()) {
+				return context;
+			}
+			else {
+				delete context;
+			}
+		}
+
+		context = new GHOST_ContextWGL(
+		    false, true, 0,
+		    NULL, NULL,
+		    WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
+		    3, 3,
+		    (debug_context ? WGL_CONTEXT_DEBUG_BIT_ARB : 0),
+		    GHOST_OPENGL_WGL_RESET_NOTIFICATION_STRATEGY);
+
+		if (context->initializeDrawingContext()) {
+			return context;
+		}
+		else {
+			MessageBox(
+			        NULL,
+			        "Blender requires a graphics driver with at least OpenGL 3.3 support.\n\n"
+			        "The program will now close.",
+			        "Blender - Unsupported Graphics Driver!",
+			        MB_OK | MB_ICONERROR);
+			delete context;
+			exit();
+		}
+
+#elif defined(WITH_GL_PROFILE_COMPAT)
+		// ask for 2.1 context, driver gives any GL version >= 2.1 (hopefully the latest compatibility profile)
+		// 2.1 ignores the profile bit & is incompatible with core profile
+		context = new GHOST_ContextWGL(
+		        false, true, 0,
+		        NULL, NULL,
+		        0, // no profile bit
+		        2, 1,
+		        (debug_context ? WGL_CONTEXT_DEBUG_BIT_ARB : 0),
+		        GHOST_OPENGL_WGL_RESET_NOTIFICATION_STRATEGY);
+
+		if (context->initializeDrawingContext()) {
+			return context;
+		}
+		else {
+			delete context;
+		}
+#else
+#  error // must specify either core or compat at build time
+#endif
+
+	return NULL;
+}
+
+/**
+ * Dispose of a context.
+ * \param   context Pointer to the context to be disposed.
+ * \return  Indication of success.
+ */
+GHOST_TSuccess GHOST_SystemWin32::disposeContext(GHOST_IContext *context)
+{
+	delete context;
+
+	return GHOST_kSuccess;
+}
+
+
 bool GHOST_SystemWin32::processEvents(bool waitForEvent)
 {
 	MSG msg;
diff --git a/intern/ghost/intern/GHOST_SystemWin32.h b/intern/ghost/intern/GHOST_SystemWin32.h
index 099d14e68ae..6bf2c5b8d6f 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.h
+++ b/intern/ghost/intern/GHOST_SystemWin32.h
@@ -132,6 +132,21 @@ public:
 	    const bool exclusive = false,
 	    const GHOST_TEmbedderWindowID parentWindow = 0);
 
+
+	/**
+	 * Create a new offscreen context.
+	 * Never explicitly delete the window, use disposeContext() instead.
+	 * \return  The new context (or 0 if creation failed).
+	 */
+	GHOST_IContext *createOffscreenContext();
+
+	/**
+	 * Dispose of a context.
+	 * \param   context Pointer to the context to be disposed.
+	 * \return  Indication of success.
+	 */
+	GHOST_TSuccess disposeContext(GHOST_IContext *context);
+
 	/***************************************************************************************
 	 ** Event management functionality
 	 ***************************************************************************************/
diff --git a/intern/ghost/intern/GHOST_SystemX11.cpp b/intern/ghost/intern/GHOST_SystemX11.cpp
index 9b617a34e1a..0de6e2f7d4a 100644
--- a/intern/ghost/intern/GHOST_SystemX11.cpp
+++ b/intern/ghost/intern/GHOST_SystemX11.cpp
@@ -57,6 +57,12 @@
 
 #include "GHOST_Debug.h"
 
+#if defined(WITH_GL_EGL)
+#  include "GHOST_ContextEGL.h"
+#else
+#  include "GHOST_ContextGLX.h"
+#endif
+
 #ifdef WITH_XF86KEYSYM
 #include <X11/XF86keysym.h>
 #endif
@@ -113,6 +119,7 @@ GHOST_SystemX11(
     : GHOST_System(),
       m_start_time(0)
 {
+	XInitThreads();
 	m_display = XOpenDisplay(NULL);
 	
 	if (!m_display) {
@@ -379,6 +386,98 @@ createWindow(const STR_String& title,
 	return window;
 }
 
+
+/**
+ * Create a new offscreen context.
+ * Never explicitly delete the context, use disposeContext() instead.
+ * \return  The new context (or 0 if creation failed).
+ */
+GHOST_IContext *
+GHOST_SystemX11::
+createOffscreenContext()
+{
+	// During development:
+	//   try 4.x compatibility profile
+	//   try 3.3 compatibility profile
+	//   fall back to 3.0 if needed
+	//
+	// Final Blender 2.8:
+	//   try 4.x core profile
+	//   try 3.3 core profile
+	//   no fallbacks
+
+#if defined(WITH_GL_PROFILE_CORE)
+	{
+		const char *version_major = (char*)glewGetString(GLEW_VERSION_MAJOR);
+		if (version_major != NULL && version_major[0] == '1') {
+			fprintf(stderr, "Error: GLEW version 2.0 and above is required.\n");
+			abort();
+		}
+	}
+#endif
+
+	const int profile_mask =
+#if defined(WITH_GL_PROFILE_CORE)
+		GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
+#elif defined(WITH_GL_PROFILE_COMPAT)
+		GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;
+#else
+#  error // must specify either core or compat at build time
+#endif
+
+	GHOST_Context *context;
+
+	for (int minor = 5; minor >= 0; --minor) {
+		context = new GHOST_ContextGLX(
+		        false,
+		        0,
+		        (Window)NULL,
+		        m_display,
+		        (GLXFBConfig)NULL,
+		        profile_mask,
+		        4, minor,
+		        GHOST_OPENGL_GLX_CONTEXT_FLAGS | (false ? GLX_CONTEXT_DEBUG_BIT_ARB : 0),
+		        GHOST_OPENGL_GLX_RESET_NOTIFICATION_STRATEGY);
+
+		if (context->initializeDrawingContext())
+			return context;
+		else
+			delete context;
+	}
+
+	context = new GHOST_ContextGLX(
+	        false,
+	        0,
+	        (Window)NULL,
+	        m_display,
+	        (GLXFBConfig)NULL,
+	        profile_mask,
+	        3, 3,
+	        GHOST_OPENGL_GLX_CONTEXT_FLAGS | (false ? GLX_CONTEXT_DEBUG_BIT_ARB : 0),
+	        GHOST_OPENGL_GLX_RESET_NOTIFICATION_STRATEGY);
+
+	if (context->initializeDrawingContext())
+		return context;
+	else
+		delete context;
+
+	return NULL;
+}
+
+/**
+ * Dispose of a context.
+ * \param   context Pointer to the context to be disposed.
+ * \return  Indication of success.
+ */
+GHOST_TSuccess
+GHOST_SystemX11::
+disposeContext(GHOST_IContext *context)
+{
+	delete context;
+
+	return GHOST_kSuccess;
+}
+
 #if defined(WITH_X11_XINPUT) && defined(X_HAVE_UTF8_STRING)
 static void destroyIMCallback(XIM /*xim*/, XPointer ptr, XPointer /*data*/)
 {
diff --git a/intern/ghost/intern/GHOST_SystemX11.h b/intern/ghost/intern/GHOST_SystemX11.h
index e60cab6a194..1ad8277a431 100644
--- a/intern/ghost/intern/GHOST_SystemX11.h
+++ b/intern/ghost/intern/GHOST_SystemX11.h
@@ -171,6 +171,26 @@ public:
 	    const GHOST_TEmbedderWindowID parentWindow = 0
 	    );
 
+
+	/**
+	 * Create a new offscreen context.
+	 * Never explicitly delete the context, use disposeContext() instead.
+	 * \return  The new context (or 0 if creation failed).
+	 */
+	GHOST_IContext *
+	createOffscreenContext(
+	    );
+
+	/**
+	 * Dispose of a context.
+	 * \param   context Pointer to the context to be disposed.
+	 * \return  Indication of success.
+	 */
+	GHOST_TSuccess
+	disposeContext(
+	    GHOST_IContext *context
+	    );
+
 	/**
 	 * Retrieves events from the system and stores them in the queue.
 	 * \param waitForEvent Flag to wait for an event (or return immediately).
diff --git a/intern/ghost/intern/GHOST_WindowCocoa.mm b/intern/ghost/intern/GHOST_WindowCocoa.mm
index 309c19f92af..2b986428fd3 100644
--- a/intern/ghost/intern/GHOST_WindowCocoa.mm
+++ b/intern/ghost/intern/GHOST_WindowCocoa.mm
@@ -1005,7 +1005,7 @@ GHOST_Context *GHOST_WindowCocoa::newDrawingContext(GHOST_TDrawingContextType ty
 
 #if defined(WITH_GL_PROFILE_CORE)
 			GL_CONTEXT_CORE_PROFILE_BIT,
-			3, 2,
+			3, 3,
 #else
 			0, // no profile bit
 			2, 1,