Add GLFW_COCOA_GRAPHICS_SWICTHING

This provides control over whether the context should participate in
macOS Automatic Graphics Switching.

Closes #377.
Closes #935.

README.md

@@ -133,6 +133,7 @@ information on what to include when reporting a bug.
   (#749,#842)
 - Added macOS specific `GLFW_COCOA_RETINA_FRAMEBUFFER` window hint
 - Added macOS specific `GLFW_COCOA_FRAME_AUTOSAVE` window hint (#195)
+- Added macOS specific `GLFW_COCOA_GRAPHICS_SWITCHING` window hint (#377,#935)
 - Added `GLFW_INCLUDE_ES32` for including the OpenGL ES 3.2 header
 - Removed `GLFW_USE_RETINA` compile-time option
 - Bugfix: Calling `glfwMaximizeWindow` on a full screen window was not ignored
@@ -236,6 +237,7 @@ skills.
  - Cameron King
  - Peter Knut
  - Christoph Kubisch
+ - Konstantin Käfer
  - Eric Larson
  - Robin Leffmann
  - Glenn Lewis

docs/window.dox

@@ -421,6 +421,23 @@ __GLFW_COCOA_FRAME_AUTOSAVE__ specifies whether to activate frame autosaving
 using the window title specified at window creation.  This is ignored on other
 platforms.
 
+@anchor GLFW_COCOA_GRAPHICS_SWITCHING_hint
+__GLFW_COCOA_GRAPHICS_SWITCHING__ specifies whether to in Automatic Graphics
+Switching, i.e. to allow the system to choose the integrated GPU for the OpenGL
+context and move it between GPUs if necessary or whether to force it to always
+run on the discrete GPU.  This only affects systems with both integrated and
+discrete GPUs.  This is ignored on other platforms.
+
+@par
+Simpler programs and tools may want to enable this to save power, while games
+and other applications performing advanced rendering will want to leave it
+disabled.
+
+@par
+A bundled application that wishes to participate in Automatic Graphics Switching
+should also declare this in its `Info.plist` by setting the
+`NSSupportsAutomaticGraphicsSwitching` key to `true`.
+
 
 @subsubsection window_hints_values Supported and default values
 
@@ -461,6 +478,7 @@ GLFW_OPENGL_DEBUG_CONTEXT     | `GLFW_FALSE`                | `GLFW_TRUE` or `GL
 GLFW_OPENGL_PROFILE           | `GLFW_OPENGL_ANY_PROFILE`   | `GLFW_OPENGL_ANY_PROFILE`, `GLFW_OPENGL_COMPAT_PROFILE` or `GLFW_OPENGL_CORE_PROFILE`
 GLFW_COCOA_RETINA_FRAMEBUFFER | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
 GLFW_COCOA_FRAME_AUTOSAVE     | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
+GLFW_COCOA_GRAPHICS_SWITCHING | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
 
 
 @section window_events Window event processing

include/GLFW/glfw3.h

@@ -852,6 +852,7 @@ extern "C" {
 
 #define GLFW_COCOA_RETINA_FRAMEBUFFER 0x00023001
 #define GLFW_COCOA_FRAME_AUTOSAVE     0x00023002
+#define GLFW_COCOA_GRAPHICS_SWITCHING 0x00023003
 /*! @} */
 
 #define GLFW_NO_API                          0

src/cocoa_window.m

@@ -340,6 +340,14 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
 
 - (void)applicationDidChangeScreenParameters:(NSNotification *) notification
 {
+    _GLFWwindow* window;
+
+    for (window = _glfw.windowListHead;  window;  window = window->next)
+    {
+        if (window->context.client != GLFW_NO_API)
+            [window->context.nsgl.object update];
+    }
+
     _glfwPollMonitorsNS();
 }
 

src/internal.h

@@ -303,6 +303,9 @@ struct _GLFWctxconfig
     int           robustness;
     int           release;
     _GLFWwindow*  share;
+    struct {
+        GLFWbool  offline;
+    } nsgl;
 };
 
 /*! @brief Framebuffer configuration.

src/nsgl_context.m

@@ -160,6 +160,18 @@ GLFWbool _glfwCreateContextNSGL(_GLFWwindow* window,
     ADD_ATTR(NSOpenGLPFAAccelerated);
     ADD_ATTR(NSOpenGLPFAClosestPolicy);
 
+    if (ctxconfig->nsgl.offline)
+    {
+        ADD_ATTR(NSOpenGLPFAAllowOfflineRenderers);
+        // NOTE: This replaces the NSSupportsAutomaticGraphicsSwitching key in
+        //       Info.plist for unbundled applications
+        // HACK: This assumes that NSOpenGLPixelFormat will remain
+        //       a straightforward wrapper of its CGL counterpart
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 100800
+        ADD_ATTR(kCGLPFASupportsAutomaticGraphicsSwitching);
+#endif /*MAC_OS_X_VERSION_MAX_ALLOWED*/
+    }
+
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= 101000
     if (ctxconfig->major >= 4)
     {

src/window.c

@@ -345,6 +345,9 @@ GLFWAPI void glfwWindowHint(int hint, int value)
         case GLFW_COCOA_FRAME_AUTOSAVE:
             _glfw.hints.window.ns.frame = value ? GLFW_TRUE : GLFW_FALSE;
             break;
+        case GLFW_COCOA_GRAPHICS_SWITCHING:
+            _glfw.hints.context.nsgl.offline = value ? GLFW_TRUE : GLFW_FALSE;
+            break;
         case GLFW_CENTER_CURSOR:
             _glfw.hints.window.centerCursor = value ? GLFW_TRUE : GLFW_FALSE;
             break;