Initial OpenGL deprecation (#4458)

- Only on macOS
- Only a subset of the uses are deprecated, see radar://42257568

src/OpenGL/CGLContext.cs

@@ -32,6 +32,7 @@ using ObjCRuntime;
 using Foundation;
 
 namespace OpenGL {
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	public class CGLContext : INativeObject, IDisposable {
 		IntPtr handle;
 

src/OpenGL/CGLEnums.cs

@@ -21,9 +21,11 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 using System;
+using ObjCRuntime;
 
 namespace OpenGL {
 
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	public enum CGLErrorCode : uint
 	{
 		NoError            = 0,		/* no error */
@@ -48,6 +50,7 @@ namespace OpenGL {
 
 	}
 
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	public enum CGLPixelFormatAttribute : uint
 	{
 		AllRenderers = 1,

src/OpenGL/CGLPixelFormat.cs

@@ -32,6 +32,7 @@ using ObjCRuntime;
 using Foundation;
 
 namespace OpenGL {
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	public class CGLPixelFormat : INativeObject, IDisposable {
 		internal IntPtr handle;
 

src/appkit.cs

@@ -8466,10 +8466,6 @@ namespace AppKit {
 		[Export ("initWithData:")]
 		IntPtr Constructor (NSData attribs);
 
-		// TODO: wrap the CLContext and take a CLContext here instead.
-		//[Export ("initWithCGLPixelFormatObj:")]
-		//IntPtr Constructor (IntPtr cglContextHandle);
-
 		[Export ("getValues:forAttribute:forVirtualScreen:")]
 		void GetValue (ref int /* GLint = int32_t */ vals, NSOpenGLPixelFormatAttribute attrib, int /* GLint = int32_t */ screen);
 
@@ -26007,6 +26003,7 @@ namespace AppKit {
 	}
 #endif
 
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	[BaseType (typeof(CAOpenGLLayer))]
 	interface NSOpenGLLayer
 	{

src/coreanimation.cs

@@ -1465,6 +1465,7 @@ namespace CoreAnimation {
 	}
 
 #if MONOMAC
+	[Deprecated (PlatformName.MacOSX, 10, 14, message : "Use 'Metal' Framework instead.")]
 	[BaseType (typeof (CALayer))]
 	interface CAOpenGLLayer {
 		[Export ("layer"), New, Static]

src/coreimage.cs

@@ -204,10 +204,6 @@ namespace CoreImage {
 	[BaseType (typeof (NSObject))]
 	[DisableDefaultCtor]
 	interface CIContext {
-		// When we bind OpenGL add these:
-		//[Export ("contextWithCGLContext:pixelFormat:colorSpace:options:")]
-		//CIContext ContextWithCGLContextpixelFormatcolorSpaceoptions (CGLContextObj ctx, CGLPixelFormatObj pf, CGColorSpaceRef cs, NSDictionary dict, );
-
 #if !MONOMAC || XAMCORE_2_0
 		[iOS (9,0)][Mac (10,11)]
 		[Static]
@@ -361,13 +357,6 @@ namespace CoreImage {
 		[Export ("contextForOfflineGPUAtIndex:")]
 		[Static]
 		CIContext FromOfflineGpu (int gpuIndex);
-
-		// When we bind CGLContext
-		//+(CIContext *)contextForOfflineGPUAtIndex:(unsigned int)index
-		//    colorSpace:(nullable CGColorSpaceRef)colorSpace
-		//    options:(nullable CI_DICTIONARY(NSString*,id) *)options
-		//    sharedContext:(nullable CGLContextObj)sharedContext NS_AVAILABLE_MAC(10_10);
-		
 #endif
 
 		[iOS (9,0)][Mac (10,11)]