Add list of known macOS bugs to the gl-natives README

gl-natives/README.md

@@ -1,5 +1,30 @@
 # OpenRS2 GL Natives
 
+## Known bugs
+
+### macOS performance
+
+OpenJDK's `nativeGetTopmostPlatformWindowUnderMouse` function is very slow on
+macOS. On lower-end hardware, such as a 2011 Mac Mini, the rendering loop
+completely freezes whenever the mouse moves. More information is available in
+the [JetBrains Runtime issuer tracker][macos-perf].
+
+The performance is significantly better if the [JetBrains Runtime][jbr] is used
+instead of OpenJDK.
+
+### macOS lighting quality
+
+The lighting quality is very poor on a Mac Mini with an integrated Intel HD
+Graphics 3000 card: some polygons are far too dark, and they tend to flicker
+between bright and dark as the camera angle changes, instead of transitioning
+smoothly.
+
+I'm not yet sure if this is a bug specific to macOS, the Intel HD Graphics 3000
+drivers or the card itself. I don't believe it is the reimplemented
+bindings - the same problem happens with the original jaggl bindings and build
+667 of the client. I also think it is unlikely to be the client, as the same
+client code works on Windows and Linux.
+
 ## Copyright
 
 Copyright (c) 2019 OpenRS2 Authors
@@ -15,3 +40,6 @@ more details.
 
 You should have received a copy of the GNU Lesser General Public License along
 with OpenRS2 GL Natives. If not, see <https://www.gnu.org/licenses/>.
+
+[macos-perf]: https://youtrack.jetbrains.com/issue/JBR-444
+[jbr]: https://confluence.jetbrains.com/display/JBR/JetBrains+Runtime