STR 1373: adds vsync control to OpenGL contexts on macOS

Windows and X11 to follow, no idea about Wayland.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/Fl_Gl_Window_Driver.H b/src/Fl_Gl_Window_Driver.H
index 839c5bc93..79f696905 100644
--- a/src/Fl_Gl_Window_Driver.H
+++ b/src/Fl_Gl_Window_Driver.H
@@ -69,6 +69,8 @@ public:
   virtual void swap_buffers() {}
   virtual void resize(int /*is_a_resize*/, int /*w*/, int /*h*/) {}
   virtual char swap_type();
+  virtual void swap_interval(int) { }
+  virtual int swap_interval() { return -1; }
   virtual int flush_begin(char&) {return 0;}
   virtual void gl_hide_before(void *&) {} // the default implementation may be enough
   static Fl_Gl_Choice *find_begin(int m, const int *alistp);