MacOS Mojave: restore support of gl_start()/gl_finish().

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@13107 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/mac.H

@@ -197,6 +197,7 @@ public:
   static void GLcontext_release(NSOpenGLContext*);
   static void GLcontext_makecurrent(NSOpenGLContext*);
   static void GL_cleardrawable(void);
+  static void gl_start(NSOpenGLContext*);
   void destroy(void);
   void map(void);
   void unmap(void);

src/Fl_cocoa.mm

@@ -2425,9 +2425,11 @@ static CGContextRef prepare_bitmap_for_layer(int w, int h ) {
     Fl_X::q_release_context();
     through_drawRect = NO;
     window->clear_damage();
-    CGImageRef cgimg = CGBitmapContextCreateImage(layer_gc);  // requires 10.4
-    layer.contents = (id)cgimg;
-    CGImageRelease(cgimg);
+    if (layer_gc) {
+      CGImageRef cgimg = CGBitmapContextCreateImage(layer_gc);  // requires 10.4
+      layer.contents = (id)cgimg;
+      CGImageRelease(cgimg);
+    }
   }
 }
 -(void)viewFrameDidChange
@@ -4808,6 +4810,17 @@ void Fl_Paged_Device::print_window(Fl_Window *win, int x_offset, int y_offset)
   this->print_widget(win, x_offset, y_offset + bt); // print the window inner part
 }
 
+void Fl_X::gl_start(NSOpenGLContext *ctxt) {
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_8
+  if (views_use_CA) {
+    Fl_X::q_release_context();
+    [(FLView*)[fl_window contentView] viewFrameDidChange];
+    [(FLView*)[fl_window contentView] layer].contentsScale = 1.;
+  }
+#endif
+  [ctxt update]; // supports window resizing
+}
+
 
 /* Returns the address of a Carbon function after dynamically loading the Carbon library if needed.
  Supports old Mac OS X versions that may use a couple of Carbon calls:

src/gl_start.cxx

@@ -68,7 +68,7 @@ void gl_start() {
   }
   fl_set_gl_context(Fl_Window::current(), context);
 #ifdef __APPLE__
-  Fl_X::GLcontext_update(context); // supports window resizing
+  Fl_X::gl_start(context);
 #elif !defined(WIN32)
   glXWaitX();
 #endif