Cairo: introduce Fl::cairo_flush() in FLTK API

Flushing the Cairo context is necessary on Windows to make Cairo
drawings appear on the device (screen). This new method makes it easy
for user code to do this correctly after using Cairo drawings.

- add Fl::cairo_flush(cairo_t *)
- document Fl::cairo_flush(cairo_t *)
- reformat Cairo doxygen docs and code (partially)
- use the new method in Fl_Cairo_Window
- use the new method in test/cairo_test.cxx
- other minor (text) changes in test/cairo_test.cxx
- add test/cairo_test to the demo menu (test/demo.menu)

1 files changed, 1 insertions, 2 deletions

diff --git a/FL/Fl_Cairo_Window.H b/FL/Fl_Cairo_Window.H
index 65a8d5eeb..2470dd0fe 100644
--- a/FL/Fl_Cairo_Window.H
+++ b/FL/Fl_Cairo_Window.H
@@ -102,8 +102,7 @@ protected:
         Fl::cairo_make_current(this);
       draw_cb_(this, Fl::cairo_cc());
       // flush Cairo drawings: necessary at least for Windows
-      cairo_surface_t *s = cairo_get_target(Fl::cairo_cc());
-      cairo_surface_flush(s);
+      Fl::cairo_flush(Fl::cairo_cc());
     }
   }