Add Fl_Scheme_Choice widget and use it in test programs

This widget offers the selection of all known FLTK schemes as a simple
widget based on Fl_Choice.

Some test and demo programs use Fl_Scheme_Choice to enable the developer
or user to switch schemes quickly for comparison.

Todo:
 - add features to add new schemes during runtime (partially done)
 - update status when the scheme is changed by Fl::scheme("...")

1 files changed, 38 insertions, 0 deletions

diff --git a/FL/Fl_Scheme_Choice.H b/FL/Fl_Scheme_Choice.H
new file mode 100644
index 000000000..e45befcdd
--- /dev/null
+++ b/FL/Fl_Scheme_Choice.H
@@ -0,0 +1,38 @@
+//
+// Scheme Choice header for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2022-2023 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+#ifndef FL_Fl_Scheme_Choice_H_
+#define FL_Fl_Scheme_Choice_H_
+
+#include <FL/Fl.H>
+#include <FL/Fl_Scheme.H>
+#include <FL/Fl_Choice.H>
+
+class Fl_Scheme_Choice : public Fl_Choice {
+
+protected:
+  static void scheme_cb_(Fl_Widget *w, void *);
+
+public:
+  Fl_Scheme_Choice(int X, int Y, int W, int H, const char *L = 0);
+  int handle(int event) FL_OVERRIDE;
+
+  // set the current value according to the active scheme
+  virtual void init_value();
+
+}; // class Fl_Scheme_Choice
+
+#endif // FL_Fl_Scheme_Choice_H_