Improve subclassing cababilities of Fl_Tile (STR 2791)

- remove static variables and functions
- make move_intersection() virtual
- add (protected) cursor access methods

These changes were inspired by STR 2791 where the user proposing an
enhancement was not able to subclass Fl_Tile properly. This commit
fixes the mentioned issues and enables subclassing without copying
internal code.

1 files changed, 17 insertions, 3 deletions

diff --git a/FL/Fl_Tile.H b/FL/Fl_Tile.H
index af104a4eb..a7de02fea 100644
--- a/FL/Fl_Tile.H
+++ b/FL/Fl_Tile.H
@@ -1,7 +1,7 @@
 //
 // Tile header file for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2016 by Bill Spitzak and others.
+// Copyright 1998-2023 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
@@ -29,10 +29,24 @@ public:
   int handle(int event) FL_OVERRIDE;
   Fl_Tile(int X, int Y, int W, int H, const char *L=0);
   void resize(int X, int Y, int W, int H) FL_OVERRIDE;
-  void move_intersection(int oldx, int oldy, int newx, int newy);
+  virtual void move_intersection(int oldx, int oldy, int newx, int newy);
   FL_DEPRECATED("in 1.4.0 - use move_intersection(p) instead",
-  void position(int oldx, int oldy, int newx, int newy)) { return move_intersection(oldx, oldy, newx, newy); }
+  void position(int oldx, int oldy, int newx, int newy)) { move_intersection(oldx, oldy, newx, newy); }
   void position(int x, int y) { Fl_Group::position(x, y); }
+
+protected:
+  int cursor_;                  ///< current cursor index (0..3)
+  Fl_Cursor *cursors_;          ///< points at the array of 4 cursors (may be overridden)
+
+  /** Returns the cursor for cursor index n.
+    \see Fl_Tile::set_cursor(int)
+  */
+
+  Fl_Cursor cursor(int n) {
+    return cursors_[n];
+  }
+
+  void set_cursor(int n);       // set one of n (0..3) cursors
 };
 
 #endif