Adds the FL_AUTO_DELETE_EVENT to suppress auto delete.

Language wrappers can have major issues with FLTK auto deleting
all children of a group if a group is deleted. This event gives individual
widget the opportunity to override auto delete.

1 files changed, 15 insertions, 1 deletions

diff --git a/src/Fl_Group.cxx b/src/Fl_Group.cxx
index 2576efea7..134b49998 100644
--- a/src/Fl_Group.cxx
+++ b/src/Fl_Group.cxx
@@ -375,6 +375,19 @@ Fl_Group::Fl_Group(int X,int Y,int W,int H,const char *l)
   \internal If the Fl_Group widget contains the Fl::focus() or the
   Fl::pushed() widget these are set to sensible values (other widgets
   or the Fl_Group widget itself).
+
+  \note FLTK's auto-delete feature efficiently manages widget hierarchies in
+  C++ applications by automatically cleaning up. However, this feature can
+  cause issues when FLTK is used with reference-counting languages like Python,
+  where automatic deletion might interfere with reference counting. To address
+  this, auto-delete can be disabled for individual widgets. When
+  \ref Fl_Group::clear() is called, it sends an \ref FL_AUTO_DELETE event to
+  each widget. If a widget returns 1 in response to this event, it will not
+  be deleted. In a Python wrapper, this behavior would typically involve
+  decrementing the widget's reference count instead of deleting it.
+
+  \see Fl_Group::remove(int), Fl_Group::delete_child(int),
+  Fl_Group::~Fl_Group()
 */
 void Fl_Group::clear() {
   savedfocus_ = 0;
@@ -417,7 +430,8 @@ void Fl_Group::clear() {
       } else {                          // slow removal
         remove(idx);
       }
-      delete w;                         // delete the child
+      if (w->handle(FL_AUTO_DELETE_EVENT)==0)
+        delete w;                       // delete the child
     } else {                            // should never happen
       remove(idx);                      // remove it anyway
     }