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tl;dr : sorry for the long text. Withdrawing my first idea, I suggest we move child related data to the children and not allocate it as part of the parent, and create a standardised interface for that.
Ok, I see the points.
So changing Fl_Pack is not realistic. And since Fl_Flex is in fltk_rs, it's probably wise to keep the method names as is. Fl_Groups seems to avoid successfully to have pointers dangle, or we would know about it.
I am just very much in favour to point at something else only once, because otherwise there are just too many locations to keep track of. For example, if I delete and Widget, it may have a parent that links back to it, but it also may be resizable, so my parent may have a second pointer. Now with Fl_Flex, there may be just another pointer that tells me that my widget has a fixed size.
This is by no means a drama, but if it is possible to avoid it easily, I would. So here are my ideas:
- Storing relative width and height was a bad idea by me, because different Groups may want to store very different things per child.
- Making the Group handle an array of widget data (Fl_Group::init_size()) or widget pointers (Fl_Group::resizable()) is inherently unsafe, even if we got away with it for 30 years. But that's also part of what kept us from implementing new Groups with better resizing options like Flex and Grid.
- Making Fl_Group::insert(), remove(), and clear() virtual would make implementing Flex and Grid easier and safe.
So I withdraw my original idea and suggest that we add a group_data pointer to every widget. This pointer is reserved for use by the current parent exclusively, and the parent can store whatever it wants. It should delete that data when removing a widget, but if it doesn't, the widget removes the data when being deleted (no leak). If it is added to a new Group, the new Group will simply replace the group_data with its own data.
Yes, it adds a pointer to Fl_Widget, but OTOH it removes pointers and code in Fl_Group.
To have a little code, I suggest:
class _Fl_Group_Data { public:
virtual ~Fl_Group_Data(); };
class Fl_Widget { ~Fl_Widget() { ... group_data(NULL); } void group_data(_Fl_Group_Data*); // replace current group data with new group data _Fl_Group_Data *group_data(); };
class Fl_Fancy_Group { class _Fl_Fancy_Group_Data : public _Fl_Group_Data { double width_factor; int initial_width; ... }; void insert(FL_Widget *w) { w->group_data(new _Fl_Fancy_Group_Data(50.0, w->w())); ... } void remove(Fl_Widget *w) { ... w->group_data(NULL); // will call 'delete' for us } };
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