On 7/13/21 2:36 PM, Greg Ercolano wrote:
Our docs for Fl_Group should probably both describe and show recommended examples
for how to delete widgets from the group (i.e. remove() and destroy), showing proper
techniques especially in contexts where one has to be careful (or used to have to be),
such as when deleting from callbacks vs. event handlers vs. other situations.
Since the best way to get traction on this is to suggest a change and seek input, as it's easier to make corrections to someone else's suggestion than to suggest something from scratch. ; )
For Fl_Group, we could perhaps add a section to the class description, something along the lines of (I'm not actually the one to write this, as I'm not sure all the ins and outs of when we supported what.. I think we used to have an article about this but I couldn't find it):
Removing vs. Deleting Children..and include some example code showing the proper use in a callback() vs handle() vs other contexts. Again, I'm probably not the one to write this, as I'm not familiar with all the internals and possible gotchyas.
Child widgets can be removed from the group without destruction using remove(int) or remove(Fl_Widget*), allowing the widget to remain allocated so it can later be reparented elsewhere.
To delete as well as destroy a child widget, you can use any one of:
- Fl::delete_widget(w) which will schedule destruction on the next iteration of the app loop
- In fltk 1.3.x (and up, 'x' unknown) you can simply use the c++ 'delete' operator to destroy the widget, and that automatically schedules it for removal just like Fl::delete_widget()
- In fltk 1.1.x (and back) order of execution was important; you had to use Fl_Group::remove() first, then c++ delete.
- ..etc..
Similarly, docs for Fl_Browser::remove() and Fl_Tree::remove() should elaborate on how they also
destroy the items, so as not to be confused with Fl_Group::remove() (which does not), and in the
case of Fl_Tree, what happens with Fl_Widget's that have been associated with tree items, and how
to properly reassign or destroy those.
This should be easy, just a small elaboration to the existing docs (in green):
Fl_Browser::remove(int) Remove entry for given line number, making the browser one line shorter. This frees the memory associated with the browser item immediately. You must call redraw() to make any changes visible.
Fl_Tree::remove(Fl_Tree_Item* item) Remove the specified 'item' from the tree.
assigned to the item with Fl_Tree_Item::widget(), To destroy an FLTK widget assigned to the item, you can do that cleanly this way:
remove() frees the memory associated with the specified Fl_Tree_Item immediately. remove() does not affect any FLTK widget
'item' may not be NULL. If the item has children, all those are removed too. If item being removed has focus, no item will have focus.
// Delete the Fl_Tree_Item 'item' and any associated FLTK widget Fl_Widget *w = item->widget(); // save any widget for the item tree->remove(item); // remove the item, destroying it if ( w ) Fl::delete_widget(w); // delete the widget last, if there was one
For more info, see Fl_Group section on deleting FLTK child widgets. Note that after a remove(), any widget assigned to the item will remain a child of Fl_Tree's Fl_Group, which will continue to 'own' the widget.
This allows the widget to be reassigned to another item without having to recreate it. Destroying the tree will automatically destroy any child fltk widgets.
I think specific details regarding proper deleting of FLTK widgets should appear
There may be other widgets besides Fl_Browser and Fl_Tree that may need elaboration on whether memory is freed or not with methods like remove().
only in Fl_Group, and other docs simply refer to that documenation as needed,
so there aren't multiple descriptions of the process.
Fl_Tree::remove(Fl_Tree_Item* item) Remove the specified 'item' from the tree.
remove() frees the memory associated with the specified Fl_Tree_Item immediately. remove() does not affect any FLTK widget
'item' may not be NULL. If the item has children, all those are removed too. If item being removed has focus, no item will have focus.
assigned to the item with Fl_Tree_Item::widget(), To destroy an FLTK widget assigned to the item, you can do that cleanly this way: [..]
Hmm, it might be better to move the description of how to
remove a widget assigned to an item
with Fl_Tree_Item::widget() to the docs for that method, and
simply refer to that here
in remove()'s docs, e.g.
remove() does not destroy any FLTK widget
assigned to the item with widget(Fl_Widget*).
For more on how to manage that, see Fl_Tree_Item::widget().
This way anyone not even using widget() assignment doesn't
have to see a lot of detail
in the remove() docs that doesn't concern them.
On 7/13/21 2:36 PM, Greg Ercolano wrote:
Our docs for Fl_Group should probably both describe and show recommended examples
for how to delete widgets from the group (i.e. remove() and destroy), showing proper
techniques especially in contexts where one has to be careful (or used to have to be),
such as when deleting from callbacks vs. event handlers vs. other situations.
Since the best way to get traction on this is to suggest a change and seek input, as it's easier to make corrections to someone else's suggestion than to suggest something from scratch. ; )
For Fl_Group, we could perhaps add a section to the class description, something along the lines of (I'm not actually the one to write this, as I'm not sure all the ins and outs of when we supported what.. I think we used to have an article about this but I couldn't find it):
Removing vs. Deleting Children
Child widgets can be removed from the group without destruction using remove(int) or remove(Fl_Widget*), allowing the widget to remain allocated so it can later be reparented elsewhere.
To delete as well as destroy a child widget, you can use any one of:
- Fl::delete_widget(w) which will schedule destruction on the next iteration of the app loop
- In fltk 1.3.x (and up, 'x' unknown) you can simply use the c++ 'delete' operator to destroy the widget, and that automatically schedules it for removal just like Fl::delete_widget()
- In fltk 1.1.x (and back) order of execution was important; you had to use Fl_Group::remove() first, then c++ delete.
..and include some example code showing the proper use in a callback() vs handle() vs other contexts. Again, I'm probably not the one to write this, as I'm not familiar with all the internals and possible gotchyas.
- ..etc..
Similarly, docs for Fl_Browser::remove() and Fl_Tree::remove() should elaborate on how they also
destroy the items, so as not to be confused with Fl_Group::remove() (which does not), and in the
case of Fl_Tree, what happens with Fl_Widget's that have been associated with tree items, and how
to properly reassign or destroy those.
This should be easy, just a small elaboration to the existing docs (in green):
Fl_Browser::remove(int) Remove entry for given line number, making the browser one line shorter. This frees the memory associated with the browser item immediately. You must call redraw() to make any changes visible.
Fl_Tree::remove(Fl_Tree_Item* item) Remove the specified 'item' from the tree.
assigned to the item with Fl_Tree_Item::widget(), To destroy an FLTK widget assigned to the item, you can do that cleanly this way:
remove() frees the memory associated with the specified Fl_Tree_Item immediately. remove() does not affect any FLTK widget
'item' may not be NULL. If the item has children, all those are removed too. If item being removed has focus, no item will have focus.
// Delete the Fl_Tree_Item 'item' and any associated FLTK widget Fl_Widget *w = item->widget(); // save any widget for the item tree->remove(item); // remove the item, destroying it if ( w ) Fl::delete_widget(w); // delete the widget last, if there was one
Note that operator delete allows NULL as argument, but it's also fine to use if(w) and also Fl::delete_widget(w) (if you're paranoid). I would explain the last part in the text (too lazy now).
// Delete the Fl_Tree_Item 'item' and any associated FLTK widget Fl_Widget *w = item->widget(); // save any widget associated with the item item->widget(0); // disconnect the widget
tree->remove(item); // remove the item, destroying it delete w; // delete the widget, if there was one
For more info, see Fl_Group section on deleting FLTK child widgets. Note that after a remove(), any widget assigned to the item will remain a child of Fl_Tree's Fl_Group, which will continue to 'own' the widget.
This allows the widget to be reassigned to another item without having to recreate it. Destroying the tree will automatically destroy any child fltk widgets.
I think specific details regarding proper deleting of FLTK widgets should appear
only in Fl_Group, and other docs simply refer to that documenation as needed,
so there aren't multiple descriptions of the process.
There may be other widgets besides Fl_Browser and Fl_Tree that may need elaboration on whether memory is freed or not with methods like remove().
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