I'm trying to edit a cell in a Tree_View with a List_Store, and saw in GtkAda's User Guide that it offers the On_Edited procedure. I set up a callback this way with the following procedure:

procedure Editing_Done
( Self : access Gtk_Cell_Renderer_Text_Record'Class;
Path : Glib.UTF8_String; -- this is the row
New_Text : Glib.UTF8_String
) is
begin
Tio.Put_Line( Get_Property(Self, Gtk.Cell_Renderer_Text.Text_Property)'Image ); -- line 1
Tio.Put_Line(Path'Image); -- line 2
Tio.Put_Line(New_Text'Image); -- line 3
Set_Property(Self, Gtk.Cell_Renderer_Text.Text_Property, New_Text);
Self.Stop_Editing( False );
Tio.Put_Line( Get_Property(Self, Gtk.Cell_Renderer_Text.Text_Property)'Image ); -- line 4
end Editing_Done;

I didn't really expect this to work, and it doesn't, but here's what I have verified it does do, in order:

* prints the data that was in the cell before editing (line 1)
* prints the row that was edited (line 2)
* prints the new text (line 3)
* prints the data that is in the cell as the procedure ends (line 4)

Lines 3 and 4 agree, which is great! But what I see in the TreeView is that the cell reverts after editing to the value in Line 1.

My questions:

1) The documentation of On_Edited states that I am supposed to "update the model and store New_Text at the position indicated by Path." How do I get the model? I understand that "Path" indicates the row in the List_Store / TreeView, but Get_Model's
Signature requires a TreeView, which I do not have.

2) What else might I be missing from a correct implementation of the On_Edited callback?

thanks in advance
john perry

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On 2022-05-30 07:28, John Perry wrote:

I'm trying to edit a cell in a Tree_View with a List_Store, and saw in GtkAda's User Guide that it offers the On_Edited procedure. I set up a callback this way with the following procedure:

procedure Editing_Done
( Self : access Gtk_Cell_Renderer_Text_Record'Class;
Path : Glib.UTF8_String; -- this is the row
New_Text : Glib.UTF8_String
) is
begin
Tio.Put_Line( Get_Property(Self, Gtk.Cell_Renderer_Text.Text_Property)'Image ); -- line 1
Tio.Put_Line(Path'Image); -- line 2
Tio.Put_Line(New_Text'Image); -- line 3
Set_Property(Self, Gtk.Cell_Renderer_Text.Text_Property, New_Text);
Self.Stop_Editing( False );
Tio.Put_Line( Get_Property(Self, Gtk.Cell_Renderer_Text.Text_Property)'Image ); -- line 4
end Editing_Done;

I didn't really expect this to work, and it doesn't, but here's what I have verified it does do, in order:

* prints the data that was in the cell before editing (line 1)
* prints the row that was edited (line 2)
* prints the new text (line 3)
* prints the data that is in the cell as the procedure ends (line 4)

Lines 3 and 4 agree, which is great! But what I see in the TreeView is that the cell reverts after editing to the value in Line 1.

My questions:

1) The documentation of On_Edited states that I am supposed to "update the model and store New_Text at the position indicated by Path." How do I get the model? I understand that "Path" indicates the row in the List_Store / TreeView, but Get_Model's

Signature requires a TreeView, which I do not have.

On_* procedures are useless most of the time. Instead, you have to
instantiate Gtk.Handlers.User_Callback with a parameter indicating the
widget:

package Edited_Handlers is
new Gtk.Handlers.User_Callback
( Gtk_Cell_Renderer_Text_Record,
My_Widget_Where_The_Tree_View_Lives_Ptr
);

The parameter could be Tree_Vuew as well, but having a widget is always
a better design.

Usually you derive your widget from some container like Gtk_Grid. The
extension holds children and anything else you would need. E.g.:

type My_Widget_Where_The_Tree_View_Lives is new Gtk_Grid_Record with
View : Gtk_Tree_View;
Store : Gtk_List_Store;
Fancy_Button : Gtk_Button;
...
end record;

Define Gtk_New and override Initialize. In the Initialize after you
called Gtk_Grid's Initialize you create all children and connect to the
signal "editing-done" to the renderer:

procedure Editing_Done
( Self : access Gtk_Cell_Renderer_Text_Record'Class;
Path : UTF8_String;
New_Text : UTF8_String;
Widget : My_Widget_Where_The_Tree_View_Lives_Ptr
)

Now when it is called you have the tree View and the list store (= the
model) in the callback. Use Get_Iter_From_String in order to get the
iterator from Path. Change the store at the iterator if you accept the
edit. That's all.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

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On_* procedures are useless most of the time.

I guess you mean in GtkAda? I've found them invaluable in other contexts. If so, that's disappointing. To be fair, in the hours of reading on this I did notice that Gtk+ itself makes this difficult; the On_* procedures seem to be a GtkAda enhancement.

In the end I made it work with an On_* design, but it was your suggestion that helped! I used the second form of On_Edited and passed a TreeView in the slot. To get the model:

Tree_View: Gtk_Tree_View := Gtk_Tree_View(Self);
Model: Gtk_Tree_Model := Get_Model( Tree_View );
Iter : Gtk_Tree_Iter := Get_Iter_From_String(Model, Path);
Store: Gtk_List_Store := Gtk_List_Store( To_Object(Model) );

Getting the rest wasn't too hard after I had that. What I hadn't understood at first was that the Model had to be converted from the Interface via the To_Object function.

Thank you very much, and also for the quick answer!

john perry

PS If anyone knows how to make the first form of On_Edited work, I'd be delighted to know.

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On 2022-05-30 09:46, John Perry wrote:

On_* procedures are useless most of the time.

I guess you mean in GtkAda?

Yes.

I've found them invaluable in other contexts. If so, that's disappointing. To be fair, in the hours of reading on this I did notice that Gtk+ itself makes this difficult; the On_* procedures seem to be a GtkAda enhancement.

Yes, GtkAda adds a typed layer on top of untyped GTK signals.

In the end I made it work with an On_* design, but it was your suggestion that helped! I used the second form of On_Edited and passed a TreeView in the slot. To get the model:

Tree_View: Gtk_Tree_View := Gtk_Tree_View(Self);
Model: Gtk_Tree_Model := Get_Model( Tree_View );
Iter : Gtk_Tree_Iter := Get_Iter_From_String(Model, Path);
Store: Gtk_List_Store := Gtk_List_Store( To_Object(Model) );

Getting the rest wasn't too hard after I had that. What I hadn't understood at first was that the Model had to be converted from the Interface via the To_Object function.

If that is OK to you, but in production code you need a lot of stuff to
do in a handler, most of it is unrelated to the tree view. This is why a
custom widget is always advisable. Using a slot is a matter of taste/ I
never use slots and avoid run-time type conversions.

BTW, derived widgets is also a GtkAda feature, in GTK a derived widget
require a lot of work. In GtkAda they are trivial.

Typically in a renderer edit commit you would maintain undo/redo
buffers, change the active cell for smooth navigation, [un]gray/hide a
couple of buttons (like Save). Same goes with the buttons and basically
with all signals.

The design pattern you need to keep in mind is that a signal sent to a
visual element like renderer or button, logically, is rather sent to
some container widget a couple layers above. If you do not follow this
logic, you will have a very complicated fragile code.

PS If anyone knows how to make the first form of On_Edited work, I'd be delighted to know.

The first form can be used with a static layout and global variables. (:-))

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

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On Monday, May 30, 2022 at 1:57:30 PM UTC-5, Dmitry A. Kazakov wrote:

In the end I made it work with an On_* design...

If that is OK to you, but in production code you need a lot of stuff to
do in a handler, most of it is unrelated to the tree view.

I agree with what you write, and learned a bit. I've never been in a situation where I had to implement a TreeView-like object before, so I never had to think about it much. I probably won't pursue it since the project I'm working on is a small, personal
project with corresponding amounts of time available.

BTW, derived widgets is also a GtkAda feature, in GTK a derived widget require a lot of work. In GtkAda they are trivial.

Interesting! I'll probably look into this more at some future point.

thanks again
john perry

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