[Solved] Flickering issue when moving CheckboxList item

[loaded]

Hi All,
I am trying to make a simple layer manager with CheckboxList component. Thanks to the help of friends on the forum I created a simple working example. My current problem is that the flickering when moving the relevant layers up or down isn't really a major problem, but it would be great if it could be solved visually.
I would appreciate it if the experts in the business could take a look at the relevant demo. Respects.

[jcmontherock]

No issue for me: no flickering. W11/2.2.6 X64.

[cappe]

works fine for me, I use linux

[wp]

No flicker here either (Win 11, Laz/main (32bit) FPC 3.2.2).

Alternatively you could try a TListview with activated checkboxes (ListView1.Checkboxes := true); query the checked states from the corresponding TListItem property.

See attached demo (tested to work on Win, Linux/gtk2. It does not work on cocoa but there the customdrawn Checklistbox does not work either).

[paweld]

Draw only if indexes change:

Code: Pascal  [Select][+][-]

1. procedure TForm1.CheckListBox1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
2. var
3.   c1, c2: Boolean;
4. begin
5.   if ssleft in shift then
6.   begin
7.     move_lay_son := CheckListBox1.ItemIndex;
8.     if move_lay_son = move_lay_ilk then
9.       exit;
10.     c1 := CheckListBox1.Checked[move_lay_ilk];
11.     c2 := CheckListBox1.Checked[move_lay_son];
12.     CheckListBox1.Exchange(move_lay_ilk, move_lay_son);
13.     CheckListBox1.Checked[move_lay_ilk] := c2;
14.     CheckListBox1.Checked[move_lay_son] := c1;
15.     move_lay_ilk := move_lay_son;
16.   end;
17. end;          

[KodeZwerg]

No flicker here either (Win 11, Laz/main (32bit) FPC 3.2.2).

Alternatively you could try a TListview with activated checkboxes (ListView1.Checkboxes := true); query the checked states from the corresponding TListItem property.

See attached demo (tested to work on Win, Linux/gtk2. It does not work on cocoa but there the customdrawn Checklistbox does not work either).

You forgot about the issue that he got so I've upgraded a little.
Set property DragMode for ListView1 to dmAutomatic
create OnDragDrop event with something like this:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListView1DragDrop(Sender , Source: TObject; X , Y: Integer);
2. var
3.   MyItem : TListItem;
4. begin
5.   if Source = ListView1 then
6.     with Source as TListView do
7.       begin
8.         if (GetItemAt(X,Y) <> nil) then
9.           begin
10.             MyItem := Items.Insert(GetItemAt(X,Y).Index);
11.             MyItem.Assign(Selected);
12.             Selected.Delete;
13.           end;
14.       end;
15. end;

create OnDragOver event with something like this:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListView1DragOver(Sender , Source: TObject; X , Y: Integer;
2.   State: TDragState; var Accept: Boolean);
3. begin
4.   If Source = ListView1 then
5.     Accept := True
6.     else
7.     Accept := False;
8. end;

But I am unsure about how to display the content while you are dragging...

[loaded]

Dear brothers jcmontherock, cappe, wp, paweld  and KodeZwerg, I would like to thank each and every one of you. I took your precious time, I hope one day I will have the opportunity to offer you all a coffee 
I am looking for solutions for this for now as I am interested in wp and KodeZwerg Checkbox. But your advice is very valuable for me, it was good to learn about them.
paweld's suggestion worked.