[SOLVED] TComboBox and its Items[]

[Blaazen]

Can someone point me where is TComboBox notified that its Items changed?

When I do

Code: [Select]

ComboBox1.Items[0]:='dfzuk'; how TComboBox knows that it has to repaint itself.
I'm looking to sources and I cannot find any event or so.

Thanks

[Never]

hello Blaazen
this is not an answer ... i'm not able to find it like you but found this
http://delphi.about.com/od/vclusing/a/drawincombobox.htm
and thought it might help

[taazz]

Can someone point me where is TComboBox notified that its Items changed?

When I do

Code: [Select]

ComboBox1.Items[0]:='dfzuk'; how TComboBox knows that it has to repaint itself.
I'm looking to sources and I cannot find any event or so.

Thanks

This is done in the WSCustomComboBox class for example in the QT widget set it has a TQtComboStrings class declared which overrides the put internal method calling the setItemIndex to force a refresh. Didn't looked close enough for the other widget sets but I suspect something similar is done there too.

[engkin]

As Taazz mentioned, it gets replaced with a ws related strings class:

Code: [Select]

procedure TCustomComboBox.InitializeWnd;
..
  // get the interface based item list
  NewStrings:= TWSCustomComboBoxClass(WidgetSetClass).GetItems(Self);
...

For Win32:

Code: [Select]

class function TWin32WSCustomComboBox.GetItems(const ACustomComboBox: TCustomComboBox): TStrings;
var
  winhandle: HWND;
begin
  winhandle := ACustomComboBox.Handle;
  Result := TWin32ComboBoxStringList.Create(winhandle, ACustomComboBox);
  GetWin32WindowInfo(winhandle)^.List := Result;
end;


Code: [Select]

  TWin32ComboBoxStringList = class(TWin32ListStringList)
...


Code: [Select]

  TWin32ListStringList = Class(TStrings)
...


[howardpc]

And the TWin32ListStringList.Insert method includes a

Code: [Select]

   ...Windows.SendMessage{or SendMessageW}(..., FFlagAddString, ....);
where FFlagAddString is an alias for LB_ADDSTRING

[Blaazen]

Thanks, I'm designing TCheckComboBox, as proposed recently here, and I was looking where to hook.

[taazz]

Check also the lb_change message might suit your case better.