Restrict TComboBox dropdown

[Blaazen]

Hi,
any idea how to restrict TComboBox dropdown - other than Enabled:=False?
I'm working on TCheckComboBox. It is readonly, Style=csOwnerDrawFixed.
See screenshot. I need that - let's say - left half of the component will toggle the state while right half will dropdown list. It is probably not problem with Windows (it has always "Edit") but GTK2 and Qt4 always dropdown (on left-mouse down).

Currently, I hooked on WMLButtonDown(); which is triggered before dropdown but I cannot find way to restrict dropdown.
I tried for example:

Code: [Select]

ControlState:=ControlState-[csLButtonDown, csClicked];I guess it is not easy since it is native component.

Thanks.

[engkin]

Based on reading the source code (and only reading):
GTK2:

Code: [Select]

class procedure TGtk2WSCustomComboBox.SetDroppedDown(
...
  case ADroppedDown of
    True : gtk_combo_box_popup(Combo);
    False: gtk_combo_box_popdown(Combo);
  end;
end;
In GTK2, gtk_combo_box_pop[up/down]  are called only in:
  TGtk2WSCustomComboBox.SetDroppedDown
which is called directly/indirectly through:
  TCustomComboBox
    procedure KeyDown - using property DroppedDown
    property DroppedDown
    procedure SetDroppedDown - setter of property DroppedDown

I assume if you override SetDroppedDown and pass the call to it when you want or neglect the call when you don't need it to go through seems to be ok, maybe?

[Never]

This might give you an idea
http://embarcadero.newsgroups.archived.at/public.delphi.vcl.components.using/200910/0910223332.html

or maybe a coditional call to Abort in ondropdown event?

[Blaazen]

I tried message-methods approach and overriding SetDroppedDown as well but no luck.

[Never]

This

Code: [Select]

procedure TForm1.ComboBox1DropDown(Sender: TObject);
begin
  Abort;
end;
blocks the list to drop down
Also this one

Code: [Select]

procedure TForm1.ComboBox1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  ComboBox1.Style:=csSimple;
end;

procedure TForm1.ComboBox1MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  ComboBox1.Style:=csOwnerDrawFixed
end; but needs screen to stop update until  mouse up

[Blaazen]

Yes but only in Windows. It has no effect in Qt and it blocks GTK2 so I have to execute: killall -9 gdb

[Blaazen]

I will solve it with TTimer with a very small interval (~5 ms). It seems to be the only way.

[Never]

i think i found something

Code: [Select]

procedure TForm1.ComboBox1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
   ComboBox1.DroppedDown:=false;
end;
does the job easy and clean

[Blaazen]

It doesn't work on Qt4 and GTK2 too.

[Never]

just read this [ http://qt-project.org/forums/viewthread/3150  ] for qt
is it possible ? to change the width, height and border style of the dropdown area and reset it back again ?

[zeljko]

Currently, I hooked on WMLButtonDown(); which is triggered before dropdown but I cannot find way to restrict dropdown.

Just set Msg.Result to 1 in WMLButtonDown(), then it should result with TRUE in WS and that should work.

[Blaazen]

Thanks, but it doesn't work too.

And I wasn't right, DropDown is triggered before WMLButtonDown.

[Blaazen]

Finally, I hooked on DrawItem();, there's a negligible flickering but it's better solution than TTimer.

[zeljko]

Thanks, but it doesn't work too.

And I wasn't right, DropDown is triggered before WMLButtonDown.

hm....strange. My wild guess is that it should trigger in order mousedown,dropdown,mouseup (if mouseup need to be triggered).
How it looks in delphi ?

[Blaazen]

Quick test in Delphi7: DropDown is before MouseDown too, so in this regard is Lazarus compatible.