How a Combobox with the csOwnerDrawFixed Style can behave like the csDropDown style?

问题

I'm using a TComboBox component with the style property set to csOwnerDrawFixed, I implement the OnDrawItem And everything works fine, Now I want which the combobox to behave like when had the csDropDown style (with the csOwnerDrawFixed style behaves like the csDropDownList style) , I mean with a inner editor. is this possible?

回答1:

Delphi's TComboBox wrapper doesn't support an owner draw editable style, but the underlying Windows control does, and it's easy to enable it.

Create a new descendant class like so:

TComboBox = class(StdCtrls.TComboBox)
public
  procedure CreateParams(var Params: TCreateParams); override;
end;

procedure TComboBox.CreateParams(var Params: TCreateParams);
begin
  inherited;
  if Assigned(OnDrawItem) then
    Params.Style := Params.Style or CBS_OWNERDRAWFIXED
end;

Set the Style to csDropDown and assign OnDrawItem like you're already doing.

回答2:

None of the OwnerDraw styles support the presence of an edit box in the TComboBox. You will have to use a separate TEdit instead.

来源：https://stackoverflow.com/questions/9797961/how-a-combobox-with-the-csownerdrawfixed-style-can-behave-like-the-csdropdown-st