Question

I am trying to create a custom control based on the TCustomComboBox in Delphi 2007, But I am stuck on the first hurdle.

I am trying to override the way the drop down is displayed, primarally the text that is displayed, looking at the source for TCustomComboBox in stdctrls.pas it looks like i just need to override DrawItem but it is not working, as the code in my overridden method is never executed.

I have looked a several open source components source code to see how they do it, but I am still at a loss.

Here is what I have so far (not much admittedly)

type   TKeyValueComboBox = class(TCustomComboBox)   private     { Private declarations }     //FColumns:Integer;   protected     { Protected declarations }     procedure DrawItem(Index: Integer; Rect: TRect; State: TOwnerDrawState);override;    public     { Public declarations }     constructor Create(AOwner: TComponent); override;     destructor Destroy; override;   published end; 

And

procedure TKeyValueComboBox.DrawItem(Index: Integer; Rect: TRect;   State: TOwnerDrawState); begin   TControlCanvas(Canvas).UpdateTextFlags;   if Assigned(OnDrawItem) then OnDrawItem(Self, Index, Rect, State)   else   begin     Canvas.FillRect(Rect);     Canvas.TextOut(Rect.Left + 2, Rect.Top, Items[Index]+'-HELLO');   end; end; 

Does anyone know what method I need to use to get my overridden version of fire? or what I am doing wrong?

Any help would be appreciated.

Answer 1

There also is a property that has to be set, from memory it’s DrawingStyle := dsCustomDraw Put that in the constructor or Loaded.