Remove / Hide border of TTrackBar

Question

I have a TTrackBar on my form, but would like it to not have the border around it:

ie. only the blue arrow should be visible - the border (and the content, ie the area that the arrow navigates in) should be invisible (could be solved by setting the color to clBtnFace if need be).

I have tried many things to hide this (in an overridden Create CONSTRUCTOR):

BevelEdges:=[];
BevelInner:=TBevelCut.bvNone;
BevelOuter:=TBevelCut.bvNone;
BevelKind:=TBevelKind.bkNone;
BorderWidth:=0;
Brush.Color:=clBtnFace;
ParentCtl3D:=FALSE;
Ctl3D:=FALSE;

but it doesn't appear to make any difference.

Is there a way to achieve my goal?

Answer 1

I believe you can override the track bar's CNNotify message method to handle the NM_CUSTOMDRAW notification when dwDrawStage = CDDS_ITEMPREPAINT and dwItemSpec = TBCD_CHANNEL, setting the result to CDRF_SKIPDEFAULT:

procedure TTrackBar.CNNotify(var Message: TWMNotifyTRB);
begin

  if
    (Message.NMHdr.code = NM_CUSTOMDRAW)
      and
    (Message.NMCustomDraw.dwDrawStage = CDDS_ITEMPREPAINT)
      and
    (Message.NMCustomDraw.dwItemSpec = TBCD_CHANNEL)
  then
    Message.Result := CDRF_SKIPDEFAULT
  else
    inherited;

end;

Don't forget to set ShowSelRange = False and TickStyle = tsNone.