How-to-Draw-a-Radio-Button-for-a-TListBox-Item-in-Delphi


            Title: How to Draw a Radio Button for a TListBox Item in Delphi
Delphi's TListBox VCL component displays a collection of items in a scrollable list. The MultiSelect property determines if a user can select more than one item. When MultiSelect is set to false (default state) a ListBox acts as a TRadioButton list container (similar to TRadioGroup). 
Here's how to draw a radio button for each of the items in a List Box (meaningful only if MultiSelect is false) :
Note: Drop a TListBox on a Form, add several strings to its Items property:
 procedure TRadioListBoxForm.FormCreate(Sender: TObject) ;
 begin
 //or use Object Inspector to assign the
 //OnDrawItem event handler,
 //Style and ItemHeight properties...
 ListBox1.Style := lbOwnerDrawFixed;
 ListBox1.ItemHeight := 20;
 ListBox1.OnDrawItem := ListBox_DrawItem;
 end;
 
 procedure TRadioListBoxForm.ListBox_DrawItem(
 Control: TWinControl;
 Index: Integer;
 Rect: TRect;
 State: TOwnerDrawState) ;
 const
 IsSelected : array[Boolean] of Integer = (DFCS_BUTTONRADIO, DFCS_BUTTONRADIO or DFCS_CHECKED) ;
 var
 optionButtonRect: TRect;
 listBox : TListBox;
 begin
 listBox := Control as TListBox;
 with listBox.Canvas do
 begin
 FillRect(rect) ;
 
 optionButtonRect.Left := rect.Left + 1;
 optionButtonRect.Right := Rect.Left + 13;
 optionButtonRect.Bottom := Rect.Bottom;
 optionButtonRect.Top := Rect.Top;
 
 DrawFrameControl(Handle, optionButtonRect, DFC_BUTTON, IsSelected[odSelected in State]) ;
 
 TextOut(15, rect.Top + 3, listBox.Items[Index]) ;
 end;
 end; 
Note: the Style property sets ListBox1 owner drawing to true. The OnDrawItem is used to draw a radio button for each of the items.
VCL Delphi
