Delphi: Change rich edit format without changing selection

If you are using Microsoft's Rich Edit control v2+ then you can change a paragraph's format without selecting that paragraph if you use the ITextDocument COM interface.

var
   rich_edit_ole: IRichEditOle;
   doc_dispatch: IDispatch;
   doc, range: Variant;
begin
   if RichEdit_GetOleInterface(rich_edit.Handle, rich_edit_ole) then begin
      OleCheck(rich_edit_ole.QueryInterface(IDispatch, doc_dispatch));
      // Use Variants because we do not have Delphi declarations for
      // the ITextDocument and ITextRange interfaces.
      doc := doc_dispatch;
      range := doc.Range(start_char, end_char);
      range.SpaceAfter := 12;
   end;

Note that you are not using Rich Edit v2+ if you use Delphi's inbuilt TRichEdit. TRichEdit specifically requests v1, which does not support the Text Object Model (TOM). I use Alexander Obukhov's TRichEdit98.