RichEdit scrollen verhindern

[Popov]

Mal als Grundlage, musst noch etwas Arbeit für Feintuning reinstecken:

Delphi-Quellcode:

function GetCurLine(Memo: TCustomMemo): Longint;
begin
  with Memo do
    Result := SendMessage(Handle, EM_LINEFROMCHAR, SelStart, 0);
end;

function GetCurCol(Memo: TCustomMemo): Longint;
begin
  with Memo do
    Result := SelStart - SendMessage(Handle, EM_LINEINDEX, GetCurLine(Memo), 0);
end;

procedure TempCanvas(Font: TFont; Text: string; out TextWidth, TextHeight: Integer);
begin
  with TBitmap.Create do
  try
    Canvas.Font.Assign(Font);
    TextWidth := Canvas.TextWidth(Text);
    TextHeight := Canvas.TextHeight(Text);
  finally
    Free;
  end;
end;

procedure TForm1.Memo1KeyPress(Sender: TObject; var Key: Char);
const
  MaxLen = 100;
  MaxHeight = 100;
var
  Memo: TMemo;
  LineIndex,
  LineCol,
  TextWidth,
  TextHeight: Integer;
  s: string;
begin
  Memo := Sender as TMemo;

  LineIndex := GetCurLine(Memo);
  LineCol := GetCurCol(Memo);

  s := Memo.Lines[LineIndex];
  TempCanvas(Memo.Font, s + Key, TextWidth, TextHeight);

  if TextWidth > MaxLen then
    if Ord(Key) >= 32 then
      Key := #0;

  Memo.Lines[LineIndex] := s;

  while (Memo.Lines.Count * TextHeight) > MaxHeight do
    Memo.Lines.Delete(Memo.Lines.Count - 1);
end;