richedit 避免滚动条滚动时重绘

Question

procedure TfrmXWBL.FormPaint(Sender: TObject);
var
  aCanvas: Tcanvas;
  X1, X2, Y,t,i: Integer;
  byLineLength: BYTE;begin
aCanvas := TCanvas.Create;
Y := RichEdit1.Height;
   try   aCanvas.Handle := GetDC(RichEdit1.Handle);
   t:=2+richedit1.DefAttributes.Height+6;
   aCanvas.Pen.Color:=clskyblue;
   acanvas.Pen.width:=1;
   for i := 0 to RichEdit1.Lines.Count - 1 do
   begin
   //RichEdit1.
      With aCanvas do
      Begin
         Begin
         MoveTo(RichEdit1.Left+2,t); // Draw line after 80 characters
         LineTo(RichEdit1.Width-1,t);
      End;
   end;
   t:=t+richedit1.DefAttributes.Height+5;
    end
   Finally
      ReleaseDC(RichEdit1.Handle,aCanvas.Handle);
      aCanvas.Free;
   End;
end;
各位高手，我想在richedit中的每行加一条线分隔，但是当richedit中的内容过多时，滚动滚动条就会把原来绘好的线条抹去。有没有办法在滚动滚动条时，原来划的行线保留。谢谢！

Answer 1

控件发生变动肯定要重绘的，如果不重绘会发生问题，你也不希望控件里面用鼠标选择的文字跟你看到的不一样吧。你要保留这个线，只能在RichEdit的onPaint事件中实现

Answer 2

RichEdit的onPaint事件中实现
加上你上面的代码

Answer 3

RichEdit有全WMPaint消息，如果能截获到这个消息，添加上你的重绘代码就行了。

Answer 4

interface
uses
  Messages, Windows,  Graphics,  ComCtrls;type
  TMyRichEdit = class(TRichEdit)
    procedure WMPaint(var Message: TWMPaint); message WM_PAINT;
  end;implementation{ TMyRichEdit }procedure TMyRichEdit.WMPaint(var Message: TWMPaint);
var
  ACanvas: Tcanvas;
  X1, X2, Y,t,i: Integer;
  byLineLength: BYTE;
begin
  inherited;
  aCanvas := TCanvas.Create;
  Y := Self.Height;
  try
    ACanvas.Handle := GetDC(Self.Handle);
    t:=2+Self.DefAttributes.Height+6;
    aCanvas.Pen.Color:=clskyblue;
    acanvas.Pen.width:=1;
    for i := 0 to Self.Lines.Count - 1 do
    begin
      With ACanvas do
      Begin
        Begin
          MoveTo(Self.Left+2,t); // Draw line after 80 characters
          LineTo(Self.Width-1,t);
        End;
      end;
      t:=t+Self.DefAttributes.Height+5;
    end
  Finally
    ReleaseDC(Self.Handle,ACanvas.Handle);
    ACanvas.Free;
  End;
end;然后动态创建这个控件即可