请问一下如何实现两个richedit同步滚动

Question

类似于文本比较工具
我自己写的实现方式来回滚动几次后，滚动条的位置就有一点差异了，请教高手好的实现方式

Answer 1

就是发消息，发 WM_VScroll或WM_HScroll消息

Answer 2

下面是我写的部分代码，一般情况下没问题，但是来回滚动几次之后差了几行了，找不出原因procedure TfrmPcfCompare.FormCreate(Sender: TObject);
begin
  PRichEdWndProc_Before := MakeObjectInstance(RichEdWndProc_Before);
  POldWndProc_Before := Pointer(SetWindowLong(RedtBeforeModify.Handle, GWL_WNDPROC,
    Integer(PRichEdWndProc_Before)));  PRichEdWndProc_After := MakeObjectInstance(RichEdWndProc_After);
  POldWndProc_After := Pointer(SetWindowLong(RedtAfterModify.Handle, GWL_WNDPROC,
    Integer(PRichEdWndProc_After)));  RedtBeforeModify.Perform(EM_SCROLLCARET,0,0);
  RedtAfterModify.Perform(EM_SCROLLCARET,0,0);
end;procedure TfrmPcfCompare.RichEdWndProc_Before(var Msg: TMessage);
begin
  Msg.Result:=CallWindowProc(POldWndProc_Before,RedtBeforeModify.Handle,Msg.Msg,Msg.wParam,Msg.lParam);
  if(Msg.Msg = WM_VSCROLL)and(LOWORD(Msg.wParam)=SB_THUMBTRACK) then
  begin
    RedtAfterModify.Perform(Msg.Msg,Msg.wParam,Msg.lParam);
    SetScrollPos(RedtAfterModify.Handle,SB_VERT,HIWORD(Msg.wParam),True);
  end;
  if(Msg.Msg=WM_HSCROLL)and(LOWORD(Msg.WParam)=SB_THUMBTRACK) then
  begin
    RedtAfterModify.Perform(Msg.Msg,Msg.wParam,Msg.lParam);
    SetScrollPos(RedtAfterModify.Handle,SB_HORZ,HIWORD(Msg.wParam),True);
  end;
  if (Msg.Msg=WM_MOUSEWHEEL) and RedtBeforeModify.Focused then
    SendMessage(RedtAfterModify.Handle,Msg.Msg,Msg.WParam,Msg.LParam);
end;procedure TfrmPcfCompare.RichEdWndProc_After(var Msg: TMessage);
begin
  Msg.Result:=CallWindowProc(POldWndProc_After,RedtAfterModify.Handle,Msg.Msg,Msg.wParam,Msg.lParam);
  if(Msg.Msg = WM_VSCROLL)and(LOWORD(Msg.wParam)=SB_THUMBTRACK) then
  begin
    RedtBeforeModify.Perform(Msg.Msg,Msg.wParam,Msg.lParam);
    SetScrollPos(RedtBeforeModify.Handle,SB_VERT,HIWORD(Msg.wParam),True);
  end;
  if(Msg.Msg=WM_HSCROLL)and(LOWORD(Msg.WParam)=SB_THUMBTRACK) then
  begin
    RedtBeforeModify.Perform(Msg.Msg,Msg.wParam,Msg.lParam);
    SetScrollPos(RedtBeforeModify.Handle,SB_HORZ,HIWORD(Msg.wParam),True);
  end;
  if(Msg.Msg=WM_MOUSEWHEEL) and RedtAfterModify.Focused then
    SendMessage(RedtBeforeModify.Handle,Msg.Msg,Msg.WParam,Msg.LParam);
end;