滚动条

 

WINDOWS发送消息

This function sends the specified message to a window or windows. SendMessage calls the window 
procedure for the specified window and does not return until the window procedure has processed the 
message. The PostMessage function, in contrast, posts a message to a thread's message queue and 
returns immediately. 

LRESULT SendMessage(
  HWND hWnd, 
  UINT Msg, 
  WPARAM wParam, 
  LPARAM lParam 
); 

DELPHI的发送消息

function TControl.Perform(
        Msg: Cardinal;
        WParam: WPARAM;
        LParam: LPARAM
): LRESULT;

如
Memo1.Perform(WM_HSCROLL, SB_LEFT, 0); 

水平滚动条

水平滚动条消息    WM_HSCROLL                                         
SendMessage(Memo1.Handle, WM_HSCROLL, MAKEWPARAM(SB_THUMBPOSITION, 50), 0);  //滚动至此               
SendMessage(Memo1.Handle, WM_HSCROLL, SB_LEFT, 0);                           //左边缘           
SendMessage(Memo1.Handle, WM_HSCROLL, SB_RIGHT, 0);                          //右边缘               
SendMessage(Memo1.Handle, WM_HSCROLL, SB_PAGELEFT, 0);                       //向左翻页               
SendMessage(Memo1.Handle, WM_HSCROLL, SB_PAGERIGHT, 0);                      //向右翻页           
SendMessage(Memo1.Handle, WM_HSCROLL, SB_LINELEFT, 0);                       //向左滚动           
SendMessage(Memo1.Handle, WM_HSCROLL, SB_LINERIGHT, 0);                      //向右滚动    

垂直滚动条

垂直滚动条消息    WM_VSCROLL                                        
SendMessage(Memo1.Handle, WM_VSCROLL, MAKEWPARAM(SB_THUMBPOSITION, 50), 0); //滚动至此 50为位置  滚动到指定行号       
SendMessage(Memo1.Handle, WM_VSCROLL, SB_TOP, 0);                           //顶部            
SendMessage(Memo1.Handle, WM_VSCROLL, SB_BOTTOM, 0);                        //底部            
SendMessage(Memo1.Handle, WM_VSCROLL, SB_PAGEUP, 0);                        //向上翻页        
SendMessage(Memo1.Handle, WM_VSCROLL, SB_PAGEDOWN, 0);                      //向下翻页        
SendMessage(Memo1.Handle, WM_VSCROLL, SB_LINEUP, 0);                        //向上滚动        
SendMessage(Memo1.Handle, WM_VSCROLL, SB_LINEDOWN, 0);                      //向下滚动    

获得滚动条的位置

The GetScrollPos function retrieves the current position of the scroll box (thumb) in the specified 
scroll bar. The current position is a relative value that depends on the current scrolling range. 
For example, if the scrolling range is 0 through 100 and the scroll box is in the middle of the 
bar, the current position is 50. 
int GetScrollPos(          
    HWND hWnd,
    int nBar
);

var
  h, v: Integer;
begin
  h := GetScrollPos(Memo1.Handle, SB_HORZ);
  v := GetScrollPos(Memo1.Handle, SB_VERT);
  Caption := Format('水平数值=%d 垂直数值=%d', [h, v]);
end;

显示和隐藏滚动条

//隐藏MEMO水平滚动条
ShowScrollBar(Memo1.Handle,SB_HORZ,false);
//隐藏MEMO垂直滚动条
ShowScrollBar(Memo1.Handle,SB_VERT,false);

 判断 滚动条是否出现

procedure TForm1.Button1Click(Sender: TObject);
begin
  if (GetWindowlong(Memo1.Handle, GWL_STYLE) and WS_VSCROLL) > 0 then
    ShowMessage('Vertical scrollbar is visible!');
  if (GetWindowlong(Memo1.Handle, GWL_STYLE) and WS_HSCROLL) > 0 then
    ShowMessage('Horizontal scrollbar is visible!');
end;

http://blog.163.com/fj_lfx/blog/static/377536832010419102554448/