TShape Control鼠标拖拽问题？

[Jonvy2016]

我以下代码是想当鼠标拖拽ShpST1是，松开鼠标后ShpST1在 鼠标当前位置 ，可是当我仅在ShpST1内拖拽时，会跑到莫名奇妙的位置，当拖拽在ShpST1外部时，则能满足要求？这是什么原因？怎样解决？
在ShpST1内拖拽时得到的位置X,Y不是Form1的X,Y吗？

procedure TForm1.FormDragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
if (Sender is TShape) then
accept:=true;
end;


procedure TForm1.ShpST1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin

if (Source is TShape) then
accept:=true;
end;

procedure TForm1.ShpST1EndDrag(Sender, Target: TObject; X, Y: Integer);
begin
ShpST1.Brush.Color:=clHighLight;

ShpST1.Left:=X-ShpST1.Width div 2;
ShpST1.Top:=Y-ShpST1.Height div 2;

end;

procedure TForm1.ShpST1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if Button=mbLeft then
(Sender as TShape).BeginDrag(false);
end;

[ooolinux]

试试这个代码，BCB的，可以拖动Button1：

//---------------------------------------------------------------------------
void __fastcall TForm1::Button1MouseDown(TObject *Sender,
      TMouseButton Button, TShiftState Shift, int X, int Y)
{
    ReleaseCapture();
    SendMessage( Button1->Handle, WM_NCLBUTTONDOWN, HTCAPTION, 0);    
}
//---------------------------------------------------------------------------

[jinjazz]

procedure TForm1.ShpST1EndDrag(Sender, Target: TObject; X, Y: Integer); begin ShpST1.Brush.Color:=clHighLight; ShpST1.Left:=X-ShpST1.Width div 2; ShpST1.Top:=Y-ShpST1.Height div 2; end; 这个中的X和Y是屏幕的坐标，不是Form的坐标

[Jonvy2016]

那怎么变成 Form的X,Y坐标呢？

引用 2 楼 jinjazz 的回复:

procedure TForm1.ShpST1EndDrag(Sender, Target: TObject; X, Y: Integer); begin ShpST1.Brush.Color:=clHighLight; ShpST1.Left:=X-ShpST1.Width div 2; ShpST1.Top:=Y-ShpST1.Height div 2; end; 这个中的X和Y是屏幕的坐标，不是Form的坐标

[日立奔腾浪潮微软松下联想]

var P: TPoint; begin P := Form1.ScreenToClient(Point(X, Y)); ShpST1.Left:=P.X-ShpST1.Width div 2; ShpST1.Top:=P.Y-ShpST1.Height div 2; //...