Drawing line on desktop very slow on Win 7

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Delphi

API

Im using this code to draw a line with a mouse on top of all windows, Im using mouse hook to get mouse coordinates and on each mouse movement while right mouse button is down I'm drawing the line. Im using NOTXORPEN so I will be able to delete the line only by drawing it again.

Init

ScreenDC := GetDcEx(GetDesktopWindow,0,DCX_LOCKWINDOWUPDATE);

PenHandle := CreatePen(PS_SOLID,HitStorage.GetPenWidth,10);

SelectObject(ScreenDC ,PenHandle);
OldPenMode := SetRop2(ScreenDC, R2_NOTXORPEN);  // Setting the PenMode to NotXor

MoveToEx(ScreenDC, X, Y, Nil);                  //Move The Pen Position to the Cursor Position

I'm using this code on each mouse movement :

LineTo(ScreenDC, X, Y);                      // Draw a Line between the previous Point to the Current Point

This code worked for 95,98,2000,XP windows ... and now with windows 7 its very very very slow!

For general, I wrote a mouse gestures program (written in 1999) in Delphi 3 using ONLY Windows API (mouse hook was written in VC because of Delphi BUG in version 3). The program is doing exactly what StrokeIt is Doing but somehow StrokeIt managed to figure out the solution to this annoying problem.

StrokeIt Site for Downloading :
http://www.tcbmi.com/strokeit/[^]

Please Help ,
Thanks!!