>>>It's not a bug. Your assumption that shape is centered horizontaly from the beginning is incorrect.
>>
>>Where I have written this ???????
>
>DEBUGOUT "start centered", ...
>

If top and bottom margin are equal, it is centered !

>>
>>>The shape center is one pixel closer to the top border of the form than to the bottom.
>>
>>Sergey, please,
>>run the code with NNHEIGHT 1, 2 and 3, 4
>>With 2 it is ok,
>>with 1 it is not moved
>>with 3 it is moved to a incorrect position
>>with 4 it is correct
>>......
>
>It's moved to the correct position according to Anchor = 512 and original position of the shape center. The problem is that center of the shape with odd height is 1 pixel closer to it's top border than the bottom one.

Sergey,
- run this,
- look outputs
- run with NSIZE 3

Now, I hope you can see the bug.

ACTIVATE WINDOW "debug output"

#DEFINE NSIZE  4
PUBLIC oform1

oform1=NEWOBJECT("form1")
oform1.Show
RETURN

DEFINE CLASS form1 AS form

	Top = 0
	Left = 0
	BACKCOLOR = 255
	Height = NSIZE	+	2
	Width = 130+ NSIZE	+	2
	DoCreate = .T.
	Caption = ""
	Name = "Form1"
	resizable = .F.

	ADD OBJECT shape1 AS shape WITH ;
		Top = 1,	;
		Left = 1, ;
		Height = NSIZE , ;
		Width = 130+NSIZE , ;
		Anchor = 512+256, ;
		Name = "Shape1",;
		ENABLED = .f.


	PROCEDURE shape1.Init
		DEBUGOUT "top Border",this.top,"bottom border",thisform.Height-this.Height-this.top
		DEBUGOUT "left Border",this.Left,"right border",thisform.Width-this.Width-this.left
	ENDPROC


	PROCEDURE shape1.Move ( nLeft, nTop, nWidth, nHeight )
		DEBUGOUT "top",ntop,"left",nLeft;
               ,"bottom",thisform.Height-nHeight-ntop;
               ,"Right",thisform.Width-nWidth-nleft
	ENDPROC

		PROCEDURE Activate
			FOR K=1  TO 200
			this.Move(0,0,thisform.Width+2,thisform.Height+2)
			this.draw
			NEXT
			
ENDDEFINE

If you are not able to see,
ask to yourself this issue:
I can anchor a even sized to the center of the container,
but for a odd sized object i cannot
then => bug on computation.

Fabio