984c984,988
<     set x0  [expr {$bd-1}]
---
>     # Do not draw items on the canvas in the negative x region of the canvas
>     # otherwise they will not be visible.
>     # B. Schofield
>     expr {($bd == 0)?[set x0 0]:[set x0 [expr {$bd-1}]]}
>  
