Hi,
        In a fresh 3.4 image if you evaluate: TwoWayScrollPane new
openInWorld
        You'll see that the left arrow button from the horizontal
scrollbar is missing.

        The reason is the slider blocking the button. The method
Scrollbar>>totalSliderArea is wrongly calculating the slider's bounds
when the scrollbar is horizontal and the #ScrollbarWithoutMenuButton
preference is disabled (it's default value).

from preamble:

"Change Set:            HorizontalScrollBarMissingLeftButton
Date:                   3 April 2003
Author:                 Hernán Tylim

This change set fix a problem with the left arrow button of the
horizontal scrollbars.

The slider's bounds on horizontal scrollbars were wrongly calculated
causing the slider to block the left arrow button.

This cs fix the method that calculates the slider bounds
(ScrollBar>>totalSliderArea)." 
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