When selecting an item in the file browser only adjust the horizontal scroll position if:

• the item itself would not be fully visible in the current position
• the item is expanded and one of its visible children would not be fully visible in the current position
• a visible item on the same level as the selected one would not be fully visible (this is up to debate, prolly needs to be tested live to see how it feels)

See also discussion at PICARD-2050