This is a wish bug for enabling 45 degree or 90 degree snapping feature for polygon selection tool. while making selection if we press modifier key ( Shift control or alt which ever is convenient according to you) we should be able to snap the selection to straight line or 45 degree slant. this will help to make accurate straight line selection while in the middle of polygon selection. Reproducible: Always
*** This bug has been marked as a duplicate of bug 334515 ***