Tab behaviour inconsistent

Insertion of \t in a text widget has two different kinds of behaviour, depending on how the tab stops were set.

a) With the default 8 characters per tab, the effect of inserting \t is to move the insertion point to the next tab stop to the right.

b) If you set (with -tabs) other tab stops, the effect of the nth \t in a line is to attempt to position the insertion pont at the nth tab stop. If this is not possible (insertion point already to right of nth stop) then \t inserts a single space.

The behaviour of tabs should be consistent, regardles of how tab stops were set. My personal preference would be for behaviour a), which I think is what most people would expect.

Illustrative script file attached.