Created attachment 277271 [details] [review]
fix

Solve it with a hammer :)

Given it's a rare user-initiated action, I don't think it's worth it spending time and increasing code complexity on anything more sophisticated.

Works for me.  Mind adding a macro for the number of bits and rewrite pieces based on it instead of a comment?

Created attachment 277350 [details] [review]
fix v2

Do you mean something like this?

Yep.  Thanks.

Comment on attachment 277350 [details] [review]
fix v2

b446923

*** Bug 682689 has been marked as a duplicate of this bug. ***

Reopening.

If the bottom right character of a rectangular selection is further extended to the right (because it's a CJK or TAB) and then the selection is cleared (just click anywhere) then it's not properly updated.

Created attachment 278945 [details] [review]
fix for deselecting cjk/tab in rect mode

Comment on attachment 278945 [details] [review]
fix for deselecting cjk/tab in rect mode

9ef0dcf

And there's one more.

With Monospace 8 (6x13) font, have an English letter followed by a CJK/TAB. Start a rectangular selection with the English letter, towards the right.

When the selection appears first, it's the English letter, plus about 1.5 cells of the CJK/TAB highlighted.

It's no longer repeatable during the same selection process (i.e. by dragging, but not releasing the mouse) so I guess it has something to do with the drag threshold.  Also, the behavior varies with different font sizes.

Created attachment 278951 [details] [review]
fix for starting a rectangular selection

There were 4 calls to start_selection() in the code, 2 of them immediately followed by extend_selection() with identical parameters, and 2 not.  start_selection() doesn't do any cell invalidation, extend_selection() does.  This patch makes start_selection() call extend_selection() so it's no longer the caller's responsibility not to forget about it.

Comment on attachment 278951 [details] [review]
fix for starting a rectangular selection

73745f9