#999 \t causes trouble with justified text

[Anonymous]

If \t is included in text that is center or right
justified (using tag configure -justify) the tab
characters appear on the screen as small rectangles -
of the style often used for unavailable characters.

This occurs with Tk8.3 on windows (possibly others, I
don't know)

This looks excessively yucky!

I guess there are possible situations in which \t makes
no sense in justified text. In these cases I would
suggest the best course is not to write anything on the
screen for the \t character, and to raise an error
which could be processed or ignored using catch

[Donal K. Fellows]

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Could someone provide a test script? Tabs should not be
displayed at all, given that they should instead just move
you to the next tab stop in a text widget...

NB: should not show up at all on UNIX/X where unrecognised
characters are simply not drawn (this difference is not due
to Tk, but rather X itself IIRC.)

[Nobody/Anonymous]

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OK, here is a script illustrating the problem. The boxes are
certainly visible on windoze, haven't tried this on X.

Ian

# illustrating the justified tab problem

text .t -font {times 12}
pack .t

.t tag configure cen -justify center
.t insert end "This line does not contain tabs\n" cen
.t insert end "This one \tdoes,\thowever" cen

[Vince Darley]

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Reproduced with Tk 8.5a0.

What we need is a coherent proposal for how tags and tabs
and justify and lmargin1/2 should interact.

What is the desired behaviour in this case? Show a single
space? Show nothing?

[Vince Darley]

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The same problem occurs with right justification.

I believe the following proposal is reasonably coherent:

(i) when right justifying each tab inserts a gap back to the
previous tab stop (from which right justification then
continues)

(ii) when centering, there is no sensible logical result, so
I think the only thing which would be useful would be to
insert a gap so that the next character is at the offset
from the first character that it would be if we were left
justifying. This will at least allow tabs to be used to
arrange a regular tabular layout of information, say, where
the whole tablular layout is centered, but tabs are used
within to ensure regularity.