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Re: Mixed L2R and R2L paragraphs and horizontal scroll

From: martin rudalics
Subject: Re: Mixed L2R and R2L paragraphs and horizontal scroll
Date: Mon, 01 Feb 2010 09:34:41 +0100
User-agent: Thunderbird (Windows/20090302)

>> Technically columns are numbered by counting characters following the
>> last newline in the buffer text.
> Eh?  Clearly they're not, because things like tabs expand into multiple
> columns...  Columns are a display concept, not a buffer concept.

Expanding tabs does not depend on displaying the surrounding text but
looks into the variable `tab-width' which is buffer-local and not
related in any sense to display.  Also, you can call a function like
`move-to-column' without ever displaying the associated buffer.

Or, for example, put an overlay with some string as a before-string
property into a buffer and display that buffer so the overlay is shown.
The characters of the overlay are displayed but the columns they occupy
on screen are not counted.

But you're right in that for non-displayable characters or characters
displayed as octals, columns do not count from the last newline either.
And the column numbers supplied by some compilers together with warnings
or error messages are mostly pretty useless for finding the corresponding
position in the source.

So I think we should be able to meet somewhere in the middle ;-)

Anyway - the point I wanted to make was that the number of a column does
not depend on the size of the window displaying the character at that
column or whether text in that window has been scrolled horizontally.


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