Re: Line lengths appear to mismatch actual terminal columns as given by /dev/vcsaX

[Thomas Dickey]

On Fri, Jul 15, 2016 at 01:30:17PM -0400, Storm Dragon wrote:
> Howdy,
> We are in the midst of writing a console based screen reader, and noticed
> this problem while trying to navigate things like Mutt.  It could be fixed if
> ncurses would finish filling in the line with space or something.  In the
> case we found, the link reported 160 columns, but the ncurses line only had
> 143.  This causes weird stuff like reading half the from and subject info in
> mutt on 1 line, then the rest and the start of the next on another line.

It sounds as if your screen reader doesn't work well with optimized
screen output.

As ncurses paints a page for the first time, it may omit trailing blanks
if it assumes their background would be colored appropriately by clearing
the screen.

Also, ncurses may skip over several blanks (known to be cleared) if it
knows that it has a cheaper way to move (via cursor-addressing) than
writing the blanks.  Your screen reader might notice this.

I think that you can reduce (but not eliminate) the optimization
by modifying the terminal description.  For the background-coloring
versus spaces, the simple thing to try would be setting TERM to
"color-xterm", which lacks the "bce" (background color erase) feature
that seems to be a problem.

-- 
Thomas E. Dickey <address@hidden>
http://invisible-island.net
ftp://invisible-island.net

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