On Sun, Apr 16, 2000 at 07:26:33PM +1000, Herbert Xu wrote:
> First an explanation of the problem:
>
> Consider this sequence of chars being written to /dev/tty1:
>
> printf "\033[47m%81s\n\033[0m"
>
> (assuming the console's width is 80 chars, otherwise replace 81 with width+1).
>
> This should produce one line of spaces with a white background, and then
> exactly one space with a white background at the beginning of the second
> line.
>
> It works as expected if no scrolling occurs. However, when the second line
> requires scrolling, the result is two lines comprised of spaces with a
> white background. The reason being the current console driver fills new
> lines produced by scrolling with the video_erase_char *at* the time of
> scrolling. Thus if video_erase_char changes later while the cursor is on
> the new line, it will not affect the characters at the end of that line.
>
> There is only one application that I know of which is affected by this, and
> that is colour ls when you use a background colour other than the default.
>
> The same problem exists with xterm/rxvt and all X terminal emulators based
> on those two.
>
> It does not affect kvt/putty, both of which don't fill new lines with the
> same video_erase_char even when attributes change.
>
> Attached is a patch against 2.2.14 that tries to address this problem by
> noting when video_erase_char changes, and fills in the spaces to the end
> of the line when a subquent cr/nl/ri happens.
>
> I'd like to know if there are applications out there which is broken by
> this change.
Yuck! :) The current behavior is how it's _always_ worked as far as I
can remember, and I know back from when I wrote an ANSI editor in my BBS
times that the programs back then used to depend on this. There is
another similar issue with "\033[K"... This can be used to clear the
current line from the cursor to the end of the line. I really like the
ability to have it clear to the end of the line with the current
background color (can be used to easily paint a line with the current
background color). I remember I used to use this and Telix would break,
but most other terminal programs got it right...
Erase color when scrolling is a similar issue. I don't think this should
be changed...
Simon-
[ Stormix Technologies Inc. ][ NetNation Communications Inc. ]
[ sim@stormix.com ][ sim@netnation.com ]
[ Opinions expressed are not necessarily those of my employers. ]
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