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Re: Deuce display problem and possible fix

I'll look into this.  I wonder if there's a corresponding bug in
'delete-display-lines' that has no observable effects.

"Chris Double" <chris@double.co.nz> wrote in message
wkbsjhtqv7.fsf@double.co.nz">news:wkbsjhtqv7.fsf@double.co.nz...
> When editing a file using the Deuce editor (either in the Functional
> Developer IDE or standalone-deuce) there is a small re-display
> problem.
>
> The problem is when inserting text (a newline for example) before the
> end of the file, causing the lines below it to move down. The last
> line, if it is not pushed off the end of the window, redisplays merged
> with the line before it. For example, a file with contents:
>
> ---------
> line 1
> line 2
> line 3
> line 4<eof>
> ---------
>
> Where <eof> is end of file. Insert a new line before 'line 3' then
> line 3 and line 4 will be moved down but will appear merged together
> on one line. That is, both lines are displayed at the same 'y'
> position.
>
> If the file is:
>
> ---------
> line 1
> line 2
> line 3
> line 4
> <eof>
> ---------
>
> Then the problem does not appear as the merged line is empty. All
> appears ok. I tracked the problem down to 'insert-display-lines' where
> the <display-line> was not having its y position updated. Changing the
> portions of 'insert-display-lines' to match the following fixes the
> problem:
>
> -------------------
>   // Fix the Y positions of the lines we moved down,
>   // unless they're off the bottom of the screen now
>   block (return)
>   without-bounds-checks
>   for (i :: <integer> from index + n below n-slots,
>        line = next file://line-next-in-buffer(next, buffer, skip-test: #f)
>        then line-next-in-buffer(line, buffer, skip-test: #f),
>        while: line)
>     let dline :: <display-line> = lines[i];
> -------------------
>
> The changed line is the one containing the '//line-next' comment. The
> text after the '//' is what is originally there, I replaced it with
> 'next'. It's the 'next' display line that wasn't getting the update
> 'y' position. The call to 'line-next-in-buffer' returned #f as there
> is no following line and the loop is not processed.
>
> Any comments as to whether this is the right place to fix the problem
> are appreciated.
>
> Chris.
> --
> http://www.double.co.nz/dylan
>
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References: