Re: Help me find the bug in my terminal-based editor

[Amirouche Boubekki]

Le dim. 3 févr. 2019 à 22:22, Mike Gran <address@hidden> a écrit :

> On Sun, Feb 03, 2019 at 02:07:00PM +0100, Amirouche Boubekki wrote:
> > Hello,
> >
> >
> > I have a strange bug in my terminal-based editor.
> > The code can be found at https://framagit.org/a-guile-mind/zk
> >
> > To install you will need guile-bytestructures and guile-pfds.
> >
> > Then:
> >
> >   git clone https://framagit.org/a-guile-mind/zk
> >   cd zk
> >   make dev
> >
> > You will also need to change the following line:
> >
> >   https://framagit.org/a-guile-mind/zk/blob/master/zk/termbox.scm#L174
> >
> > Then you can type:
> >
> >   make run
> >
> > This will clear the terminal and display the content of 'zk.scm'.
> >
> > If you type 'enter' key, it should add a newline at the start
> > of the buffer. It does, but rendering has glitches. If you resize
> > the window it will remove the glitches.
>
> I did build and run your program, passing the output through teseq to
> see which control codes it was writing out.  As far as I can tell, the
> glitch you are seeing is in your code, and it not a mysterious
> console bug.
>
> Teseq tells me that after I hit carriage return, your program moves to
> the top-left corner, does a line-feed (pushing everything down and
> putting the cursor in line 2, column 1) prints some spaces over all
> the characters in line 2, jumps to column 16, and then writes "ice-9
> match)))"
>
> It works after resizing because after resizing, you move to 1,1 and then
> emit an "erase in page".
>
> To use teseq, I typed "script" which starts a console session that gets
> saved in the "typescript" file, and then I called "teseq typescript" on
> the output.
>
> Regards,
> Mike Gran
>
>
Thanks a lot. I was looking for something like teseq.

I found the bug, here is the diff:

diff --git a/zk.scm b/zk.scm
index 76ae863..ad8aa5c 100644
--- a/zk.scm
+++ b/zk.scm
@@ -334,7 +334,8 @@ main loop."

 (define (%%container-render-char x0 y0 view-x max-x)
   (lambda (x y char)
-   (tb-change-cell (+ x0 x) (+ y0 y) char TB-WHITE TB-DEFAULT)))
+    (unless (equal? char (char->integer #\newline))
+      (tb-change-cell (+ x0 x) (+ y0 y) char TB-WHITE TB-DEFAULT))))

 (define (%%container-render buffer x0 y0 view-x view-y width height)
   (let* ((head (buffer-take-lines buffer (+ view-y height)))

I was sending #\newline char as integer to tb-change-cell which was not
expected,
and create some kind of panic in the escape sequences sent to terminal.
Indeed the
newline end up in teseq as a line feed (LF). I endup finding the bug by
comparing line
by line the teseq output of azul.scm and zk.scm.

Thanks again!