On Fri, 11 Jan 2002, McCallion, Martin wrote:
>
> > It seems to me that the screen-at-a-time nature of 5250 would
> > make it a very difficult task to port Lynx to the AS/400.
> >
>
> Surely the thing to do would be to run it in QSHELL, since that's an
> approximation of a Unix environment?  That would handle the
> line-at-a-time scrolling issues.

It's not line-at-a-time scrolling issues that I feel would be an issue,
it's the screen-at-a-time 5250 i/o.

On a 5250 display, the AS/400 sends an entire screen to the terminal.  The
terminal displays the screen to the user, and allows the user to move
around the screen, type in the input fields, etc...  control does not go
back to the AS/400 until you hit ENTER or a function key.

In Lynx, when you press the down-arrow, the cursor moves to the next link
on the page -- with 5250, this would not be possible.   When you hit the
space bar, it pages down -- this would not be possible.   When you hit the
'G' key, it brings up a "URL to open:" prompt.   This would not be
possible (unless you hit ENTER after the G key).

It makes no difference whether you're running QSHELL on the AS/400, or
not.  It's the way that 5250 terminals work that is the issue, so if
you're accessing QSHELL from a 5250 terminal, you have the same exact
restrictions.   In fact, a normal program would work FAR better than
QSHELL, since QSHELL's input comes from a single command line at the
bottom of the screen, and that would really be non-intuitive in a web
browser.

Therefore, I was stating that you'd want to start from scratch if you
wanted to make a 5250-based web browser.  You'd want to make something
that was specifically designed for 5250 displays.  Instead of the various
Lynx functions,  such as "H)elp O)ptions P)rint G)o", you'd want to use
F1, F2, etc.   When those keys are pressed, it would automatically pass
control to the program, which is much more intuitive.

When rendering the HTML to display on the screen, you'd want to use a
user-defined data stream.  DSM might be an option for this.  Sending the
5250 codes directly would also work...   this would allow you to position
input fields, display attributes, etc anywhere you wanted them, depending
on the document instead of having to know the layout of the web page in
advance :)

As I said... all of this is possible.   You could make something that's a
lot like Lynx, which became a really nice utility.   But it would be a lot
of work.




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