Re: LYNX-DEV Mainframes, 3270 and Lynx FORMs

[Klaus Weide]

[cc'd because of distribution lag]

On Mon, 8 Sep 1997, Kevin Ternes wrote:

> Here's a problem that I don't think we'll be able to solve but I want to
> give it one last try.  First, here's an overview of what we are doing:
> 
> We have Internet/intranet web services already set up and a bunch of PC
> Netscape users.  We also have a bunch of users who access a mainframe
> via 3270 terminals and that's all they have.  So, the mainframe has a
> commercial application set up for them called A-Net which is basically a
> telnet client which provides the users a means to access UNIX shell
> accounts.  The users' shell is the rsh (the restricted POSIX shell) and
> their /etc/profile launches Lynx.

Did you have to modify Lynx in any way for this to work, or do you have to
use specific options of run-time flags for lynx?  Or did you have to
compile Lynx in some special way, maybe using replacement libraries (for
example, for curses), or some other modifications on the UNIX side to make
this A-Net work?

> Everything appears to work great except for FORM textboxes.  

Does that include both TEXTAREA and INPUT TYPE=text fields?

> The first
> time a user accesses a FORM, he can enter anything he wants and move in
> and out of the text box and easily edit what he enters and then submit
> the FORM.  However, if the user uses back to return to the FORM (to do
> something like refine a query), he cannot edit the string in the textbox
> that he entered before submitting.  He can _add_ to what is in the text
> box, but he cannot delete anything or change it.

I assume the same kind of problem occurs if the form field contains some
default text (e.g. 
       <TEXTAREA>
       edit this text...
       </TEXTAREA>
in the HTML)?

Also, in that environment, is there a way to do a screen REFRESH of which
Lynx is aware - i.e. not local withing the terminal or between the 
terminal and emulator, but Lynx gets sent a Control-L character?
If yes, what is the effect? 

> For instance, if the first query was "one AND two", then after going
> back he could change it to "one AND two AND three"  but he cannot change
> it to "one OR two" or "one AND three".  If you know how 3270s work, it
> sort of makes sense that this could happen.

What happens if the user fills in a field, then (without submitting) pages
down to the next screen, then up again?  can the text be modified?

What I am getting at with my questions: as far as Lynx's output is
concerned, when the screen is painted, the only difference between the
filled-in text in such a form field and the free space is that the latter
is filled with underscore characters.  So how does the A-Net software, or
whatever is between it and the 3270 terminal, know which parts of the
screen should be made editable?

My only guess is that it applies some heuristic which gives a sequence of
'_' characters some special significance (maybe in connection with some
text attributes only).  If that is the case, would it help to delay
filling-in of the text - first write all-underscores, then refresh() the
screen, then fill in the text and do a (partial?) refresh again?
If my wild guesses have something to do with reality, you might be able to
modify the Lynx code to do that without too many changes.


      Klaus

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