Re: CDK & Terminal Resizing

[Thomas Dickey]

On Fri, 8 Apr 2011, Marc Smith wrote:

> Hi,
>
> I didn't see a separate list for "ncurses user questions", so I'm
> assuming this list is for that as well. If not, I'd appreciate it if
> anyone could redirect me to the right place.
>
> So, I'm using CDK (5.0.20081105) (ncurses 5.7) to develop a text user
> interface. Resizing terminals doesn't seem to play nice with the CDK
> widgets -- the text on the screen is messed up after resizing the
> terminal to something smaller than what was started with and then back
> to the original size (or bigger).

yes - it doesn't do that...

I'd done this more/less for dialog.  It was much simpler than CDK would 
be.

> I've experimented with other ncurses related things (mc, dialog, etc.)
> and they seem to resize correctly. I understand I can catch the
> SIGWINCH via KEY_RESIZE / getch() and I am able to do that, but I'm
> not sure how I can make the widgets resize "nicely". I've tried using
> refreshCDKScreen() and others, but I can't get it.

There's more than one thing which would have to be done.
When the keypad() function is enabled (which it is), then
the ncurses getch/wgetch returns KEY_RESIZE when it has updated
stdscr/curscr to respond to the SIGWINCH.

At that point, in dialog, I provided for a jump back to the initialization
region of a widget, so it would then fall into the getch-loop.

CDK wraps calls to wgetch in getchCDKObject.  Some are buried down a level 
or two, making it impractical to "jump back" (other than a setjmp).

I think, that to make SIGWINCH work here, CDK would have to be reorganized 
to use some sort of event-loop (keeping the wgetch's at that level), and 
to add a list of the widgets, which the event-loop function could adjust 
in one place.

Alternatively (closer to how CDK is done now), it could have a method 
added to each widget to tell it to resize.

> I'm sure this is something that could be modified in CDK for the
> widgets to resize nicely, but how can I do this in my own program
> without modifying CDK? Any ideas?

You'd have to (in effect) write your own resize functions and register 
them as callbacks.  It's probably doable (since the WINDOW's are exposed 
in the widget structures), but rather tedious to implement for the whole
library.

--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net