[Simh] Multiple sim_video windows?

[Mark Pizzolato]

On Friday, March 15, 2019 at 10:01 AM, Paul Koning wrote:
> > On Mar 15, 2019, at 12:52 PM, Mark Pizzolato <Mark at infocomm.com>
> wrote:
> >
> > On Wednesday, March 13, 2019 at 1:40 AM, Lars Brinkhoff wrote:
> >> I'm using the upcoming SIMH KA10 simulator to restore MIT's
> >> Incompatible Timesharing System.  This is a multiuser system.  As
> >> such, there is a need for multiple user interfaces.  The AI lab
> >> PDP-10 had many display and input
> >> devices:
> >> ...
> >> I would like to be able to open up more windows: one for the color
> >> scope, and perhaps another one for the tablet.  As far as I
> >> understand, sim_video is limited to just one window.
> >
> > Well, if there really were configurations which had software support that can
> > still be found today that actually drove multiple display devices simultaneously
> > then the current sim_video is certainly insufficient.  Adding multiple video
> > display window support is a project unto itself and dragging the display layer
> > along with it is added complexity.  If you want to do that, feel free and I'll help
> > when needed, but since your project is driving the need I'm not sure we'll be
> > getting a long list of folks willing to jump in as well...
> 
> I thought that libSDL (which is what's underneath) is limited to one window.
> The documentation says that's not so.  That said, I found libSDL to be quite
> limited when I tried to use it to display emulated plotter output.  The problem
> there was that it's much bigger (pixel wise) than the screen and handling that
> was problematic.

Sim_video currently presumes a single window used for display and stores the window context and state information in static or global data.  There is nothing in libSDL that presumes a single window for an application.  The earliest libSDL implementation might have had some of the constraints you mention, but SIMH support for libSDL 1.2 is now deprecated due to the wide availability of libSDL 2.0 on all modern platforms.  When sim_video was just being developed, libSDL had just been released and wasn't widely available.

> I've used wxWidgets a lot for portable windowing applications.  I wonder if it
> might make an attractive alternate base for sim_video.

Another potential solution, but migrating to something like that would be a big project on its own.

- Mark