X11 expertise on ancient HW sought... (4-plane visual (overlay) via X-server on MS-WIndows)

David Brownlee abs at absd.org
Thu Feb 1 14:43:59 CST 2018

On 31 January 2018 at 08:21, Dimitris Theodoropoulos
<dimitris.theo.gr at gmail.com> wrote:
> I believe that my case is identical to the original message of the list and
> 24-bit is required.
> The problematic visual (the one which is not provided by the external
> X-server) is the following (I cite an extract from xdpyinfo on the original
> system):
>   visual:
>     visual id:    0x36
>     class:    PseudoColor
>     depth:    4 planes
>     available colormap entries:    16
>     red, green, blue masks:    0x0, 0x0, 0x0
>     significant bits in color specification:    4 bits
> At another part of xdpyinfo, I also get the following info:
> screen #0:
>   dimensions:    1280x1024 pixels (342x274 millimeters)
>   resolution:    95x95 dots per inch
>   depths (4):    8, 12, 24, 4
> Please forgive my technical ineptitude, in case I did not answer your
> question, but I am not experienced in this domain.

OK, so it looks like it might be looking for a PseudoColor display,
which I'm not sure is supported by current X11 (*), check if your
MacOS server is supporting PseudoColor - I think Apple dropped it
around a decade or so ago.

You *might* be able to run Xephyr to present a sub XServer which can
run 8 bit PseudoColor (its freely available under (*nix), not sure
about Windows.

(*) Current X11 on x86 looks to have dropped PseudoColor, though there
may be some odd VESA or other target drivers. Current X11 on non x86
hardware still supports 8bit, 4bit and other crazy historical
bitdepths, which is awesome in its own right, but probably not
directly useful in this context.

So if it is PseudoColor and your target display is Windows, some
increasingly crazy options:

Native Windows X servers
- Look for a Windows Xephyr port and run under MobaXterm or similar
- Find a really ancient (read, probably crashes a lot and may not work
on recent Windows) Windows X server which support PseudoColor
- Fire up a Linux VM and run Xephyr in there with the display set to MobaXterm

Run your actual other OS image on a really fast PC in an emulator
which simulates the actual display hardware it needs

Using some other OS in a VM full screen as an X server
- Check to see if there is some way to get the Linux VM to use a VESA
or some other driver which comes in 8 bit
- Fire up an ancient Linux (or similar) with X11 PseudoColor support in a VM
- Fire up a modern (or even older) *nix for hardware which is native 8
or 4 bpp in qemu (I said increasingly crazy)

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