Switching between virtual desktops

[Andruk Tatum]

"Well, Im supposing I'll be able to switch between desktops so fast that
I'll be able to keep up with the refresh rate and with human eye's
perception of image change, so that the screen doesnt go black and the
user doesnt notice his screen is acting like a super fast slideshow
(switching frames all the time)."

I'm a complete newbie to X, so take everything I say with a grain of
salt, but I doubt that you'll be able to do this without purchasing some
good (read: expensive) hardware and doing some _heavy_ hacking on X and
some heavy hard hacking.  My understanding of video signals tells me
that this probably won't work.  I would hazard a guess and simply say
that your usage case is at least close to impossible, if not completely
impossible.

I've implemented a pong-like animation using just hardware on a Xilinx
FPGA over the VGA port, but I don't think you'll be able to find an FPGA
with >2 VGA outputs.  This means that you may be forced to design and
implement your own circuit from scratch, which is not a trivial task.

Heck, best of luck to you if you decide to try to implement it anyway,
though.  Be sure to post pics and a rough guide of what you did and how
to do it if the project becomes unique enough to warrant it.

-- andruk

Luca Bezerra wrote:
> Well, I have no experience on any of the areas of the questions above,
> so my answers will be based solely on my guessings and on what I've
> learned from researching on the internet.
>
> - You are potentially flooding applications with map/unmap requests
> (due to the virtual desktop switching), but let's assume you have a
> custom window manager which doesn't do that.
> A: Ok, moving on...
>
> - How will you ever get something async like the X protocol to
> synchronize with this external hardware?
> A: I had no clue about X being asyncronous, or about what that means
> on this subject.. I'd really appreciate if you could give me more info
> about that :)
>
>
> - Virtual desktops belong to a single user, how do you expect them to
> behave nicely for multiple users?
> A: I dont know if I didnt get what you meant, but here's the answer to
> what I think you meant. The idea isnt of multiple logins sharing the
> same X session (and their virtual desktops). What Im trying to do is
> to have a unique user (lets say "John") logged in. After I log in as
> John, its like I have simply 4 regular virtual desktops, each one with
> a browser open. The system will work as if I were constantly switching
> the desktops. Let's say I go to D1 and move my cursor 1/2", go to D2
> and type letter 'a', go to D3 and do "alt+tab" and then go back to D1
> and move another 1/2", and so on. The way I see, it'd be like a single
> person using multiple desktops really fast, not really multiple users
> (at least the operating system wouldnt see it that way, would it?).
>
> - What about the mouse pointer, isn't it kind of expensive/slow to
> render many software cursors on an old system?
> A: As I said, based solely on my researches, I dont really think that
> would be a problem. Existing (and functional) multiseat systems do use
> multiple mice and keyboard and they get along pretty well...
>
> - What happens to refresh rate?
> A: Assuming you're talking about when I cut the image flow to one
> monitor and switch it to another, how is that first monitor going to
> keep the image in there while no image is really being sent to it, the
> answer is.. Well, Im supposing I'll be able to switch between desktops
> so fast that I'll be able to keep up with the refresh rate and with
> human eye's perception of image change, so that the screen doesnt go
> black and the user doesnt notice his screen is acting like a super
> fast slideshow (switching frames all the time).
> ------------------------------------------------------------------------
>
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