[9fans] Understanding /dev/draw

[Chris McGee <newton688@gmail.com>]

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Hi All,

I'm looking at creating an alternate filesystem for /dev/draw, /dev/mouse
and /dev/kbd that hooks up to a web server providing HTML interfaces (e.g.
canvas) for Plan 9 UI. I've been reading over the manual pages, which are
quite detailed, which is great, but there are some points of confusion for
me.

In particular, /dev/draw's interface and documentation keep referring to
the concept of a "window" indirectly. It seems that in some cases the
server providing /dev/draw needs to track windows and refresh them. But,
what defines a window in this protocol? Is every image a window or only
some of them?

Also, I'm trying to understand how off-screen images, such as fonts are
loaded. It seems that every image must be associated with a screen and be
given a position within the screen. So, how do you prevent the image from
being visible to the user?

Hopefully, if I can understand some of the high-level concepts here then
the manual page will be all that I need. Does anyone have experience with
this area or could point me to information that might help clarify it?

My next step will probably be to figure out how libmemdraw does all of this
on top of a frame buffer.

Thanks,
Chris

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