From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu,  9 Feb 1995 13:54:55 -0500
From: serge@euler.Berkeley.EDU serge@euler.Berkeley.EDU
Subject: Brazil in Tucson.
Topicbox-Message-UUID: 077bd478-eac8-11e9-9e20-41e7f4b1d025
Message-ID: <19950209185455.1dTC2-EmXsCEUN6Qk-nfneY18MoATDtuKQnOmEabLjw@z>

The abstract in http://www.cs.arizona.edu/people/tics/#pike seems very
interesting, albeit all too brief and tantalizing (would there per any
chance be any more Brazil information available)?  In particular, the
following excerpt raises some intriguing questions:

	For example, the graphics model of the system has been completely
	replaced. Brazil uses a data-based model in which applications
	transmit graphical updates as rectangular blocks of pixels to be
	written directly to the screen or window, rather than the
	traditional description of how to draw the update. This unifies
	traditional user interfaces and video at the lowest levels of the
	system, which, coupled with the model of the file name space
	inherited from Plan 9, makes it possible to display video on the
	display under control of the window system but without the window
	system needing to touch the data: the application can drive the
	display directly.

That is, how does this interact with the current trend for ever more
intelligent graphics controllers, which, e.g. presumably have special
instructions for drawing lines, polygons, etc.?  Also, what does this
due for the communication bandwidth?  I.e., with the ``old'' model,
to draw a line, you would send something like the following packet

	type	= LINE	1 - 8 bytes
	start.x	= XXX	1 - 8 bytes
	start.y	= YYY	1 - 8 bytes
	end.x	= XX2	1 - 8 bytes
	end.y	= YY2	1 - 8 bytes

for a total of (roughly) 5 to 40 bytes.  On the other, hand, with the
new model, the size appears to be unbounded, even for the same line, e.g.


	start.x			= XXX	1 - 8 bytes
	start.y			= YYY	1 - 8 bytes
	end.x			= XX2	1 - 8 bytes
	end.y			= YY2	1 - 8 bytes
	data[Y0][X0].pixel	= RGB	1 - 8 bytes
	data[Y0][X1].pixel	= RGB	1 - 8 bytes
	...
	data[YN][XM].pixel	= RGB	1 - 8 bytes

Does this also mean, that, e.g. a line from (0, 0) to (1024,1024) would
require an entire rectangle of data to be sent?  (Or just individual
dots, which would be nearly as expensive, since you would have to
transmit the coordinates of each?)

Finally, how does one deal with device (e.g. black and white versus gray
scale versus pseudo color versus true color) independence, if the data is
sent directly to the display?  Thank you very much.