Re: MacOSX

[Chris Hanson]

Mac OS X doesn't use Display PostScript for 2D drawing.

It also doesn't use "Display PDF," whatever that is.  And it doesn't 
use OpenGL for 2D drawing either.

Mac OS X uses a system called Quartz that incorporates a number of 
different things.  There's the Window Server, which just manages 
screen rectangles and handles events.  Then there's Core Graphics, a 
shared library that implements the same imaging model as PostScript 
Level 3 and PDF 1.4 (by and large) with significant extensions for 
alpha compositing.  PDF is simply the Mac OS X graphics metafile 
format; Quartz can "record" graphics commands as PDF and "play back" 
PDF files, in the same way that Windows GDI uses WMF and the classic 
Mac's QuickDraw uses PICT.

What this means is that all drawing into a window's back buffer done 
within the application's context; the buffer is shared between the 
application and the window server.  This is why I say there's no 
Display PostScript or Display PDF; in NEXTSTEP, Display PostScript 
"physically" sent tokenized PostScript commands from an application 
to the window server for rendering.  In Mac OS X, drawing is done by 
making direct function calls to Core Graphics, eliminating both the 
tokenizing and process-switch overhead at the expense of network 
transparency.

With Mac OS X 10.2, some machines (those with sufficiently powerful 
graphics hardware) gain the ability to use Quartz Extreme.  This is a 
marketing name for an enhanced Window Server that offloads some 
window-management and window-compositing work to the GPU using 
OpenGL, freeing up the main CPU(s) for other work.  The contents of 
windows, however, are still entirely rendered in software by Core 
Graphics.

  -- Chris

--
Chris Hanson, bDistributed.com, Inc.  |  Email: cmh@bDistributed.com
Custom Application Development        |  Phone: +1-847-372-3955
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