🚀 go-pugleaf

In article <4faq6h$nq6@news.mpd.tandem.com>, Joseph Crowe <jcrowe> wrote:

] mem@jhu.edu (Mel Martinez) wrote:
] >
] >DialogManager event loops DO yield the cpu context (they have to poll for
] >user events after all).  Thus background tasks WILL get cpu time (by
] >processing NULL events).  The problem with modes is that they trap all
] >USER events and restrict the users choices.  The (mis)use of modal dialogs
] >has nothing to do with any fundamental aspect of the underlying
] >multitasking model - this can happen on either a CMT or PMT system.
] 
]    Understand, that while background processes already running may get
] resources while the app is polling the user, the user cannot switch to another
] app, nor start another app until (s)he responds to the dialogue box.  This is
] absolutely not true on 1) the Amiga, 2) UNIX workstations running some type of
] GUI.  I, as a fairly active Mac user, find this very counterproductive. 
] 

You seem to not understand the distinction between events, upon which
processes react, and processor time, which of course powers those
processes.

The problem with modal dialogs has nothing to do with how processor time
is allocated.  The problem with modal dialogs is that one process is
allowed to mask and trap all user input events, and not allow the user to
select which process he sends input to.

To trap all events, depending on the API, one would simply tell the event
manager of the windowing system that myprocess wants all mouseclicks in
the display area trapped and sent through myprocess before anyother
process sees them, even if outside any window belonging to myprocess, and
also that any keypresses come to myprocess as well.  If myprocess does not
pass events it doesn't need back into the event queue, other processes
will not see any user events.  This puts the system into a mode.

It has absolutely nothing to do with cooperative or preemptive
multitasking and can indeed happen on just about any system.  If you think
X windows is invulnerable to lock ups, then you are sadly mistaken.

Cheers,

Dr. Mel Martinez
The Johns Hopkins University
Dept. of Physics
mem@jhu.edu