[SDL] using an image as mouse cursor

David Olofson david at olofson.net
Tue Jan 25 08:58:39 PST 2005


On Tuesday 25 January 2005 12.46, Roger D. Vargas wrote:
> El mar, 25-01-2005 a las 14:47, Olof Bjarnason escribió:
> > Think of the event queue like a QUEUE; if there are several
> > clients (events) waiting today (this time around the loop), you
> > may want to serve all of them today (this time around the loop)
> > and not tomorrow (next time around the loop), because otherwise
> > the queue will soon reach all over town (the event queue will
> > fill up). The while loop takes care of the events this time
> > around the loop, and the if takes "one customer per day"!
>
> Well, my problem is i was considering this queue as infinite, I
> mean, I thought there is ALWAYS an event in the queue, because
> always the users is moving mouse, clicking or pressing keys.

Unfortunately, no mouse available to the average user has that kind of 
resolution and/or frame rate. What looks like "always" to a human is 
"every now and then" to a computer, if even that. :-)

(Your average CPU executes some 50 million instructions between each 
event from a good, properly configured mouse. That's 600000 printed 
pages of asm code, or somewhere around 100000 printed pages of some 
high level language.)


That said, to many applications, there is normally nothing to do if 
there is no event to process, so you pretty much use the event 
mechanism as the "time base" or driving force of the application. No 
events, no cycles consumed. Simple, yet very effective.

Games, however, as opposed to "normal" GUI applications, almost 
*never* work like this, so you're better off basically forgetting all 
about traditional GUI event handling when dealing with games. For 
"action" games, you should preferably use the refresh rate (or the 
best frame rate you can achieve) as your time base, rather than any 
form of user input events. If smooth animation is less critical, or 
minimal CPU usage is important, you can use some form of periodic 
timer, which makes things more similar to, but still different from, 
"normal" GUI programming. (Of course, any application that has 
animations and stuff going on while waiting for user input is in a 
gray zone. :-)


//David Olofson - Programmer, Composer, Open Source Advocate

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