My quest to SDL in Perl

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I think this thing started when Silveira Neto posted his code snippet on Pygame animating the tile set he has been creating for a long time. I knew for a long time that Perl supported SDL and that Frozen Bubble is written in Perl, but I have never tried it myself.

Working with graphics wasn't new to me, back in the days I played with BASIC, I wrote a blackjack program with animated cards, some time later - already in Linux, I played a bit with vgalib. I've been also thinking for a while on the concept of how to evaluate the progress of time in a game environment.

If you join this with the fact that I now have a 1yo kid, it kinda urged me to writing something in SDL for him. The idea was quite simple, as he doesn't coordinate mouse and keyboard movement yet, the game would simply present random images and sounds as there was any event at all.

So I started by using a simple event loop for the SDL events, and a timer to evaluate the time lapse and draw the game. To my surprise, using the timer caused segfaults, because the timer callback runs in a different thread in SDL, but the binding didn't provide any support for it and all I got was kaboom.

I worked around this issue by using Event, a simple event library I already used some other places, to implement the timer. It worked like charm, as there was events in SDL, it was creating rects of random sizes and colors that would last for a random amount of time, fading to black.

Then I thought: Ok, now let's proceed to audio. To my surprise, the callbacks for procedural audio generation were simply missing - Frozen Bubble only plays pre-produced audio files - and my idea was to produce random audio (not noise, but sounds in random frequencies). This was the push I needed to get to the redesign branch in github and start porting the app to it.

Lots of research later, with the help of kthakore++ and the tips from Nicholas++, we managed to have a working version of SDL based on threads and threads::shared. This was a very great moment. I must confess I always kept some envy from python people because of the - so I thought - better support for threads in Python. At some point in this path I found out that Python doesn't support threads at all, because they have a Global Interpreter Lock, which basically means that POE implements the same kind of scalability than Python (and it also explained why the people at ce.gov.br have so much trouble with zope scalability). So now not only we have a thread-enabled SDL binding, but it is *really* threaded, which means that the audio callback will really run at the same time as the timer callback , which will also run together with the event loop. And now I'm happy to know that Perl does have a better threading support than Python - yeah, I know envy is a bad thing, but... whatever...

After I finished Tecla, the app for my 1yo kid, I decided to play with Game::PerlInvaders, which I saw some time ago and I knew some things I could improve. The result is in the branch refact_ruoso at github.

I should make another post, with the details on how tecla and the rewrite of Game::PerlInvaders work, but that's it for now.

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2 Comments

Neat! Invite Nicholas to SDL too! I was also impressed with your write straight to memory with substr for the audio.

If you want co-maint on Game::PerlInvaders just send me your PAUSE id..

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This page contains a single entry by Daniel Ruoso published on January 8, 2010 10:17 AM.

Analog ASCII Clock was the previous entry in this blog.

Writing games in Perl - part 1 - Bouncing Ball is the next entry in this blog.

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