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« on: March 03, 2020, 05:55:38 PM »
A lot of that depends on your level of experience with the code in question, as well as the platform you're targeting. In the case of MegaZeux I have a reasonable understanding of the platform code due to refactoring (reorganizing, basically) and extending the clipboard handling code, so I had a pretty good idea of where to look when I started digging things apart.
As far as getting to that point, it's like taking something apart. Whenever you dive into someone else's code you're always going to be at a disadvantage. Like artists, every programmer has their own ideas on the best way to accomplish certain goals. One of the methods that I tend to use is to determine which section I want to change and search through the code for references to that particular thing. From there I have a few options—I can tweak certain values to see if I can change the result of something, place debug print statements throughout the code to see what happens in certain conditions, or run the thing through a debugger and have it stop at certain lines to observe the contents of variables. Unfortunately, the best way to do this depends on your knowledge of the code and the exact thing that you're trying to accomplish, so there's no real one size fits all solution.
To give you an idea of how I approached the Vita port, I first started off by installing the development tools and making sure that I could build and run Vita homebrew. You always want to use sample code with your tools, not run something that someone else built. You want to be able to generate the file on your PC, send it to the target, and run it from there. This allows you to make sure that your toolchain (the set of tools that convert readable source code to machine code) is sane (functional) and that the packaging tools (that is, the programs that take the toolchain's output and converts it into something you can install on the system) are functional.
After verifying that, I took a look at the capabilities of the system and the available libraries. MegaZeux's preferred graphics, audio, and input library is SDL 2.0, with SDL 1.3 being a good fallback. It has several options for playing back tracker music (libxmp, libmodplug, and mikmod), Vorbis files (libvorbis and tremor), and also supports RAD (Reality Adlib Tracker).
The Vita SDK supports SDL 2.0, which basically gave me audio, video, and input for free. The system is a reasonably powerful quad-core ARM processor. I know that the 3DS port of MegaZeux could handle RAD playback, and since the Vita is faster I was reasonably sure it could as well (and it does). The CPU supports floating point instructions, so I could use libvorbis instead of tremor. Additionally, it has plenty of memory (512MB) so it's nowhere near as limited as many of the other portables that it supports.
So, the next step is to just try building it. The original build I made was fairly minimal, as I wanted to be able to just run MegaZeux and have something display on the screen. I built it with no audio support, targeting SDL 2.0. That's when I ran into that little issue with the Vita's inability to traverse directories. The game won't even compile since those functions simply don't exist in the Vita's userspace APIs. I rewrote them, then used some C trickery to remap those functions to my custom ones, and was able to come up with a working build.
It worked. I was able to load a world. I didn't have audio, so I couldn't hear anything, and I didn't have working input so I couldn't actually play the game, but I could see the title sequence doing its thing. From there, it was just a matter of making an organized list and running through the required features point by point, and honestly it became a bit of a blur after a while. This is largely where the collaboration aspect came up, too. Lachesis is the lead developer of MegaZeux and knows the source like the back of her hand, so whenever I'd run into trouble she would advise me where to look and I'd generally work out a solution. Collaborating and working off of another dev's experience is pretty key with stuff like that.
A huge part of the "heavy development" phase is just staying organized. Figure out the problems, prioritize them, tackle them one by one, and test the shit out of everything. It's much easier to handle a large problem if you take care of it step by step.
Also, yeah, everything Vita-related went up in value ever since the systems were busted wide open. I was planning to get a PSTV to verify compatibility but it ended up being way too expensive for what it was, like rivaling the PS4 in price. :|
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