SDL/examples

Examples

What is this?

In here are a collection of standalone SDL application examples. Unless otherwise stated, they should work on all supported platforms out of the box. If they don't please file a bug to let us know.

What is this SDL_AppIterate thing?

SDL can optionally build apps as a collection of callbacks instead of the usual program structure that starts and ends in a function called main. The examples use this format for two reasons.

First, it allows the examples to work when built as web applications without a pile of ugly #ifdefs, and all of these examples are published on the web at examples.libsdl.org, so you can easily see them in action.

Second, it's example code! The callbacks let us cleanly break the program up into the four logical pieces most apps care about:

• Program startup
• Event handling
• What the program actually does in a single frame
• Program shutdown

A detailed technical explanation of these callbacks is in docs/README-main-functions.md (or view that page on the web on the wiki).

I would like to build and run these examples myself.

When you build SDL with CMake, you can add -DSDL_EXAMPLES=On to the CMake command line. When you build SDL, these examples will be built with it.

But most of these can just be built as a single .c file, as long as you point your compiler at SDL3's headers and link against SDL.

What is the license on the example code? Can I paste this into my project?

All code in the examples directory is considered public domain! You can do anything you like with it, including copy/paste it into your closed-source project, sell it, and pretend you wrote it yourself. We do not require you to give us credit for this code (but we always appreciate if you do!).

This is only true for the examples directory. The rest of SDL falls under the zlib license.

What is template.html and highlight-plugin.lua in this directory?

This is what examples.libsdl.org uses when generating the web versions of these example programs. You can ignore this, unless you are improving it, in which case we definitely would love to hear from you!

What is template.c in this directory?

If writing new examples, this is the skeleton code we start from, to keep everything consistent. You can ignore it.

How are the thumbnails/onmouseover media created?

(Since I have to figure this out every time.)

This is how Ryan is doing it currently.

• rm -f frame*.bmp
• Temporarily add #include "../../save-rendering-to-bitmaps.h" after any SDL includes in the example program.
• Launch the example app, interact with it, let it run for a few seconds, quit.
• This will dump a "frameX.bmp" file for each frame rendered.

• Make a video in webp format from the bitmaps (this assumes the bitmaps were stored at 60fps, you might have to tweak).

  ffmpeg -framerate 60 -pattern_type glob -i 'frame*.bmp' -loop 0 -quality 40 -r 10 -frames:v 40 onmouseover.webp
  

You might need to start in the middle of the video, or mess with quality or number of frames to generate, ymmv.

• Pick a frame for the thumbnail, make it a .png, and run that png through pngquant for massive file size reduction without any obvious loss in quality:

  convert frame00000.bmp cvt.png ; pngquant cvt.png --output thumbnail.png ; rm -f cvt.png