Raspberry Pi

 ================================================================================

 Requirements:

 Raspbian (other Linux distros may work as well).

 ================================================================================

  Features

 ================================================================================

 * Works without X11

 * Hardware accelerated OpenGL ES 2.x

 * Sound via ALSA

 * Input (mouse/keyboard/joystick) via EVDEV

 * Hotplugging of input devices via UDEV

 ================================================================================

  Raspbian Build Dependencies

 ================================================================================

 sudo apt-get install libudev-dev libasound2-dev libdbus-1-dev

 You also need the VideoCore binary stuff that ships in /opt/vc for EGL and 

 OpenGL ES 2.x, it usually comes pre-installed, but in any case:

 sudo apt-get install libraspberrypi0 libraspberrypi-bin libraspberrypi-dev

 ================================================================================

  NEON

 ================================================================================

 If your Pi has NEON support, make sure you add -mfpu=neon to your CFLAGS so

 that SDL will select some otherwise-disabled highly-optimized code. The

 original Pi units don't have NEON, the Pi2 probably does, and the Pi3

 definitely does.

 ================================================================================

  Cross compiling from x86 Linux

 ================================================================================

 To cross compile SDL for Raspbian from your desktop machine, you'll need a

 Raspbian system root and the cross compilation tools. We'll assume these tools

 will be placed in /opt/rpi-tools

     sudo git clone --depth 1 https://github.com/raspberrypi/tools /opt/rpi-tools

 You'll also need a Raspbian binary image.

 Get it from: http://downloads.raspberrypi.org/raspbian_latest 

 After unzipping, you'll get file with a name like: "<date>-wheezy-raspbian.img"

 Let's assume the sysroot will be built in /opt/rpi-sysroot.

     export SYSROOT=/opt/rpi-sysroot

     sudo kpartx -a -v <path_to_raspbian_image>.img

     sudo mount -o loop /dev/mapper/loop0p2 /mnt

     sudo cp -r /mnt $SYSROOT

     sudo apt-get install qemu binfmt-support qemu-user-static

     sudo cp /usr/bin/qemu-arm-static $SYSROOT/usr/bin

     sudo mount --bind /dev $SYSROOT/dev

     sudo mount --bind /proc $SYSROOT/proc

     sudo mount --bind /sys $SYSROOT/sys

 Now, before chrooting into the ARM sysroot, you'll need to apply a workaround,

 edit $SYSROOT/etc/ld.so.preload and comment out all lines in it.

     sudo chroot $SYSROOT

     apt-get install libudev-dev libasound2-dev libdbus-1-dev libraspberrypi0 libraspberrypi-bin libraspberrypi-dev libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxi-dev libxinerama-dev libxxf86vm-dev libxss-dev

     exit

     sudo umount $SYSROOT/dev

     sudo umount $SYSROOT/proc

     sudo umount $SYSROOT/sys

     sudo umount /mnt

 There's one more fix required, as the libdl.so symlink uses an absolute path 

 which doesn't quite work in our setup.

     sudo rm -rf $SYSROOT/usr/lib/arm-linux-gnueabihf/libdl.so

     sudo ln -s ../../../lib/arm-linux-gnueabihf/libdl.so.2 $SYSROOT/usr/lib/arm-linux-gnueabihf/libdl.so

 The final step is compiling SDL itself.

     export CC="/opt/rpi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-gcc --sysroot=$SYSROOT -I$SYSROOT/opt/vc/include -I$SYSROOT/usr/include -I$SYSROOT/opt/vc/include/interface/vcos/pthreads -I$SYSROOT/opt/vc/include/interface/vmcs_host/linux"

     cd <SDL SOURCE>

     mkdir -p build;cd build

     LDFLAGS="-L$SYSROOT/opt/vc/lib" ../configure --with-sysroot=$SYSROOT --host=arm-raspberry-linux-gnueabihf --prefix=$PWD/rpi-sdl2-installed --disable-pulseaudio --disable-esd

     make

     make install

 To be able to deploy this to /usr/local in the Raspbian system you need to fix up a few paths:

     perl -w -pi -e "s#$PWD/rpi-sdl2-installed#/usr/local#g;" ./rpi-sdl2-installed/lib/libSDL2.la ./rpi-sdl2-installed/lib/pkgconfig/sdl2.pc ./rpi-sdl2-installed/bin/sdl2-config

 ================================================================================

  Apps don't work or poor video/audio performance

 ================================================================================

 If you get sound problems, buffer underruns, etc, run "sudo rpi-update" to 

 update the RPi's firmware. Note that doing so will fix these problems, but it

 will also render the CMA - Dynamic Memory Split functionality useless.

 Also, by default the Raspbian distro configures the GPU RAM at 64MB, this is too

 low in general, specially if a 1080p TV is hooked up.

 See here how to configure this setting: http://elinux.org/RPiconfig

 Using a fixed gpu_mem=128 is the best option (specially if you updated the 

 firmware, using CMA probably won't work, at least it's the current case).

 ================================================================================

  No input

 ================================================================================

 Make sure you belong to the "input" group.

     sudo usermod -aG input `whoami`

 ================================================================================

  No HDMI Audio

 ================================================================================

 If you notice that ALSA works but there's no audio over HDMI, try adding:

     hdmi_drive=2

 to your config.txt file and reboot.

 Reference: http://www.raspberrypi.org/phpBB3/viewtopic.php?t=5062

 ================================================================================

  Text Input API support

 ================================================================================

 The Text Input API is supported, with translation of scan codes done via the

 kernel symbol tables. For this to work, SDL needs access to a valid console.

 If you notice there's no SDL_TEXTINPUT message being emitted, double check that

 your app has read access to one of the following:

 * /proc/self/fd/0

 * /dev/tty

 * /dev/tty[0...6]

 * /dev/vc/0

 * /dev/console

 This is usually not a problem if you run from the physical terminal (as opposed

 to running from a pseudo terminal, such as via SSH). If running from a PTS, a 

 quick workaround is to run your app as root or add yourself to the tty group,

 then re-login to the system.

     sudo usermod -aG tty `whoami`

 The keyboard layout used by SDL is the same as the one the kernel uses.

 To configure the layout on Raspbian:

     sudo dpkg-reconfigure keyboard-configuration

 To configure the locale, which controls which keys are interpreted as letters,

 this determining the CAPS LOCK behavior:

     sudo dpkg-reconfigure locales

 ================================================================================

  OpenGL problems

 ================================================================================

 If you have desktop OpenGL headers installed at build time in your RPi or cross 

 compilation environment, support for it will be built in. However, the chipset 

 does not actually have support for it, which causes issues in certain SDL apps 

 since the presence of OpenGL support supersedes the ES/ES2 variants.

 The workaround is to disable OpenGL at configuration time:

     ./configure --disable-video-opengl

 Or if the application uses the Render functions, you can use the SDL_RENDER_DRIVER

 environment variable:

     export SDL_RENDER_DRIVER=opengles2

 ================================================================================

  Notes

 ================================================================================

 * When launching apps remotely (via SSH), SDL can prevent local keystrokes from

   leaking into the console only if it has root privileges. Launching apps locally

   does not suffer from this issue.