DXX-Rebirth for the Raspberry Pi

BUILDING:
=========
Make sure you have installed (the development packages of) all of the required
libraries (libsdl, libphysfs, ...). For building, you will also need scons (and
for that, python).  Most linux distributions should contain all the required
packages, debain/raspbian do so for sure. Using a distribution with hardfp ABI
is recommended for optimal performance. I developed/tested this on a raspbian
wheezy. 

Multiple build configurations are possible for the Pi, depending on whether you
wish to use the legacy vendor graphics driver or experimental Mesa VC4 driver.

To build against the legacy vendor graphics driver (recommended for most users):

scons raspberrypi=1

If you're using a firmware release older than 1.20160921-1, it's highly
recommended that you upgrade, but if that's not an option, you must manually
specify the original GLES/EGL library names:

scons raspberrypi=1 egl_lib=EGL opengles_lib=GLESv2

This assumes that the development files (libs/headers) for the VideoCore APIs 
are located in /opt/vc. You can use rpi_vc_path to specify another location.

If you wish to build for Raspberry Pi 4B or the experimental Mesa VC4 driver:

scons raspberrypi=mesa

This will select the GL interface with SDL2 by default, but you can select
GLES & SDL1 by adding "opengles=1 sdl2=0". Keep in mind that as of Raspbian buster,
the Mesa packages no longer ship with GLESv1 headers, making GLES builds impossible.
Additionally, SDL2 is highly recommended, as its KMSDRM video driver is the only
way to run DXX-Rebirth on a Raspberry Pi 4B outside of an Xorg session.

For all other options, check "scons -h".

Currently, there is no direct support for crosscompiling.

RUNNING:
========
The game should run with X11 or directly on the console (libsdl with fbcon/
directfb driver). 

NOTE: *** PLEASE USE THE 128/128MB MEMORY SPLIT *** 

The game might completely freeze or diplay messed up graphics in
out-of-(GPU)-memory situations. If you want to run it with the 192/64MB memory
split, you might be able to do so by setting the texture filter to "NONE" in
the graphics options. (This disables mip mapping and reduces the memory
requirements of the textures. Note that the "BILINEAR" filter still uses
mipmapping). 

If the game freezes during the "Prepare for Descent" phase when loading a
level, you probably do not have enough GPU memory.

RUNNING ON X11:
===============
Recommendation is to use fullscreen mode. However, you can run in "windowed"
mode, too. The game will open an X11 window in that case, and the actual game
output will be an overlay of the same size, but not at the same position, and
always on top (and completely out of control of the X Server). Game input is
still handled via the X11 window, so make sure it has the focus.

RUNNING ON THE CONSOLE:
=======================
libsdl supports running directly on the Linux console. While the SDL Video mode
is technically not required on the RPi, we still have to use it to get all the
input events we need. libsdl seems to have problems on the RPi, I always get a
crash in libsdl when trying to change the resolution. To avoid such crashes,
the code will try to detect if it is running on the console and activate a hack
to prevent switching the resolution. Note that the in-game framebuffer
resolution can still be changed, the RPi will just scale the output to the
initial resolution (in "fullscreen" mode). "Windowed" mode will just result in
unscaled output. As libsdl creates a black screen, you will not be able to have
the "Window" on top of the linux console output :(

NOTE: You might need root privileges to use the libsdl fbcon/directfb drivers.

BUGS, SUGGESTIONS AND FEEDBACK:
===============================

The RPi patch was written by:
	Marcel Heinz <derhass@arcor.de>

Send bug reports, suggestions and other feedback regarding the operation
on the RPi to me via email.

						-- derhass, 2012-08-09