shim: Initial commit

Author: Sean Cross

Makefile

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+all: bcm_host.c
+	gcc -c bcm_host.c -o bcm_host.o -fPIC `sdl-config --cflags`
+	gcc -fPIC -shared -lEGL -lGLESv1_CM -Wl,-soname,libbcm_host.so.1 bcm_host.o -o libbcm_host.so.1.0

README.md

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+Minecraft: Pi Edition wrapper
+=============================
+
+This is a wrapper for Minecraft: Pi Edition's OpenGL ES drivers.  It makes
+several assumptions about running on a Raspberry Pi, some of which are not
+valid on our system (Kosagi Novena).  Namely, it suffers from the following:
+
+* Requires libbcm, which does not exist outside Broadcom chips
+* Does not pass the window object to eglContextCreate()
+* Calls init()/destroy() multiple times, which crashes our vendor's GL drivers
+* Links against libGLESv2.so but uses GLES 1.0
+
+This library and runtime environment aim to solve these problems.
+
+Usage
+-----
+
+To compile our libbcm replacement, simply run "make".
+
+Then download Minecraft from http://pi.minecraft.net/ and extract it so
+that minecraft-pi is in the current directory.
+
+Copy /usr/lib/libGLESv1_CM.so or /usr/lib/arm-linux-gnueabihf/libGLESv1_CM.so
+to this directory and rename it to libGLESv2.so
+
+Finally, run minecraft-pi with the following invokation:
+
+    LD_PRELOAD=./libbcm_host.so LD_LIBRARY_PATH=$PWD ./minecraft-pi
+
+Gotchas
+-------
+
+Minecraft is run at full-screen for performance reasons.  Unfortunately,
+the Minecraft program doesn't have an "Exit" function, so you'll have to
+come up with your own way of killing it.
+
+Design
+------
+
+There are counters that monitor how many times various functions are
+called.  Minecraft seems to initialize EGL and then tear it down again
+right away, which causes our vendor's driver to crash.  To get around
+this, we count how many times each driver is invoked, and only call
+the real egl functions after a certain number of invocations.