Install Allegro from source on Ubuntu

1. Install general system dependencies.

   sudo apt install git cmake build-essential

2. Install various dependencies.

   sudo apt install libdumb1-dev \
                    libflac-dev \
                    libfreetype6-dev \
                    libgl1-mesa-dev \
                    libglu1-mesa-dev \
                    libgtk-3-dev \
                    libjpeg-dev \
                    libopenal-dev \
                    libphysfs-dev \
                    libpng-dev \
                    libpulse-dev \
                    libtheora-dev \
                    libvorbis-dev \
                    libwebp-dev \
                    libxext-dev \
                    libxxf86vm-dev \
                    libxrandr-dev \
                    libxinerama-dev \
                    libxpm-dev \
                    libopusfile-dev

3. Download Allegro's source from git and navigate to its directory.

   git clone https://github.com/liballeg/allegro5.git
   cd allegro5

   Naturally, you can replace the repository to something else if you want grab the code from, e.g., a GitHub fork.

4. If you want MP3 support, download the header-only MiniMP3 library as follows:

   mkdir -p deps/include
   cd deps/include
   curl -O https://raw.githubusercontent.com/lieff/minimp3/master/minimp3.h
   curl -O https://raw.githubusercontent.com/lieff/minimp3/master/minimp3_ex.h
   cd ../..

5. Configure and build Allegro.

   mkdir build
   cd build
   cmake ..
   make -j$(nproc)

   If you're reproducing some sort of bug or developing a new feature, it can be helpful to build Allegro in debug mode by issuing cmake .. -DCMAKE_BUILD_TYPE=Debug. The default CMAKE_BUILD_TYPE is RelWithDebInfo.

6. Test by running an example.

   cd examples
   ./ex_draw_bitmap