Lys is a library and wrapper for pain-free graphics programming with
Futhark. It works by using
rules to automatically generate a wrapper program in C that uses
SDL2 to display graphics and handle user
events, whose behaviour is controlled by calling a Futhark program
with specially defined entry points.
Trying the Demo (assuming that you have git-cloned this repository)
Make sure that the requirements described below are satisfied. Then execute the commands:
$ futhark pkg sync $ make $ ./lys
A window should now open and you should be able to navigate the white
object with the arrow keys and the mouse. Change object to a square by
s, and back to a circle by pressing
c. Exit by pressing
Download the package like any other Futhark package:
$ futhark pkg add github.com/diku-dk/lys $ futhark pkg sync
Then create a
Makefile with the following contents:
Finally create a Futhark program
lys.fut that defines at least a
lys of module type
lys (example). Run
make and a binary called
lys will be compiled.
If you don't want your binary to be called
lys, set the
PROGNAME to whatever you wish. For example, if you use
PROGNAME=spetakel include lib/github.com/diku-dk/lys/common.mk
then Lys will look for a Futhark program
spetakel.fut and generate a
spetakel. The file
spetakel.fut should still define
a module called
It is also possible to use Lys as a general library, in which case you write both the Futhark file and the corresponding C file. This gives you more flexibility in how you use the built-in text overlay and how you initialise Lys' state, but keeps the default event-render SDL loop.
Lys is written in C, and requires a working C compiler and the SDL2 and SDL2-ttf libraries with associated header files. On Debian-like systems (including Ubuntu), this can be installed with
# apt install libsdl2-dev libsdl2-ttf-dev
# yum install SDL2-devel SDL2_ttf-devel
On macOS with Homebrew, run
$ brew install sdl2 sdl2_gfx sdl2_image sdl2_ttf
On Windows... well, if you know how, please tell us!
These keybindings are common for all lys programs:
- ESC: Exit the program, or escape mouse grabbing.
- F1: Toggle showing text.
Common command-line options
./lys --help to see the available options.
Using the CUDA backend
By default, the build rules defined in
lib/github.com/diku-dk/lys/common.mk use Futhark's OpenCL backend.
You can change it to use Futhark's CUDA backend by setting
LYS_BACKEND=cuda, either in the Makefile or as an environment
Using the sequential backend
LYS_BACKEND=c. Be aware that this is strictly single-threaded C
with few optimisations. It might be quite slow.