libliftoff

Lightweight KMS plane library.

libliftoff eases the use of KMS planes from userspace without standing in your way. Users create "virtual planes" called layers, set KMS properties on them, and libliftoff will pick hardware planes for these layers if possible.

Resources:

• Blog post introducing the project
• FOSDEM 2020 talk

libliftoff is used in production by gamescope on Steam Deck devices, and work is underway to integrate it with wlroots.

Building

Depends on libdrm. Requires universal planes and atomic.

meson build/
ninja -C build/

Usage

See liftoff.h and the example/ directory. See doc/compositor.md for compositor guidelines.

Here's the general idea:

struct liftoff_device *device;
struct liftoff_output *output;
struct liftoff_layer *layer;
drmModeAtomicReq *req;
int ret;

device = liftoff_device_create(drm_fd);
output = liftoff_output_create(device, crtc_id);

liftoff_device_register_all_planes(device);

layer = liftoff_layer_create(output);
liftoff_layer_set_property(layer, "FB_ID", fb_id);
/* Probably setup more properties and more layers */

req = drmModeAtomicAlloc();
ret = liftoff_output_apply(output, req);
if (ret < 0) {
	perror("liftoff_output_apply");
	exit(1);
}

ret = drmModeAtomicCommit(drm_fd, req, DRM_MODE_ATOMIC_NONBLOCK, NULL);
if (ret < 0) {
	perror("drmModeAtomicCommit");
	exit(1);
}
drmModeAtomicFree(req);

Contributing

Report bugs and send pull requests on GitLab.

We use the Wayland/Weston style and contribution guidelines, see Weston's contributing document.

License

MIT