prism

Vulkan-native, HDR-native Wayland compositor.

Color management is first-class from day 1: every render element carries its source color description; every output its target. The renderer composites in a BT.2020 absolute-nits linear fp16 intermediate; the per-output encode pass calibrates, tone-maps, and encodes for scanout (sRGB or PQ). Direct scanout is an optimization on top of that path, not a separate path.

Status

A working multi-output, multi-GPU compositor. It brings up every connected output across both AMD GPUs with vblank-driven double-buffered scanout, takes keyboard and pointer input, composites real clients (alacritty, mpv, Firefox, nautilus), decodes YUV video (NV12/P010), drives config-driven HDR output signaling (PQ), and plays HDR video end-to-end — native and cross-GPU-mirrored. Per-display color calibration (3D LUT, CTM, response curve) is config-driven and EDID-keyed, with a live-reload loop through prism-tune. Protocol behavior is gated by a WLCS conformance harness.

Notable gaps: tone mapping (decode/encode still hard-clip), touch input, output/connector runtime hotplug, and the subpixel-FIR + dither encode fragments. See docs/status.md for the full picture and docs/deferred-work.md for the backlog.

Documentation

• docs/status.md — what's built and verified, and the subcommand reference.
• docs/architecture.md — crate layering, runtime object graph, renderer/protocol/DRM decisions.
• docs/color-management.md — the color/HDR design, amdgpu KMS quirks, calibration data flow.
• docs/reuse-map.md — what we depend on from smithay/niri vs. what we own.
• docs/deferred-work.md — the backlog, grouped by subsystem.

Workspace layout

Crate	Role
prism-frame	Renderer-independent frame description (Element, FrameDescription, ColorDescription, color matrices, opaque handles)
prism-renderer	Vulkan renderer (ash). Per-GPU instance. Decode → composite → encode pipeline.
prism-drm	KMS frontend — DrmCompositor-equivalent + per-output scanout buffer pool + modifier negotiation
prism-layout	Window layout + per-surface state (ported from niri)
prism-input	Input routing + pointer hit-testing (libinput → seat → focused surface)
prism-animation	Spring/curve animation engine + frame clock (ported from niri)
prism-config	KDL config schema (ported from niri-config)
prism-protocols	Wayland protocol wiring (smithay handlers), the PrismState machine, buffer import
prism-ipc	IPC types for talking to a running compositor
prism-tune	Closed-loop color calibration tool (IPC client + colorimeter + patch surface)
prism-wlcs	WLCS conformance-test integration shim (cdylib)
prism-shmtest	Minimal xdg-shell shm client for end-to-end TTY testing
prism	The compositor binary

The load-bearing boundary is prism-frame: layout/input/protocol code describes frames without ever seeing a Vulkan type, which keeps renderer concerns from leaking outward (and lets the protocol stack run headless for conformance tests). The renderer is one concrete ash-backed type per GPU — no Renderer trait polymorphism. See docs/architecture.md.

Building

cargo check

Needs Vulkan dev headers, libinput, libseat, libdrm, libgbm, wayland-server, and glslangValidator (the build shells out to it to compile shaders). On Arch:

sudo pacman -S vulkan-headers vulkan-validation-layers libinput libseat libdrm \
               wayland mesa glslang

Running

prism run drives every connected output on the TTY; scripts/tty-test.sh launches it alongside the in-tree prism-shmtest client. The full subcommand reference (including prism-tune for calibration) is in docs/status.md.

License

GPL-3.0-or-later (matching the niri / smithay ecosystem we depend on).