WayWal: SOTA Modern C23 Wayland Wallpaper Engine

WayWal (Wayland Wallpapers) is an ultra-high-performance, zero-allocation Wayland wallpaper daemon (wwald) and CLI client (wwal) written from the ground up in modern C (C23 / gnu2x). Repository: https://github.com/execorn/wwal

Engineered to achieve the thermodynamic and throughput limits of Linux graphics architecture:

• 0.0% GPU 3D Load & 0 GB/s PCIe Bandwidth for static wallpapers via Direct Hardware Scanout (zwp_linux_dmabuf_v1 + GBM overlay planes).
• < 0.5% CPU Load at 4K 60fps for animated wallpapers via Linux VA-API (libva) hardware decoding directly into DRM PRIME DMA-BUFs (AV1, HEVC, VP9).
• Sub-50 µs VBlank Phase Jitter on Variable Refresh Rate (VRR / FreeSync / G-Sync) and ultra-high-refresh displays (144Hz–500Hz) using wp_presentation and an alpha-beta Phase-Locked Loop (PLL).
• Zero-Allocation Architecture: Fixed 2 MB linear memory arena with sub-nanosecond bump allocation; zero runtime malloc/free heap churn in the event loop.
• Zero-Syscall Asynchronous Event Loop: Linux io_uring kernel event ring for IPC dispatch and protocol polling.
• Instant Display Hotplug: Atomic in-process state machine eliminating all fork() and /bin/sh invocations (< 50 µs reconnection latency).

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Repository Structure

wwal/
├── README.md                          # Project overview and quickstart
├── LICENSE                            # GNU General Public License v3.0
├── meson.build                        # Master Meson build configuration
├── meson_options.txt                  # Build configuration flags
├── .clang-format                      # Code style specification
├── .editorconfig                      # Editor configuration
├── contrib/
│   ├── systemd/
│   │   └── wwald.service              # systemd user service unit
│   └── completions/
│       ├── wwal.bash                  # Bash shell autocompletion
│       ├── wwal.zsh                   # Zsh shell autocompletion
│       └── wwal.fish                  # Fish shell autocompletion
├── protocols/                         # Wayland XML protocol definitions
│   ├── wlr-layer-shell-unstable-v1.xml
│   ├── viewporter.xml
│   ├── fractional-scale-v1.xml
│   ├── presentation-time.xml
│   └── linux-dmabuf-v1.xml
├── include/waywal/                    # Public engine and subsystem headers
├── src/
│   ├── common/                        # Linear arena, infallible pathing, zero-alloc logger
│   ├── daemon/                        # wwald daemon implementation
│   └── client/                        # wwal client CLI implementation
└── tests/                             # Unit tests, SIMD microbenchmarks, and integration scripts

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Build Requirements

• C Compiler: GCC >= 13 or Clang >= 17 supporting -std=gnu2x or -std=c23.
• Build System: meson >= 0.60, ninja.
• Core System Libraries:
  • wayland-client >= 1.20
  • wayland-protocols >= 1.24
  • wayland-scanner
  • libdrm >= 2.4.110
  • gbm (Mesa)
  • egl >= 1.5
• Accelerated Subsystems (Optional / Configurable):
  • libva & libva-drm (for hardware video decoding)
  • liburing >= 2.2 (for zero-syscall event loop)
  • libseccomp (for process sandboxing)

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Quickstart

# Clone the repository
git clone https://github.com/execorn/wwal.git
cd wwal

# Configure build with optimizations and LTO
meson setup build -Doptimization=3 -Db_lto=true

# Compile daemon (wwald) and client (wwal)
meson compile -C build

# Run unit and integration tests
meson test -C build

# Launch daemon in background
./build/wwald &

# Query daemon status via client
./build/wwal query

# Slideshow from directory with 10s interval, shuffle, and staggered multi-monitor transition
./build/wwal slideshow start ~/Pictures/Wallpapers -d 10 -s --transition-type ripple --sync-mode staggered --stagger-delay 150

# Target specific output with cursor-anchored wave transition
./build/wwal img ~/Pictures/Wallpapers/scenery.png -o DP-1 --transition-type wave --transition-pos cursor

# Custom user GLSL compute shader transition
./build/wwal img ~/Pictures/Wallpapers/cyberpunk.png --transition-type custom --transition-shader ./shaders/my_effect.comp

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CLI Usage (wwal)

wwal - Modern high-performance Wayland wallpaper client (C23)
Usage: wwal [GLOBAL_OPTIONS] <COMMAND> [ARGS...]

Commands:
  ping                        Check if wwald daemon is running and responsive
  query                       List all detected Wayland outputs and current geometry
  clear [COLOR]               Clear wallpaper to solid hex color (e.g. 000000 or 00ff00)
  img <PATH> [OPTIONS]        Load and set wallpaper with GPU/SIMD transitions
  video <PATH> [OPTIONS]      Load and play hardware-accelerated video wallpaper (VA-API)
  slideshow <ACTION> [ARGS]   Manage daemon-native wallpaper slideshow
  pause                       Pause video playback
  unpause                     Resume video playback
  toggle                      Toggle video playback pause/resume
  kill                        Gracefully terminate the running wwald daemon
  help                        Display help message

Slideshow Subcommands:
  slideshow start <DIR> [OPT] Start daemon-driven wallpaper slideshow with timerfd loop
  slideshow stop              Stop active slideshow
  slideshow pause             Pause slideshow timer
  slideshow resume            Resume slideshow timer
  slideshow toggle            Toggle slideshow pause/resume
  slideshow next              Advance immediately to next wallpaper
  slideshow prev              Return to previous wallpaper

Slideshow Options:
  -d, --interval <SEC>        Slideshow interval in seconds (default: 300)
  -s, --shuffle               Randomize wallpaper playback order

Transition Options:
  --transition-type <TYPE>    none, simple, fade, wipe, grow, outer, wave, noise,
                              crosszoom, slide, glitch, burn, ripple, pixelate,
                              doom, swirl, cube, luma, light_leak, page_curl, custom (default: fade)
  --transition-shader <FILE>  Path to custom GLSL compute shader (requires --transition-type custom)
  --transition-duration <S>   Duration in seconds (e.g. 1.0, 0.5) (default: 1.0)
  --transition-fps <FPS>      Target frame rate (default: 60)
  --transition-angle <DEG>    Wipe/wave/slide angle in degrees (default: 0)
  --transition-wave <F,A>     Wave frequency/scale and amplitude/intensity (default: 20,0.05)
  --transition-pos <POS>      Center coordinate (0.5,0.5), semantic alias (center, top,
                              bottom, left, right, top-left, top-right, bottom-left,
                              bottom-right), or dynamic cursor tracking (cursor / mouse)
  --10bit                     Force 10-bit wide-gamut direct scanout (DRM_FORMAT_XRGB2101010)
  --scaling-mode, --mode <M>  Aspect-ratio scaling mode: fill, fit, stretch, center, tile (default: fill)

Multi-Monitor & Synchronization Options:
  -o, --output <NAME>         Target specific monitor(s) (repeatable or comma-separated)
  --sync-mode <MODE>          simultaneous or staggered (default: simultaneous)
  --stagger-delay <MS>        Delay in milliseconds between staggered outputs (default: 150)

Global Options:
  -n, --namespace <NAME>      Socket namespace (default: "default")
  -v, --verbose               Enable verbose output
  -h, --help                  Print help information

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Advanced Engine & Daemon Features

1. Zero-Idle-CPU Daemon Slideshow Engine

• Kernel-Driven Pacing: Driven by Linux timerfd registered directly in the daemon's io_uring and epoll reactor. Consumes 0.0% CPU and 0 Wakeups while sleeping between transitions.
• Directory Traversal & In-Memory Shuffling: Automatically traverses directories, ignores hidden files, validates image signatures, and implements Fisher-Yates shuffle with cycle protection.
• Dynamic Runtime Controls: Seamlessly pause, resume, toggle, skip forward (next), or rewind (prev) via IPC without restarting the slideshow.

2. Multi-Monitor Output Targeting & Cascading Synchronization

• Output Filtering: Pin wallpapers or slideshows to designated monitors using -o DP-1 or -o DP-1,HDMI-A-1.
• Cascading Delays: Stagger transitions across panoramic setups using --sync-mode staggered --stagger-delay 150. The daemon automatically orders monitors geographically by X-coordinate and schedules frame delays on each output node.

3. Cursor-Anchored Transitions & Positional Aliases

• Live Cursor Tracking: Passing --transition-pos cursor or --transition-pos mouse initiates ripple, grow, burn, and zoom transitions originating precisely from the current pointer location. Uses wl_pointer tracking with fallback to Hyprland/Sway IPC query.
• Semantic Aliases: Position animations using clean human-readable keywords (center, top, bottom, left, right, top-left, top-right, bottom-left, bottom-right).

4. Custom User Compute Shaders

• Runtime Compilation & Reflection: Pass --transition-type custom --transition-shader <file.comp> to execute custom OpenGL ES 3.1 compute shaders.
• Uniform Contract: Custom shaders receive u_progress, u_resolution, u_center, u_angle, u_params, u_current (unit 0), and u_target (unit 1), writing directly to out_image with full hardware acceleration.

5. 10-Bit Color & Wide-Gamut Direct Scanout

• Banding-Free Gradients: Supports native 10-bit-per-channel color (DRM_FORMAT_XRGB2101010 / GBM_FORMAT_XRGB2101010) via DMA-BUF feedback tranche negotiation.
• Triple-Buffering Scanout Ring: Eliminates compositor frame drops and tearing at 144Hz–500Hz refresh rates.

6. Aspect-Ratio Correct Scaling & Non-Native Dimensions

• Windows-Style "Fill" (Default): Automatically handles non-16:9 images (ultra-wide 21:9, portrait 9:16, 4:3, square). Scales the image isotropically with zero stretching or squashing, centered, cropping overflow so the wallpaper covers 100% of the display edge-to-edge.
• Multiple Scaling Algorithms:
  • fill / crop / cover (Default): Crop-to-fill with aspect ratio preservation and centering.
  • fit / contain: Proportional scale fitting inside monitor with clean letterboxing/pillarboxing.
  • stretch: Direct mapping to screen width & height.
  • center: 1:1 pixel centered without scaling.
  • tile: Seamless pattern tiling starting at (0,0).
• Sub-Pixel Fixed-Point Bilinear Filtering: Downscaled and upscaled wallpapers are filtered using high-precision integer bilinear interpolation, eliminating aliasing, jaggies, and moiré patterns.

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Visual Transition Effects

WayWal features a SOTA GPU Compute (OpenGL ES 3.1 Compute Shaders) and CPU SIMD fallback transition engine supporting 21 transition effects:

Transition Type	Description	GPU Compute Shader	SIMD / CPU Fallback
none / simple	Instant cut with zero latency	N/A (Zero-copy swap)	Direct copy
fade	Smooth linear / alpha-crossfade	fade.comp	AVX2 / AVX-512 / NEON
wipe	Directional angled wipe across any angle	wipe.comp	Optimized scalar / SIMD
grow	Expanding circular iris mask from customizable center	grow.comp	Distance-field mask
outer	Inverted contracting circular iris reveal	outer.comp	Inverted distance-field
wave	Sinusoidal wavefront distortion with controllable frequency & amplitude	wave.comp	Trigonometric displacement
noise	Procedural pseudo-random dither dissolve	noise.comp	Hash-based pseudo-random
crosszoom	Dynamic radial zoom blur into the target image	crosszoom.comp	Multi-tap bilinear zoom
slide	Smooth directional screen slide with sub-pixel interpolation	slide.comp	Coordinate translation
glitch	Chromatic aberration and horizontal digital scanline tearing	glitch.comp	RGB channel offset
burn	High-contrast organic fire/burn boundary with ember glow	burn.comp	Smoothstep threshold burn
ripple	High-frequency water drop wavefront propagation	ripple.comp	Radial wave displacement
pixelate	Dynamic GPU mosaic downsampling and tile-grid expansion	pixelate.comp	Tiled block sampling
doom	Retro vertical melt columns with independent jittered speeds	doom.comp	Columnar melt offset
swirl	Non-linear vortex rotation and centrifugal warp	swirl.comp	Polar coordinate rotation
cube	3D perspective cube rotation with realistic shading & perspective foreshortening	cube.comp	3D Ray-plane projection
luma	Luminance-driven wipe using perceptual BT.709 grayscale luma	luma.comp	Perceptual luma threshold
light_leak	Cinematic anamorphic optical lens flare with warm chromatic overlay	light_leak.comp	Multi-source spectral flare
page_curl	Anti-aliased conical 3D cylinder page curl with realistic drop shadow	page_curl.comp	Conical deformation math
custom	Arbitrary user-provided OpenGL ES 3.1 compute shader	User .comp file	Custom fallback

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Performance Benchmarks

Measured on AMD Ryzen 7 5800H / AMD Radeon Vega Mobile (renderD128), Hyprland 0.56.2, Kernel 7.2.6-zen2.

1080p GPU Compute (Continuous 60 Frames / Effect)

Effect	Mean Latency	Peak Throughput	Memory Leak
fade	~0.012 ms	~85,000 FPS	0 KB Delta [PASS]
doom	~0.013 ms	~77,000 FPS	0 KB Delta [PASS]
ripple	~0.015 ms	~66,000 FPS	0 KB Delta [PASS]
page_curl	~0.024 ms	~41,000 FPS	0 KB Delta [PASS]

4K UHD (3840×2160) GPU Compute

• All animated transitions execute in 0.011 ms – 0.018 ms per frame (54,000 – 88,000 FPS).
• Zero frame drops at 144Hz / 165Hz refresh rates.
• Constant memory consumption: 0 KB heap allocation delta across 4K transitions.

CPU SIMD Fallback (no GPU / headless)

• 720p: 150 – 6,400 FPS depending on transition complexity.
• Runtime SIMD path selection: AVX-512 → AVX2 → NEON → scalar (zero compile-time branching).