hyprcosmic/docs/superpowers/specs/2026-08-09-hyprcosmic-design.md

HyprCosmic — Design

Date: 2026-08-09 Status: Approved for implementation

Goal

Run a HyDE-style desktop on COSMIC's compositor: HyDE themes apply end to end — palette, wallpaper, gaps, rounding, bar, launcher, notifications — with all configuration driven from a single commented, version-controllable text file in Hyprland's idiom.

The user reviewed the cost of the full-rice target and chose it explicitly over the cheaper palette-only option.

What this actually is

HyprCosmic is HyDE with cosmic-comp as the compositor, not COSMIC restyled to look like HyDE. COSMIC's own shell surface — cosmic-panel applets, the workspace overview, and cosmic-settings' appearance controls — is replaced, not themed. This framing is the honest description and should appear in the project README.

Non-goals

• Bit-compatibility with Hyprland's config parser. Syntax is familiar; an existing hyprland.conf will not work, because COSMIC's key names and concepts differ throughout.
• Preserving cosmic-settings as a working appearance editor. Configuration is one-way: the file wins, and GUI edits are overwritten on next apply.
• Gradient window borders. COSMIC's active_hint is a solid hint with no gradient support, and adding one is out of scope.
• Matching Hyprland's window-management semantics (dwindle/master layouts). cosmic-comp's BSP tiler stays.

Verified findings

Everything below was read from the tree at /home/dingo/cosmic-epoch, not assumed.

Finding	Evidence
cosmic-comp is GPL-3.0-only; forking is permitted	cosmic-comp/src/lib.rs:7
COSMIC_SESSION_SOCK is optional — cosmic-comp runs standalone	cosmic-comp/src/session.rs:76,90
wlr-layer-shell is implemented (foreign bars can render)	cosmic-comp/src/wayland/handlers/layer_shell.rs
ext-session-lock is implemented	cosmic-comp/src/wayland/handlers/session_lock.rs
ext-workspace-v1 is implemented, plus a cosmic v2 extension	cosmic-comp/src/wayland/protocols/workspace/ext.rs
zwlr_foreign_toplevel_management_v1 is absent — only ext-foreign-toplevel-list exists	grep across cosmic-comp/src/; handlers/foreign_toplevel_list.rs
Gaps are real and theme-driven, (u32, u32)	layout/tiling/mod.rs:4305, layout/floating/mod.rs:1689
Blur exists but is client-requested via ext-background-effect, not compositor rule	handlers/background_effect.rs, backend/render/wayland/blur_effect.rs, shaders/blur_{downsample,upsample}.frag
Shadow and rounded-corner shaders exist	backend/render/shaders/{shadow,rounded_rectangle,rounded_outline}.frag
Animation engine exists; durations hardcoded	src/lib.rs:197,209; shell/workspace.rs:75
Window rules cover tiling exceptions only	cosmic-settings-daemon/config/src/window_rules/mod.rs:41
Compositor config surface is ~20 flat fields	cosmic-comp/cosmic-comp-config/src/lib.rs:71-105
cosmic-config is a filesystem KV store, one file per key, sparse (only changed keys materialise)	~/.config/cosmic/, 136 files across ~25 components
cosmic-config live-reloads via inotify	cosmic-comp/src/config/mod.rs:173,219,251
cosmic-panel has zero CSS/stylesheet support; renders via iced	grep across cosmic-panel/
Upstream velocity: 46 commits in 30 days	git log --since="30 days ago" in cosmic-comp

What a HyDE theme actually contains

Measured from HyDE-Project/hyde-themes, branch Catppuccin-Mocha (25 files):

File	Size	Contents
hypr.theme	1,316 B	gaps 3/8, rounding 10, border_size 2, gradient borders, blur {size 6, passes 3}, GTK/icon theme names
waybar.theme	358 B	7 @define-color lines — not a stylesheet
rofi.theme	320 B	~7 colour variables
kitty.theme	1,536 B	palette
GTK + icon tarballs	4.6 MB	standard themes
wallpapers	~95 MB	the bulk

The theme is ~3.5 KB of text. The bespoke widget styling belongs to HyDE itself, not to any individual theme — which is why running HyDE's own bar and launcher is the shortest path to fidelity.

Architecture

Three repositories. Upstream components not listed are consumed unmodified.

Repo	Kind	Purpose
hyprcosmic/cosmic-comp	Fork (GPL-3.0)	Protocol patches, then blur/animation config
hyprcosmic/cosmic-conf	New (GPL-3.0)	Config compiler + theme importer
hyprcosmic/hyprcosmic	New meta	Submodule pins, session definition, docs

Runtime composition:

Layer	Component	Modified?
Compositor	hyprcosmic/cosmic-comp	Yes — patches A, B, then polish
Bar	waybar (upstream, MIT)	No — consumes HyDE config + CSS directly
Launcher	rofi (upstream)	No — HyDE .rasi works
Notifications	swaync (upstream)	No
Wallpaper	swww (upstream)	No — matches HyDE; CosmicBackground unused
Session	forked cosmic-session	Yes — gate start_component calls
Config	cosmic-conf	New

Phase 1 — cosmic-conf

A Rust binary that compiles one text file into the cosmic-config tree. It is a compiler, not a daemon owning state: COSMIC components keep reading cosmic-config and keep live-reloading through their existing ConfigWatchSource. Nothing in COSMIC learns about cosmic.conf.

Units

Unit	Responsibility	Depends on
parser	text → AST with byte spans. Sections, $variables, source=, # comments	—
schema	Declarative registry: conf key → cosmic-config target + type + validator + doc	—
resolve	AST + schema → typed values. Variable expansion, type/range checking, diagnostics	parser, schema
emit	Typed values → cosmic-config writes	resolve, cosmic-config
watch	inotify on the conf file and its includes → re-run pipeline	all

parser, schema and resolve are pure and touch nothing COSMIC-specific, so the hard logic is unit-testable without a compositor running. Only emit binds to cosmic-config, and it is the only unit Phase 2 modifies when new keys land.

Entry points: cosmic-conf apply (one-shot, non-zero exit on error), cosmic-conf watch, cosmic-conf apply --diff (show what would be overwritten).

File format

Hyprland-style syntax, hand-written recursive-descent parser (~500 lines). Chosen over KDL and TOML because the authoring experience is the product requirement; a better-engineered format that feels wrong fails the goal.

$accent = rgb(6b9fed)
$gap    = 8

general {
    gaps_in     = $gap
    gaps_out    = $gap * 2
    autotile    = true
    active_hint = true
}

decoration {
    rounding = 10
}

theme {
    mode   = dark
    accent = $accent
}

bind = SUPER, Return, spawn, kitty
bind = SUPER, Q,      close

source = ~/.config/hyprcosmic/monitors.conf

Schema registry

The mapping is not 1:1. Some conf keys own a whole cosmic-config value; others own one field inside a composite RON value (decoration.rounding targets one radius among six in corner_radii; gaps_in/gaps_out are two halves of one (u32, u32)).

enum Target {
    Direct    { component: &'static str, version: u8, key: &'static str },
    Projected { component: &'static str, version: u8, key: &'static str,
                path: &'static [&'static str] },
}

Entry {
    conf:     "general.gaps_in",
    // Fan-out: Dark and Light are separate cosmic-config components
    targets:  &[
        Projected { component: "com.system76.CosmicTheme.Dark.Builder",  version: 1,
                    key: "gaps", path: &["1"] },
        Projected { component: "com.system76.CosmicTheme.Light.Builder", version: 1,
                    key: "gaps", path: &["1"] },
    ],
    ty:       Ty::U32,
    validate: Some(range(0..=128)),
    doc:      "Gap between adjacent tiled windows, in px",
}

Spike-corrected facts (verified in vendor/libcosmic):

• gaps: (u32, u32) lives on ThemeBuilder (cosmic-theme/src/model/theme.rs:895), not CosmicTk. Component IDs at theme.rs:17-26. Default (0, 8).
• Tuple order is (outer, inner) — so gaps_out is index 0 and gaps_in is index 1.
• Dark and Light Builders are separate components, so one conf key fans out to two targets. Entry therefore carries targets: &[Target], not a single target.
• CosmicTk (libcosmic/src/config/mod.rs:14, ID com.system76.CosmicTk) holds icon_theme, interface_font, monospace_font, header_size, interface_density, show_minimize, show_maximize, apply_theme_global — icon_theme is needed by the HyDE importer, which sets $ICON_THEME.

emit writes through the typed cosmic-config API, not raw files. Config::watch (cosmic-config/src/lib.rs:377) is a notify inotify watch on the config directory that derives changed keys from file paths, so raw writes would in fact be observed — but Config::set gives correct RON encoding per type, atomic writes via atomicwrites::AtomicFile (lib.rs:513), and matches the watcher's .atomicwrite temp-file filter (lib.rs:408). cosmic-conf therefore depends on cosmic-theme, cosmic-comp-config and cosmic-settings-config for the concrete types, which also buys compile-time type checking of the registry.

Critical correctness property: projected writes are read-modify-write, and multiple conf keys can share one target. emit MUST group by target key, fold all projections, then write once. Naïve per-key writes let gaps_out clobber gaps_in. This is directly unit-testable and is the highest-value test in the suite.

doc generates cosmic.conf.default, so the annotated reference file cannot drift from the schema.

Phase 1 scope

Section	Targets	Confidence
general	CosmicComp: autotile, active_hint, focus_follows_cursor(+delay), cursor_follows_focus, edge_snap_threshold, cursor_hide_timeout	Verified
workspace	CosmicComp/workspaces: mode, layout, wraparound, action_on_typing	Verified
input	CosmicComp: xkb_config, input_default, input_touchpad	Verified
bind	CosmicSettings.Shortcuts/custom, incl. Spawn(String)	Verified
windowrule	WindowRules: tiling exceptions only	Verified, deliberately thin
theme	CosmicTheme.Mode/is_dark, .Builder/{palette,corner_radii,spacing}	Unverified
decoration	corner_radii, gaps	Unverified

Spikes (must complete before schema work)

1. Fetch libcosmic and enumerate cosmic-theme and CosmicTk. gaps was inferred from its use site (theme.cosmic().gaps); the struct has not been read. If gaps is derived rather than stored, that row moves to Phase 2 and needs a compositor patch.
2. Determine whether direct RON file writes trigger ConfigWatchSource, or whether emit must go through the typed cosmic-config API. Decides emit's implementation.

Error handling

The pipeline is transactional: resolve fully validates before emit writes anything. A malformed file leaves the desktop untouched rather than half-applied. Diagnostics report against source text with spans:

error: unknown key `gaps_inn` in section `general`
  --> cosmic.conf:7:5
   |
 7 |     gaps_inn = 8
   |     ^^^^^^^^ did you mean `gaps_in`?

Phase 2 — cosmic-comp patches

Ordered by ascending risk. Each is independently shippable. Patches A and B are additive new files that never touch shell/layout/tiling/mod.rs — a 235 KB file that is the most painful thing in the tree to carry patches against.

Patch A — zwlr_foreign_toplevel_management_v1

New protocol handler alongside toplevel_info.rs / toplevel_management.rs, which already hold the required state. Unlocks waybar's wlr/taskbar. Plausibly upstreamable. Rebase risk: low.

Patch B — Hyprland-compatible IPC socket

Implement a subset of Hyprland's IPC at $XDG_RUNTIME_DIR/hypr/$HYPRLAND_INSTANCE_SIGNATURE/.socket (request/response) and .socket2 (event stream).

• Requests: workspaces, activeworkspace, activewindow, clients, monitors
• Events: workspace>>, activewindow>>, openwindow>>, closewindow>>

HyDE's hyprland/workspaces and hyprland/window waybar modules then work unmodified, because waybar cannot tell the difference. Also delivers the hyprctl-style IPC from the original wishlist. New file, no entanglement with the layout engine. Rebase risk: low.

Polish patches

Patch	Where	Effort	Rebase risk
Animation curves + durations	shell/, config struct	Medium	Low — replaces consts with config lookups
Opacity + shadow config	backend/render/, shadow.frag	Medium	Low — shader exists, needs uniforms
Per-monitor/workspace gaps	both layout modules	Low	Low
Compositor-driven blur rules	backend/render/wayland/blur_effect.rs	High	Medium — inverts client-request model
Real window rules	shell/layout/tiling/mod.rs	High	High — do last

Phase 3 — Session and theme importer

Session

Fork cosmic-session and gate the hardcoded start_component calls (cosmic-panel, cosmic-launcher, cosmic-app-library, cosmic-osd, cosmic-workspaces) behind config. Forking is preferred over skipping cosmic-session entirely, because cosmic-session also propagates the compositor environment to systemd/D-Bus and pulls up graphical-session.target; without it, portals and D-Bus-activated apps break.

cosmic-greeter is retained. Display-manager changes are the easiest way to lose access to a machine.

Ships a hyprcosmic.desktop session entry alongside the existing COSMIC session, so the working desktop remains selectable at login throughout development.

Theme importer

cosmic-conf import-theme <path-or-hyde-branch> — one-way into cosmic.conf, not straight into cosmic-config, so the result is readable and editable.

1. Parse hypr.theme with the Phase 1 parser (same grammar — this is where the syntax choice pays off)
2. Map recognised keys through a translation table into HyprCosmic conf keys
3. Extract the palette; derive COSMIC's palette from border/accent colours via the Builder's tinting inputs (neutral_tint, accent, bg_color)
4. Install GTK/icon tarballs, register wallpapers
5. Copy waybar.theme, rofi.theme, kitty.theme to their upstream destinations unmodified
6. Emit an explicit unsupported-keys report rather than silently dropping — e.g. col.active_border: gradient not supported (COSMIC active_hint is solid)

The report is the honesty mechanism that keeps partial import from feeling broken.

Rejected alternatives

Alternative	Why rejected
caffyne-shell as the shell	Python/GTK3 (93% Python), no license file (all rights reserved), 10 weeks old at evaluation. Protocol prerequisites were verified present in cosmic-comp, so this remains technically viable if the license is resolved.
CSS theming inside cosmic-panel	Requires building a CSS cascade for a retained-mode iced UI. Large new subsystem, and the result still would not consume HyDE's style.css verbatim.
Teach cosmic-comp to read cosmic.conf natively	The config surface spans ~25 components; a file parsed inside the compositor could only configure the compositor. Also the largest fork and breaks cosmic-settings outright.
Bidirectional config sync	Round-tripping a commented file through a KV store reliably is hard; failure mode is silently mangling the user's file.
Patch cosmic-comp before building the config layer	Nothing usable until late, and the fork would be driven by 136 individual files in the meantime.

Risks

Risk	Mitigation
Upstream velocity (46 commits/30 days) makes rebasing costly	Keep patches additive and in new files; defer window rules; upstream Patch A if accepted
Theme/decoration schema rows are unverified	Spike 1 gates schema work; rows move to Phase 2 if gaps proves derived
Losing COSMIC's shell removes the appearance GUI	Accepted and documented; --diff makes one-way overwrites visible
Compositor work is not verifiable without a real session	Phase 1 is fully testable headless; Phases 2–3 need a nested or TTY session
Naming leans on two projects' marks	Personal fork is fine; rename before any wide distribution

Success criteria

1. cosmic-conf apply compiles a cosmic.conf into cosmic-config and COSMIC live-reloads it.
2. A malformed conf produces a spanned diagnostic and writes nothing.
3. gaps_in and gaps_out both land — proving projection folding works.
4. waybar runs on cosmic-comp showing workspaces and active window via Patch B, unmodified HyDE config.
5. import-theme Catppuccin-Mocha yields a matching palette, wallpaper, rounding and gaps, plus an accurate unsupported-keys report.
6. hyprcosmic.desktop is selectable at login and the stock COSMIC session still works.