WSI supported-feature comparison

This is the implementation ledger for sparkles:wsi and a source-pinned comparison with nine third-party designs. It answers a narrower question than the fifteen-library research synthesis: what can an application obtain through each subject's window-system-facing API across the four Sparkles desktop targets?

Last reviewed: August 21, 2026

IMPORTANT

An internal backend implementation is not automatically a public capability. Qt QPA is explicitly marked internal; raylib and OpenTK may delegate a platform; and raw-window-handle intentionally creates no window or event. Those are architectural facts, not quality rankings.

Every capability-bearing sparkles:wsi commit updates the first column and cites its test evidence. planned is a contract only, partial is implemented with a named semantic/platform gap, and verified means the evidence lanes in SPEC §11 are complete.

Legend

Mark	Meaning
✓	verified public capability across the subject's claimed desktop platforms
◐	public but semantically/platform incomplete for the F row
◇	delegated to another WSI/backend rather than owned by the subject
internal	implemented by a private/internal platform abstraction, not a supported standalone API
—	absent
N/A	intentionally outside the subject's scope

Pinned revisions

The source trees follow the repository research convention: existing language buckets under $REPOS/<lang> are reused; no flat $REPOS clones are introduced.

Subject	Revision reviewed	Local evidence root	Positioning
sparkles:wsi	this branch	libs/wsi, this spec tree	native WSI implementation in progress
GLFW 3	1e59848 (after 3.5.1)	$REPOS/c/glfw	focused window/input library
raylib	dbc56a8 (6.0)	$REPOS/c/raylib	game framework; desktop WSI delegated to GLFW by default
SDL3	b53f1b0	$REPOS/c/sdl	broad public platform abstraction
SFML 3	d8b93d1 (after 3.1.0)	$REPOS/cpp/sfml	multimedia window library; no Wayland backend
Qt QPA	Qt Base f18845a, Wayland 9638a7d	$REPOS/cpp/qtbase, $REPOS/cpp/qtwayland	internal Qt platform abstraction
Gio	c035a61 (after 0.10.2)	$REPOS/go/gio	immediate-mode app/window integration
winit	81b2729	$REPOS/rust/winit	callback-first window/event library
raw-window-handle	1b85948 (after 0.6.2)	$REPOS/rust/raw-window-handle	typed borrowed/owned handles only
OpenTK 5	5.0-pre.16 (bf55b84)	$REPOS/csharp/opentk, tag object	prerelease PAL2; native Win32/X11/macOS plus SDL component backend

F01–F17 matrix

The row definitions are normative in feature requirements. For third parties, ✓ means the public surface substantially covers the row on the desktop backends the library itself claims; the platform table immediately below makes missing Sparkles targets visible.

ID	sparkles:wsi	GLFW 3	raylib	SDL3	SFML 3	Qt QPA	Gio	winit	raw-window-handle	OpenTK 5
F01 first pixel/init	partial	✓	◇	✓	◐	internal	✓	✓	N/A	◐
F02 resize	partial	✓	◇	✓	◐	internal	✓	✓	N/A	◐
F03 modal-loop survival	planned	◐	◇	✓	◐	internal	✓	✓	N/A	◐
F04 frame pacing	planned	◐	◐	◐	◐	internal	✓	◐	N/A	◐
F05 loop wake/external sources	partial	◐	—	◐	—	internal	◐	◐	N/A	✓
F06 keyboard/keymap	partial	✓	✓	✓	◐	internal	✓	✓	N/A	◐
F07 IME/text input	partial	◐	◐	✓	◐	internal	✓	✓	N/A	◐
F08 DPI/runtime rescale	planned	◐	◐	✓	◐	internal	✓	✓	N/A	◐
F09 outputs/hotplug	planned	✓	◐	✓	◐	internal	◐	✓	N/A	✓
F10 pointer capture/raw	planned	✓	✓	✓	◐	internal	◐	✓	N/A	◐
F11 scroll fidelity	planned	◐	◐	✓	◐	internal	✓	✓	N/A	◐
F12 cursors	planned	✓	◐	✓	✓	internal	✓	✓	N/A	✓
F13 decorations	planned	✓	◇	✓	◐	internal	✓	✓	N/A	◐
F14 state/vetoable close	planned	✓	◐	✓	✓	internal	✓	✓	N/A	✓
F15 grabbed popup	planned	—	—	✓	—	internal	—	—	N/A	—
F16 clipboard + DnD	planned	◐	◐	◐	◐	internal	◐	◐	N/A	◐
F17 threading/reentrancy	partial	✓	◇	✓	◐	internal	✓	✓	N/A	◐

Reading the dense rows

• GLFW commits text but has no public pre-edit model; clipboard is text and file-drop is receive-only; frame pacing remains application/graphics-API work.
• raylib's desktop window semantics mostly inherit GLFW, while its public event surface deliberately simplifies scroll, display and window-state detail.
• SDL3 has the broadest public C surface in this set. F05 remains partial because it has wake/user events and hooks but no portable public external-fd integration; F16 lacks a general public drag-source peer to its drop target.
• SFML implements X11, Win32 and Cocoa directly but no Wayland client. Rows that would otherwise be complete therefore remain partial for Sparkles' four-desktop target.
• Qt implements most rows, often deeply, but QPA is a private plugin contract. Public applications consume QWindow/QtGui rather than QPA as a standalone WSI library.
• Gio integrates editor/IME state and frame scheduling unusually well; grabbed native popup windows and a full bidirectional data-transfer surface are not its abstraction.
• winit provides strong window/input/lifecycle coverage but intentionally omits clipboard and native popup abstractions; file hover/drop is receive-side only.
• raw-window-handle's N/A cells are correct success: it standardizes handle handoff without claiming lifecycle or events.
• OpenTK 5 PAL2 is prerelease. Its component model is broad, but Wayland currently comes through its SDL component rather than the native X11/Win32/macOS implementations.

Platform ownership

Subject	Wayland	X11	Win32	AppKit	Cross-platform fallback/delegation
sparkles:wsi	native partial	native partial	native partial	native partial	SDL only as explicit separate package
GLFW 3	native	native	native	native	optional Wayland libdecor decoration helper
raylib	delegated GLFW	delegated GLFW	delegated GLFW	delegated GLFW	GLFW default; other ports exist outside this desktop row
SDL3	native	native	native	native	runtime video-driver selection
SFML 3	—	native	native	native	none
Qt QPA	plugin	plugin	plugin	plugin	internal plugin selection
Gio	native	native	native	native	platform files selected by Go build constraints
winit	native	native	native	native	backend chosen by target/runtime
raw-window-handle	handle variants	handle variants	handle variants	handle variants	no implementation
OpenTK 5	SDL ◇	native + SDL	native + SDL	native + SDL	PAL2 component selection, prerelease

Architectural comparison

Subject	Loop ownership	Public coordinate default	Typed renderer handle	Threading rule	Dependency posture
sparkles:wsi	Event Horizon only; native sources attach	logical plus mandatory physical surface metrics	closed backend sum	UI/main thread	OS APIs only in native core
GLFW 3	application polls/waits	screen coordinates plus explicit framebuffer pixels	per-platform native getters	main thread required on macOS; documented restrictions	X11/Wayland client libraries; optional libdecor
raylib	application frame loop	physical-ish pixels through simplified API	public native handle helper is backend-dependent	delegated/backend rule	GLFW by default plus graphics/audio stack
SDL3	poll/wait or main callbacks	platform-native logical policy plus pixel queries	property bag/native properties	main-thread API annotations	owns platform backends; optional helpers
SFML 3	application poll/wait	pixels	getNativeHandle, type varies by platform	window thread restrictions by platform	native X11/Win32/Cocoa, no Wayland
Qt QPA	Qt dispatcher owns loop	device-independent Qt coordinates	private QPlatform* objects and native interfaces	GUI thread	Qt plugin stack
Gio	callback/event channel around platform loop	device-independent units with metric	renderer selected inside app driver, not generic public raw handle	platform main thread plus Go event loop	direct platform code
winit	callback-first ApplicationHandler	physical-native with explicit logical conversion	raw-window-handle traits	main thread by default/required on AppKit	direct backends plus Rust ecosystem helpers
raw-window-handle	N/A	N/A	its entire public purpose	handle safety/lifetime contract only	zero WSI implementation
OpenTK 5	component event queue/poll/wakeup	pixel-oriented component values	typed WindowHandle plus Vulkan component	component/backend-specific	native PAL2 plus selectable SDL

Handle handoff specifically

Subject	Shape	Lifetime signal	Cross-backend misuse resistance
sparkles:wsi	closed display/window sum with exact variants	ready through destruction start	compile-/match-time variant
GLFW 3	separate native-access functions per platform	documented window lifetime	function/platform selected by caller
raylib	backend-dependent GetWindowHandle-style value	window lifetime	weak; generic pointer/value
SDL3	typed property keys over an SDL window	window/property lifetime	runtime property lookup
SFML 3	platform typedef WindowHandle	window lifetime	build-target type
Qt QPA	internal platform-native interfaces	QObject/platform object lifetime	runtime plugin/native-interface type
Gio	renderer integration is internal to app driver	frame/window driver lifetime	not a general public handoff
winit	HasWindowHandle/HasDisplayHandle	borrowed handle tied to owner	strong typed variants
raw-window-handle	borrowed/owned display and window enums	explicit borrow/ownership traits	strong typed variants
OpenTK 5	WindowHandle discriminated platform handle	component window lifetime	typed enum/fields, prerelease

Primary source anchors

The matrix was read against these public contracts and backend seams; the broader behavioral rationale remains in the linked research deep-dives.

• GLFW: glfw3.h, wl_window.c, and the Sparkles GLFW deep-dive.
• raylib: raylib.h, rcore.c, and rcore_desktop_glfw.c.
• SDL3: SDL_video.h, SDL_events.h, and the Sparkles SDL3 deep-dive.
• SFML 3: WindowBase.hpp, Event.hpp, and the direct X11, Win32, and Cocoa implementations.
• Qt QPA: qplatformwindow.h, qwindow.h, the qwindowswindow.cpp plugin, and the Sparkles Qt QPA deep-dive.
• Gio: app.go, os.go, ime.go, and the native Wayland, X11, Windows, and macOS drivers.
• winit: event.rs, window.rs, and the Sparkles winit deep-dive.
• raw-window-handle: lib.rs, borrowed.rs, and owned.rs.
• OpenTK 5: PAL2 README, IWindowComponent, WindowHandle, and the native Windows, X11, macOS, and SDL components.

Sparkles evidence log

Date	Revision	Matrix changes	Evidence
2026-08-20	5c17ddf21	initialized all F01–F17 cells as planned; no implementation credit claimed	normative spec plus pinned source audit
2026-08-20	M1 shared-input preparation	no F cell changed; consolidated geometry, cell conversion, and pointer-shape imports before the WSI package consumes them	dub test :input, :ui-sdl3, :ui-raylib
2026-08-20	M3 core working tree	no native F cell changed; added unit-explicit values, generation ids, lossless events, typed handles/errors, pure backend selection, and a bounded non-reentrant recording lifecycle	dub test :wsi (11 tests); checked build; win32-ldc2 core compile
2026-08-21	M1 bounded UTF conversion	no F cell changed; added shared allocation-free UTF-8/UTF-16 conversion for the future Win32 IMM32 and AppKit adapters, including safe NUL-terminated variants	dub test :base (461 tests; 6 UTF-16 conversion cases)
2026-08-21	M2–M4 Win32 lifecycle, input + host wait	F01, F02, F05, F06, F07, and F17 → partial; added native HWND lifecycle, typed handle, metrics, queued key/text/IMM32 events, and the Event Horizon User32/IOCP hosted wait	cross-compile plus Wine/Xvfb HWND/resize/close, scan-code + UTF-16 input, IMM32 pre-edit/commit, IOCP timer/foreign-waker smoke
2026-08-21	M2/M3 AppKit lifecycle + host wait	no F cell state changed; extended partial F01, F02, F05, and F17 coverage with native NSWindow lifecycle, typed handles, point/pixel metrics, and the Event Horizon CFRunLoop/kqueue hosted wait	arm64 macOS NSWindow first draw/resize/close, main-thread rejection, kqueue timer/foreign-waker smoke
2026-08-21	M2/M3 X11 lifecycle + foreign fd	no F cell state changed; extended partial F01, F02, F05, and F17 coverage with native XCB lifecycle, typed handles, ordered metrics/close events, and the Event Horizon OpPollAdd path	Xvfb XCB create/expose/resize/close/destroy, wrong-thread rejection, timer/foreign-waker smoke; cancelAndWait unit
2026-08-21	M2/M3 Wayland lifecycle + foreign fd	no F cell state changed; completed four-platform partial F01, F02, F05, and F17 coverage with asynchronous registry discovery, immediate configure acknowledgement and OpPollAdd readiness	no-compositor gate plus headless Weston configure/maximize/destroy, wrong-thread, timer/foreign-waker and cancellation smoke
2026-08-21	M3/M6 native Vulkan surface bridge	WSI7 and INT2 → partial; added typed Wayland/XCB/Win32 surface plans, target-native Vulkan dispatch, present-device selection and a Wayland native-I/O borrow around ICD display access	dub test :vulkan, :vulkan-wsi, :ui-sdl3; headless Weston handle → surface → present-device → re-arm; Win32 cross/Wine ABI plan
2026-08-21	M6 shared Vulkan presentation resources	no feature cell changed; extended partial WSI7/INT2 with one backend-neutral CommandPool, FrameSync, Swapchain, acquire/resize decisions and deferred-retirement implementation consumed by native WSI and SDL	dub test :vulkan-wsi (18), :ui-sdl3 (24); existing SDL Vulkan triangle builds unchanged and --help runs
2026-08-21	M6 native Wayland Vulkan triangle	no feature cell state changed; extended partial WSI7/INT2 with the first native frame loop — configure/frame/expose-paced presents, swapchain rebuild on compositor resize, and the native-I/O borrow widened to cover acquire and present ICD display access	native Mutter 150-frame run with --resize-stress under VK_LAYER_VALIDATE_SYNC=1; no-compositor SKIP and --help gates scripted; dub test :vulkan-wsi (19), :ui-sdl3 (24); one shared renderer builds both hosts
2026-08-21	M6 X11/Win32 runtime surface probes	no feature cell state changed; extended partial WSI7/INT2 with live-ICD runtime probes on the two remaining Linux/Windows backends — typed XCB and HWND handles create a real surface, select a present-capable device, and the integrated wait dispatches after the driver ran	Xvfb XCB probe (lavapipe fallback when hardware ICDs cannot present) and winevulkan/Wine Win32 probe, both scripted with honest SKIP gates the lanes refuse
2026-08-21	M6 scripted Wayland presentation gate	no feature cell state changed; the native triangle reports the SDL handoff comparison counters (framesOver50ms/framesOver100ms, reaps, maxDispatchMs, slow-dispatch traces) and the presentation gate no longer needs a live desktop session	Weston X11-backend-in-Xvfb lane with the client pinned to lavapipe: 150 frames with --resize-stress under VK_LAYER_VALIDATE_SYNC=1, 4 compositor resizes, 5 swapchains, 0 out-of-date, 0 frames over 50 ms; lane scripted in verify-native-wayland-triangle.sh
2026-08-21	M4 X11 keyboard slice	no F06 state change; extended partial F06 coverage with the X11 column — evdev-keycode physical identity, left/right/numpad location, core-state modifiers, and press/repeat/release with XKB detectable auto-repeat requested at open	Xvfb XTEST shift-chorded press/release round trip through the integrated loop; pure location/modifier/held-key model tests in dub test :wsi (14); logical keys stay deferred to the xkbcommon slice
2026-08-21	M4 Wayland keyboard slice	no F06 state change; extended partial F06 coverage with the Wayland column — wl_seat binding with capability arrival/departure, keymap-fd consumption, keyboard focus from enter/leave, and press/release through one shared evdev-location/xkb-real-modifier policy also adopted by X11	full-stack lane: XTEST chord into Xvfb → Weston X11 backend → wl_keyboard → queued KeyboardEvent with left-shift location and chorded modifier state; the smoke maps a real shm buffer under the native-I/O borrow; dub test :wsi (15)
2026-08-21	M4 AppKit keyboard slice	no F06 state change; completed partial F06 physical coverage on all four backends — the content view takes first responder, keyDown/keyUp queue Carbon virtual-keycode identity/location/repeat, and modifier keys translate from flagsChanged flag state	arm64 macOS 26.6 smoke posts a synthetic left-shift chord through the real responder chain and drains it back as KeyboardEvents; pure location/modifier model tests in dub test :wsi (14 on macOS)
2026-08-21	conformance suite consolidation	no feature cell changed; every cross-backend behavior assertion (ordered sequences, ready metrics, expose/frame opportunities, wrong-thread rejection, typed handles, resize reporting, chorded keys, single-wait timer/waker progress, close semantics, generation-safe destruction) moved into one sparkles.wsi.conformance suite; platform smokes became thin drivers	recording fake passes the value contract inside dub test :wsi (16); X11 10/0, Wayland 8/2 headless and 9/1 chord lane, Win32 10/0 plus IMM32 addendum under Wine, AppKit 10/0 on arm64 macOS 26.6 — all against identical assertions
2026-08-21	vulkan-wsi probe consolidation	no feature cell changed; the three native surface probes now share one sparkles.vulkan_wsi.conformance check — window → typed handles → present-capable context on the live ICD → single-wait progress — with the native-I/O borrow applied by introspection wherever the backend exposes it; VulkanContext teardown is RAII	Xvfb XCB probe, headless-Weston Wayland probe, winevulkan/Wine Win32 probe, the scripted presentation gate, dub test :vulkan-wsi (19) and :ui-sdl3 (24) all green against the shared check
2026-08-21	M4 logical keys on all four backends	no F06 state change; extended partial F06 with layout-derived unshifted LogicalKey identity everywhere — xkbcommon behind Wayland (keymap fd compiled under the listener) and X11 (core device map, state from the core mask), MAPVK_VK_TO_CHAR on Win32, charactersIgnoringModifiers on AppKit with private-range function keys as named	the shared conformance chord now asserts the unshifted spelling on every backend: X11 10/0 and both Wayland lanes under Xvfb/Weston, Win32 under Wine, AppKit on arm64 macOS 26.6; keysym classifier model test in dub test :wsi (17)
2026-08-21	M4 pointer and scroll slice	F11 → partial; extended partial WSI5 with pointer button/motion/enter/leave and scroll values on all four backends under one sign convention — Wayland frame-accumulated axes with source/discrete, X11 legacy wheel buttons, Win32 TrackMouseEvent-paired enter/leave plus wheel, AppKit hit-tested clicks (acceptsFirstMouse) with precise deltas and the inverted flag	conformance click property (exact position on X11/Win32) and scroll property on X11 12/0 Xvfb, Wayland 10/2 kiosk-Weston lane, Win32 12/0 Wine, AppKit 11/1 arm64 macOS; injection via XTEST buttons, SendMessageW, posted NSEvents, and the gated external injector
2026-08-21	M4 scale and outputs slice	F08/F09 → partial; Wayland windows derive scale from entered outputs (max policy), request the matching buffer scale, and report one atomic logical/physical/scale transition, with OutputEnteredEvent tracking the active output set; a conformance expectedScale property waits for the environment-declared factor	kiosk-Weston lane at --scale=2: metrics reach scale 2 with physical = logical × 2 while chord/click/scroll still pass (11/2); Wine phase documents the per-monitor 96-DPI limitation honestly (12/1, scale skipped) — native Windows CI owes that column
2026-08-21	M4 cursor slice	F12 → partial; the seven shared CSS-named PointerShape shapes plus per-window visibility on all four backends — vendored cursor-shape-v1 server-side shapes on Wayland, core cursor-font glyphs on X11, stock IDC_* on WM_SETCURSOR for Win32, stock NSCursor on AppKit — with unsupported reported as a typed error	cursor conformance property on every lane: X11 13/1 Xvfb, Wayland 9/5 headless and 12/2 kiosk, Win32 13/1 Wine with GetCursor proving the applied IDC_IBEAM, AppKit 12/2 with currentCursor is IBeamCursor on arm64 macOS 26.6
2026-08-21	M4 drag-capture slice	F10 → partial; a drag leaving the window keeps reporting — Win32 gains implicit SetCapture from first press to last release (unwound on WM_CAPTURECHANGED), X11 relies on the automatic core grab, AppKit on window drag routing — and the conformance drag property requires the release to arrive with outside coordinates	X11 14/1 (release at 700,500 beyond a 640x480 window; the lane Xvfb screen grew past the window for the property to be expressible), Win32 14/1 with GetCapture proving engagement and release under Wine, AppKit 13/2 with the outside release routed to the mouseDown view; Wayland skips (kiosk fullscreen has no outside; the compositor owns its implicit grab)
2026-08-22	M4 Wayland key-repeat slice	no F06 state change; closed the Wayland repeat gap in partial F06 — the backend synthesizes KeyAction.repeat from the compositor's wl_keyboard.repeat_info schedule (delay then steady interval, rate 0 disables, most recent repeating key wins, release/leave/capability-loss stop it) with at most one Event Horizon timer op in flight and a cancelAndWait reap on detach	shared hold-a-repeating-key conformance property: X11 15/1 Xvfb (server detectable auto-repeat via a held XTEST key), kiosk-Weston lane 13/3 where Weston filters the X server's repeat so every observed repeat is this client's synthesis (signal-file hold choreography with the external injector); Win32 14/2 and AppKit 13/3 skip honestly (posted events do not auto-repeat); schedule model test in dub test :wsi (18)
2026-08-22	M4 Wayland text-input slice	extended partial F07 with the Wayland column — vendored text-input-unstable-v3, the per-seat text input auto-enabled on the compositor's enter (IMM32's always-on role), double-buffered batches applied atomically on done (commit before pre-edit, fields reset per cycle), byte-offset cursor/selection mapped into the shared composition vocabulary with one underline segment, and an active composition ended by exactly one empty event; surrounding-text deletion is stashed but awaits a vocabulary event	pure batch/mapping model tests in dub test :wsi (20, ldc2+dmd); all Linux lanes re-run green (X11 15/1, headless Weston 9/7, kiosk 13/3 — the code is inert there because Weston implements only text-input-v1, which is why the live-IME runtime proof is recorded as owed to a text-input-v3 compositor rather than claimed)
2026-08-22	M4 X11 XIM slice	extended partial F07 with the X11 column — xcb-imdkit's XIM client rides the backend's single XCB connection (xcb_xim_filter_event inside the ordinary pump: the hosted wait stays the only wait, closing M2's open question), per-window input contexts created serially and focus-followed, every key forwarded to a live IM first (commit → owned validated UTF-8 TextCommittedEvent; unconsumed → bounced back through the unchanged delivery path), inert without a server on $XMODIFIERS	end-to-end lane: an in-tree test XIM server (xcb-imdkit server API, @im=test) commits "xim" for one keycode and bounces all others — X11 16/1 under Xvfb with chord/hold/click/scroll/drag all passing THROUGH the IM roundtrip; other lanes skip honestly (headless Weston 9/8, kiosk 13/4, Wine 14/3 + IMM32 addendum); dub test :wsi 20 under ldc2+dmd
2026-08-22	M4 AppKit NSTextInputClient slice	completed partial F07's column set — the content view adopts NSTextInputClient (registered via class_addProtocol: D's extern (Objective-C) has no adoption syntax and inputContext is nil without conformance), keyDown routes through the input context after the physical key, insertText commits validated UTF-8 (NSString/NSAttributedString discriminated by respondsToSelector:) and ends marked text with one empty event, setMarkedText maps UTF-16-unit selection to byte offsets (astral scalars count two) with underline + selected segments	the shared IME-commit property runs live on AppKit — a posted "x" returns as TextCommittedEvent through the real NSTextInputContext — and an AppKit addendum drives the protocol exactly as the context does (kana marked text with selected middle, replacing commit, single composition-end, unmark idempotence): 14/3 + marked-text round trip on arm64 macOS 26.6; UTF-16-unit mapping model-tested; found: a required protocol method (validAttributesForMarkedText) is called during context creation itself