WindowKit

WindowKit is a Swift package for macOS window models, hit-testing contracts, placement geometry, live window discovery, and live window control. It is a foundation library for building window managers, tiling tools, automation utilities, and productivity apps.

It focuses on reusable window primitives rather than app workflows. Host apps are responsible for permissions onboarding, gesture recognition, persistence, shortcuts, UI, and automation policy.

The package is split into two libraries:

• WindowKit: window snapshots, filters, hit-testing contracts, screen models, placement values, and control/provider protocols.
• WindowKitAppKit: live Core Graphics, AppKit, and Accessibility-backed facades for querying, hit-testing, and placement.

Why WindowKit?

• Clean separation between reusable window value/geometry contracts and live Core Graphics, AppKit, or Accessibility integrations.
• Explicit host-app responsibility boundaries for permissions, shortcuts, persistence, UI, and automation policy.
• Protocol-based window abstractions for host apps that need deterministic geometry checks.
• Point-based hit-testing for cursor-based window discovery.
• Reusable placement and screen-movement primitives for deterministic window geometry.

Use Cases

WindowKit can serve as the window systems layer beneath:

• tiling window managers and keyboard-driven layout tools
• cursor-based window pickers and snap tools
• launcher extensions that need focused-window or point-based window actions
• automation utilities that need deterministic geometry and Accessibility-backed control

Architecture

Host App
  |
  v
WindowKit
  models, filters, hit-testing contracts, placement, control/provider protocols
  |
  | contracts
  v
WindowKitAppKit
  Core Graphics queries, AppKit screens, running applications, AX controllers, role metadata
  |
  v
macOS AppKit / Accessibility APIs

Requirements

• macOS 14 or later
• Swift 6.0 or later

Installation

Add this package to your Swift Package dependencies:

.package(url: "https://github.com/naviapps/window-kit.git", from: "2.0.0")

Then add the product that matches your use case. Use WindowKit by itself for models, protocols, hit-testing abstractions, and geometry. Add both products when you use live Core Graphics, AppKit, or Accessibility integration:

.product(name: "WindowKit", package: "window-kit"),
.product(name: "WindowKitAppKit", package: "window-kit"),

Documentation

• WindowKit API reference
• WindowKitAppKit API reference

Basic Usage

Use WindowKit when you need window models, protocols, and geometry:

import CoreGraphics
import WindowKit

let screen = WindowScreen(
  frame: CGRect(x: 0, y: 0, width: 1440, height: 900),
  visibleFrame: CGRect(x: 0, y: 44, width: 1440, height: 812)
)
let frame = WindowPlacementCalculator.frame(
  for: .grid(columns: 2, rows: 1, column: 0, row: 0, columnSpan: 1, rowSpan: 1),
  in: screen.visibleFrame,
  inset: 8
)

Use WindowKitAppKit when you want live macOS integration:

import CoreGraphics
import WindowKit
import WindowKitAppKit

@MainActor
func placeFocusedWindow() throws -> (selected: WindowSnapshot?, topmost: WindowSnapshot?) {
  let query = WindowSnapshotQuery()

  let snapshots = try query.snapshots()
  let firstWindowIdentifier = snapshots.first?.windowIdentifier
  let selectedSnapshot = try firstWindowIdentifier.flatMap { try query.snapshot(for: $0) }
  let hitTester = WindowHitTester()
  let mouseLocation = CGPoint(x: 120, y: 80)
  let topmost = hitTester.topmost(at: mouseLocation)

  let placer = WindowPlacer()
  try placer.place(
    .grid(columns: 2, rows: 1, column: 1, row: 0, columnSpan: 1, rowSpan: 1),
    for: .focused
  )
  return (selectedSnapshot, topmost)
}

Window snapshots are immutable app-facing models for filtering, hit-testing, placement decisions, and deterministic tests without holding live system references. Snapshots include the process identifier, Core Graphics window identifier, owner metadata, title, and a finite standardized frame. In WindowKitAppKit, WindowSnapshotQuery.snapshots() throws WindowSnapshotQueryError.windowListUnavailable when macOS does not return a readable window list. WindowSnapshotQuery.snapshot(for:) reads a single known Core Graphics window identifier and still applies the query filter. Use WindowSnapshotProviding when host-app services should depend on a mockable snapshot source instead of a concrete query, and WindowSnapshotResolving when they only resolve a known window.

WindowSnapshotFilter supports both include and exclude sets for owner bundle identifiers, owner process identifiers, and window identifiers. Include sets are allow-lists when non-empty; exclude sets are applied after include sets. The AppKit query can also limit snapshots to the first matching entry in the order returned by the macOS window list. Use WindowSnapshotFilter.includes(_:) when host-owned providers need the same deterministic filtering semantics without depending on WindowKitAppKit.

Hit-testing is available through the same small app-facing facade shown above. Use WindowHitTesting when host-app services should depend on a mockable hit-testing source instead of a concrete hit tester.

Responsibility Boundary

WindowKit owns platform-neutral window values, placement calculations, screen selection, and protocol contracts. WindowKitAppKit owns AppKit and Accessibility-backed live adapters.

WindowKit intentionally does not own:

• permission request or onboarding UI
• gesture recognition or input monitoring
• window rule engines, presets, or user preference persistence
• application activation policy
• animation history or app-specific workflow coordination

Those concerns should live in the host app or a package with that direct responsibility.

Placement and Screens

WindowPlacementCalculator clamps insets to the available area. Grid placements clamp invalid columns, rows, and spans into the available grid. Grid columns start from the left, and rows start from the bottom in the selected screen-area coordinate space. Centered placements clamp width and height ratios to 0...1.

WindowScreen standardizes full and visible frames at construction. WindowScreenTarget.containingWindow selects the screen containing the target window center. WindowKit screen-selection primitives support forgiving fallback semantics so host apps can decide whether a missing screen is recoverable or exceptional. Use WindowScreenSelector when custom host-app controllers need the same deterministic screen ordering and target resolution as WindowPlacer; selector APIs order input screen lists before applying ordered-index and fallback selection. Use WindowScreenMovement when custom host-app controllers need the same finite, deterministic screen-to-screen movement geometry without using live Accessibility control.

In WindowKitAppKit, WindowPlacer uses forgiving screen selection by default. When screens exist but a requested point, display identifier, ordered index, or current window screen cannot be matched, placement and screen moves fall back instead of throwing. An empty screen list always throws. Pass screenFallback: .none to WindowPlacer.place or WindowPlacer.moveToAdjacentScreen when a missing screen should throw WindowPlacerError.screenNotFound.

Accessibility

WindowKitAppKit uses macOS Accessibility APIs for live window control. Host apps are responsible for declaring and guiding the required permissions, handling denied access, and choosing when to prompt users.

Window discovery, querying, and hit-testing read window metadata returned by macOS, including process identifiers, app names, bundle identifiers, window titles, and frames for standard-layer windows. Host apps are responsible for their own privacy disclosures, logging choices, and any Screen Recording or Accessibility permission flows needed by their product.

Raw AX resolver details are implementation details. The public Accessibility-backed AXWindowController surfaces app-facing failures through WindowAccessibilityError, with application and window resolution failures preserving the WindowTarget that could not be resolved. Each failure includes a WindowAccessibilityOperation; underlying failures are further classified by WindowAccessibilityOperationFailure instead of raw AX error values. Unrecognized future AXError values are surfaced as WindowAccessibilityOperationFailure.unrecognizedAXError. AX success reported through a failure path is surfaced as WindowAccessibilityOperationFailure.unexpectedSuccess instead of exposing success as a failure. Unmatched window role metadata is represented as WindowRole.unclassified(accessibilityRole:accessibilitySubrole:) so host apps can inspect the raw Accessibility role labels without treating them as a known classification. Role-unavailable values are not classified from subrole metadata alone. Host apps should depend on the WindowKit protocols and construct the public WindowKitAppKit adapters only at their live system boundary.

The package does not request permissions, collect analytics, transmit data, or persist window data by itself.

Development

Run the package check with:

make check

GitHub Actions runs the same check on pull requests and pushes to main.

WindowKit models, protocols, hit-testing abstractions, and geometry primitives are designed to be tested without live Core Graphics, AppKit, or Accessibility dependencies. WindowKitAppKit keeps live system behavior behind small controllers and providers so host apps can substitute their own implementations in tests.

Contributing

See CONTRIBUTING.md. Release notes are in CHANGELOG.md.

Security

Report vulnerabilities privately. See SECURITY.md.

License

WindowKit is released under the MIT License. See LICENSE.