Problem
macOS has no first-party window-snapping beyond the basic split-view gesture. SnapWM adds grid-based snapping and keyboard-driven window placement for people who want more control than the OS gives out of the box.
Constraints
- No public “move this window” API on macOS — window manipulation has to go through the Accessibility API, which is permission-gated and not designed for high-frequency use.
- Needed to detect drag gestures and keyboard shortcuts system-wide without a kernel extension, which meant a CGEvent tap running under Accessibility permissions rather than anything sandboxed.
Architecture
Architecture diagram — available on request
A SwiftUI menu-bar app owns configuration and the snap-zone overlay UI. A CGEvent tap listens for drag and keyboard events system-wide; window moves and resizes are then applied through the Accessibility API (AXUIElement) against the focused window.
Stack
Swift, SwiftUI, macOS Accessibility API, CGEvent tap.
My role
Solo project — design, implementation, and working through AXUIElement’s quirks across macOS versions.
Outcome
A working daily-driver window manager, built primarily to fix how macOS handles multi-window workflows for my own use.