CornerFix

CornerFix is now an injected macOS window sharpener instead of the old display-overlay experiment.

The previous version only drew caps over the edges of the display, which did not actually change application window corners. This rewrite follows the same broad model as apple-sharpener: a small injected dynamic library runs inside target apps and forces standard windows to use a configurable corner radius, while a CLI updates shared settings live through Darwin notifications.

Screenshot

What It Does

• Forces ordinary titled app windows toward square corners
• Supports live enable/disable without app restarts
• Supports live radius changes from 0...24
• Supports per-app overrides keyed by bundle identifier
• Supports presets, reset, reload, and config listing from the CLI
• Avoids most obvious system UI by filtering special window classes and non-normal window levels
• Falls back to 0 radius in fullscreen mode to reduce visual artifacts

Project Layout

• src/sharpener/CornerFixSharpener.m: injected library entry point and runtime hooks
• src/sharpener/CFXSwizzle.m: minimal method-swizzling helper
• src/common/CFXShared.*: shared preference and Darwin-notification helpers
• src/cli/main.m: cornerfixctl command-line controller
• src/inject/main.m: cornerfix-inject launch-based injector
• src/testapp/: unsigned local Cocoa app for payload validation
• examples/: example command workflows
• scripts/install.sh, scripts/uninstall.sh: install tooling
• LOADER.md: loader integration notes
• COMPATIBILITY.md: compatibility test matrix
• libcornerfix.dylib.blacklist: example processes to avoid injecting

Build

make
make install

Artifacts:

• build/libcornerfix.dylib
• build/cornerfixctl
• build/cornerfix-inject
• build/CornerFixTestApp.app

Usage

Build first, then inject build/libcornerfix.dylib with build/cornerfix-inject or your preferred loader/tweak framework.

Examples:

./build/cornerfix-inject --app ./build/CornerFixTestApp.app
./build/cornerfix-inject --app ./build/CornerFixTestApp.app --check
./build/cornerfix-inject --bundle-id com.apple.TextEdit
./build/cornerfixctl on
./build/cornerfixctl off
./build/cornerfixctl toggle
./build/cornerfixctl --radius 0
./build/cornerfixctl --preset soft
./build/cornerfixctl --app com.apple.Safari --radius 0
./build/cornerfixctl list
./build/cornerfixctl config-path
./build/cornerfixctl effective-config
./build/cornerfixctl --app com.apple.Safari effective-config
./build/cornerfixctl doctor
./build/cornerfixctl reload
./build/cornerfixctl --status

More CLI details: CLI.md Loader notes: LOADER.md Compatibility matrix: COMPATIBILITY.md Testing guide: TESTING.md

Example workflows:

• examples/basic-workflow.sh
• examples/ammonia-style-usage.sh
• examples/per-app-overrides.sh
• examples/reset-and-reload.sh
• examples/testapp-injection.sh

Install / Uninstall

Default install prefix is /usr/local.

make install
make uninstall

You can override the destination:

make install PREFIX=/opt/cornerfix

For local testing in restricted environments, you can override the settings plist path:

CFX_SETTINGS_PATH=/tmp/cornerfix-settings.plist ./build/cornerfixctl list

Injection Notes

This project is designed for an injection-based workflow similar to Ammonia-style tweaks. It is not a sandboxed App Store style app, and it is not SIP-safe in the same sense as the old overlay approach.

If you plan to load it broadly across apps, you should:

• use a loader that supports process blacklists
• avoid injecting into system daemons and shell infrastructure
• test on a secondary machine or non-critical install first

Limitations

• macOS private window internals change between releases, so view-hierarchy targeting may need updates
• some apps use custom rendering paths and may not respond cleanly
• no claim is made that this is safe for production machines with strict macOS security enabled

Future Updates

Planned hardening and feature work:

• tighten settings-file permissions and ownership checks for the shared plist
• add an optional validation token or similar guard for live reload signaling
• improve install-time path validation and safety checks
• narrow default injection targets and expand blacklist handling
• document a clearer security model and operational risks
• add richer per-app tools such as import/export of override profiles
• add diagnostics commands for active config path, effective app settings, and loader troubleshooting
• add optional debug logging controls for window matching and hook application

License

MIT