[zolferfigueiredo]

What

A Display Mode shortcut that works like Win+P on Windows: choose from the keyboard which screens are on, or mirror them.

• Where: Settings > Shortcuts > ⋯ > Extra. The row shows when more than one screen is connected, and stays once it has a shortcut. There's no default shortcut.
• The list: every combination of screens (Screen 1 Only, Screen 2 Only, Screens 1 + 2, ...), then Mirror All Screens. Each row shows the screen names under the numbers. With 5 or more screens the list is taller than the room on screen, so it scrolls and keeps the highlighted row in view; a list that fits has no scroll bar.
• Screen numbers: while the list is open, each screen that's on shows its number in its middle, big, black with a white border. Numbers follow the Next Display order and don't change while a screen is off.
• Keys: hold the modifiers and press the key again to move the highlight; let go to apply. A single press leaves the list open for the arrow keys, Return or a click. Esc or clicking elsewhere closes it without changes.
• Icon: a new displayModeTemplate in the style of the other action icons (two screens in a frame).
• URL: rectangle://execute-action?name=display-mode.
• Docs: a section in README.md and README.zh-Hans.md, and display-mode in the URL action list.

Screenshot

How it works

• Mirroring uses the public CoreGraphics display configuration API.
• Turning a screen off uses the private CGSConfigureDisplayEnabled (falling back to SLSConfigureDisplayEnabled), looked up at runtime with dlsym, so nothing links against it. When neither exists, the list offers only every screen on plus Mirror All Screens.
• Turning a screen off is applied for Rectangle's lifetime only (forAppOnly), so quitting Rectangle turns it back on. If every screen still on is disconnected, the screens Rectangle turned off come back on.
• All of it lives in Rectangle/DisplayMode.swift. Elsewhere the change is the new action, one early return in ShortcutManager.execute, and the conditional row in the Extra section. The picker reuses StackBadgeManager.navigationKey and ScreenDetection.order.

Translations

The 5 new strings are translated into 12 languages: de, es, es-419, fa, fr, hi, it, ja, pt-BR, uk, zh-Hans and zh-Hant. English, Spanish (es, es-419), Brazilian Portuguese (pt-BR) and Italian (it) have been checked and are marked translated. The others are marked needs_review in the catalog until a native speaker checks them; corrections are welcome.

Tests

• xcodebuild test: all 730 tests pass, including new DisplayModeTests for the option order, the per-screen configuration, a 32-row list (5 screens) that stays on screen and scrolls to its last row, and a list that fits with no room kept for a scroll bar.
• Tried on a Mac with 3 screens (built-in plus two externals): the list opens, the shortcut moves the highlight, and the screen numbers show.
• Not confirmed on hardware yet: that turning a screen off takes effect on current macOS, and what happens when the screen with the menu bar is turned off.

Known limits

• Screen names come from macOS, so two identical monitors show macOS's own "(1)" and "(2)", which can differ from the screen numbers here.

[rxhanson]

Thanks for continuing to contribute! I'm currently cleaning up some of the commonly tread paths in Rectangle, and I'll let you know when I'm done so the conflicts can be resolved all at once instead of continuously. At that time, I'll be working through my backlog of pull requests to review.

[zolferfigueiredo]

Amazing! Take your time. Let me know when I should fix the conflicts;
My pleasure to contribute to this project;