4. Usability Requirements

4.1. User interface

4.1.1. Graphical environment

4.1.1.1. Features

• USR-TAP-USA-IFC-001 The OS MUST provide a tiling window manager.
• USR-TAP-USA-IFC-002 The OS MAY provide a scrolling window manager.
• USR-TAP-USA-IFC-003 The solution MUST allow keyboard navigation.
• USR-TAP-USA-IFC-004 The solution MUST display a list of default keybinds.
• USR-TAP-USA-IFC-005 Said list of shortcuts MUST allow hiding.
• USR-TAP-USA-IFC-006 The solution MUST be modern enough for compatibility and features (fractional scaling, multiple refresh rates, HDR, etc.) and receive long-term updates.

4.1.1.2. Acceptance criteria

• Windows tile automatically upon being opened, dividing the area of the screen into halves or quarters.

• A list of keyboard shortcuts is shown upon initial startup.

• The list of shortcuts can be disabled, or toggled.

• The solution is actively maintained.

• Optionally, windows are opened to the right of the currently focused window, without resizing it, like in scrolling window managers.

4.1.2. Animations

4.1.2.1. Features

• USR-TAP-USA-IFC-007 The graphical interface MUST have simple animations, if any.
• USR-TAP-USA-IFC-008 The graphical interface MAY be devoid of any animations.
• USR-TAP-USA-IFC-009 The animations MUST be fast (< 0.5 seconds).

4.1.2.2. Acceptance criteria

• The animations are smooth and simple.
• The animations do not come in the way of the user’s experience.

4.1.3. Focus and screen real estate

4.1.3.1. Features

• The graphical interface MUST optimize the use of the screen’s surface area:
  • USR-TAP-USA-IFC-010 Windows MUST be lightly decorated.
  • USR-TAP-USA-IFC-011 Windows MUST either be maximized or split according to the requirement on tiling/scrolling window management.
  • USR-TAP-USA-IFC-012 Any gaps between windows MUST be thinner than 3 pixels or absent.
• Any dock, taskbar or widget MUST NOT interfere with the daily use of the OS:
  • USR-TAP-USA-IFC-013 A dock, status bar or widget panel MUST allow hiding OR small and discreet (bar height < 1/30 * window height).
  • USR-TAP-USA-IFC-014 Notification popups MUST be small (<= 6 * bar height).
  • USR-TAP-USA-IFC-015 Notifications MUST disappear from the screen after a timeout (<= 5 seconds).

4.1.3.2. Acceptance criteria

• The window decorations are limited to small buttons (~ status bar height).
• Windows take up almost all the available screen space (98%).
• Gaps and bars/docks/widgets hide away when unused.
• Notifications last for 5 seconds or less and are small.

4.1.4. Keyboard navigation

4.1.4.1. Features

• USR-TAP-USA-IFC-016 The graphical interface MUST be preconfigured with the default keyboard shortcuts (see appendix).

4.1.4.2. Acceptance criteria

• The specified keyboard shortcuts are enabled out-of-the-box.

4.1.5. Input method

4.1.5.1. Features

• USR-TAP-USA-IFC-017 The OS MUST provide Colemak-DH input method.
• USR-TAP-USA-IFC-018 The OS SHOULD provide QWERTY input method.
• USR-TAP-USA-IFC-019 The OS MUST provide a way for the user to configure what input methods they need (GUI & XKB configuration files).

4.1.5.2. Acceptance criteria

• The required input methods are present.
• The relevant configuration files can be edited by the user.