feat(html): mobile virtual keyboard and touch UX improvements

[someonegg]

Summary

This PR delivers a mobile-focused UX upgrade for ttyd and includes related fixes in the same series.

Commits included:

• fix(html): handle lineHeight layout recalculation
• fix(html): stabilize ios keyboard viewport and background
• feat(html): mobile virtual keyboard
• feat(html): mobile touch selection

Features

Virtual Keyboard Panel

• A draggable on-screen keyboard appears automatically on touch devices.
• Uses a dynamic top section (2 rows, 6 keys) and a fixed bottom section.
• Built-in dynamic keys include:
  • action keys: enter, space, batch_input
  • navigation keys: up, down, left, right, home, end, pageup, pagedown, wheel_up, wheel_down
  • common symbols and lowercase letters a-z
• Custom key IDs from mobileKeyboardCustomKeys can also be used in mobileKeyboardLayouts.
• Fixed section provides Esc, Tab, Shift, Alt, Ctrl, and Copy/Paste.
• Drag the header bar to reposition the panel anywhere on screen.
• Tap (or click) the header bar to cycle dynamic layouts in configured order.
• Tap modifier keys to toggle their state (highlighted when active).
• Copy/Paste button switches between copy and paste based on text selection.

Tap Selection

• Double-tap: select the word under the cursor.
• Triple-tap: select the entire line.
• Shift + Triple-tap: select all visible lines in the current viewport.
• Alt + Triple-tap: select all text in the terminal buffer.

Hold Repeat

• Hold starts after mobileKeyboardHoldDelayMs (default: 300 ms).
• Non-wheel keys repeat at mobileKeyboardHoldIntervalMs (default: 120 ms).
• Wheel keys repeat at mobileKeyboardHoldWheelIntervalMs (default: 120 ms).
• Modifiers apply to key repeat; wheel repeat ignores modifiers.

Details

Client Options

• -t enableMobileKeyboard=true: enable the mobile virtual keyboard panel, auto-detect touch (default: false). On touch devices this also controls selection-copy behavior: when enabled, tap selection is on and automatic copy-on-selection is off; when disabled, tap selection is off and automatic copy-on-selection is on
• -t mobileKeyboardOpacity=0.8: set the keyboard panel opacity (default: 0.72, range: 0.0-1.0)
• -t mobileKeyboardScale=1.2: set the keyboard panel scale (default: 1.0)
• -t 'mobileKeyboardCustomKeys=[{"id":"tmux_copy_mode","label":"C-b [","combo":["Ctrl+b","["]}]': define custom dynamic keys (array of {id,label,combo}; combo is a sequence like Ctrl+b, [). id must match ^[a-z][a-z0-9_]{0,31}$, and __proto__, prototype, constructor, toString, valueOf are forbidden. The default web UI predefines six tmux keys: tmux_copy_mode (C-b [), tmux_detach (C-b d), tmux_new_window (C-b c), tmux_prev_window (C-b p), tmux_next_window (C-b n), tmux_list_windows (C-b w)
• -t 'mobileKeyboardLayouts=[["home","up","end","left","down","right"]]': set dynamic layouts for the top section (6 keys per layout). In the default web UI, 3 pages are active by default: page 1 ["home","up","end","left","down","right"], page 2 ["enter","up","batch_input","left","down","right"], page 3 ["enter","up","space","tmux_next_window","down","tmux_list_windows"]
• Per-key auto layout switch: each mobileKeyboardLayouts item can also be an object {"key":"xxx","page":n}. When page is set, pressing that key sends its action first, then switches to the target layout page (page is 1-based). Invalid, non-integer, or out-of-range page values are ignored for switching while key dispatch still works.
• -t mobileKeyboardHoldDelayMs=300: set hold trigger delay in milliseconds for mobile virtual keys (default: 300)
• -t mobileKeyboardHoldIntervalMs=120: set hold repeat interval in milliseconds for non-wheel keys (default: 120)
• -t mobileKeyboardHoldWheelIntervalMs=120: set hold repeat interval in milliseconds for wheel keys (default: 120)

Main Files

• html/src/components/terminal/xterm/mobile-keyboard.ts (new)
• html/src/components/terminal/xterm/index.ts (integration/lifecycle/options/events)
• html/src/components/app.tsx (defaults)
• html/src/style/index.scss (mobile panel/touch styles)
• man/ttyd.man.md (source markdown docs)
• man/ttyd.1 (generated from man/ttyd.man.md)

Testing

Automated

cd html
yarn run check
yarn test
yarn run build

Manual Checklist

• iOS Safari/Chrome: mobile keyboard panel renders and can be dragged.
• iOS Safari/Chrome: virtual keys send expected input.
• iOS Safari/Chrome: modifier key toggle feedback works.
• iOS Safari/Chrome: copy/paste actions work from the mobile panel.
• iOS Safari/Chrome: hold-repeat behavior works with configured timing.
• iOS Safari/Chrome: multi-tap selection behavior works as expected.
• Desktop behavior remains unchanged.
• Android device testing (not available in current environment).

Compatibility

• Mobile enhancements are touch-device oriented and configurable via client options.
• Existing desktop interaction model remains unchanged.
• No breaking CLI/API changes introduced.

[someonegg]