AccessibleCaret

AccessibleCaret is a pair of raindrop shape handles at both ends of selection highlight, or it is a single handle at the blinking caret in a text area. It assists the user to change the range of the selection highlight or the position of the blinking caret on platforms with touch-event support.

Meta Bug

Bug 1124074 tracks all the open issues.

Gecko implementation details

Preferences

  • layout.accessiblecaret.enabled_on_touch (Enabled on Firefox with touch-event support since 51.)

  • layout.accessiblecaret.enabled (Defaults off, but it can be turn on to force enable AccessibleCaret.)

  • layout.accessiblecaret.hide_carets_for_mouse_input (Defaults on. Turn this on to debug AccessibleCaret on desktop browser with mouse events.)

AccessibleCaretEventHub State Transition Diagram

This diagram depicts the state transition of the state machine in AccessibleCaretEventHub, which handles external events and callbacks.

Note that the diagram omits some callbacks which do not cause a state transition such as NotifySelectionChanged or Reflow.

This table is a mapping of the real events and callback to the actions described on the edge of the diagram:

Real events or callbacks

Actions

eMouseDown or eTouchStart

Press

eMouseMove or eTouchMove

Move

eMouseUp or eTouchEnd or eTouchCancel

Release

eMouseLongTap

Long tap

AsyncPanZoomStarted()

Scroll start

AsyncPanZoomStopped()

Scroll end

NotifyBlur()

Blur
../_images/AccessibleCaretEventHubStates.png

Debug Tips

  • Dump AccessibleCaret log from command line: run MOZ_LOG=AccessibleCaret:5 ./mach run.

  • Dump AccessibleCaret log by using a preference: Open about:config and add a pref logging.AccessibleCaret with value debug or verbose (case matters).

  • AC_LOG() is useful to add new logs.

Developers

Current maintainer

Developers Emeritus