Update to TinyMCE 4.x
1. Prepare core and Larry skin for improved accessibility
2. Implement full keyboard navigation in main mail view
TinyMCE 4.0.24
Fix list focus in non-keyboard mode: restore old behavior
Enable keyboard navigation on treelist widgets with cursor keys
Update to TinyMCE 4.x
Improve mail view document structure with headings, roles, labels and aria-attributes
Make TinyMCE4 buttons smaller
Fix Spell button with TinyMCE4
Allow <> characters in spellchecking text
Forward keyboard event through 'menu-open' command to enable keyboard navigation
Declare content language for proper text-to-speech support
Further accessibility improvements regarding keyboard navigation and document structure
Improve keyboard navigation on compose screen: define tabindex groups + enable keyboard controls of contacts list widget
Moved popup-menu functions to Roundcube core for seamless integration of (stackable) skin and core menus
Avoid scrolling when list gets back focus (on invisible focus element)
Set aria-selected and aria-expanded state attributes
Fix treelist keyboard navigation + assign aria-level attributes to treeitems
Use localized labels for voice-only headings and link texts
Set aria-* attributes for autocompletion fields and widgets