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The following is how Mozilla determines what elements can be focused and which can not:
*elements that are hidden (display: none) cannot be focused
*elements that have the CSS visibility property set to collapse or hidden are not focusable.
* an HTML element in an editor is not focusable
* an HTML element cannot be focused if it has a disabled attribute.
* an XML element cannot be focused unless it has a link/xlink.
*a XUL element that implements nsIDOMXULControlElement cannot be focused if its disabled property is true.
*otherwise the focusability of an element is determined by the -moz-user-focus property. If it is set to 'ignore' or 'none, the element cannot be focused. Other values allow focus.
*the value of -moz-user-focus is overriden for HTML elements if they have a tabindex attribute
* the value of -moz-user-focus is overriden for an enabled XUL element that implements nsIDOMXULControlElement if its tabIndex property returns a value greater or equal to zero.
*you can focus a scrollable HTML element -- one with overflow set to 'scroll' or 'auto' -- if you change the focus with the tab key, but not by using the mouse.
Some HTML elements such as form elements have additional focus rules.
On the Mac, there's a system setting "Full Keyboard Access", which can be used to toggle between
this model and a model where only listboxes, trees and textboxes can be focused.
The following XUL elements implement nsIDOMXULControlElement:
button, caption, checkbox, colorpicker, description, label, listbox, listitem, menu, menuitem, menulist, radio, radiogroup, richlistbox, richlistitem, tab, tabs, textbox, tree
The following XUL elements have -moz-user-focus set to normal:
browser, editor, iframe
*elements that are hidden (display: none) cannot be focused
*elements that have the CSS visibility property set to collapse or hidden are not focusable.
* an HTML element in an editor is not focusable
* an HTML element cannot be focused if it has a disabled attribute.
* an XML element cannot be focused unless it has a link/xlink.
*a XUL element that implements nsIDOMXULControlElement cannot be focused if its disabled property is true.
*otherwise the focusability of an element is determined by the -moz-user-focus property. If it is set to 'ignore' or 'none, the element cannot be focused. Other values allow focus.
*the value of -moz-user-focus is overriden for HTML elements if they have a tabindex attribute
* the value of -moz-user-focus is overriden for an enabled XUL element that implements nsIDOMXULControlElement if its tabIndex property returns a value greater or equal to zero.
*you can focus a scrollable HTML element -- one with overflow set to 'scroll' or 'auto' -- if you change the focus with the tab key, but not by using the mouse.
Some HTML elements such as form elements have additional focus rules.
On the Mac, there's a system setting "Full Keyboard Access", which can be used to toggle between
this model and a model where only listboxes, trees and textboxes can be focused.
The following XUL elements implement nsIDOMXULControlElement:
button, caption, checkbox, colorpicker, description, label, listbox, listitem, menu, menuitem, menulist, radio, radiogroup, richlistbox, richlistitem, tab, tabs, textbox, tree
The following XUL elements have -moz-user-focus set to normal:
browser, editor, iframe
