ACTION-1490: Propose spec text edit for issue-610: comboboxes should allow complex children elements

Reassigned to Matt from JamesN in 19 Nov 2015 meeting

Proposal in mck-action1490 branch:
http://rawgit.com/w3c/aria/mck-action1490/aria/aria.html

Objectives:
1. Allow combobox to popup grid, tree, and dialog in addition to listbox.
2. Allow aria-controls so screen reader users can see a rendering of the popup in reading mode.
3. Remove ambiguities from the spec to improve understanding and simplify authoring.
4. Do it all without breaking any existing implementations.

Note: browser and assistive technology impact is extremely small. The authoring changes proposed are already largely supported by both browsers and assistive technologies. The 3 minor exceptions are:
1. Screen readers will need to recognize the aria-controls relationship when focus is inside the popup in order to properly handle escape key processing.
2. Screen readers will need to recognize boolean values for aria-autocomplete in addition to the ARIA 1.0 token values.
3. When authors provide a boolean value for aria-autocomplete, browsers will need to allow the boolean values. The ARIA 1.0 tokens would also still be allowed.

The changes in the mck-action1490 branch are:
1. Reword the combobox definition.
2. Added normative statement saying the popup must be one of listbox, tree, grid, or dialog.
3. Specify authors SHOULD use aria-controls but MAY use aria-owns to specify the relationship between the input and the popup.
4. Added normative author MUST for correct use of aria-expanded.
5. Reword and simplify the focus management language.
6. Remove all text about aria-autocomplete except an author SHOULD statement referring to the new boolean definition of aria-autocomplete.
7. Update the example code to match the new authoring requirements.
8. Add a reference to the APG.
9. Change the superclass to input.
10. Remove the required owned elements.

Based on today's lively discussion, I have revised my proposal for action 1490[1], which is in branch mck-action1490[2].

mck-action1490 branch: http://rawgit.com/w3c/aria/mck-action1490/aria/aria.html

The revisions from today's discussion include:
1. Remove implicit value of aria-orientation for combobox.
2. Remove combobox note about XForms.
3. Change combobox aria-autocomplete authoring requirements to state that aria-autocomplete be set to either "both" if autocomplete is provided in the textbox or "list" if it is not.
4. Restored token values for aria-autocomplete and clarified their definitions.

As previously described, the objectives of action 1490 are:
1. Allow combobox to popup grid, tree, and dialog in addition to listbox.
2. Allow aria-controls instead of aria-owns so the pop-up is not a child of the single line text input. This enables screen readers to include a rendering of the pop-up outside of the text input in their reading view or buffer.
3. Remove ambiguities from the spec to improve understanding and simplify authoring.
4. Do it all without breaking any existing implementations.

Note: the changes included in action 1490 have little or no effect on browser implementations and require only minor adjustments in the logic of some screen readers to support the aria-controls relationship when processing the escape key.

Now, the changes in the mck-action1490 branch are:
1. Reworded the combobox definition.
2. Added normative statement saying the popup must be one of listbox, tree, grid, or dialog.
3. Added normative MUST statement requiring authors to associate the input with the pop-up.
4. Specified that authors SHOULD use aria-controls but MAY use aria-owns to specify the relationship between the input and the popup.
5. Added normative author MUST statement requiring correct use of aria-expanded.
6. Reworded and simplify the focus management language.
7. Eliminated confusing language about aria-autocomplete and specified that authors SHOULD use either "both" if the text input provides suggestions or "list" if it does not.
8. Updated the example code to match the new authoring requirements.
9. Added a reference to the APG.
10. Changed the superclass to input.
11. Remove the required owned elements.
12. Clarified the value definitions for aria-autocomplete.

See this ARIA list post for another combobox coding pattern proposal:
https://lists.w3.org/Archives/Public/public-aria/2016Feb/0294.html

Modified the definition of aria-activedescendant for special case comboboxes. Added the following paragraph:
"
A special use case is a combobox where its textbox has DOM focus, and that textbox employs an aria-activedescendant attribute to reference the currently active listbox option. The referenced listbox option is not in fact a descendant of the textbox itself, but of its parent combobox element. Even so, the aria-activedescendant property is treated by user agents as the active descendant of the combobox, and not the textbox.
"

In situ:
http://rawgit.com/w3c/aria/mck-action1490-activedescendant/aria/aria.html#aria-activedescendant

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Changes made as a result of March 10, 2016 meeting

Note: The revised combobox proposal is now in branch action1490-combobox:
http://rawgit.com/w3c/aria/action1490-combobox/aria/aria.html#combobox

The branch includes the following changes as a result of the Mar 10 discussion.

1. Revised definition so that it does not imply that listbox and grid are classified as popups as opposed to elements that popup.

2. elivated the following normative aria-autocomplete statement from author SHOULD to author MUST:
If the combobox provides autocompletion behavior for the text input as described in aria-autocomplete,
authors MUST set aria-autocomplete on the textbox element to the value that corresponds to the provided behavior.

3. Added an author MUST statement that restricts the role of the popup element to listbox, tree, grid, or dialog.
And, correspondingly added listbox, tree, grid, and dialog as required owned elements.

Please respond to Bryan's post:
https://lists.w3.org/Archives/Public/public-aria/2016Mar/0200.html

Changes merged into master: https://github.com/w3c/aria/commit/a0a9166791
https://rawgit.com/w3c/aria/master/aria/aria.html#combobox

Closing this action.