Docs: add accessibility/keyboard callout to popovers, tweak tooltips …

…callout (#28851)

- Add same advice about keyboard/AT handling to popovers as a callout; also add information about not adding excessive content or interactive controls (and the suggestion to opt for a modal)
- Tweak the tooltips callout for consistency

site/docs/4.3/components/popovers.md

@@ -136,6 +136,17 @@ Enable popovers via JavaScript:
 
 {% highlight js %}$('#example').popover(options){% endhighlight %}
 
+{% capture callout %}
+### Making popovers work for keyboard and assistive technology users
+
+To allow keyboard users to activate your popovers, you should only add them to HTML elements that are traditionally keyboard-focusable and interactive (such as links or form controls). Although arbitrary HTML elements (such as `<span>`s) can be made focusable by adding the `tabindex="0"` attribute, this will add potentially annoying and confusing tab stops on non-interactive elements for keyboard users, and most assistive technologies currently do not announce the popover's content in this situation. Additionally, do not rely solely on `hover` as the trigger for your popovers, as this will make them impossible to trigger for keyboard users.
+
+While you can insert rich, structured HTML in popovers with the `html` option, we strongly recommend that you avoid adding an excessive amount of content. The way popovers currently work is that, once displayed, their content is tied to the trigger element with the `aria-describedby` attribute. As a result, the entirety of the popover's content will be announced to assistive technology users as one long, uninterrupted stream.
+
+Additionally, while it is possible to also include interactive controls (such as form elements or links) in your popover (by adding these elements to the `whiteList` or allowed attributes and tags), be aware that currently the popover does not manage keyboard focus order. When a keyboard user opens a popover, focus remains on the triggering element, and as the popover usually does not immediately follow the trigger in the document's structure, there is no guarantee that moving forward/pressing <kbd>TAB</kbd> will move a keyboard user into the popover itself. In short, simply adding interactive controls to a popover is likely to make these controls unreachable/unusable for keyboard users and users of assistive technologies, or at the very least make for an illogical overall focus order. In these cases, consider using a modal dialog instead.
+{% endcapture %}
+{% include callout.html content=callout type="warning" %}
+
 ### Options
 
 Options can be passed via data attributes or JavaScript. For data attributes, append the option name to `data-`, as in `data-animation=""`.

site/docs/4.3/components/tooltips.md

@@ -107,9 +107,7 @@ The required markup for a tooltip is only a `data` attribute and `title` on the
 {% capture callout %}
 ##### Making tooltips work for keyboard and assistive technology users
 
-You should only add tooltips to HTML elements that are traditionally keyboard-focusable and interactive (such as links or form controls). Although arbitrary HTML elements (such as `<span>`s) can be made focusable by adding the `tabindex="0"` attribute, this will add potentially annoying and confusing tab stops on non-interactive elements for keyboard users. In addition, most assistive technologies currently do not announce the tooltip in this situation.
-
-Additionally, do not rely solely on `hover` as the trigger for your tooltip, as this will make your tooltips impossible to trigger for keyboard users.
+You should only add tooltips to HTML elements that are traditionally keyboard-focusable and interactive (such as links or form controls). Although arbitrary HTML elements (such as `<span>`s) can be made focusable by adding the `tabindex="0"` attribute, this will add potentially annoying and confusing tab stops on non-interactive elements for keyboard users, and most assistive technologies currently do not announce the tooltip in this situation. Additionally, do not rely solely on `hover` as the trigger for your tooltip, as this will make your tooltips impossible to trigger for keyboard users.
 {% endcapture %}
 {% include callout.html content=callout type="warning" %}