When a modal RadWindow is shown all other focusable elements on the page get their tabIndex attributes set to -1 to achieve the modal effect. Here are the implications related to your case:
- we cannot know if some of the elements are inside other RadWindows, RadToolTips or other custom popups
- even if similar checks are added (that could cover only our controls), proper behavior for such elements cannot be defined - leaving their original tabIndex values will make the popup non-modal because they will be able to take focus to the main page; on the other hand we cannot know if one of them is going to be shown in order to attempt to keep and restore its z-index values.
Usually, only one modal popup should be present on the page, because its wai-aria definition is a dialog that holds the user focus until it is closed or submitted, so opening another modal popup should, by definition, take the focus away from the first, breaking its function.
If the first popup is closed before the second is opened the elements in it should have their proper tabIndex values restored.
Another thing you can consider is using an entire page for the RadWindow contents, instead of its ContentTemplate. Thus, the second popup's contents will be in a separate context and the first modal popup will not be able to reach them (nor will the user while the popup is not shown).
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