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Frequently Asked Question #1

Question: My menus seem unable to cover form elements, Flash, and Java applets, and IFrames, that exist below them in z-order. The form elements always show through! This behavior is common to all form elements in Navigator, but only the <select> element in Explorer. The problem persists no matter how I set the z-index of the form or its elements. Why?

Answer: The persistence of form element and Flash/Java applet/IFrame visibility is not affected by the z-order of in-page positioned elements. This behavior is documented by the browser vendors, and there is little we can do to avoid it.

You can read about the problem, illustrated with many in-page examples at the DHTML Diner: Positioned Elements and OS Controls, Applets and Plug-ins

HierMenus work arounds primarily take one of two possible approaches:

1. Hide the form elements/applets when the menus are displayed, and restore them when the menus are hidden.

2. Use an iframe mask between the menus and the element (this technique works only in Internet Explorer 5.5/6).

Page elements can be hidden by way of the HM_f_ToggleElementList function included in the HierMenus 6 HM_Loader.js file, used in combination with the TopUponDisplay, ChildUponDisplay, TopUponHide, and ChildUponHide parameters. Further information pertaining to each of these components can be found at these links:

Bulletin 6: HM_f_ToggleElementList
TopUponHide
TopUponDisplay
ChildUponHide
ChildUponDisplay

The Internet Explorer only IFRAME masking technique can be utilized by way of the HM_f_IEMaskCreate, HM_f_IEMaskToggle, and HM_f_IEMaskMove methods included in the HM_Loader.js file. Further description of these functions and how to implement them can be found at these links:

Using the Custom Code in HM_Loader.js
HM_OnMove
HM_OnVisibilityToggle
HM_OnMenuCreated

Finally, for Flash applets in particular, you may also want to have a look at Macromedia's own documentation on the subject:

http://www.macromedia.com/support/flash/ts/documents/wmode.htm
http://www.macromedia.com/support/flash/ts/documents/flash_top_layer.htm

This question is also addressed as Known Issue #1 on our known issues list.