I managed to create a subform to be used as an alternative for Acrobat Dialog. Basically, its a popup to capture some data and append it to existing fields in the main form.
I created the subform with solid background to ensure all other fields behind the form are not clickable.
The only issue I am facing is that when the subform is made "visible", and though it is in front of all other objects of the parent form, yet when you hover over a field which is behind the subform, you could still see it is becoming visible, and you can click it, and edit such field. This behavior is actually confusing.
Is it possible to make the fields behind the subform (popup) inaccessible?
I just added a dummy button at the top of the subform, and made its background "None", added property access='protected' using XML view, cleared the caption and expand it to same size as the parent subform. It worked. I tweaked appearance to make it look like 3D window and now the popup is working like a charm.
This was actually a solution to help us move away from Acrobat Dialog which doesn't work under HTML5. I hope this solution works well in HTML5 too.