If you ever created your own SAP CRM WebUI components and add them to an overview page, you probably faced this strange behavior of the assignment block border that disappeared:
When the system is rendering assignment blocks of an overview page, static method CHECK_CONTENT from class CL_THTMLB_UTIL is used to determine if a border should be rendered. How? It's very simple: it checks if one of the following tags was used in the corresponding AB:
As a result, if you're trying to display an assignment block comprising with an thtmlb form (like the one in the picture above), no border will be rendered...
If you're facing the same issue, you have at least two workarounds available. First you can add every <div> tag needed to render the border, see following picture:
However, there is a second very simple trick that you can use to by-pass this limitation: make the system think that your assignment block uses one of those tags by adding the following code in your html page:
Et voilà! With the above code, the result is as expected: