Custom columns (IFRAME), web parts and connections

Question

We have created a number of custom columns for our client. Some of them display content using an iframe to an .ASPX page (so that some code-behind can be executed).

I was recently tasked to create a selectable filter for a "front page" of sorts - this page displays a number of lists using Web Parts. To do this, I've added a filter web part (in this case, a choice filter), and connected it to the existing web part displaying the list.

Here's the end result:

As soon as I remove the connection, the column works fine and will display the actual content of the iframe (in this case, a mail icon which can be clicked on), as opposed to just the code.

What's going on here? Is there any way around this?

PS. The column on the left is also one of our custom columns, but this one doesn't use an iframe. Sadly, I need to execute some code in some columns, so rewriting is not an option.

EDIT:

I've realized that the issue stems from the fact that SharePoint, for some weird reason, decided to encode the iframe tag and it's treated as text:

<iframe marginwidth="0" allowtransparency="true" marginheight="0" height="28" width="48" align="left" scrolling="no" frameborder="0" src=...

Obviously this doesn't happen without any connections between web parts.

Answer 1

I found why this is happening... the FDLTYPES definition for that buggy field had <Field Name="ParentType">Text</Field>.

When I changed it to Number it started to work. Still, I feel this is a workaround rather than a solution, as the whole thing doesn't behave as expected from the start, but at least the fields work.