Option for Disabled Structures to Not Use Default Value for Unwired Output Tunnels

[Jim_Kring]

IMO, the Diagram Disable Structure causes bugs, because the output tunnels of the Diagram Disable Structure are set to "Use Default if Unwired", and the default values are very often not desireable, as can be seen in the screenshot, below:

See this blog article, for more details:

http://thinkinging.com/2008/05/11/the-diagram-disable-structure-causes-bugs/

[Christina_R]

LabVIEW R&D is considering changing the behavior of newly-placed Diagram Disable structures such that, if there are tunnels of particular data types (like refnums) that should "flow through," then the structure will additionally have an Enabled frame that passes the input value directly to the output. We believe this will address the use case described here, but we invite feedback!

[Christina_R]

An update on how LabVIEW R&D plans to respond to this Idea in a future version of LabVIEW:

When dropping a Diagram Disable structure, we already create tunnels as necessary to connect the existing enclosed code in the "Disabled" frame of the new structure to the outside of the structure. We wire the tunnels to the originally connected nodes on either side of the structure boundary, but we set the tunnels to "Use Default If Unwired," and leave the other "Enabled" frame unwired.

Instead of leaving output tunnels unwired in the other frame, we will automatically detect if the value wired to the tunnel is ultimately sourced from an input tunnel (possibly through a series of intermediate nodes). If so, the tunnels will be directly wired together in the empty "Enabled" frame. Two or more output tunnels may be wired to the same input tunnel if they are connected in the original diagram. If a unique path cannot be found from an output tunnel to an input tunnel (for example, we find a constant or a different ultimate source, or the wire goes through a Case structure or other multi-diagram structure with multiple possible sources), we will leave the output tunnel unwired. If the datatype of the tunnel is a refnum type or a LabVIEW class, we will disable "Use Default if Unwired" on the tunnel so that the user is required to wire the input manually. For all other types, the default value will be used, retaining existing behavior.