Why does Simulink mark a subsystem in purple?

Simulink has marked a subsystem with a purple border. The border color of the block itself is still black, but there is another purple/magenta highlight border around it.

Why is this?

Answer 1

[Jonas]

Received feedback from MathWorks Support that it is a bug that the purple highlighting persists and a bug fix has been requested.

Answer 2

[Qi Li]

Hi Jonas,

Please refer to this document hilite_system for more details of highlighting style.

Best regards,

Qi

[Jonas]

Hi Qi

Thank you for your message.

But I do not think Simulink uses the hilite_system command to achieve this styling, since that command changes the ForegroundColor and BackgroundColor fields of the block, while in this case the ForegroundColor is still White, and the BackgroundColor is still Black, but there is an additional purple border around the block.

Also, this would still not explain why Simulink makes this annotation.

I have seen that MATLAB r2020b performs the same highlighting for a Goto and From block, to mark its corresponding block:

But I don't know why it has indicated a subsystem in my case.

[Jonas]

I have noticed that if I close the model and reopen, the subsystem is not marked in purple anymore. However, when I go inside the subsystem and click on a Goto block, it markes a corresponding From block and ALSO marks the subsystem it is in. Upon de-clicking the Goto block, the From block is unmarked with the purple but the subsystem is still marked in purple and I cannot get rid of it.