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ControlSystemStudio / cs-studio

Control System Studio is an Eclipse-based collections of tools to monitor and operate large scale control systems, such as the ones in the accelerator community.
https://controlsystemstudio.org/
Eclipse Public License 1.0
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Latest data point not plotted after a disconnect #2727

Closed rjwills28 closed 3 months ago

rjwills28 commented 3 months ago

An issue was introduced in https://github.com/ControlSystemStudio/cs-studio/pull/2713 where we attempted to show PV disconnections in the data browser. In the current implementation we attempt to detect a 'disconnect' messages in the metadata of a data item and add an extra data point to signal this. On the following next() call to the iterator it uses the previous message (which was just replaced with the disconnect) to make sure no data is missed.

It turns out there is a particular case that causes a problem when it is the final message from the archiver that contains the disconnect. What this means is that now the next() function never gets called as the iterator is empty (so hasNext() returns false) and so we can miss the following (i.e. latest) value. This means that the value after the last disconnect does not get plotted.

This PR contains a fix for this where I have updated the hasNext() method of the iterator to return true if we still need to process the most recent message (meaning that next() will be called one final time).

rjwills28 commented 3 months ago

Hi @shroffk, would you mind taking a look at this PR if you have a moment?