Qt and RTI DDS interaction---Need some guidance

Question

I am making a GUI where I have multiple forms on QStackedWIdget. Now I want the data in these forms to be updated as and when available. The data will be recieved through RTI DDS. Can some one suggest me some examples or links where the GUI data is updated from Non GUI thread.

Thank You.

Answer 1

You have several options at your disposal. I will explain the one that seems to suit your situation best, as far as I can assess from your question.

First you need to know that on the subscriber side, there are three different possible kinds of interaction between your application and the DDS DataReaders: polling, listeners and waitsets. Polling basically means that your application queries the DataReader when it deems necessary, for example at a fixed rate. Using listeners means that your application provides the middleware with some callback functions which get invoked whenever new data has arrived. Waitsets are similar to a socket select, where your application thread is blocked until data arrives, or a time-out occurs -- typically followed by an action to access the DataReader.

For GUI applications, it is common to use a polling mechanism as opposed to a listener approach that you are probably using. In stead of reading the data as it arrives, and immediately updating the GUI widgets, you can let your GUI read or take data from the DataReaders at a fixed rate, for example at 5 Hz.

With that approach, you take control over when you access DDS and you can do it at the exact rate required, no matter how fast the data gets updated inside your DataReader. Additionally, your question of data being updated by a non-GUI thread is resolved, because you access the DDS DataReader from your own context.

A potential disadvantage of using polling could be that the updating of the widgets happens with some delay, for example if you poll at 5 Hz, your maximum extra delay will be 200 msec. That is usually not a problem for GUI applications though.