We are exploring ways of being able to view rootana histograms and plots on webpages, rather than in custom GUIs. The current scheme is based on building webpages based on data served up by the ROOT web server : THttpServer.
The rootana analyzer has a command line option to allow the initialization of a THttpServer. For instance, doing
with the programs in rootana/examples; this creates an instance of the THttpServer on port 8088.
We have a test MIDAS instance available here
The default browser (the one that ROOT provides) for the rootana histograms is available here
Not that we have proxied both the MIDAS server and the THttpServer through APACHE in this case.
You can use the above link to explore the histograms created by the rootana program and plot them. You can see that I have histograms being filled with datafrom V792 (charge) and V1720 (waveforms); note that this is just simulated data.
- The webpage currently only works for looking at the histograms online. You
could run rootana on a file and use this webpage to look at the plots; but I don't know how to get the webpage to tell rootana to only process one event at a time, so this isn't so useful. But maybe the idea of using a webpage to look at a particular file doesn't make much sense anyway.
- The webpage doesn't know anything about MIDAS events; all it know about are
the histograms that it can grab. For instance, this is a problem with the V1720 histograms. If you overlay the first two histogram you should in principle see two peaks that are close together; at least that is what the data looks like in the underlying MIDAS events.
But when viewed with my webpage you often see that the two peaks are far apart. This is because the webpage has grabbed the information for the waveform for one channel, then rootana changed to the next event and then the information for the waveform for the second channel. So you are actually looking at the waveforms for different events, which is confusing.
I can imagine ugly ways of working around this; for instance, I could ensure that the waveform histogram are only filled every second, so that two AJAX would be for the same event. But even that wouldn't always work.
- When you pause the webpage, you can't switch between different channels,
display types, etc. That is because the webpage only has the information for the histogram that it is currently plotting; it doesn't have information for any other histograms, so can't show them without un-pausing.
In fact, I'm not really sure what the concept of 'pausing' means in this context, given problem ii).
- I haven't implemented any histogram reset functionality yet. I think that in
principle this THttpServer does support the idea of sending commands back to the program, so I think that this is solvable.
- Currently I can only plot histograms that are ROOT TH1* format. It should be
- The AJAX data transfers are on the main thread; I'll need to fix that to use
the same asynchronous type transfers that Konstantin was writing for MIDAS.
- There is some problem with the rootana server when I first restart it.
Somehow I have to 'initialize' the rootana server by visiting the default ROOT online browser page. If I haven't done that then my AJAX requests don't work. This needs debugging
I guess that problems i), ii) and iii) are probably problems that we also had with roody (not sure about i). They may be problems that are inherent to trying to decouple the generation of the histograms from their display.