message: [doxygen] Add description about EMCAL trigger selection task
diff: @@ -153,6 +153,56 @@ for(auto p : *triggerpatches){
  }
  ~~~
  +## Selection of triggered events using trigger patches
  +
  +In some case, i. e. in simulation or in order to select noise, EMCAL-triggered events need to be selected
  +using trigger patches. The wagon *PWG::EMCAL::AliAnalysisTaskEmcalTriggerSelection* performs the selection
  +of EMCAL-triggered events based on period-dependent configurations and adds a container with all the trigger
  +decisions for the various supported Level1-triggers to the event. Users can access the trigger decision
  +container in their task and use it for their event selection.
  +
  +### 1. Add task to the analysis
  +
  +In a simple user analysis do
  +
  +~~~{.cxx}
  +gROOT->LoadMacro(Form("%s/PWG/EMCAL/AddEmcalTriggerSelectionTask.C", gSystem->Getenv("ALICE_PHYSICS)));
  +PWG::EMCAL::AliAnalysisTaskEmcalTriggerSelection *trgseltask = AddEmcalTriggerSelectionTask();
  +trgseltask->SetGlobalDecisionContainerName("EmcalTriggerDecision");
  +trgseltask->AutoConfigure(kDataset);
  +~~~
  +
  +Within the train wagon, call the macro *PWG/EMCAL/AddEmcalTriggerSelectionTask.C* with the arguments (no arguments).
  +In the wagon configuration add
  +
  +~~~{.cxx}
  +__R_ADDTASK__->SetGlobalDecisionContainerName("EmcalTriggerDecision");
  +__R_ADDTASK__->AutoConfigure(kDataset);
  +~~~
  +
  +kDataset should be the name of a supported dataset. Please refer to the description of class PWG::EMCAL::AliAnalysisTaskEmcalTriggerSelection
  +for supported datasets.
  +
  +### 2. Use the trigger selection in your analysis
  +
  +In case the trigger selection task is added to the analysis, users can access it and use it for event selection. The
  +trigger seletion results are store in a trigger decision container (PWG::EMCAL::AliEmcalTriggerDecisionContainer). The
  +trigger decision container hold the trigger decision objects, consisting of the final trigger decision (fired yes/no),
  +the maximum trigger patch firing the trigger and all trigger patches firing the trigger. If one is just interested in
  +the event selection result it is sufficient to query the IsEventSelected method of the trigger decision container with
  +the valid name of the Level1 trigger to be selected.
  +
  +The following code demonstrates how to select EG1 events using the EMCAL trigger decision container
  +
  +~~~{.cxx}
  +auto triggercont = static_cast<PWG::EMCAL::AliEmcalTriggerDecisionContainer *>(fInputEvent->FindListObject(fNameTriggerDecisionContainer));
  +if(!triggercont){
  + AliErrorStream() << "Trigger decision container not found in event - not possible to select EMCAL triggers" << std::endl; }
  + return false;
  +if(!triggercont->IsEventSelected(fTriggerSelectionString)) return false;
  +~~~
  +
  +
  ## Trigger bit setup
  Trigger bits are used to store online trigger selection by the STU as well as offline trigger selection.
  