ROOT Grapher

This project is a playground for students. It contains a simple TCanvas integrated into the Qt GUI. In theory the project should converge into a simple histogram extractor from the *.root files.

Prerequisites

• One needs ot have Qt installed (together with the QtCreator, better if you have local installation)
• ROOT has to be compiled and installed (also local installation)
• C++ skills
• Git knowledge

Building the project

• Fork the repository to your own page
• Clone your own fork of the repository
• Open the project in QtCreator
• You will be offered to specify the build options
• Edit root-grapher.pro file to match the ROOT installation folder
• Run Build

The simple window should appear. If you click the Change File button - the ROOT histogram will appear there.

Task

Ideological Goals

• Getting used to the Git workflow
• Improving ROOT and Qt skills
• Practicing object-oriented programming

Current Structure

The project contains following files:

• root-grapher.pro - project file
• main.cpp - main file, in Qt contains only the class instantination
• mainwindow.h(cpp) - the MainWindow class describing the GUI
• mainwindow.ui - graphical form to build the interface
• canvas.h(cxx) - simple implementation of the TCanvas in Qt

Practical Goals and Hints

The *.root histogram browser has to be developed, based on the existing code. It should be a super simple analogy of the TBrowser. The development has to be done in your own Git fork.

For the moment once you push the button "Change File", the method on_change_file_clicked() is called: it creates a simple random-filled histogram and plots it using the plot_data(TObject *pGraph) method. As one can see, the method accepts generic TObject file as the input, so any type of graphical data can be sent there: TH1F, TGraph, whatever...

The goal, is to replace the existing method, which is executed once the "Change File" button is clicked, with the real method, which opens the file system browser and shows only *.root files. The example is described here, for instance.

Once the file has been chosen, the object-oriented programming comes. The new class has to be instantiated and called QROOTFile. This class should contain the std::map<std::string, TObject*> private object, which is the map of the histogram (graph) name and its reference. When the QROOTFile constructor is called (takes a file name as the argument), it should open the *.root file (TFile), and load the histograms into the map. As the map is private, there should be a dedicated class method to get a histogram by its name, to get a list of histogram names, etc.

Once this is done, the hist_list object of the MainWindow (just a list widget) has to be filled with the histogram names, so that user can select the histogram and it will be immidiately displayed in the canvas. Once the file is changed, the list has to be updated.

During the development, the code should be periodically commited in order to make version control possible. Once the development is done, the pull (merge) request has to b submitted to the initial (upstream) repository.