Open the app:

1. Entry.cpp creates the app and call NewWindow() in MainWindow.cpp.
2. NewWindow() in MainWindow.cpp store the App in Core.cpp with SetApp() and get the AppWindow object in Core.cpp with GetAppWindow(), then assign variables.
3. NewWindow() creates a FilePanel and initialize it with FilePanel->init() method
4. NewWindow() creates an EditAreaHolder and initialize it with EditAreaHolder->init() method
5. NewWindow() Construct HeaderBar with LoadHeaderBar() function
6. NewWindow() Sets the offset of FilePanel, load css, and other properties
7. NewWindow() Creates a new EditArea that doesn't open any file by calling NewEditArea() from Core.cpp with nullptr as parameter. Then show the EditArea in EditAreaHolder

Open a folder:

1. Click on File button at the left-hand side of the headerbar. It will show a drop-down menu. Click Open folder and LoadFolderClicked()in HeaderBar.cpp will be triggered.
2. LoadFolderClicked() calls OpenFileChooser() with parameter false. Now a FileDialog is opened and wait for user to choose a folder.
3. After chosen, FolderSelected() will be called. And run ReadAsRootFolder().
4. ReadAsRootFolder() creates a FPFolderButton by NewFolderButton() from Core.cpp and initialize it. Then call FilePanel->AddNewRootFolder() to show it as root folder
5. When user expand the content of the folder button by triggering ToggleFolder(), it will call ReadFolder() from FileManager.cpp and add FPFileButton/FPFolderButton under GtkBox *Content

Open a file:

1. Click on File button at the left-hand side of the headerbar. It will show a drop-down menu. Click Open file and LoadFileClicked()in HeaderBar.cpp will be triggered.
2. LoadFileClicked() calls OpenFileChooser() with parameter true. Now a FileDialog is opened and wait for user to choose a file.
3. After chosen, FileSelected() will be called and run OpenFile().