...
For this purpose it presents two radiobuttons to the user:
- New installation
- Modify installation
It uses the reserved internal IzPack variable modifyvariable modify.izpack.install as input and output for controlling the behavior of other panels, like the TargetPanel.
Further, it may check the $INSTALL_PATH/.installationinformation file, which must have been written by a previous installation to be able to modify it.
If "Modify installation" is chosen the installers loads packs already installed in a previous installation and removes them from the packs to be actually installed. Therefore, on subsequentially opening a PacksPanel, there is just the set of packs presented to the user, which actually haven't been installed to this time.
Further this has influence on PathInputPanel and TargetInputPanel TargetPanel, requiring them to not only check the existing target installation path, but also the .installationinformation file. The installation is not allowed to go on if this condition is not fulfilled.
...