Launcher Guide

A launcher is a beamline button that runs an external Python GUI as a separate process. Use it when you want to surface an existing standalone tool from the PyStream toolbar without pulling its dependencies into PyStream itself.

Adding a launcher

1. Copy src/pystream/beamlines/bl32ID/_launcher_template.py to a new file in your beamline directory (e.g. mygui.py).

2. Edit SCRIPT_PATH (or the list of candidate paths), BUTTON_TEXT, and the class name (e.g. MyGuiDialog).

3. Import the class in the beamline’s __init__.py and add it to __all__.

4. In src/pystream/pystream.py _create_beamlines_bar(), add a hasattr(module, 'MyGuiDialog') branch wired to a small _open_my_gui() handler that instantiates the dialog. See _open_xanes_gui() for a working example.

5. Restart PyStream.

The launcher spawns the script with sys.executable and start_new_session=True so it survives PyStream exit. If the script isn’t found, the user gets a dialog with the candidate paths and any installation hint you put in the description.