I'm going to build a QGIS standalone application. According to the requirements full extent equals to the extent of a predefined rectangle (say bounding box of a parcel). The application should start in full extent view. When zoomed in the user is restricted to only pan inside the area given by full extent (using pan tool or sliding scrollbars), similar to the issue in this question.
Which is the appropriate QGIS API function or how can I mimic this behaviour using Python?