I'm currently working on QGIS plugin as part of a school project. One feature of this plugin is going to be the possibility to transform coordinates from one EPSG code to another.
Therefore it would be the most useful and user-friendly way to let the user open the "project properties" dialog by clicking a specific button in the plugin, in this dialog he chooses the CRS he wants to use and on closing the dialog the chosen value is taken to the plugin code so I can use it for the transformation itself.
I already searched in the QGIS API but without any success. I made it to open some other menus via the "iface" reference in my code, but unfortunately not the one you open by clicking in QGIS at to bottom right corner, left of the bubble which opens the message view.
Hope I made my problem as understandable as possible, if not feel free to ask more details.