I have to write a desktop application to edit data stored in a XML file. The format is defined by a XML schema file (.xsd). The format is quite complex. 
Are there tools which can generate a basic GUI automatically? It's not yet decided which language to use. I have experience in Python and C++ using wxWidgets and C# (.NET 1) using Windows Forms.
If the GUI will be simple and you don't bother about the geometry of the components(widgets) in the dialogs, Qt will be a good option. Actually I'm working on a similar task for my project, and my goal was to validate the form data by using an XML file.
Using Qt, it is possible to access any widget on the dialog at run-time by using its object name. So that validation can be applied to the dialog contents.
Creating any dialogs will be even easier, since you will have the widget type and certain information and using layouts, fascinating results can be obtained.
Create a GUI from a XML schema automatically