How do I make an export addon pre-populate filename with name of the selected object?

Question

I’m creating an export/import add-on (similar to STL import/export add-on) and I would like the suggested filename in the file browser to take the name of the currently selected object in the scene or a generic filename if multiple objects are selected. My add-on uses the bpy_extras.io_utils’s ExportHelper.

In the example below, for a new, unsaved blend file, the default filename is untitled.sur (sur is the extension the file exported by my addon). I would like this name to be “Icosphere.sur” since the object “Icosphere” is selected in the scene.

Answer 1

Set in the invoke method.

As noted in these answers the IO helpers have invoke and check methods that are doing some things behind the scenes.

https://blender.stackexchange.com/a/198924/15543

https://blender.stackexchange.com/a/207665/15543

The export helper invoke method, that if not set sticks in the name Untitled, simply change this to that of the context object.

def invoke(self, context, _event):
    import os
    if not self.filepath:
        blend_filepath = context.blend_data.filepath
        if not blend_filepath:
            blend_filepath = context.object.name # <=== UPDATE
        else:
            blend_filepath = os.path.splitext(blend_filepath)[0]

        self.filepath = blend_filepath + self.filename_ext

    context.window_manager.fileselect_add(self)
    return {'RUNNING_MODAL'}