layout of graphics in the page
Currently, poppler-glib only provides the layout of text (poppler_page_get_text_layout), images (poppler_page_get_image_mapping), etc. As far as I can see, there is currently no way to detect the position of graphics in the page, the kind drawn by commands like m, l, v, etc.
For example, the box is not an image in the enclosed file. More generally, it seems not possible to detect the position of a diagram made of lines, rectangles, Bezier curves, etc.