/usr/include/gdkmm-2.4/gdkmm/ is in libgtkmm-2.4-dev 1:2.24.5-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gdkmm-2.4/gdkmm/bitmap.h
/usr/include/gdkmm-2.4/gdkmm/color.h
/usr/include/gdkmm-2.4/gdkmm/colormap.h
/usr/include/gdkmm-2.4/gdkmm/cursor.h
/usr/include/gdkmm-2.4/gdkmm/device.h
/usr/include/gdkmm-2.4/gdkmm/display.h
/usr/include/gdkmm-2.4/gdkmm/displaymanager.h
/usr/include/gdkmm-2.4/gdkmm/dragcontext.h
/usr/include/gdkmm-2.4/gdkmm/drawable.h
/usr/include/gdkmm-2.4/gdkmm/event.h
/usr/include/gdkmm-2.4/gdkmm/gc.h
/usr/include/gdkmm-2.4/gdkmm/general.h
/usr/include/gdkmm-2.4/gdkmm/image.h
/usr/include/gdkmm-2.4/gdkmm/list.h
/usr/include/gdkmm-2.4/gdkmm/pixbuf.h
/usr/include/gdkmm-2.4/gdkmm/pixbufanimation.h
/usr/include/gdkmm-2.4/gdkmm/pixbufanimationiter.h
/usr/include/gdkmm-2.4/gdkmm/pixbufformat.h
/usr/include/gdkmm-2.4/gdkmm/pixbufloader.h
/usr/include/gdkmm-2.4/gdkmm/pixmap.h
/usr/include/gdkmm-2.4/gdkmm/private/
/usr/include/gdkmm-2.4/gdkmm/private/bitmap_p.h
/usr/include/gdkmm-2.4/gdkmm/private/color_p.h
/usr/include/gdkmm-2.4/gdkmm/private/colormap_p.h
/usr/include/gdkmm-2.4/gdkmm/private/cursor_p.h
/usr/include/gdkmm-2.4/gdkmm/private/device_p.h
/usr/include/gdkmm-2.4/gdkmm/private/display_p.h
/usr/include/gdkmm-2.4/gdkmm/private/displaymanager_p.h
/usr/include/gdkmm-2.4/gdkmm/private/dragcontext_p.h
/usr/include/gdkmm-2.4/gdkmm/private/drawable_p.h
/usr/include/gdkmm-2.4/gdkmm/private/event_p.h
/usr/include/gdkmm-2.4/gdkmm/private/gc_p.h
/usr/include/gdkmm-2.4/gdkmm/private/image_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixbuf_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixbufanimation_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixbufanimationiter_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixbufformat_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixbufloader_p.h
/usr/include/gdkmm-2.4/gdkmm/private/pixmap_p.h
/usr/include/gdkmm-2.4/gdkmm/private/rectangle_p.h
/usr/include/gdkmm-2.4/gdkmm/private/region_p.h
/usr/include/gdkmm-2.4/gdkmm/private/rgbcmap_p.h
/usr/include/gdkmm-2.4/gdkmm/private/screen_p.h
/usr/include/gdkmm-2.4/gdkmm/private/types_p.h
/usr/include/gdkmm-2.4/gdkmm/private/visual_p.h
/usr/include/gdkmm-2.4/gdkmm/private/window_p.h
/usr/include/gdkmm-2.4/gdkmm/rectangle.h
/usr/include/gdkmm-2.4/gdkmm/region.h
/usr/include/gdkmm-2.4/gdkmm/rgb.h
/usr/include/gdkmm-2.4/gdkmm/rgbcmap.h
/usr/include/gdkmm-2.4/gdkmm/screen.h
/usr/include/gdkmm-2.4/gdkmm/types.h
/usr/include/gdkmm-2.4/gdkmm/visual.h
/usr/include/gdkmm-2.4/gdkmm/window.h
/usr/include/gdkmm-2.4/gdkmm/wrap_init.h