now make compiles fine, I just have these warnings:
screenshot.c: In function ‘select_area_button_press’:
screenshot.c:229:3: warning: passing argument 1 of ‘gdk_event_get_root_coords’ from incompatible pointer type [enabled by default]
In file included from /usr/include/gtk-3.0/gdk/gdkdisplay.h:31:0,
from /usr/include/gtk-3.0/gdk/gdkscreen.h:32,
from /usr/include/gtk-3.0/gdk/gdkapplaunchcontext.h:31,
from /usr/include/gtk-3.0/gdk/gdk.h:32,
from /usr/include/gtk-3.0/gtk/gtk.h:30,
from screenshot.c:25:
/usr/include/gtk-3.0/gdk/gdkevents.h:1196:11: note: expected ‘const union GdkEvent *’ but argument is of type ‘struct GdkEventButton *’
screenshot.c:248:11: warning: ‘gdk_display_warp_pointer’ is deprecated (declared at /usr/include/gtk-3.0/gdk/gdkdisplay.h:101): Use 'gdk_device_warp' instead [-Wdeprecated-declarations]
screenshot.c: In function ‘select_area_motion_notify’:
screenshot.c:261:3: warning: passing argument 1 of ‘gdk_event_get_root_coords’ from incompatible pointer type [enabled by default]
In file included from /usr/include/gtk-3.0/gdk/gdkdisplay.h:31:0,
from /usr/include/gtk-3.0/gdk/gdkscreen.h:32,
from /usr/include/gtk-3.0/gdk/gdkapplaunchcontext.h:31,
from /usr/include/gtk-3.0/gdk/gdk.h:32,
from /usr/include/gtk-3.0/gtk/gtk.h:30,
from screenshot.c:25:
/usr/include/gtk-3.0/gdk/gdkevents.h:1196:11: note: expected ‘const union GdkEvent *’ but argument is of type ‘struct GdkEventMotion *’