Set GTK_API to 3.0/3.4. I can promise this will not build. Now to begin the porting process
Replace GDK_Escape with GDK_KEY_Escape
Use gdk_pixbuf_get_from_window
Replace all uses of GdkDrawable with GdkWindow
Switch GdkRegion for cairo_region_t
Use cairo_rectangle_int_t not GdkRectangle
Replace gdk_region_new with cairo_region_new
Replace gdk_region_copy with cairo_region_copy
Use cairo_region_destroy
Move to cairo_region_create_rectangle
Replace use of gdk_region_offset with cairo_region_translate
Move to cairo_region_union_rectangle
Use cairo_region_intersect
Move to cairo_region_subtract
Some porting work on preview-widget.c
Alternative monitor edge algoritm to fix GNOME bug #684212, and side-by-side tiling (mostly backported from Mutter).
Merge pull request #1 from MaartenBaert/master

Bugfix and side-by-side tiling