code/modules/unit_tests/~nova/custom_sprites/workspace.dm

/proc/custom_sprite_test_region_workspace	A region workspace over two regions on the first row: "1" at x 0-3, "2" at x 4-7.
/proc/custom_sprite_test_canvas_mismatch	Returns where the window's canvas, as an update encodes it, differs from the drawing: the first pixel of a view it carries that doesn't decode to the pixel there, or null when every one does, as a whole encode would.