More than 2000 lines of code less in app/, instead of
if (instance->member)
{
g_object_unref/g_free/g_whatever (instance->member);
instance->member = NULL;
}
we now simply use
g_clear_object/pointer (&instance->member);
Add virtual function validate() so subclasses can construct arbitrary
buffers on-the-fly. The default implementation blits from the
projection graph like before. Add boolean property "whole-tile" which
allows for switching between always validating entire tiles, and
validating the parts of the tile that are actually dirty.