(I'm confused why the preprocessor checks were not needed.)
They are not needed because the original code in Digikam was redundant. The patch simply removed the redundancy!
Ok. You're dealing with a C++ dunce here, remember? I still don't grasp pointers, ->, this, and other C++ related weirdness.
Because both David and I built digikam against libpng 1.5 and 1.4.9 respectively, with the preprocessor check patch, apparently the checks did not cause any harm but are unnecessary.
I guess nice try but I'm still a C++ dunce. :-)
Darrell