Sir:
Probably, I managed to build openCV with GTK2 and GTK3 from source. They sit in two different directories. Currently, I am reluctant to proceed, because opencv_test_xxx binaries report many errors.
Despite these errors, I tried to force link to these libraries using LD_LIBRARY_PATH and other tricks. I think I made one step ahead.
With gtk2.0, mousewheel events, mousebutton flags ARE functional.
With gtk3, they are NOT.
Sir:
Several steps ahead.
Most probably, the situation I ran into, is not an openCV bug. It looks like it happens at library mix-up.
GTK3 version works, so does GTK2 version. When LD_LIBRARY_PATH disagree with g++ -L flag, it happens.
Probably, configuration error.
Incompatible library did not choke, but worked incorrectly, I assume.