I decided to repeat the tests systematically on the two panels displaying the same file.
These are the only versions I can still use (Vista Business Pack 2, TDM-GCC 4.7.1, wxWidgets unicode 2.8.12):
16.01, 10118, 10127, 10816, 10856, 10868, 10912, 19022 :
The upper pane prints the selected text.
The lower pane prints the entire file !!
I will try to search in the source, but I do not know where to look?
Do you know which functions handle printing?