highgui: change behaviour of cv::waitKey

[alalek]

DO NOT MERGE Testing only.
Discussion is here: #7105

[StevenPuttemans]

@alalek even though ABI compliance is an issue there, I am still considering this as an issue. The compiler will not complain with this code, but in C++ at runtime all instances of waitKey will be replaced by their inline counterpart. This is possible in C++, however Python does not support this functionality as far as I am aware.

Did you create a python test sample trying to actually use this code?

[StevenPuttemans]

Also I guess the ABI issues will always stick, because due to the inline, the code will get a changed behaviour and thus not support backwards compatibility. Therefore I still guess the double functionality is the best way to go, to avoid ABI issues also.

[alalek]

C++ user code uses replaced version, which can be selected by specified define.
Python code can use only one version which is compiled into cv2 module (no selection is allowed). I tried to run interactive Python code like this and it works fine:

import cv2
cv2.imshow('key', 0)
print(cv.waitKey())

P.S. I believe this Linux/GCC ABI problem can be resolved. On Windows there is no ABI issue (inlined cv::waitKey is still exported from DLL)

[StevenPuttemans]

👍 okay seems valid then!

[vpisarev]

can we hide these details in a .cpp file?