Bug#969960: libopencv-dev: please support foreign installation

[Helmut Grohne]

Package: libopencv-dev
Version: 4.2.0+dfsg-6+b3
Severity: wishlist

The package libopencv-dev presently cannot be installed for foreign
architectures. Doing so would be useful to enable cross building against
opencv.

libopencv-dev depends on libopencv4.2-java. This package is presently
Multi-Arch: foreign (though #969957 asks to remove that). It depends on
libopencv4.2-jni, which depends on the opencv libraries. Due to the
Multi-Arch: foreign, the opencv stack needs to be installed natively.
libopencv-dev also depends on the foreign opencv libraries. This happens
to conflict on a number of lower layer libraries, which are not
presently coinstallable. Examples include libfabric1, libogdi4.1 or
libgdal27.

Once removing the Multi-Arch: foreign annotation, the dependency on
libopencv4.2-java will simply become unsatisfiable for foreign
installations.

Would it be possible to enable installing opencv without java bindings?
It is also possible to install it without python bindings at present.
Once the libopencv4.2-java dependency is dropped, libopencv-dev can be
installed without issues. How about demoting libopencv4.2-java to
Recommends?

In case that is not possible, it would be good to hava a way to install
/usr/lib/<triplet>/cmake/opencv4/OpenCVConfig.cmake without having to
install the java bindings. That file presently resides in libopencv-dev.
So the other option would be splitting libopencv-dev into another
package that doesn't depend on java and ships this file.

Thank you for considering

Helmut