openshot.developers team mailing list archive

[TJ <ubuntu@xxxxxxxxxxx>]

I thought I'd let you know where I'm at.

I suspended testing of the openshot 'alpha' packages yesterday evening
because I got to the point where I was attempting to execute the
installed openshot.

It was failing because the Python package "mlt" (Debian: "python-mlt")
was not yet installed.

I spent today figuring out how to add the required make processing to
the mlt "debian/rules" Makefile.

The core of the issue is the Debian package being generated
("python-mlt") must (Debian policy) use python-support or similar - it
is not allowed to install binary objects directly into the
"/usr/lib/pythonX.Y/{site,dist}-packages/" directories.

This is done since user systems may have several Python versions
installed, and these will not be known at build-time. python-support
handles the logistics of matching the versions of the built binaries to
the end-users installed Python versions.

Now, python-support expects to be creating a 'pure' python package and
so the CDBS (Common Debian Build System) scripts used by the mlt package
that invoke python-support will try to operate against *every* binary
package declared in "debian/control" - not just selected 'python-only'
packages. This is a big problem since only "python-mlt" should be
processed this way.

The second issue is that the Python packaging system, distutils, is
designed to build binary libraries from C/C++ files for Python
Extensions automatically. In the case of "mlt" however it has its own
"src/swig/python/build" script (SWIG == Simplified Wrapper and Interface
Generator) which creates the binaries using certain constructs that
would be very difficult to transpose to a Python distutils.setup()
script.

The solution I developed was to create a new SWIG
"build-for-python-support" shell script that is called from CDBS
overrides in "debian/rules" only for the "python-mlt" package. These
ensure the created binary library and object files, and the python
script and egg-info, are put in the Debian temporary package-build
directories ("debian/python-mlt/").

I manually dissected the "python-adns" package to learn what the final
file payout for python-support should be, and extracted the Debian
"postinst" and "prerm" shell scripts, transposed them for "python-mlt",
and included them in the mlt "debian/" directory.

The end result is that "debian/rules" uses the existing mlt SWIG build
system to create the wrapper files and put them in the correct system
locations, and CDBS correctly builds the "python-mlt" package and
includes the python-support postinst and prerm scripts that are run on
the end-user's system at package install and removal, respectively.

Right now I'm optimising the code in "debian/rules" since I spotted some
redundant actions.

Once I'm happy I'll commit the new code my local "mlt" git repository
and then publish the updated package to my video-editors PPA.

I retested openshot with "python-mlt" installed and it didn't throw up
an error when importing "mlt" so that looks good. I have other openshot
errors to resolve in the launcher code before openshot will start and I
can test it properly.

At that point I'll publish a package to my PPA for you guys to install
and test to ensure it doesn't introduce any regression or bugs due to
the refactoring I've done to streamline the installation.