PGF backend, fix #1116, #1118 and #1128

[pwuertz]

This PR contains the fixes for #1116, #1118 and #1128.

[mdboom]

On a machine that still has the "too old" TeX, I now get this, which is correct -- they are known failures (and I've turned off the KnownFailure class here just so I can see exactly where they are coming from).

>nosetests-2.7 matplotlib.tests.test_backend_pgf
/home/mdboom/python/lib/python2.7/site-packages/matplotlib/__init__.py:768: UserWarning: Bad val "True" on line #12
        "text.hinting: True
"
        in file "/home/mdboom/.matplotlib/matplotlibrc"
        hinting should be 'auto', 'native', 'either' or 'none'
  "%s"\n\t%s' % (val, cnt, line, fname, msg))
EEE
======================================================================
ERROR: matplotlib.tests.test_backend_pgf.test_xelatex
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mdboom/python/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/testing/decorators.py", line 47, in failer
    raise KnownFailureTest(msg) # An error here when running nose means that you don't have the matplotlib.testing.noseclasses:KnownFailure plugin in use.
KnownFailureTest: xelatex + pgf is required

======================================================================
ERROR: matplotlib.tests.test_backend_pgf.test_pdflatex
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mdboom/python/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/testing/decorators.py", line 51, in failer
    raise KnownFailureDidNotFailTest(msg)
KnownFailureDidNotFailTest: pdflatex + pgf is required

======================================================================
ERROR: matplotlib.tests.test_backend_pgf.test_rcupdate
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mdboom/python/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/testing/decorators.py", line 47, in failer
    raise KnownFailureTest(msg) # An error here when running nose means that you don't have the matplotlib.testing.noseclasses:KnownFailure plugin in use.
KnownFailureTest: xelatex and pdflatex + pgf required

----------------------------------------------------------------------
Ran 3 tests in 5.867s

However, on a machine where I upgraded the TeX to TeXLive 2012, I'm getting this:

.FF
======================================================================
FAIL: matplotlib.tests.test_backend_pgf.test_pdflatex
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mdboom/python/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/testing/decorators.py", line 39, in failer
    result = f(*args, **kwargs)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 39, in backend_switcher
    result = func(*args, **kwargs)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 91, in test_pdflatex
    compare_figure('pgf_pdflatex.pdf')
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 55, in compare_figure
    raise ImageComparisonFailure('images not close: %s vs. %s' % (actual, expected))
ImageComparisonFailure: images not close: /home/mdboom/Work/tmp/matplotlib/tests/result_images/test_backend_pgf/pgf_pdflatex.pdf vs. /home/mdboom/Work/tmp/matplotlib/tests/result_images/test_backend_
pgf/expected_pgf_pdflatex.pdf

======================================================================
FAIL: matplotlib.tests.test_backend_pgf.test_rcupdate
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mdboom/python/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/testing/decorators.py", line 39, in failer
    result = f(*args, **kwargs)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 39, in backend_switcher
    result = func(*args, **kwargs)
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 119, in test_rcupdate
    compare_figure('pgf_rcupdate%d.pdf' % (i+1))
  File "/home/mdboom/python/lib/python2.7/site-packages/matplotlib/tests/test_backend_pgf.py", line 55, in compare_figure
    raise ImageComparisonFailure('images not close: %s vs. %s' % (actual, expected))
ImageComparisonFailure: images not close: /home/mdboom/Work/tmp/matplotlib/tests/result_images/test_backend_pgf/pgf_rcupdate2.pdf vs. /home/mdboom/Work/tmp/matplotlib/tests/result_images/test_backend
_pgf/expected_pgf_rcupdate2.pdf

----------------------------------------------------------------------
Ran 3 tests in 4.909s

I've put my PDF files up here:

http://mdboom.github.com/scraps/pgf_pdflatex.pdf

http://mdboom.github.com/scraps/pgf_rcparams2.pdf

As for the Python 3 stuff, I plan to tackle #983 today, and that should hopefully get the python 3 tests running for you.

[pwuertz]

Downloading pgf_rcparams2.pdf doesn't work for me, but from the pgf_pdflatex.pdf you uploaded I get that the default fonts of our latex environments are slightly different. The difference is very minimal and shouldn't cause the test to fail. When I wrote the tests I lowered the default tolerance of 1e-3 to 1e-4 because the test didn't recognize when I changed the fonts from serif to sans. Seems that tol=1e-4 is too restrictive. I reverted the tolerance back to 1e-3. Does this work for you?

[pwuertz]

Oh.. and that knownfailureif-decorator confuses me.. for some reason, the pdflatex test actually worked with your old tex distribution.. and the test raised a KnownFailureDidNotFailTest exception. What I'm actually looking for is a decorator that doesn't try to verify if the test really fails and blames me if it succeeds :).

[mdboom]

If I change the tolerance to 5e-3, it works for me.

[pwuertz]

So tol=1e-3 didn't work for you neither? I'm using 5e-3 now. Furthermore, I discovered SkipTest in nose.plugins.skip which does exactly what I wanted. It doesn't require that a test that is marked as known-to-fail actually fails.

[pwuertz]

Ahh ok.. I now see whats the big difference between those images.. Its just ghostscript being horrible at rendering text for some (many) fonts. I checked the PDFs using the gnome viewer and gimp (both cairo based) and saw no difference. The gs converted PNG files both look horrible but in a different way.

[mdboom]

I first tried a tol of 1e-3, but that was still too strict. 5e-3 was the lowest I could go to get the tests to pass.

That's a bummer about gs -- we could probably move to another renderer down the road, but not for this release. I think we just raise the tolerance for now.

[pwuertz]

I finished running the tests using python3. Some additional ResourceWarning messages are emitted when using py3. I got rid of the ones being traced back to backend_pgf.py. These remain:

/usr/lib/python3.2/subprocess.py:650: ResourceWarning: unclosed file <_io.FileIO name=11 mode='rb'>

Nothing to be concerned about though. I think these fixes are good to go.

[mdboom]

Thanks for working through this so quickly!