[OpenJDK 2D-Dev] RFR: 8233006: freetype incorrectly adjusts advances when emboldening rotated glyphs

[Philip Race]

Bug : https://bugs.openjdk.java.net/browse/JDK-8233006
Webrev : http://cr.openjdk.java.net/~prr/8233006

The bug here is that the freetype function for synthesising bold is not 
ready to handle rotation.

In the process I noticed it did not adjust the advance used by the 
fractional metrics case,
even though the outline is bolded.

Also, in what seems to be a completely wrong thing to do, freetype would
widen the advance of glyphs which have zero advance.

So I decided that the best thing to do was to write our own.
A chunk of the heavy lifting - widening the outline - is still done by 
freetype
but there were a lot of details to get right and test.

I wrote a test to visualise the problem but the actual test checks by 
looking
at the bounding rectangle of the drawn pixels and compares its height to
the declared metrics of the font, failing if they disagree by too much.

Note that the code path is only exercised when synthetic bolding is needed.
So real bold fonts don't test this code.
Since there's not an easy way to say which fonts have real bold, I 
decided the
test should use a BOLD version of every font on the system, which on almost
all systems will test some significant number of such cases.
I kept the UI for visualising as it will be useful for later debugging 
of failures.

Also it made me notice that the case where the text was not rotated at 
all was
drawing shorter than all the other cases.
I traced this back to the fix for 8203485 which added a macro FT26Dot6ToInt
and used it to get the integer advance in the unrotated, integer metrics 
case.
The idea there wasn't completely wrong, but I don't think it was 
completely right either.
I got rid of the macro and instead used the same FT26Dot6ToFloat macro 
as used
in the rotation cases. So we now return the exact floating point value 
to the calling
Java code. That then can round appropriately as it needs to. This fixed 
the inconsistency
and the test for 8203485 still passes as do all other tests.
This change will likely lead to some cases where unrotated advances now 
round up one pixel wider,
but so far it looks correct to me. They'll be restored to something more 
like what they were
before 8203485, since that removed rounding and added truncation instead 
to fix a problem
with the rounding being incorrect for rotations because it could round 
down when it should round up.
Now we just let the Java code handle it.

I've run these tests on all platforms and they pass. Mac isn't using 
this freetype path so it is not affected
but it is still good to know the tests pass there ...

-phil