The main problems
-----------------
o If FT_STROKER_LINEJOIN_BEVEL was specified, unlimited miter
joins (not bevel joins) were generated. Indeed, the meanings of
`miter' and `bevel' were incorrectly reversed (consistently) in
both the code and comments.
o The way bevel joins were constructed (whether specified
explicitly, or created as a result of exceeding the miter limit)
did not match what is required for stroked text in PostScript or
PDF.
The main fixes
--------------
o The behaviour of FT_STROKER_LINEJOIN_BEVEL has been corrected.
o A new line join style, FT_STROKER_LINEJOIN_MITER_FIXED, has been
introduced to support PostScript and PDF miter joins.
o FT_STROKER_LINEJOIN_MITER_VARIABLE has been introduced as an
alias for FT_STROKER_LINEJOIN_MITER.
Additionally, a variety of stroking errors have been fixed. These
would cause various artifacts (including points `at infinity'),
especially when stroking poor quality fonts.
See
http://lists.gnu.org/archive/html/freetype-devel/2011-07/msg00001.html
for example documents. The FreeType stroker now produces results
very similar to that produced by GhostScript and Distiller for these
fonts.
Other problems
--------------
The following problems have been resolved:
o Inside corners could be generated incorrectly. Intersecting the
inside corner could cause a missing triangular area and other
effects.
The intersection point can only be used if the join is between
two lines and both lines are long enough. The `optimization'
condition in `ft_stroker_inside' has been corrected; this
requires the line length to be passed into various functions and
stored in `FT_StrokerRec'.
o Incorrect cubic curves could be generated. The angle
calculations in `FT_Stroker_CubicTo' have been corrected to
handle the case of the curve crossing the +/-PI direction.
o If the border radius was greater than the radius of curvature of
a curve, then the negative sector would end up outside (not
inside) the border. This situation is now recognized and the
negative sector is circumnavigated in the opposite direction.
(If round line joins are being used, this code is disabled
because the line join will always cover the negative sector.)
o When a curve is split, the arcs may not join smoothly (especially
if the curve turns sharply back on itself). Changes in
direction between adjacent arcs were not handled. A round
corner is now added if the deviation from one arc to the next is
greater than a suitable threshold.
o The current direction wasn't retained if a the outline contained
a zero length lineto or a curve that was determined to be
`basically a point'. This could cause a spurious join to be
added.
o Cubics with close control points could be mishandled. All eight
cases are now distinguished correctly.
Other improvements
------------------
o Borders for cubic curves could be too `flat'.
FT_SMALL_CUBIC_THRESHOLD has been reduced a little to prevent
this.
o The handling and use of movable points has been simplified a
little.
o Various values are now computed only if the results are actually
needed.
o The directions of the outer and inner borders have been swapped,
as recommended by Graham Asher.
* src/base/ftstroke.c: Revised.
* include/freetype/ftstroke.h: Updated.
aecbfe1ba7