diff options
| -rw-r--r-- | flower/offset.cc | 58 |
1 files changed, 57 insertions, 1 deletions
diff --git a/flower/offset.cc b/flower/offset.cc index 7cb2677481..b7f5df4026 100644 --- a/flower/offset.cc +++ b/flower/offset.cc @@ -79,11 +79,67 @@ Offset::arg () const return atan2 (coordinate_a_[Y_AXIS], coordinate_a_[X_AXIS]); } +static inline Real +atan2d (Real y, Real x) +{ + return atan2 (y, x) * (180.0 / M_PI); +} + Real Offset::angle_degrees () const { - return arg () * 180 / M_PI; + Real x = coordinate_a_ [X_AXIS]; + Real y = coordinate_a_ [Y_AXIS]; + + // We keep in the vicinity of multiples of 45 degrees here: this is + // where straightforward angles for straightforward angular + // relations are most expected. The factors of 2 employed in the + // comparison are not really perfect for that: sqrt(2)+1 would be + // the factor giving exact windows of 45 degrees rather than what we + // have here. It's just that 2 is likely to generate nicer code + // than 2.4 and the exact handover does not really matter. + // + // Comparisons here are chosen appropriately to let infinities end + // up in their "exact" branch. As opposed to the normal atan2 + // function behavior, this makes "competing" infinities result in + // NAN angles. + if (y < 0.0) + { + if (2*x < -y) + if (-x > -2*y) // x < 0, y < 0, |x| > |2y| + return -180 + atan2d (-y, -x); + else if (-2*x >= -y) // x < 0, y < 0, |y| < |2x| <= |4y| + return -135 + atan2d (x - y, -y - x); + else // y < 0, |y| >= |2x| + return -90 + atan2d (x, -y); + else if (x <= -2*y) // x > 0, y < 0, |y| <= |2x| < |4y| + return -45 + atan2d (x + y, x - y); + // Drop through for y < 0, x > |2y| + } + else if (y > 0.0) + { + if (2*x < y) + if (-x > 2*y) // x < 0, y >= 0, |x| > |2y| + return 180 - atan2d (y, -x); + else if (-2*x >= y) // x < 0, y >= 0, |y| < |2x| <= |4y| + return 135 - atan2d (x + y, y - x); + else // y >= 0, |y| >= |2x| + return 90 - atan2d (x, y); + else if (x <= 2*y) // x >= 0, y >= 0, |y| < |2x| < |4y| + return 45 - atan2d (x - y, x + y); + // Drop through for y > 0, x > |2y| + } + else + // we return 0 for (0,0). NAN would be an option but is a + // nuisance for getting back to rectangular coordinates. Strictly + // speaking, this argument would be just as valid for (+inf.0, + // +inf.0), but then infinities are already an indication of a + // problem in LilyPond. + return (x < 0.0) ? 180 : 0; + return atan2d (y, x); } + + /** euclidian vector length / complex modulus */ |