Issue3383: old-straight-flag + smaller Stem.thickness gives no output and huge over

[lilypond.git] / lily / skyline.cc

diff --git a/lily/skyline.cc b/lily/skyline.cc
index 5073e69e14b3eaccb805a712e8979be7d9b8856f..624334ab7964f695ee0233a3e3832f753589fb38 100644 (file)
--- a/lily/skyline.cc
+++ b/lily/skyline.cc
@@ -121,30 +121,42 @@ Building::precompute (Real start, Real start_height, Real end_height, Real end)
   assert (!isinf (slope_) && !isnan (slope_));
 
   if (isinf (start))
-    {
-      assert (start_height == end_height);
-      y_intercept_ = start_height;
-    }
-  else
-    y_intercept_ = start_height - slope_ * start;
+    assert (start_height == end_height);
+
+  start_height_ = start_height;
 }
 
+// Because of the way slope is calculated as a ratio of usually small
+// differences, its precision is not sufficient for extrapolating
+// significantly from the original interval.  For that reason, we
+// don't store the y0 value that would allow more precalculation by using
+// y = x * slope + y0 
+// rather than
+// y = (x - xstart) * slope + ystart
+
 inline Real
 Building::height (Real x) const
 {
-  return isinf (x) ? y_intercept_ : slope_ * x + y_intercept_;
+  return (isinf (x) || isinf (start_)) ? start_height_
+    : slope_ * (x - start_) + start_height_;
 }
 
 void
 Building::print () const
 {
-  printf ("%f x + %f from %f to %f\n", slope_, y_intercept_, start_, end_);
+  printf ("%f (x - x0) + %f from %f to %f\n", slope_, start_height_, start_, end_);
 }
 
 inline Real
 Building::intersection_x (Building const &other) const
 {
-  Real ret = (y_intercept_ - other.y_intercept_) / (other.slope_ - slope_);
+  Real ret = start_
+    - (other.start_height_ - start_height_
+       - other.slope_ * (other.start_ - start_))
+    /(other.slope_ - slope_);
+  /* A numerically symmetric version would be
+     x = (x1+x0)/2 - (y1-y0 - (s1+s0)(x1-x0)/2)/(s1-s0)
+   */
   return isnan (ret) ? -infinity_f : ret;
 }
 
@@ -155,19 +167,6 @@ Building::leading_part (Real chop)
   end_ = chop;
 }
 
-// Returns a shift s such that (x + s, y) intersects the roof of
-// this building.  If no such shift exists, returns infinity_f.
-Real
-Building::shift_to_intersect (Real x, Real y) const
-{
-  // Solve for s: y = (x + s)*m + b
-  Real ret = (y - y_intercept_ - slope_ * x) / slope_;
-
-  if (ret >= start_ && ret <= end_ && !isinf (ret))
-    return ret;
-  return infinity_f;
-}
-
 static Real
 first_intersection (Building const &b, list<Building> *const s, Real start_x)
 {
@@ -177,7 +176,7 @@ first_intersection (Building const &b, list<Building> *const s, Real start_x)
 
       // conceals and intersection_x involve multiplication and
       // division. Avoid that, if we can.
-      if (c.y_intercept_ == -infinity_f)
+      if (c.start_height_ == -infinity_f)
         {
           if (c.end_ > b.end_)
             return b.end_;
@@ -200,16 +199,12 @@ first_intersection (Building const &b, list<Building> *const s, Real start_x)
   return b.end_;
 }
 
+// conceals returns true if *this is strictly above other at x
+
 bool
 Building::conceals (Building const &other, Real x) const
 {
-  if (slope_ == other.slope_)
-    return y_intercept_ > other.y_intercept_;
-
-  /* their slopes were not equal, so there is an intersection point */
-  Real i = intersection_x (other);
-  return (i <= x && slope_ > other.slope_)
-         || (i > x && slope_ < other.slope_);
+  return height (x) > other.height (x);
 }
 
 // Remove redundant empty buildings from the skyline.
@@ -223,7 +218,7 @@ Skyline::normalize ()
 
   for (i = buildings_.begin (); i != buildings_.end (); i++)
     {
-      if (last_empty && i->y_intercept_ == -infinity_f)
+      if (last_empty && i->start_height_ == -infinity_f)
         {
           list<Building>::iterator last = i;
           last--;
@@ -231,7 +226,7 @@ Skyline::normalize ()
           buildings_.erase (i);
           i = last;
         }
-      last_empty = (i->y_intercept_ == -infinity_f);
+      last_empty = (i->start_height_ == -infinity_f);
     }
 
   assert (buildings_.front ().start_ == -infinity_f);
@@ -250,10 +245,10 @@ Skyline::deholify ()
 
   for (right = buildings_.begin (); right != buildings_.end (); right++)
     {
-      if (center != buildings_.begin () && center->y_intercept_ == -infinity_f)
+      if (center != buildings_.begin () && center->start_height_ == -infinity_f)
         {
           Real p1 = left->height (left->end_);
-          Real p2 = right->height (right->start_);
+          Real p2 = right->start_height_;
           *center = Building (center->start_, p1, p2, center->end_);
 
           left = center;
@@ -285,7 +280,7 @@ Skyline::internal_merge_skyline (list<Building> *s1, list<Building> *s2,
       // Optimization: if the other skyline is empty at this point,
       // we can avoid testing some intersections. Just grab as many
       // buildings from s1 as we can, and shove them onto the output.
-      if (c.y_intercept_ == -infinity_f
+      if (c.start_height_ == -infinity_f
           && c.end_ >= b.end_)
         {
           list<Building>::iterator i = s1->begin ();
@@ -293,6 +288,7 @@ Skyline::internal_merge_skyline (list<Building> *s1, list<Building> *s2,
           while (i != s1->end () && i->end_ <= c.end_)
             i++;
 
+          s1->front ().start_height_ = s1->front ().height (x);
           s1->front ().start_ = x;
           result->splice (result->end (), *s1, s1->begin (), i);
           x = result->back ().end_;
@@ -303,6 +299,7 @@ Skyline::internal_merge_skyline (list<Building> *s1, list<Building> *s2,
       Real end = first_intersection (b, s2, x);
       if (s2->empty ())
         {
+          b.start_height_ = b.height (last_end);
           b.start_ = last_end;
           result->push_back (b);
           break;
@@ -311,6 +308,7 @@ Skyline::internal_merge_skyline (list<Building> *s1, list<Building> *s2,
       if (end >= x)
         {
           b.leading_part (end);
+          b.start_height_ = b.height (last_end);
           b.start_ = last_end;
           last_end = b.end_;
           result->push_back (b);
@@ -358,7 +356,7 @@ non_overlapping_skyline (list<Building> *const buildings)
   while (i != buildings->end ())
     {
       Real x1 = i->start_;
-      Real y1 = i->height (i->start_);
+      Real y1 = i->start_height_;
       Real x2 = i->end_;
       Real y2 = i->height (i->end_);
 
@@ -401,7 +399,7 @@ public:
   bool operator () (Building const &b1, Building const &b2)
   {
     return b1.start_ < b2.start_
-           || (b1.start_ == b2.start_ && b1.height (b1.start_) > b2.height (b1.start_));
+           || (b1.start_ == b2.start_ && b1.start_height_ > b2.start_height_);
   }
 };
 
@@ -611,7 +609,7 @@ Skyline::raise (Real r)
 {
   list<Building>::iterator end = buildings_.end ();
   for (list<Building>::iterator i = buildings_.begin (); i != end; i++)
-    i->y_intercept_ += sky_ * r;
+    i->start_height_ += sky_ * r;
 }
 
 void
@@ -622,7 +620,6 @@ Skyline::shift (Real s)
     {
       i->start_ += s;
       i->end_ += s;
-      i->y_intercept_ -= s * i->slope_;
     }
 }
 
@@ -667,7 +664,7 @@ Skyline::padded (Real horizon_padding) const
     {
       if (i->start_ > -infinity_f)
         {
-          Real height = i->height (i->start_);
+          Real height = i->start_height_;
           if (height > -infinity_f)
             {
               // Add the sloped building that pads the left side of the current building.
@@ -771,7 +768,7 @@ Skyline::max_height () const
   list<Building>::const_iterator i;
   for (i = buildings_.begin (); i != buildings_.end (); ++i)
     {
-      ret = max (ret, i->height (i->start_));
+      ret = max (ret, i->start_height_);
       ret = max (ret, i->height (i->end_));
     }
 
@@ -789,7 +786,7 @@ Skyline::left () const
 {
   for (list<Building>::const_iterator i (buildings_.begin ());
        i != buildings_.end (); i++)
-    if (i->y_intercept_ > -infinity_f)
+    if (i->start_height_ > -infinity_f)
       return i->start_;
 
   return infinity_f;
@@ -800,7 +797,7 @@ Skyline::right () const
 {
   for (list<Building>::const_reverse_iterator i (buildings_.rbegin ());
        i != buildings_.rend (); ++i)
-    if (i->y_intercept_ > -infinity_f)
+    if (i->start_height_ > -infinity_f)
       return i->end_;
 
   return -infinity_f;
@@ -818,7 +815,7 @@ void
 Skyline::set_minimum_height (Real h)
 {
   Skyline s (sky_);
-  s.buildings_.front ().y_intercept_ = h * sky_;
+  s.buildings_.front ().start_height_ = h * sky_;
   merge (s);
 }
 
@@ -849,7 +846,7 @@ Skyline::is_empty () const
   if (!buildings_.size ())
     return true;
   Building b = buildings_.front ();
-  return b.end_ == infinity_f && b.y_intercept_ == -infinity_f;
+  return b.end_ == infinity_f && b.start_height_ == -infinity_f;
 }
 
 void