polygon intersector: performance improvements and bugfixes

9 files changed, 545 insertions, 115 deletions

diff --git a/lib/gfxpoly/Makefile b/lib/gfxpoly/Makefile
index 35e2039f..068901aa 100644
--- a/lib/gfxpoly/Makefile
+++ b/lib/gfxpoly/Makefile
@@ -31,7 +31,7 @@ renderpoly.o: renderpoly.c wind.h poly.h renderpoly.h
 xrow.o: xrow.c xrow.h ../q.h ../mem.h
 	$(CC) -c xrow.c -o xrow.o
 
-SWF = ../librfxswf.a
+SWF = ../librfxswf.a ../libpdf.a ../libgfx.a -lstdc++ -lfontconfig
 test: ../libbase.a ../libgfx.a test.c $(OBJS) poly.h convert.h
 	$(CC) test.c $(OBJS) $(SWF) ../libbase.a ../libgfx.a -o test -lm -lz -ljpeg -lfreetype
 
diff --git a/lib/gfxpoly/active.c b/lib/gfxpoly/active.c
index 51e07969..b0ef07ca 100644
--- a/lib/gfxpoly/active.c
+++ b/lib/gfxpoly/active.c
@@ -12,27 +12,44 @@ void actlist_destroy(actlist_t*a)
     free(a);
 }
 
-void actlist_verify_and_dump(actlist_t*a, int32_t y)
+void actlist_dump(actlist_t*a, int32_t y)
 {
     segment_t*s = a->list;
-    assert(!s || !s->left);
     double lastx;
+    char bad = 0;
     while(s) {
         if(y) {
             double x = ((double)s->delta.x*(y-s->a.y)/s->delta.y)+s->a.x;
             if(s!=a->list) {
-                if(lastx>x) fprintf(stderr, "?%f<->%f? ", lastx, x);
+                if(lastx>x) 
+                    fprintf(stderr, "?%f<->%f? ", lastx, x);
             }
             lastx = x;
         }
-        assert(!s->left || s->left->right == s);
-        assert(!s->right || s->right->left == s);
         fprintf(stderr, "[%d]", s->nr);
         s = s->right;
         if(s) fprintf(stderr, " ");
         else fprintf(stderr, "\n");
     }
 }
+void actlist_verify(actlist_t*a, int32_t y)
+{
+    segment_t*s = a->list;
+    assert(!s || !s->left);
+    double lastx;
+    while(s) {
+        if(y) {
+            double x = ((double)s->delta.x*(y-s->a.y)/s->delta.y)+s->a.x;
+            if(s!=a->list) {
+                assert(lastx<=x);
+            }
+            lastx = x;
+        }
+        assert(!s->left || s->left->right == s);
+        assert(!s->right || s->right->left == s);
+        s = s->right;
+    }
+}
 
 segment_t* actlist_find(actlist_t*a, point_t p1, point_t p2)
 {
@@ -108,6 +125,18 @@ segment_t* actlist_leftmost(actlist_t*a)
     return a->list;
 }
 
+segment_t* actlist_rightmost(actlist_t*a)
+{
+    /* this is only used in checks, so it doesn't matter that it's slow */
+    segment_t*s = a->list;
+    segment_t*last = 0;
+    while(s) {
+        last = s;
+        s = s->right;
+    }
+    return last;
+}
+
 segment_t* actlist_left(actlist_t*a, segment_t*s)
 {
     return s->left;
diff --git a/lib/gfxpoly/active.h b/lib/gfxpoly/active.h
index 791e6599..f567bea9 100644
--- a/lib/gfxpoly/active.h
+++ b/lib/gfxpoly/active.h
@@ -14,13 +14,15 @@ typedef struct _actlist
 actlist_t* actlist_new();
 void actlist_destroy(actlist_t*a);
 int actlist_size(actlist_t*a);
-void actlist_verify_and_dump(actlist_t*a, int32_t y);
+void actlist_verify(actlist_t*a, int32_t y);
+void actlist_dump(actlist_t*a, int32_t y);
 segment_t* actlist_find(actlist_t*a, point_t p1, point_t p2);  // finds segment immediately to the left of p1 (breaking ties w/ p2)
 void actlist_insert(actlist_t*a, point_t p, segment_t*s);
 void actlist_delete(actlist_t*a, segment_t*s);
 void actlist_swap(actlist_t*a, segment_t*s1, segment_t*s2);
 segment_t* actlist_left(actlist_t*a, segment_t*s);
 segment_t* actlist_leftmost(actlist_t*a);
+segment_t* actlist_rightmost(actlist_t*a);
 segment_t* actlist_right(actlist_t*a, segment_t*s);
 
 #endif
diff --git a/lib/gfxpoly/convert.c b/lib/gfxpoly/convert.c
index 5615612c..f404dfc2 100644
--- a/lib/gfxpoly/convert.c
+++ b/lib/gfxpoly/convert.c
@@ -3,16 +3,16 @@
 #include <assert.h>
 #include <string.h>
 #include "../gfxdevice.h"
+#include "../mem.h"
 #include "poly.h"
 
 static edge_t*edge_new(int x1, int y1, int x2, int y2)
 {
-    edge_t*s = malloc(sizeof(edge_t));
+    edge_t*s = rfx_calloc(sizeof(edge_t));
     s->a.x = x1;
     s->a.y = y1;
     s->b.x = x2;
     s->b.y = y2;
-    s->next = 0;
     return s;
 }
 
@@ -29,7 +29,7 @@ static inline void gfxpoly_add_edge(gfxpoly_t*poly, double _x1, double _y1, doub
     }
 }
 
-gfxpoly_t* gfxpoly_fillToPoly(gfxline_t*line, double gridsize)
+gfxpoly_t* gfxpoly_from_gfxline(gfxline_t*line, double gridsize)
 {
     gfxpoly_t*p = gfxpoly_new(gridsize);
 
diff --git a/lib/gfxpoly/convert.h b/lib/gfxpoly/convert.h
index d1d5344a..93bf980f 100644
--- a/lib/gfxpoly/convert.h
+++ b/lib/gfxpoly/convert.h
@@ -3,7 +3,7 @@
 
 #include "poly.h"
 
-gfxpoly_t* gfxpoly_fillToPoly(gfxline_t*line, double gridsize);
+gfxpoly_t* gfxpoly_from_gfxline(gfxline_t*line, double gridsize);
 gfxpoly_t* gfxpoly_from_file(const char*filename, double gridsize);
 
 #endif //__poly_convert_h__
diff --git a/lib/gfxpoly/poly.c b/lib/gfxpoly/poly.c
index 97289892..bdbddf32 100644
--- a/lib/gfxpoly/poly.c
+++ b/lib/gfxpoly/poly.c
@@ -10,9 +10,15 @@
 #include "xrow.h"
 #include "wind.h"
 
-//#define DEBUG
-//#undef assert
-//#define assert(x)
+#define DEBUG
+#define CHECKS
+
+#ifndef CHECKS
+#ifdef assert
+#undef assert
+#endif
+#define assert(x)
+#endif
 
 char point_equals(const void*o1, const void*o2)
 {
@@ -55,7 +61,7 @@ typedef struct _status {
     edge_t*output;
     xrow_t*xrow;
     windrule_t*windrule;
-#ifdef DEBUG
+#ifdef CHECKS
     dict_t*seen_crossings; //list of crossing we saw so far
     dict_t*intersecting_segs; //list of segments intersecting in this scanline
     dict_t*segs_with_point; //lists of segments that received a point in this scanline
@@ -84,9 +90,13 @@ int compare_events(const void*_a,const void*_b)
     event_t* b = (event_t*)_b;
     int d = b->p.y - a->p.y;
     if(d) return d;
-    /* we should schedule start events after end/intersect.
-       The order of end/intersect doesn't actually matter, however,
-       so this might be doing too much */
+    /* we need to schedule end before intersect (so that a segment about
+       to end has a chance to tear up a few other segs first) and start
+       events after intersect (so that start segments don't position themselves
+       between two segments about to intersect (not a problem as such, but makes
+       things slower)). Horizontal lines come last, because the only purpose
+       they have is to create snapping coordinates for the segments (still)
+       existing in this scanline */
     d = b->type - a->type;
     if(d) return d;
     d = b->p.x - a->p.x;
@@ -109,6 +119,15 @@ void gfxpoly_destroy(gfxpoly_t*poly)
     }
     free(poly);
 }
+int gfxpoly_size(gfxpoly_t*poly)
+{
+    edge_t* s = poly->edges;
+    int t=0;
+    while(s) {
+        s = s->next;t++;
+    }
+    return t;
+}
 char gfxpoly_check(gfxpoly_t*poly)
 {
     edge_t* s = poly->edges;
@@ -177,6 +196,13 @@ void event_dump(event_t*e)
 static inline max32(int32_t v1, int32_t v2) {return v1>v2?v1:v2;}
 static inline min32(int32_t v1, int32_t v2) {return v1<v2?v1:v2;}
 
+void segment_dump(segment_t*s)
+{
+    fprintf(stderr, "(%d,%d)->(%d,%d) ", s->a.x, s->a.y, s->b.x, s->b.y);
+    fprintf(stderr, " dx:%d dy:%d k:%f dx/dy=%f\n", s->delta.x, s->delta.y, s->k, 
+            (double)s->delta.x / s->delta.y);
+}
+
 void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t windstate, int polygon_nr)
 {
     if(y1<y2) {
@@ -204,6 +230,9 @@ void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t winds
     s->left = s->right = 0;
     s->delta.x = x2-x1;
     s->delta.y = y2-y1;
+    s->minx = min32(x1,x2);
+    s->maxx = max32(x1,x2);
+
     s->pos = s->a;
     s->polygon_nr = polygon_nr;
 #define XDEBUG
@@ -253,6 +282,8 @@ void gfxpoly_enqueue(edge_t*list, heap_t*queue, windstate_t initial, int polygon
             continue;
         }
         segment_t*s = segment_new(l->a.x, l->a.y, l->b.x, l->b.y, initial, polygon_nr);
+        if(l->tmp)
+            s->nr = l->tmp;
 #ifdef DEBUG
         fprintf(stderr, "[%d] (%d,%d) -> (%d,%d) %s\n",
                 s->nr, s->a.x, s->a.y, s->b.x, s->b.y,
@@ -284,24 +315,31 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
     /* the code that's required (and the checks you can perform) before
        it can be said with 100% certainty that we indeed have a valid crossing
        amazes me every time. -mk */
-    assert(s1!=s2);
 
-    /* we probably could precompute these */
-    int32_t minx1 = min32(s1->a.x,s1->b.x);
+#ifdef CHECKS
+    assert(s1!=s2);
+    assert(s1->right == s2);
+    assert(s2->left == s1);
     int32_t miny1 = min32(s1->a.y,s1->b.y);
-    int32_t maxx1 = max32(s1->a.x,s1->b.x);
     int32_t maxy1 = max32(s1->a.y,s1->b.y);
-    int32_t minx2 = min32(s2->a.x,s2->b.x);
     int32_t miny2 = min32(s2->a.y,s2->b.y);
-    int32_t maxx2 = max32(s2->a.x,s2->b.x);
     int32_t maxy2 = max32(s2->a.y,s2->b.y);
-
+    int32_t minx1 = min32(s1->a.x,s1->b.x);
+    int32_t minx2 = min32(s2->a.x,s2->b.x);
+    int32_t maxx1 = max32(s1->a.x,s1->b.x);
+    int32_t maxx2 = max32(s2->a.x,s2->b.x);
+    /* check that precomputation is sane */
+    assert(minx1 == s1->minx && minx2 == s2->minx);
+    assert(maxx1 == s1->maxx && maxx2 == s2->maxx);
     /* both segments are active, so this can't happen */
     assert(!(maxy1 <= miny2 || maxy2 <= miny1));
+    /* we know that right now, s2 is to the right of s1, so there's
+       no way the complete bounding box of s1 is to the right of s1 */
+    assert(!(s1->minx > s2->maxx));
+    assert(s1->minx != s2->maxx || (!s1->delta.x && !s2->delta.x));
+#endif
 
-    /* TODO: optimize this. remove y, precompute the two x values */
-    if(maxx1 <= minx2 || maxx2 <= minx1 ||
-       maxy1 <= miny2 || maxy2 <= miny1) {
+    if(s1->maxx <= s2->minx) {
         /* bounding boxes don't intersect */
         return;
     }
@@ -309,9 +347,7 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
     if(dict_contains(&s1->scheduled_crossings, s2)) {
         /* FIXME: this whole segment hashing thing is really slow */
         //fprintf(stderr, "Encountered crossing between [%d] and [%d] twice\n", s1->nr, s2->nr);
-
-        // we already know about this one
-        return;
+        return; // we already know about this one
     }
 
     double adx = s1->delta.x;
@@ -388,12 +424,17 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
     p.y = (int32_t)ceil((+lb*ady -la*bdy) / det);
 
     assert(p.y >= status->y);
-#ifdef DEBUG
+#ifdef CHECKS
+    assert(p.x >= s1->minx && p.x <= s1->maxx);
+    assert(p.x >= s2->minx && p.x <= s2->maxx);
+
     point_t pair;
     pair.x = s1->nr;
     pair.y = s2->nr;
     assert(!dict_contains(status->seen_crossings, &pair));
     dict_put(status->seen_crossings, &pair, 0);
+#endif
+#ifdef DEBUG
     fprintf(stderr, "schedule crossing between [%d] and [%d] at (%d,%d)\n", s1->nr, s2->nr, p.x, p.y);
 #endif
 
@@ -416,7 +457,7 @@ void exchange_two(status_t*status, event_t*e)
     //exchange two segments in list
     segment_t*s1 = e->s1;
     segment_t*s2 = e->s2;
-#ifdef DEBUG
+#ifdef CHECKS
     if(!dict_contains(status->intersecting_segs, s1))
         dict_put(status->intersecting_segs, s1, 0);
     if(!dict_contains(status->intersecting_segs, s2))
@@ -455,19 +496,21 @@ static void insert_point_into_segment(status_t*status, segment_t*s, point_t p)
 {
     assert(s->pos.x != p.x || s->pos.y != p.y);
 
-#ifdef DEBUG
+#ifdef CHECKS
     if(!dict_contains(status->segs_with_point, s))
         dict_put(status->segs_with_point, s, 0);
+    assert(s->fs_out_ok);
 #endif
 
-    assert(s->fs_out_ok);
     if(s->fs_out) {
 #ifdef DEBUG
-        fprintf(stderr, "[%d] receives next point (%d,%d) (drawing)\n", s->nr, p.x, p.y);
+        fprintf(stderr, "[%d] receives next point (%d,%d)->(%d,%d) (drawing)\n", s->nr, 
+                s->pos.x, s->pos.y, p.x, p.y);
 #endif
         // omit horizontal lines
         if(s->pos.y != p.y) {
-            edge_t*e = malloc(sizeof(edge_t));
+            edge_t*e = rfx_calloc(sizeof(edge_t));
+            e->tmp = s->nr;
             e->a = s->pos;
             e->b = p;
             assert(e->a.y != e->b.y);
@@ -482,12 +525,69 @@ static void insert_point_into_segment(status_t*status, segment_t*s, point_t p)
     s->pos = p;
 }
 
-/* possible optimizations:
-   1.) keep two different active lists around, one for negative and one for
-       positive slopes
-   2.) delay starting events until after this function (tricky, because we *do*
-       need the start coordinates)
-*/
+/* by restricting the recalculation of line segments to a range between the lowest
+   and the highest modified segment, we only do about a 33% overprocessing of fill
+   styles. (update: that statistic might be outdated now that xmin/xmax are double) */
+typedef struct _segrange {
+    double xmin;
+    segment_t*segmin;
+    double xmax;
+    segment_t*segmax;
+} segrange_t;
+
+static inline char xpos_eq(segment_t*s1, segment_t*s2, int y)
+{
+    if(XPOS_EQ(s1, s2, y)) {
+        return 1;
+    }
+    return 0;
+}
+
+void segrange_adjust_endpoints(segrange_t*range, int y)
+{
+#ifdef CHECK
+    /* this would mean that the segment left/right of the minimum/maximum
+       intersects the current segment exactly at the scanline, but somehow
+       wasn't found to be passing through the same snapping box */
+    assert(!min || !min->left || !XPOS_EQ(min, min->left, y));
+    assert(!max || !max->right || !XPOS_EQ(max, max->right, y));
+#endif
+
+    segment_t*min = range->segmin;
+    segment_t*max = range->segmax;
+    if(min) while(min->left && xpos_eq(min, min->left, y)) {
+        min = min->left;
+    }
+    if(max) while(max->right && xpos_eq(max, max->right, y)) {
+        max = max->right;
+    }
+    range->segmin = min;
+    range->segmax = max;
+}
+void segrange_test_segment_min(segrange_t*range, segment_t*seg, int y)
+{
+    if(!seg) return;
+    /* we need to calculate the xpos anew (and can't use start coordinate or
+       intersection coordinate), because we need the xpos exactly at the end of
+       this scanline.
+       TODO: might be faster to use XPOS_COMPARE here (see also _max)
+     */
+    double x = XPOS(seg, y);
+    if(!range->segmin || x<range->xmin) {
+        range->segmin = seg;
+        range->xmin = x;
+    }
+}
+void segrange_test_segment_max(segrange_t*range, segment_t*seg, int y)
+{
+    if(!seg) return;
+    double x = XPOS(seg, y);
+    if(!range->segmax || x>range->xmax) {
+        range->segmax = seg;
+        range->xmax = x;
+    }
+}
+
 /*
    SLOPE_POSITIVE:
       \+     \ +
@@ -497,22 +597,26 @@ static void insert_point_into_segment(status_t*status, segment_t*s, point_t p)
        I  \    I \  -------
        +   \   +  \
 */
-static void add_points_to_positively_sloped_segments(status_t*status, int32_t y)
+static void add_points_to_positively_sloped_segments(status_t*status, int32_t y, segrange_t*range)
 {
+    segment_t*first=0, *last = 0;
     int t;
     for(t=0;t<status->xrow->num;t++) {
         box_t box = box_new(status->xrow->x[t], y);
         segment_t*seg = actlist_find(status->actlist, box.left2, box.left2);
         seg = actlist_right(status->actlist, seg);
+
         while(seg) {
             if(seg->a.y == y) {
-                // this segment just started, ignore it
+                // this segment started in this scanline, ignore it
+                seg->changed = 1;last = seg;if(!first) {first=seg;}
             } else if(seg->delta.x < 0) {
                 // ignore segment w/ negative slope
             } else {
                 double d1 = LINE_EQ(box.right1, seg);
                 double d2 = LINE_EQ(box.right2, seg);
                 if(d1>=0 || d2>=0) {
+                    seg->changed = 1;last = seg;if(!first) {first=seg;}
                     insert_point_into_segment(status, seg, box.right2);
                 } else {
                     break;
@@ -521,6 +625,8 @@ static void add_points_to_positively_sloped_segments(status_t*status, int32_t y)
             seg = actlist_right(status->actlist, seg);
         }
     }
+    segrange_test_segment_min(range, first, y);
+    segrange_test_segment_max(range, last, y);
 }
 /* SLOPE_NEGATIVE:
    |   +   /|  +  /    /
@@ -530,21 +636,27 @@ static void add_points_to_positively_sloped_segments(status_t*status, int32_t y)
    |   I    | /I   /
    |  /+    |/ +  /
 */
-static void add_points_to_negatively_sloped_segments(status_t*status, int32_t y)
+static void add_points_to_negatively_sloped_segments(status_t*status, int32_t y, segrange_t*range)
 {
+    segment_t*first=0, *last = 0;
+    int firstx,lastx;
     int t;
     for(t=status->xrow->num-1;t>=0;t--) {
         box_t box = box_new(status->xrow->x[t], y);
         segment_t*seg = actlist_find(status->actlist, box.right2, box.right2);
+        
         while(seg) {
             if(seg->a.y == y) {
-                // this segment just started, ignore it
+                // this segment started in this scanline, ignore it
+                seg->changed = 1;last = seg;if(!first) {first=seg;}
+                if(!first) {first=seg; firstx = seg->a.x;}
             } else if(seg->delta.x >= 0) {
                 // ignore segment w/ positive slope
             } else {
                 double d1 = LINE_EQ(box.left1, seg);
                 double d2 = LINE_EQ(box.left2, seg);
                 if(d1<0 || d2<0) {
+                    seg->changed = 1;last = seg;if(!first) {first=seg;}
                     insert_point_into_segment(status, seg, box.right2);
                 } else {
                     break;
@@ -553,30 +665,63 @@ static void add_points_to_negatively_sloped_segments(status_t*status, int32_t y)
             seg = actlist_left(status->actlist, seg);
         }
     }
+    segrange_test_segment_min(range, last, y);
+    segrange_test_segment_max(range, first, y);
 }
 
-static void recalculate_windings(status_t*status)
+static void recalculate_windings(status_t*status, segrange_t*range)
 {
-    /* TODO: we could use some clever second linked list structure so that we
-             only need to process points we know we marked */
+    segrange_adjust_endpoints(range, status->y);
 
-    segment_t*s = actlist_leftmost(status->actlist);
+    segment_t*s = range->segmin;
+    segment_t*end = range->segmax;
     segment_t*last = 0;
-    while(s) {
-        windstate_t wind = last?last->wind:status->windrule->start(status->num_polygons);
-        s->wind = status->windrule->add(wind, s->fs, s->dir, s->polygon_nr);
-        s->fs_out = status->windrule->diff(&wind, &s->wind);
-        s->fs_out_ok = 1;
+
+#ifdef CHECKS
+    /* test sanity: check that we don't have changed segments
+       outside of the given range */
+    s = actlist_leftmost(status->actlist);
+    while(s && s!=range->segmin) {
+        assert(!s->changed);
+        s = actlist_right(status->actlist, s);
+    }
+    s = actlist_rightmost(status->actlist);
+    while(s && s!=range->segmax) {
+        assert(!s->changed);
+        s = actlist_left(status->actlist, s);
+    }
+    /* in check mode, go through the whole interval so we can test
+       that all polygons where the fillstyle changed also have seg->changed=1 */
+    s = actlist_leftmost(status->actlist);
+    end = 0;
+#endif
+
+    if(end)
+        end = actlist_right(status->actlist, end);
+    while(s!=end) {
+#ifndef CHECK
+        if(s->changed) 
+#endif
+        {
+            segment_t* left = actlist_left(status->actlist, s);
+            windstate_t wind = left?left->wind:status->windrule->start(status->num_polygons);
+            s->wind = status->windrule->add(wind, s->fs, s->dir, s->polygon_nr);
+            fillstyle_t*fs_old = s->fs_out;
+            s->fs_out = status->windrule->diff(&wind, &s->wind);
+
+            assert(!(!s->changed && fs_old!=s->fs_out));
+            s->changed = 0;
+
+            s->fs_out_ok = 1;
 #ifdef DEBUG
-        fprintf(stderr, "[%d] %s/%d/%s/%s ", s->nr, s->dir==DIR_UP?"up":"down", s->wind.wind_nr, s->wind.is_filled?"fill":"nofill", s->fs_out?"draw":"omit");
+            fprintf(stderr, "[%d] %s/%d/%s/%s ", s->nr, s->dir==DIR_UP?"up":"down", s->wind.wind_nr, s->wind.is_filled?"fill":"nofill", s->fs_out?"draw":"omit");
 #endif
-        last = s;
+        }
         s = actlist_right(status->actlist, s);
     }
 #ifdef DEBUG
     fprintf(stderr, "\n");
 #endif
-
 }
 
 /* we need to handle horizontal lines in order to add points to segments
@@ -596,25 +741,19 @@ void intersect_with_horizontal(status_t*status, segment_t*h)
 
     while(s!=right) {
         assert(s);
-        /*
-           x1 + ((x2-x1)*(y-y1)) / dy =
-           (x1*(y2-y) + x2*(y-y1)) / dy
-        */
-        point_t p;
-        p.y = status->y;
-        p.x = XPOS(s, p.y);
+        int x = XPOS_INT(s, status->y);
 #ifdef DEBUG
         fprintf(stderr, "...into [%d] (%d,%d) -> (%d,%d) at (%d,%d)\n", s->nr,
                 s->a.x, s->a.y,
                 s->b.x, s->b.y,
-                p.x, p.y
+                x, status->y
                 );
 #endif
-        assert(p.x >= h->a.x);
-        assert(p.x <= h->b.x);
-        assert(s->delta.x > 0 && p.x >= s->a.x || s->delta.x <= 0 && p.x <= s->a.x);
-        assert(s->delta.x > 0 && p.x <= s->b.x || s->delta.x <= 0 && p.x >= s->b.x);
-        xrow_add(status->xrow, p.x);
+        assert(x >= h->a.x);
+        assert(x <= h->b.x);
+        assert(s->delta.x > 0 && x >= s->a.x || s->delta.x <= 0 && x <= s->a.x);
+        assert(s->delta.x > 0 && x <= s->b.x || s->delta.x <= 0 && x >= s->b.x);
+        xrow_add(status->xrow, x);
 
         s = actlist_right(status->actlist, s);
     }
@@ -628,6 +767,7 @@ void event_apply(status_t*status, event_t*e)
             event_dump(e);
 #endif
             intersect_with_horizontal(status, e->s1);
+            segment_destroy(e->s1);e->s1=0;
             break;
         }
         case EVENT_END: {
@@ -635,6 +775,8 @@ void event_apply(status_t*status, event_t*e)
             segment_t*s = e->s1;
 #ifdef DEBUG
             event_dump(e);
+#endif
+#ifdef CHECKS
             dict_del(status->intersecting_segs, s);
             dict_del(status->segs_with_point, s);
             assert(!dict_contains(status->intersecting_segs, s));
@@ -679,7 +821,7 @@ void event_apply(status_t*status, event_t*e)
                 char del1 = dict_del(&e->s1->scheduled_crossings, e->s2);
                 char del2 = dict_del(&e->s2->scheduled_crossings, e->s1);
                 assert(del1 && del2);
-#ifdef DEBUG
+#ifdef CHECKS
                 point_t pair;
                 pair.x = e->s1->nr;
                 pair.y = e->s2->nr;
@@ -691,7 +833,7 @@ void event_apply(status_t*status, event_t*e)
     }
 }
 
-#ifdef DEBUG
+#ifdef CHECKS
 void check_status(status_t*status)
 {
     DICT_ITERATE_KEY(status->intersecting_segs, segment_t*, s) {
@@ -732,7 +874,12 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
         int x = 0;
         char fill = 0;
 #ifdef DEBUG
-        actlist_verify_and_dump(actlist, y-1);
+        fprintf(stderr, "----------------------------------- %d\n", y);
+        actlist_dump(actlist, y-1);
+#endif
+#ifdef CHECKS
+        /* FIXME: this actually fails sometimes */
+        actlist_verify(actlist, y-1);
 #endif
         do {
             if(fill && x != e->p.x) {
@@ -790,14 +937,14 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
             if(e->type == EVENT_END)
                 segment_destroy(s);
 
+            free(e);
             e = heap_chopmax(queue);
         } while(e && y == e->p.y);
 
-        if(fill) {
-            fprintf(stderr, "Error: polygon is bleeding\n");
-            exit(0);
-        }
+        assert(!fill); // check that polygon is not bleeding
     }
+    actlist_destroy(actlist);
+    heap_destroy(queue);
 }
 
 gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
@@ -812,7 +959,7 @@ gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
     status.queue = queue;
     status.windrule = windrule;
     status.actlist = actlist_new();
-#ifdef DEBUG
+#ifdef CHECKS
     status.seen_crossings = dict_new2(&point_type);
 #endif
 
@@ -821,11 +968,17 @@ gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
     event_t*e = heap_chopmax(queue);
     while(e) {
         status.y = e->p.y;
-#ifdef DEBUG
+#ifdef CHECKS
         status.intersecting_segs = dict_new2(&ptr_type);
         status.segs_with_point = dict_new2(&ptr_type);
+#endif
+
+#ifdef DEBUG
         fprintf(stderr, "----------------------------------- %d\n", status.y);
-        actlist_verify_and_dump(status.actlist, status.y-1);
+        actlist_dump(status.actlist, status.y-1);
+#endif
+#ifdef CHECKS
+        actlist_verify(status.actlist, status.y-1);
 #endif
         xrow_reset(status.xrow);
         do {
@@ -836,16 +989,18 @@ gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
         } while(e && status.y == e->p.y);
 
         xrow_sort(status.xrow);
-        add_points_to_positively_sloped_segments(&status, status.y);
-        add_points_to_negatively_sloped_segments(&status, status.y);
-        recalculate_windings(&status);
-#ifdef DEBUG
+        segrange_t range;
+        memset(&range, 0, sizeof(range));
+        add_points_to_positively_sloped_segments(&status, status.y, &range);
+        add_points_to_negatively_sloped_segments(&status, status.y, &range);
+        recalculate_windings(&status, &range);
+#ifdef CHECKS
         check_status(&status);
         dict_destroy(status.intersecting_segs);
         dict_destroy(status.segs_with_point);
 #endif
     }
-#ifdef DEBUG
+#ifdef CHECKS
     dict_destroy(status.seen_crossings);
 #endif
     actlist_destroy(status.actlist);
diff --git a/lib/gfxpoly/poly.h b/lib/gfxpoly/poly.h
index 54d54b11..2a76a4c3 100644
--- a/lib/gfxpoly/poly.h
+++ b/lib/gfxpoly/poly.h
@@ -5,7 +5,7 @@
 #include "../q.h"
 
 typedef enum {DIR_UP, DIR_DOWN} segment_dir_t;
-typedef enum {EVENT_CROSS, EVENT_END, EVENT_START, EVENT_HORIZONTAL} eventtype_t;
+typedef enum {EVENT_CROSS, EVENT_END, EVENT_CORNER, EVENT_START, EVENT_HORIZONTAL} eventtype_t;
 typedef enum {SLOPE_POSITIVE, SLOPE_NEGATIVE} slope_t;
 
 typedef struct _point {
@@ -21,6 +21,7 @@ typedef struct _edge {
     point_t a;
     point_t b;
     fillstyle_t*style;
+    int tmp;
     struct _edge *next;
 } edge_t;
 
@@ -43,6 +44,7 @@ typedef struct _segment {
     point_t b;
     point_t delta;
     double k; //k = a.x*b.y-a.y*b.x = delta.y*a.x - delta.x*a.y (=0 for points on the segment)
+    int minx, maxx;
     
     segment_dir_t dir;
     fillstyle_t*fs;
@@ -55,14 +57,31 @@ typedef struct _segment {
 
     struct _segment*left;
     struct _segment*right;
-    
+    char changed;
+
     point_t pos;
 
     dict_t scheduled_crossings;
 } segment_t;
 
 #define LINE_EQ(p,s) ((double)(s)->delta.y*(p).x - (double)(s)->delta.x*(p).y - (s)->k)
-#define XPOS(s,ypos) ((s)->a.x + ceil(((s)->delta.x * (double)((ypos) - (s)->a.y)) / (s)->delta.y))
+
+/* x1 + ((x2-x1)*(y-y1)) / dy = 
+   (x1*(y2-y1) + (x2-x1)*(y-y1)) / dy =
+   (x1*(y2-y)  +  x2    *(y-y1)) / dy =
+   (x1*y2 - x2*y1 + x2*y - y*x1) / dy =
+   (k + x2*y - x1*y) / dy
+   (k + dx*y) / dy
+*/
+//#define XPOS(s,ypos) ((s)->a.x + ((s)->delta.x * (double)((ypos) - (s)->a.y)) / (s)->delta.y)
+#define XPOS(s,ypos) (((s)->k + (double)(s)->delta.x*ypos) / (s)->delta.y)
+
+#define XPOS_INT(s,ypos) ((int)ceil(XPOS((s),ypos)))
+#define XDIFF(s1,s2,ypos) (((s1)->k + (double)(s1)->delta.x*ypos)*(s2)->delta.y - \
+                           ((s2)->k + (double)(s1)->delta.x*ypos)*(s1)->delta.y)
+
+// rewrite as XDIFF==0?
+#define XPOS_EQ(s1,s2,ypos) (XPOS((s1),(ypos))==XPOS((s2),(ypos)))
 
 typedef struct _gfxpoly {
     double gridsize;
@@ -71,6 +90,7 @@ typedef struct _gfxpoly {
 
 gfxpoly_t* gfxpoly_new(double gridsize);
 char gfxpoly_check(gfxpoly_t*poly);
+int gfxpoly_size(gfxpoly_t*poly);
 void gfxpoly_dump(gfxpoly_t*poly);
 gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule);
 
diff --git a/lib/gfxpoly/renderpoly.c b/lib/gfxpoly/renderpoly.c
index 2373a649..06440fa1 100644
--- a/lib/gfxpoly/renderpoly.c
+++ b/lib/gfxpoly/renderpoly.c
@@ -253,8 +253,6 @@ intbbox_t intbbox_from_polygon(gfxpoly_t*polygon, double zoom)
 
     b.width = b.xmax - b.xmin;
     b.height = b.ymax - b.ymin;
-    printf("%dx%d\n", b.width, b.height);
-
     return b;
 }
 
diff --git a/lib/gfxpoly/test.c b/lib/gfxpoly/test.c
index 6e698ca2..aff9208e 100644
--- a/lib/gfxpoly/test.c
+++ b/lib/gfxpoly/test.c
@@ -26,6 +26,118 @@ gfxline_t*mkstar(int x1, int y1, int x2, int y2)
     return line;
 }
 
+gfxline_t* mkrandomshape(int range, int n)
+{
+    int i;
+    gfxline_t* line = malloc(sizeof(gfxline_t)*n*2);
+    for(i=0;i<n;i++) {
+        line[i].type = i?gfx_lineTo:gfx_moveTo;
+        line[i].x = lrand48()%range - range/2;
+        line[i].y = lrand48()%range - range/2;
+        line[i].next = &line[i+1];
+        line[n*2-i-1].type = gfx_lineTo;
+        line[n*2-i-1].x = line[i].x;
+        line[n*2-i-1].y = line[i].y;
+        line[n*2-i-1].next = &line[n*2-i];
+    }
+    line[n*2-1].next = 0;
+    line[n-1].x = line[0].x;
+    line[n-1].y = line[0].y;
+    line[n-1].next = 0;
+}
+
+gfxline_t* mkchessboard()
+{
+    gfxline_t*b = 0;
+    int x,y;
+    unsigned int r = 0;
+    int spacing = 20;
+
+    //int num_caros = 40;
+    //int l = 5;
+    //char do_centerpiece=1;
+
+    int num_caros = 4;
+    int l=1;
+    char do_centerpiece=0;
+
+    for(x=-l;x<=l;x++) 
+    for(y=-l;y<=l;y++) {
+        /* pseudo random */ 
+        r = crc32_add_byte(r, x);r = crc32_add_byte(r, y);
+        if(r&1) {
+            gfxline_t*box;
+            if(r&2) {
+                box = gfxline_makerectangle(x*spacing,y*spacing,(x+1)*spacing,(y+1)*spacing);
+            } else {
+                box = gfxline_makerectangle((x+1)*spacing,y*spacing,x*spacing,(y+1)*spacing);
+            }
+            b = gfxline_append(b, box);
+        }
+    }
+
+    int t;
+    for(t=0;t<num_caros;t++) {
+        r = crc32_add_byte(r, t);
+        int x=(r%10-5)*spacing;
+        int y=((r>>4)%10-5)*spacing;
+        int sizex = ((r>>8)%4)*spacing;
+        int sizey = sizex;
+        if(r&65536)
+            sizex = -sizex;
+        gfxline_t*l = malloc(sizeof(gfxline_t)*5);
+        l[0].type = gfx_moveTo;l[0].next = &l[1];
+        l[1].type = gfx_lineTo;l[1].next = &l[2];
+        l[2].type = gfx_lineTo;l[2].next = &l[3];
+        l[3].type = gfx_lineTo;l[3].next = &l[4];
+        l[4].type = gfx_lineTo;l[4].next = 0;
+        l[0].x = x;
+        l[0].y = y-sizey;
+        l[1].x = x+sizex;
+        l[1].y = y;
+        l[2].x = x;
+        l[2].y = y+sizey;
+        l[3].x = x-sizex;
+        l[3].y = y;
+        l[4].x = x;
+        l[4].y = y-sizey;
+        gfxline_append(b, l);
+    }
+    if(do_centerpiece)
+    for(t=0;t<5;t++) {
+        gfxline_t*l = gfxline_makerectangle(-9*spacing,-10,9*spacing,10);
+        gfxmatrix_t matrix;
+        memset(&matrix, 0, sizeof(gfxmatrix_t));
+        double ua=t*0.43;
+        matrix.m00=cos(ua);matrix.m10=sin(ua);
+        matrix.m01=-sin(ua);matrix.m11=cos(ua);
+        gfxline_transform(l, &matrix);
+        gfxline_append(b, l);
+    }
+    return b;
+}
+
+int test0()
+{
+    gfxline_t* b = mkchessboard();
+
+    gfxmatrix_t m;
+    memset(&m, 0, sizeof(gfxmatrix_t));
+    int t = 28;
+    m.m00 = cos(t*M_PI/180.0);
+    m.m01 = sin(t*M_PI/180.0);
+    m.m10 = -sin(t*M_PI/180.0);
+    m.m11 = cos(t*M_PI/180.0);
+    m.tx = 400*1.41/2;
+    m.ty = 400*1.41/2;
+    gfxline_transform(b, &m);
+
+    gfxpoly_t*poly = gfxpoly_from_gfxline(b, 0.05);
+    gfxpoly_t*poly2 = gfxpoly_process(poly, &windrule_evenodd);
+    gfxpoly_destroy(poly2);
+    gfxpoly_destroy(poly);
+}
+
 int test1()
 {
     gfxline_t*box1 = gfxline_makerectangle(50,50,150,150);
@@ -46,14 +158,17 @@ int test1()
     matrix.m01=-sin(ua);matrix.m11=cos(ua);
 
     //gfxline_transform(b, &matrix);
-    gfxpoly_t*poly = gfxpoly_fillToPoly(b, 0.05);
+
+    gfxpoly_t*poly = gfxpoly_from_gfxline(b, 0.05);
     gfxline_free(box1);
     gfxline_free(box2);
     gfxline_free(box3);
     gfxline_free(star);
 
     gfxpoly_dump(poly);
-    gfxpoly_process(poly, &windrule_evenodd);
+    gfxpoly_t*poly2 = gfxpoly_process(poly, &windrule_evenodd);
+    gfxpoly_destroy(poly2);
+    gfxpoly_destroy(poly);
 }
 
 int test_square(int width, int height, int num, double gridsize, char bitmaptest)
@@ -70,7 +185,7 @@ int test_square(int width, int height, int num, double gridsize, char bitmaptest
     line[num-1].y = line[0].y;
     line[num-1].next = 0;
     
-    gfxpoly_t*poly = gfxpoly_fillToPoly(line, gridsize);
+    gfxpoly_t*poly = gfxpoly_from_gfxline(line, gridsize);
     gfxline_free(line);
 
     windrule_t*rule = &windrule_circular;
@@ -109,23 +224,10 @@ void test3()
 #define N 100
 #define RANGE 400
 
-    int i;
-    gfxline_t* line = malloc(sizeof(gfxline_t)*N*2);
-    for(i=0;i<N;i++) {
-        line[i].type = i?gfx_lineTo:gfx_moveTo;
-        line[i].x = lrand48()%RANGE - RANGE/2;
-        line[i].y = lrand48()%RANGE - RANGE/2;
-        line[i].next = &line[i+1];
-        line[N*2-i-1].type = gfx_lineTo;
-        line[N*2-i-1].x = line[i].x;
-        line[N*2-i-1].y = line[i].y;
-        line[N*2-i-1].next = &line[N*2-i];
-    }
-    line[N*2-1].next = 0;
-
-    line[N-1].x = line[0].x;
-    line[N-1].y = line[0].y;
-    line[N-1].next = 0;
+    //gfxline_t*line = mkrandomshape(RANGE, N);
+    //windrule_t*rule = &windrule_circular;
+    gfxline_t*line = mkchessboard();
+    windrule_t*rule = &windrule_evenodd;
 
     gfxmatrix_t m;
     memset(&m, 0, sizeof(m));
@@ -149,11 +251,13 @@ void test3()
         m.m11 = cos(t*M_PI/180.0);
         m.tx = RANGE*1.41/2;
         m.ty = RANGE*1.41/2;
+        printf("%d\n", t);
+
         gfxline_t*l = gfxline_clone(line);
         gfxline_transform(l, &m);
         
-        gfxpoly_t*poly = gfxpoly_fillToPoly(l, 0.05);
-        gfxpoly_t*poly2 = gfxpoly_process(poly, &windrule_circular);
+        gfxpoly_t*poly = gfxpoly_from_gfxline(l, 0.05);
+        gfxpoly_t*poly2 = gfxpoly_process(poly, rule);
 
         tag = swf_InsertTag(tag, ST_DEFINESHAPE);
         SHAPE* s;
@@ -259,7 +363,129 @@ void test4()
     }
 }
 
+#include "../gfxdevice.h"
+#include "../pdf/pdf.h"
+
+void extract_polygons_fill(gfxdevice_t*dev, gfxline_t*line, gfxcolor_t*color) 
+{
+    gfxpoly_t*poly = gfxpoly_from_gfxline(line, 0.05);
+    printf("%d segments\n", gfxpoly_size(poly));
+
+    if(!gfxpoly_check(poly)) {
+        gfxpoly_destroy(poly);
+        printf("bad polygon\n");
+        return;
+    }
+
+    windrule_t*rule = &windrule_evenodd;
+    gfxpoly_t*poly2 = gfxpoly_process(poly, rule);
+        
+    double zoom = 1.0;
+    intbbox_t bbox = intbbox_from_polygon(poly, zoom);
+    unsigned char*bitmap1 = render_polygon(poly, &bbox, zoom, rule);
+    unsigned char*bitmap2 = render_polygon(poly2, &bbox, zoom, &windrule_evenodd);
+    if(!bitmap_ok(&bbox, bitmap1)) {
+        printf("bad polygon or error in renderer\n");
+        return;
+    }
+    if(!bitmap_ok(&bbox, bitmap2)) {
+        save_two_bitmaps(&bbox, bitmap1, bitmap2, "error.png");
+        assert(!"error in bitmap");
+    }
+    if(!compare_bitmaps(&bbox, bitmap1, bitmap2)) {
+        save_two_bitmaps(&bbox, bitmap1, bitmap2, "error.png");
+        assert(!"bitmaps don't match");
+    }
+
+    gfxpoly_destroy(poly);
+    gfxpoly_destroy(poly2);
+}
+int extract_polygons_setparameter(gfxdevice_t*dev, const char*key, const char*value) {
+    return 0;
+}
+void extract_polygons_startclip(gfxdevice_t*dev, gfxline_t*line) 
+{
+    extract_polygons_fill(dev, line, 0);
+}
+void extract_polygons_fillbitmap(gfxdevice_t*dev, gfxline_t*line, gfximage_t*img, gfxmatrix_t*imgcoord2devcoord, gfxcxform_t*cxform)
+{
+    extract_polygons_fill(dev, line, 0);
+}
+void extract_polygons_fillgradient(gfxdevice_t*dev, gfxline_t*line, gfxgradient_t*gradient, gfxgradienttype_t type, gfxmatrix_t*gradcoord2devcoord)
+{
+    extract_polygons_fill(dev, line, 0);
+}
+void extract_polygons_drawlink(gfxdevice_t*dev, gfxline_t*line, const char*action)
+{
+    extract_polygons_fill(dev, line, 0);
+}
+void extract_polygons_addfont(gfxdevice_t*dev, gfxfont_t*font)
+{
+    int t;
+    for(t=0;t<font->num_glyphs;t++) {
+        //extract_polygons_fill(dev, font->glyphs[t].line, 0);
+    }
+}
+void extract_polygons_endclip(gfxdevice_t*dev)
+{
+}
+void extract_polygons_stroke(gfxdevice_t*dev, gfxline_t*line, gfxcoord_t width, gfxcolor_t*color, gfx_capType cap_style, gfx_joinType joint_style, gfxcoord_t miterLimit)
+{
+}
+void extract_polygons_drawchar(gfxdevice_t*dev, gfxfont_t*font, int glyph, gfxcolor_t*color, gfxmatrix_t*matrix)
+{
+}
+    
+gfxdevice_t extract_polygons = 
+{
+name: "extract polygons",
+setparameter:extract_polygons_setparameter,
+startclip: extract_polygons_startclip,
+endclip: extract_polygons_endclip,
+stroke: extract_polygons_stroke,
+fill: extract_polygons_fill,
+fillbitmap: extract_polygons_fillbitmap,
+fillgradient: extract_polygons_fillgradient,
+addfont: extract_polygons_addfont,
+drawchar: extract_polygons_drawchar,
+drawlink: extract_polygons_drawlink,
+startpage: 0,
+endpage: 0,
+geterror: 0,
+finish: 0,
+internal: 0
+};
+
+void test5()
+{
+    char*dir = "pdfs";
+    DIR*_dir = opendir(dir);
+    if(!_dir) return;
+    struct dirent*file;
+    while(1) {
+        file = readdir(_dir);
+        if (!file) 
+            break;
+        if(!strstr(file->d_name, ".pdf")) 
+            continue;
+        char* filename = allocprintf("%s/%s", dir, file->d_name);
+
+        gfxsource_t*driver = gfxsource_pdf_create();
+        gfxdocument_t*doc = driver->open(driver, filename);
+        gfxdevice_t*out = &extract_polygons;
+        int t;
+        for(t=1;t<=doc->num_pages;t++) {
+            printf("%s (page %d)\n", filename, t);
+            gfxpage_t* page = doc->getpage(doc, t);
+            page->render(page, out);
+            page->destroy(page);
+            break;
+        }
+        free(filename);
+    }
+}
+
 int main()
 {
-    test3();
+    test0();
 }