X-Git-Url: http://git.asbjorn.biz/?p=swftools.git;a=blobdiff_plain;f=lib%2Fgfxpoly%2Fpoly.c;h=7036a61b59ad0dd5192d1f81c88dc48ae7979232;hp=bdbddf323197e587fb8cdc36f167e7c58114de46;hb=f7e9e8a9616f1ecb26776369fda6807cf8821a68;hpb=ae7c92fe5721f97e786a8bbe9153eadbf292460d

diff --git a/lib/gfxpoly/poly.c b/lib/gfxpoly/poly.c
index bdbddf3..7036a61 100644
--- a/lib/gfxpoly/poly.c
+++ b/lib/gfxpoly/poly.c
@@ -1,37 +1,55 @@
 #include <stdlib.h>
-#include <assert.h>
 #include <memory.h>
 #include <math.h>
 #include "../mem.h"
 #include "../types.h"
 #include "../q.h"
+#include "../MD5.h"
 #include "poly.h"
 #include "active.h"
 #include "xrow.h"
 #include "wind.h"
 
-#define DEBUG
-#define CHECKS
+static gfxpoly_t*current_polygon = 0;
+void gfxpoly_fail(char*expr, char*file, int line, const char*function)
+{
+    if(!current_polygon) {fprintf(stderr, "error outside polygon\n");exit(1);}
 
-#ifndef CHECKS
-#ifdef assert
-#undef assert
-#endif
-#define assert(x)
-#endif
+    void*md5 = init_md5();
+    
+    edge_t* s = current_polygon->edges;
+    while(s) {
+	update_md5(md5, (unsigned char*)&s->a.x, sizeof(s->a.x));
+	update_md5(md5, (unsigned char*)&s->a.y, sizeof(s->a.y));
+	update_md5(md5, (unsigned char*)&s->b.x, sizeof(s->b.x));
+	update_md5(md5, (unsigned char*)&s->b.y, sizeof(s->b.y));
+	s = s->next;
+    }
+    unsigned char h[16];
+    char filename[32+4+1];
+    finish_md5(md5, h);
+    sprintf(filename, "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x.ps",
+	    h[0],h[1],h[2],h[3],h[4],h[5],h[6],h[7],h[8],h[9],h[10],h[11],h[12],h[13],h[14],h[15]);
 
-char point_equals(const void*o1, const void*o2)
+    fprintf(stderr, "assert(%s) failed in %s in line %d: %s\n", expr, file, line, function);
+    fprintf(stderr, "I'm saving a debug file \"%s\" to the current directory.\n", filename);
+
+    gfxpoly_save(current_polygon, filename);
+    exit(1);
+}
+
+static char point_equals(const void*o1, const void*o2)
 {
     const point_t*p1 = o1;
     const point_t*p2 = o2;
     return p1->x == p2->x && p1->y == p2->y;
 }
-unsigned int point_hash(const void*o)
+static unsigned int point_hash(const void*o)
 {
     const point_t*p = o;
     return p->x^p->y;
 }
-void* point_dup(const void*o)
+static void* point_dup(const void*o)
 {
     const point_t*p = o;
     point_t*n = malloc(sizeof(point_t));
@@ -39,14 +57,14 @@ void* point_dup(const void*o)
     n->y = p->y;
     return n;
 }
-void point_free(void*o)
+static void point_free(void*o)
 {
     point_t*p = o;
     p->x = 0;
     p->y = 0;
     free(p);
 }
-type_t point_type = {
+static type_t point_type = {
     equals: point_equals,
     hash: point_hash,
     dup: point_dup,
@@ -54,13 +72,14 @@ type_t point_type = {
 };
 
 typedef struct _status {
-    int y;
-    int num_polygons;
+    int32_t y;
     actlist_t*actlist;
     heap_t*queue;
     edge_t*output;
     xrow_t*xrow;
     windrule_t*windrule;
+    windcontext_t*context;
+    segment_t*ending_segments;
 #ifdef CHECKS
     dict_t*seen_crossings; //list of crossing we saw so far
     dict_t*intersecting_segs; //list of segments intersecting in this scanline
@@ -68,35 +87,34 @@ typedef struct _status {
 #endif
 } status_t;
 
-int compare_events_simple(const void*_a,const void*_b)
+/* compare_events_simple differs from compare_events in that it schedules
+   events from left to right regardless of type. It's only used in horizontal
+   processing, in order to get an x-wise sorting of the current scanline */
+static int compare_events_simple(const void*_a,const void*_b)
 {
     event_t* a = (event_t*)_a;
     event_t* b = (event_t*)_b;
-    if(a->p.y < b->p.y) {
-        return 1;
-    } else if(a->p.y > b->p.y) {
-        return -1;
-    } else if(a->p.x < b->p.x) {
-        return 1;
-    } else if(a->p.x > b->p.x) {
-        return -1;
-    } else
-        return 0;
+    int d = b->p.y - a->p.y;
+    if(d) return d;
+    d = b->p.x - a->p.x;
+    if(d) return d;
+    return 0;
 }
 
-int compare_events(const void*_a,const void*_b)
+static int compare_events(const void*_a,const void*_b)
 {
     event_t* a = (event_t*)_a;
     event_t* b = (event_t*)_b;
     int d = b->p.y - a->p.y;
     if(d) return d;
-    /* we need to schedule end before intersect (so that a segment about
+    /* we need to schedule end after 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
+       events after end (in order not to confuse the intersection check, which
+       assumes there's an actual y overlap between active segments)). 
+       Horizontal lines come last, because the only purpose
        they have is to create snapping coordinates for the segments (still)
-       existing in this scanline */
+       existing in this scanline.
+    */
     d = b->type - a->type;
     if(d) return d;
     d = b->p.x - a->p.x;
@@ -128,6 +146,7 @@ int gfxpoly_size(gfxpoly_t*poly)
     }
     return t;
 }
+
 char gfxpoly_check(gfxpoly_t*poly)
 {
     edge_t* s = poly->edges;
@@ -155,9 +174,11 @@ char gfxpoly_check(gfxpoly_t*poly)
         int count = (ptroff_t)c;
         if(count&1) {
             fprintf(stderr, "Point (%f,%f) occurs %d times\n", p->x*poly->gridsize, p->y*poly->gridsize, count);
+            dict_destroy(d);
             return 0;
         }
     }
+    dict_destroy(d);
     return 1;
 }
 
@@ -171,6 +192,23 @@ void gfxpoly_dump(gfxpoly_t*poly)
     }
 }
 
+gfxpoly_t* gfxpoly_save(gfxpoly_t*poly, const char*filename)
+{
+    FILE*fi = fopen(filename, "wb");
+    fprintf(fi, "%% gridsize %f\n", poly->gridsize);
+    fprintf(fi, "%% begin\n");
+    edge_t* s = poly->edges;
+    while(s) {
+        fprintf(fi, "%g setgray\n", s->b.y < s->a.y ? 0.7 : 0);
+        fprintf(fi, "%d %d moveto\n", s->a.x, s->a.y);
+        fprintf(fi, "%d %d lineto\n", s->b.x, s->b.y);
+        fprintf(fi, "stroke\n");
+        s = s->next;
+    }
+    fprintf(fi, "showpage\n");
+    fclose(fi);
+}
+
 inline static event_t event_new()
 {
     event_t e;
@@ -178,7 +216,7 @@ inline static event_t event_new()
     return e;
 }
 
-void event_dump(event_t*e)
+static void event_dump(event_t*e)
 {
     if(e->type == EVENT_HORIZONTAL) {
         fprintf(stderr, "Horizontal [%d] (%d,%d) -> (%d,%d)\n", e->s1->nr, e->s1->a.x, e->s1->a.y, e->s1->b.x, e->s1->b.y);
@@ -188,6 +226,8 @@ void event_dump(event_t*e)
         fprintf(stderr, "event: segment [%d] ends at (%d,%d)\n", e->s1->nr, e->p.x, e->p.y);
     } else if(e->type == EVENT_CROSS) {
         fprintf(stderr, "event: segment [%d] and [%d] intersect at (%d,%d)\n", e->s1->nr, e->s2->nr, e->p.x, e->p.y);
+    } else if(e->type == EVENT_CORNER) {
+        fprintf(stderr, "event: segment [%d] ends, segment [%d] starts, at (%d,%d)\n", e->s1->nr, e->s2->nr, e->p.x, e->p.y);
     } else {
         assert(0);
     }
@@ -196,20 +236,20 @@ 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)
+static 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, 
+    fprintf(stderr, "[%d] (%d,%d)->(%d,%d) ", s->nr, 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)
+static void segment_init(segment_t*s, int32_t x1, int32_t y1, int32_t x2, int32_t y2, int polygon_nr)
 {
     if(y1<y2) {
         s->dir = DIR_DOWN;
     } else if(y1>y2) {
-        int x = x1;x1=x2;x2=x;
-        int y = y1;y1=y2;y2=y;
+        int32_t x = x1;x1=x2;x2=x;
+        int32_t y = y1;y1=y2;y2=y;
         s->dir = DIR_UP;
     } else {
         /* up/down for horizontal segments is handled by "rotating"
@@ -218,8 +258,8 @@ void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t winds
         s->dir = DIR_UP;
         if(x1>x2) {
             s->dir = DIR_DOWN;
-            int x = x1;x1=x2;x2=x;
-            int y = y1;y1=y2;y2=y;
+            int32_t x = x1;x1=x2;x2=x;
+            int32_t y = y1;y1=y2;y2=y;
         }
     }
     s->a.x = x1;
@@ -241,6 +281,7 @@ void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t winds
     s->nr = segment_count++;
 #endif
 
+#ifdef CHECKS
     assert(LINE_EQ(s->a, s) == 0);
     assert(LINE_EQ(s->b, s) == 0);
 
@@ -256,23 +297,25 @@ void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t winds
     assert(LINE_EQ(p, s) <= 0);
     p.x = max32(s->a.x, s->b.x);
     assert(LINE_EQ(p, s) >= 0);
+#endif
 
     dict_init2(&s->scheduled_crossings, &ptr_type, 0);
 }
 
-segment_t* segment_new(int32_t x1, int32_t y1, int32_t x2, int32_t y2, windstate_t initial, int polygon_nr)
+static segment_t* segment_new(int32_t x1, int32_t y1, int32_t x2, int32_t y2, int polygon_nr)
 {
     segment_t*s = (segment_t*)rfx_calloc(sizeof(segment_t));
-    segment_init(s, x1, y1, x2, y2, initial, polygon_nr);
+    segment_init(s, x1, y1, x2, y2, polygon_nr);
     return s;
 }
-void segment_destroy(segment_t*s)
+
+static void segment_destroy(segment_t*s)
 {
     dict_clear(&s->scheduled_crossings);
     free(s);
 }
 
-void gfxpoly_enqueue(edge_t*list, heap_t*queue, windstate_t initial, int polygon_nr)
+static void gfxpoly_enqueue(edge_t*list, heap_t*queue, int polygon_nr)
 {
     edge_t*l;
     for(l=list;l;l=l->next) {
@@ -281,10 +324,10 @@ void gfxpoly_enqueue(edge_t*list, heap_t*queue, windstate_t initial, int polygon
             fprintf(stderr, "Warning: intersector input contains zero-length segments\n");
             continue;
         }
-        segment_t*s = segment_new(l->a.x, l->a.y, l->b.x, l->b.y, initial, polygon_nr);
+        segment_t*s = segment_new(l->a.x, l->a.y, l->b.x, l->b.y, polygon_nr);
+#ifdef DEBUG
         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,
                 s->dir==DIR_UP?"up":"down");
@@ -298,7 +341,7 @@ void gfxpoly_enqueue(edge_t*list, heap_t*queue, windstate_t initial, int polygon
     }
 }
 
-void schedule_endpoint(status_t*status, segment_t*s)
+static void schedule_endpoint(status_t*status, segment_t*s)
 {
     // schedule end point of segment
     assert(s->b.y > status->y);
@@ -310,7 +353,7 @@ void schedule_endpoint(status_t*status, segment_t*s)
     heap_put(status->queue, &e);
 }
 
-void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
+static 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
@@ -350,11 +393,7 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
         return; // we already know about this one
     }
 
-    double adx = s1->delta.x;
-    double ady = s1->delta.y;
-    double bdx = s2->delta.x;
-    double bdy = s2->delta.y;
-    double det = adx*bdy - ady*bdx;
+    double det = (double)s1->delta.x*s2->delta.y - (double)s1->delta.y*s2->delta.x;
     if(!det) {
         if(s1->k == s2->k) {
             // lines are exactly on top of each other (ignored)
@@ -416,12 +455,13 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
         return;
     }
 
+    /* TODO: should we precompute these? */
     double la = (double)s1->a.x*(double)s1->b.y - (double)s1->a.y*(double)s1->b.x;
     double lb = (double)s2->a.x*(double)s2->b.y - (double)s2->a.y*(double)s2->b.x;
 
     point_t p;
-    p.x = (int32_t)ceil((-la*bdx +lb*adx) / det);
-    p.y = (int32_t)ceil((+lb*ady -la*bdy) / det);
+    p.x = (int32_t)ceil((-la*s2->delta.x + lb*s1->delta.x) / det);
+    p.y = (int32_t)ceil((+lb*s1->delta.y - la*s2->delta.y) / det);
 
     assert(p.y >= status->y);
 #ifdef CHECKS
@@ -452,7 +492,7 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
     return;
 }
 
-void exchange_two(status_t*status, event_t*e)
+static void exchange_two(status_t*status, event_t*e)
 {
     //exchange two segments in list
     segment_t*s1 = e->s1;
@@ -463,15 +503,13 @@ void exchange_two(status_t*status, event_t*e)
     if(!dict_contains(status->intersecting_segs, s2))
         dict_put(status->intersecting_segs, s2, 0);
 #endif
-    segment_t*left = actlist_left(status->actlist, s2);
-    segment_t*right = actlist_right(status->actlist, s1);
-    assert(left == s1);
-    assert(right == s2);
+    assert(s2->left == s1);
+    assert(s1->right == s2);
     actlist_swap(status->actlist, s1, s2);
-    assert(actlist_right(status->actlist, s2) == s1);
-    assert(actlist_left(status->actlist, s1) == s2);
-    left = actlist_left(status->actlist, s2);
-    right = actlist_right(status->actlist, s1);
+    assert(s2->right  == s1);
+    assert(s1->left == s2);
+    segment_t*left = s2->left;
+    segment_t*right = s1->right;
     if(left)
         schedule_crossing(status, left, s2);
     if(right)
@@ -481,7 +519,7 @@ void exchange_two(status_t*status, event_t*e)
 typedef struct _box {
     point_t left1, left2, right1, right2;
 } box_t;
-static inline box_t box_new(int x, int y)
+static inline box_t box_new(int32_t x, int32_t y)
 {
     box_t box;
     box.right1.x = box.right2.x = x;
@@ -504,13 +542,15 @@ static void insert_point_into_segment(status_t*status, segment_t*s, point_t p)
 
     if(s->fs_out) {
 #ifdef DEBUG
-        fprintf(stderr, "[%d] receives next point (%d,%d)->(%d,%d) (drawing)\n", s->nr, 
+        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 = rfx_calloc(sizeof(edge_t));
+#ifdef DEBUG
             e->tmp = s->nr;
+#endif
             e->a = s->pos;
             e->b = p;
             assert(e->a.y != e->b.y);
@@ -525,9 +565,6 @@ static void insert_point_into_segment(status_t*status, segment_t*s, point_t p)
     s->pos = p;
 }
 
-/* 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;
@@ -535,36 +572,25 @@ typedef struct _segrange {
     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)
+static void segrange_adjust_endpoints(segrange_t*range, int32_t 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
-
+#define XPOS_EQ(s1,s2,ypos) (XPOS((s1),(ypos))==XPOS((s2),(ypos)))
     segment_t*min = range->segmin;
     segment_t*max = range->segmax;
-    if(min) while(min->left && xpos_eq(min, min->left, y)) {
+
+    /* we need this because if two segments intersect exactly on
+       the scanline, segrange_test_segment_{min,max} can't tell which
+       one is smaller/larger */
+    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)) {
+    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)
+static void segrange_test_segment_min(segrange_t*range, segment_t*seg, int32_t y)
 {
     if(!seg) return;
     /* we need to calculate the xpos anew (and can't use start coordinate or
@@ -578,7 +604,7 @@ void segrange_test_segment_min(segrange_t*range, segment_t*seg, int y)
         range->xmin = x;
     }
 }
-void segrange_test_segment_max(segrange_t*range, segment_t*seg, int y)
+static void segrange_test_segment_max(segrange_t*range, segment_t*seg, int32_t y)
 {
     if(!seg) return;
     double x = XPOS(seg, y);
@@ -604,22 +630,26 @@ static void add_points_to_positively_sloped_segments(status_t*status, int32_t y,
     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);
 
+        seg = actlist_right(status->actlist, seg);
         while(seg) {
             if(seg->a.y == y) {
                 // this segment started in this scanline, ignore it
                 seg->changed = 1;last = seg;if(!first) {first=seg;}
-            } else if(seg->delta.x < 0) {
+            } else if(seg->delta.x <= 0) {
                 // ignore segment w/ negative slope
             } else {
+                last = seg;if(!first) {first=seg;}
                 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;}
+                if(d1>0 || d2>=0) {
+                    seg->changed = 1;
                     insert_point_into_segment(status, seg, box.right2);
                 } else {
-                    break;
+                    /* we unfortunately can't break here- the active list is sorted according
+                       to the *bottom* of the scanline. hence pretty much everything that's still
+                       coming might reach into our box */
+                    //break;
                 }
             }
             seg = actlist_right(status->actlist, seg);
@@ -639,27 +669,26 @@ static void add_points_to_positively_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 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) {
+            } else if(seg->delta.x > 0) {
                 // ignore segment w/ positive slope
             } else {
+                last = seg;if(!first) {first=seg;}
                 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;}
+                    seg->changed = 1;
                     insert_point_into_segment(status, seg, box.right2);
                 } else {
-                    break;
+                    //break;
                 }
             }
             seg = actlist_left(status->actlist, seg);
@@ -669,26 +698,98 @@ static void add_points_to_negatively_sloped_segments(status_t*status, int32_t y,
     segrange_test_segment_max(range, first, y);
 }
 
+/* segments ending in the current scanline need xrow treatment like everything else.
+   (consider an intersection taking place just above a nearly horizontal segment
+   ending on the current scanline- the intersection would snap down *below* the
+   ending segment if we don't add the intersection point to the latter right away)
+   we need to treat ending segments seperately, however. we have to delete them from
+   the active list right away to make room for intersect operations (which might
+   still be in the current scanline- consider two 45° polygons and a vertical polygon
+   intersecting on an integer coordinate). but once they're no longer in the active list,
+   we can't use the add_points_to_*_sloped_segments() functions anymore, and re-adding
+   them to the active list just for point snapping would be overkill.
+   (One other option to consider, however, would be to create a new active list only
+    for ending segments)
+*/
+static void add_points_to_ending_segments(status_t*status, int32_t y)
+{
+    segment_t*seg = status->ending_segments;
+    while(seg) {
+        segment_t*next = seg->right;seg->right=0;
+
+        assert(seg->b.y == status->y);
+
+        if(status->xrow->num == 1) {
+            // shortcut
+            point_t p = {status->xrow->x[0], y};
+            insert_point_into_segment(status, seg, p);
+        } else {
+            int t;
+            int start=0,end=status->xrow->num,dir=1;
+            if(seg->delta.x < 0) {
+                start = status->xrow->num-1;
+                end = dir = -1;
+            }
+            for(t=start;t!=end;t+=dir) {
+                box_t box = box_new(status->xrow->x[t], y);
+                double d0 = LINE_EQ(box.left1, seg);
+                double d1 = LINE_EQ(box.left2, seg);
+                double d2 = LINE_EQ(box.right1, seg);
+                double d3 = LINE_EQ(box.right2, seg);
+                if(!(d0>=0 && d1>=0 && d2>=0 && d3>0 ||
+                     d0<=0 && d1<=0 && d2<=0 && d3<0)) {
+                    insert_point_into_segment(status, seg, box.right2);
+                    break;
+                }
+            }
+
+#ifdef CHECKS
+            /* we *need* to find a point to insert. the segment's own end point
+               is in that list, for Pete's sake. */
+            assert(t!=end);
+#endif
+        }
+        // now that this is done, too, we can also finally free this segment
+        segment_destroy(seg);
+        seg = next;
+    }
+    status->ending_segments = 0;
+}
+
 static void recalculate_windings(status_t*status, segrange_t*range)
 {
+#ifdef DEBUG
+    fprintf(stderr, "range: [%d]..[%d]\n", SEGNR(range->segmin), SEGNR(range->segmax));
+#endif
     segrange_adjust_endpoints(range, status->y);
 
     segment_t*s = range->segmin;
     segment_t*end = range->segmax;
     segment_t*last = 0;
 
+#ifdef DEBUG
+    s = actlist_leftmost(status->actlist);
+    while(s) {
+        fprintf(stderr, "[%d]%d%s ", s->nr, s->changed,
+            s == range->segmin?"S":(
+            s == range->segmax?"E":""));
+        s = s->right;
+    }
+    fprintf(stderr, "\n");
+    s = range->segmin;
+#endif
 #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 = s->right;
     }
     s = actlist_rightmost(status->actlist);
     while(s && s!=range->segmax) {
         assert(!s->changed);
-        s = actlist_left(status->actlist, s);
+        s = s->left;
     }
     /* in check mode, go through the whole interval so we can test
        that all polygons where the fillstyle changed also have seg->changed=1 */
@@ -699,34 +800,34 @@ static void recalculate_windings(status_t*status, segrange_t*range)
     if(end)
         end = actlist_right(status->actlist, end);
     while(s!=end) {
-#ifndef CHECK
-        if(s->changed) 
+#ifndef CHECKS
+        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);
+            windstate_t wind = left?left->wind:status->windrule->start(status->context);
+            s->wind = status->windrule->add(status->context, 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;
 
+#ifdef CHECKS
             s->fs_out_ok = 1;
+#endif
 #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\n", s->nr, s->dir==DIR_UP?"up":"down", s->wind.wind_nr, s->wind.is_filled?"fill":"nofill", s->fs_out?"draw":"omit",
+		    fs_old!=s->fs_out?"CHANGED":"");
 #endif
         }
-        s = actlist_right(status->actlist, s);
+        s = s->right;
     }
-#ifdef DEBUG
-    fprintf(stderr, "\n");
-#endif
 }
 
 /* we need to handle horizontal lines in order to add points to segments
    we otherwise would miss during the windrule re-evaluation */
-void intersect_with_horizontal(status_t*status, segment_t*h)
+static void intersect_with_horizontal(status_t*status, segment_t*h)
 {
     segment_t* left = actlist_find(status->actlist, h->a, h->a);
     segment_t* right = actlist_find(status->actlist, h->b, h->b);
@@ -735,13 +836,18 @@ void intersect_with_horizontal(status_t*status, segment_t*h)
     xrow_add(status->xrow, h->a.x);
     point_t o = h->a;
 
-    left = actlist_right(status->actlist, left);
-    right = actlist_right(status->actlist, right);
+    if(!right) {
+        assert(!left);
+        return;
+    }
+
+    left = actlist_right(status->actlist, left); //first seg to the right of h->a
+    right = right->right; //first seg to the right of h->b
     segment_t* s = left;
 
     while(s!=right) {
         assert(s);
-        int x = XPOS_INT(s, status->y);
+        int32_t 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,
@@ -755,11 +861,11 @@ void intersect_with_horizontal(status_t*status, segment_t*h)
         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);
+        s = s->right;
     }
 }
 
-void event_apply(status_t*status, event_t*e)
+static void event_apply(status_t*status, event_t*e)
 {
     switch(e->type) {
         case EVENT_HORIZONTAL: {
@@ -782,13 +888,14 @@ void event_apply(status_t*status, event_t*e)
             assert(!dict_contains(status->intersecting_segs, s));
             assert(!dict_contains(status->segs_with_point, s));
 #endif
-            insert_point_into_segment(status, s, s->b);
             segment_t*left = actlist_left(status->actlist, s);
             segment_t*right = actlist_right(status->actlist, s);
             actlist_delete(status->actlist, s);
             if(left && right)
                 schedule_crossing(status, left, right);
-            segment_destroy(s);e->s1=0;
+
+            s->left = 0; s->right = status->ending_segments;
+            status->ending_segments = s;
             break;
         }
         case EVENT_START: {
@@ -797,7 +904,8 @@ void event_apply(status_t*status, event_t*e)
             event_dump(e);
 #endif
             segment_t*s = e->s1;
-            actlist_insert(status->actlist, e->p, s);
+	    assert(e->p.x == s->a.x && e->p.y == s->a.y);
+            actlist_insert(status->actlist, s->a, s->b, s);
             segment_t*left = actlist_left(status->actlist, s);
             segment_t*right = actlist_right(status->actlist, s);
             if(left)
@@ -816,6 +924,9 @@ void event_apply(status_t*status, event_t*e)
                actlist_left(status->actlist, e->s2) == e->s1) {
                 exchange_two(status, e);
             } else {
+#ifdef DEBUG
+		fprintf(stderr, "Ignore this crossing ([%d] not next to [%d])\n", e->s1->nr, e->s2->nr);
+#endif
                 /* ignore this crossing for now (there are some line segments in between).
                    it'll get rescheduled as soon as the "obstacles" are gone */
                 char del1 = dict_del(&e->s1->scheduled_crossings, e->s2);
@@ -834,7 +945,7 @@ void event_apply(status_t*status, event_t*e)
 }
 
 #ifdef CHECKS
-void check_status(status_t*status)
+static void check_status(status_t*status)
 {
     DICT_ITERATE_KEY(status->intersecting_segs, segment_t*, s) {
         if((s->pos.x != s->b.x ||
@@ -850,7 +961,7 @@ void check_status(status_t*status)
 }
 #endif
 
-static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
+static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule, windcontext_t*context)
 {
     /*
           |..|        |...........|                 |           |
@@ -864,21 +975,20 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
     fprintf(stderr, "========================================================================\n");
 #endif
     heap_t* queue = heap_new(sizeof(event_t), compare_events_simple);
-    gfxpoly_enqueue(poly->edges, queue, windrule->start(1), 0);
+    gfxpoly_enqueue(poly->edges, queue, 0);
 
     actlist_t* actlist = actlist_new();
 
     event_t*e = heap_chopmax(queue);
     while(e) {
-        int y = e->p.y;
-        int x = 0;
+        int32_t y = e->p.y;
+        int32_t x = 0;
         char fill = 0;
 #ifdef DEBUG
         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 {
@@ -886,12 +996,26 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
 #ifdef DEBUG
                 fprintf(stderr, "%d) draw horizontal line from %d to %d\n", y, x, e->p.x);
 #endif
+		assert(x<e->p.x);
                 edge_t*l= malloc(sizeof(edge_t));
                 l->a.y = l->b.y = y;
+		/* TODO: strictly speaking we need to draw from low x to high x so that left/right fillstyles add up
+		         (because the horizontal line's fill style controls the area *below* the line)
+		 */
                 l->a.x = x;
                 l->b.x = e->p.x;
                 l->next = poly->edges;
                 poly->edges = l;
+#ifdef CHECKS
+		/* the output should always be intersection free polygons, so check this horizontal
+		   line isn't hacking through any segments in the active list */
+		segment_t* start = actlist_find(actlist, l->a, l->a);
+		segment_t* s = actlist_find(actlist, l->b, l->b);
+		while(s!=start) {
+		    assert(s->a.y == y || s->b.y == y);
+		    s = s->left;
+		}
+#endif
             }
             segment_t*left = 0;
             segment_t*s = e->s1;
@@ -899,7 +1023,8 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
             windstate_t before,after;
             switch(e->type) {
                 case EVENT_START: {
-                    actlist_insert(actlist, e->p, s);
+		    assert(e->p.x == s->a.x && e->p.y == s->a.y);
+                    actlist_insert(actlist, s->a, s->b, s);
                     event_t e;
                     e.type = EVENT_END;
                     e.p = s->b;
@@ -908,8 +1033,8 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
                     heap_put(queue, &e);
                     left = actlist_left(actlist, s);
 
-                    before = left?left->wind:windrule->start(1);
-                    after = s->wind = windrule->add(before, s->fs, s->dir, s->polygon_nr);
+                    before = left?left->wind:windrule->start(context);
+                    after = s->wind = windrule->add(context, before, s->fs, s->dir, s->polygon_nr);
                     break;
                 }
                 case EVENT_END: {
@@ -917,7 +1042,7 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
                     actlist_delete(actlist, s);
 
                     before = s->wind;
-                    after = left?left->wind:windrule->start(1);
+                    after = left?left->wind:windrule->start(context);
                     break;
                 }
                 default: assert(0);
@@ -947,17 +1072,18 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
     heap_destroy(queue);
 }
 
-gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
+gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule, windcontext_t*context)
 {
+    current_polygon = poly;
     heap_t* queue = heap_new(sizeof(event_t), compare_events);
 
-    gfxpoly_enqueue(poly->edges, queue, windrule->start(1), /*polygon nr*/0);
+    gfxpoly_enqueue(poly->edges, queue, /*polygon nr*/0);
 
     status_t status;
     memset(&status, 0, sizeof(status_t));
-    status.num_polygons = 1;
     status.queue = queue;
     status.windrule = windrule;
+    status.context = context;
     status.actlist = actlist_new();
 #ifdef CHECKS
     status.seen_crossings = dict_new2(&point_type);
@@ -991,8 +1117,13 @@ gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
         xrow_sort(status.xrow);
         segrange_t range;
         memset(&range, 0, sizeof(range));
+#ifdef DEBUG
+        actlist_dump(status.actlist, status.y);
+#endif
         add_points_to_positively_sloped_segments(&status, status.y, &range);
         add_points_to_negatively_sloped_segments(&status, status.y, &range);
+        add_points_to_ending_segments(&status, status.y);
+
         recalculate_windings(&status, &range);
 #ifdef CHECKS
         check_status(&status);
@@ -1010,6 +1141,6 @@ gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
     gfxpoly_t*p = gfxpoly_new(poly->gridsize);
     p->edges = status.output;
 
-    add_horizontals(p, &windrule_evenodd); // output is always even/odd
+    add_horizontals(p, &windrule_evenodd, context); // output is always even/odd
     return p;
 }