made gfxpoly_dump print out segments in the right order
[swftools.git] / lib / gfxpoly / poly.c
index 9728989..7eb6509 100644 (file)
@@ -1,31 +1,59 @@
 #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"
+#include "convert.h"
+#include "heap.h"
 
-//#define DEBUG
-//#undef assert
-//#define assert(x)
+static gfxpoly_t*current_polygon = 0;
+void gfxpoly_fail(char*expr, char*file, int line, const char*function)
+{
+    if(!current_polygon) {
+       fprintf(stderr, "assert(%s) failed in %s in line %d: %s\n", expr, file, line, function);
+       exit(1);
+    }
+
+    void*md5 = initialize_md5();
+   
+    int s,t;
+    gfxpolystroke_t*stroke = current_polygon->strokes;
+    for(;stroke;stroke=stroke->next) {
+       for(t=0;t<stroke->num_points;t++) {
+           update_md5(md5, (unsigned char*)&stroke->points[t].x, sizeof(stroke->points[t].x));
+           update_md5(md5, (unsigned char*)&stroke->points[t].y, sizeof(stroke->points[t].y));
+       }
+    }
+    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));
@@ -33,7 +61,7 @@ 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;
@@ -47,153 +75,232 @@ type_t point_type = {
     free: point_free,
 };
 
-typedef struct _status {
-    int y;
-    int num_polygons;
-    actlist_t*actlist;
-    heap_t*queue;
-    edge_t*output;
-    xrow_t*xrow;
-    windrule_t*windrule;
-#ifdef DEBUG
-    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
-#endif
-} status_t;
-
-int compare_events_simple(const void*_a,const void*_b)
+typedef struct _event {
+    eventtype_t type;
+    point_t p;
+    segment_t*s1;
+    segment_t*s2;
+} event_t;
+
+/* 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 inline 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 inline 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 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 after intersect (so that a segment about
+       to end has a chance to tear up a few other segs first) and start
+       events after end (in order not to confuse the intersection check, which
+       assumes there's an actual y overlap between active segments, and 
+       because ending segments in the active list make it difficult to insert
+       starting segments at the right position)). 
+       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;
-    return d;
+    return 0;
+
+    /* I don't see any reason why we would need to order by x- at least as long
+       as we do horizontal lines in a seperate pass */
+    //d = b->p.x - a->p.x;
+    //return d;
 }
 
-gfxpoly_t* gfxpoly_new(double gridsize)
+#define COMPARE_EVENTS(x,y) (compare_events(x,y)>0)
+#define COMPARE_EVENTS_SIMPLE(x,y) (compare_events_simple(x,y)>0)
+HEAP_DEFINE(queue,event_t,COMPARE_EVENTS);
+HEAP_DEFINE(hqueue,event_t,COMPARE_EVENTS_SIMPLE);
+
+typedef struct _status {
+    int32_t y;
+    actlist_t*actlist;
+    queue_t queue;
+    xrow_t*xrow;
+    windrule_t*windrule;
+    windcontext_t*context;
+    segment_t*ending_segments;
+
+    gfxpolystroke_t*strokes;
+#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
+#endif
+} status_t;
+
+
+int gfxpoly_num_segments(gfxpoly_t*poly)
 {
-    gfxpoly_t*p = (gfxpoly_t*)rfx_calloc(sizeof(gfxpoly_t));
-    p->gridsize = gridsize;
-    return p;
+    gfxpolystroke_t*stroke = poly->strokes;
+    int count = 0;
+    for(;stroke;stroke=stroke->next) {
+       count++;
+    }
+    return count;
 }
-void gfxpoly_destroy(gfxpoly_t*poly)
+int gfxpoly_size(gfxpoly_t*poly)
 {
-    edge_t* s = poly->edges;
-    while(s) {
-        edge_t*next  = s->next;
-        free(s);
-        s = next;
+    int s,t;
+    int edges = 0;
+    gfxpolystroke_t*stroke = poly->strokes;
+    for(;stroke;stroke=stroke->next) {
+       edges += stroke->num_points-1;
     }
-    free(poly);
+    return edges;
 }
+
 char gfxpoly_check(gfxpoly_t*poly)
 {
-    edge_t* s = poly->edges;
+    current_polygon = poly;
     dict_t*d = dict_new2(&point_type);
-    while(s) {
-        if(!dict_contains(d, &s->a)) {
-            dict_put(d, &s->a, (void*)(ptroff_t)1);
-        } else {
-            int count = (ptroff_t)dict_lookup(d, &s->a);
-            dict_del(d, &s->a);
-            count++;
-            dict_put(d, &s->a, (void*)(ptroff_t)count);
-        }
-        if(!dict_contains(d, &s->b)) {
-            dict_put(d, &s->b, (void*)(ptroff_t)1);
-        } else {
-            int count = (ptroff_t)dict_lookup(d, &s->b);
-            dict_del(d, &s->b);
-            count++;
-            dict_put(d, &s->b, (void*)(ptroff_t)count);
-        }
-        s = s->next;
+    int s,t;
+    gfxpolystroke_t*stroke = poly->strokes;
+    for(;stroke;stroke=stroke->next) {
+       /* In order to not confuse the fill/wind logic, existing segments must have
+          a non-zero edge style */
+       assert(stroke->fs);
+
+       /* put all the segments into dictionaries so that we can check
+          that the endpoint multiplicity is two */
+       for(s=0;s<stroke->num_points;s++) {
+           point_t p = stroke->points[s];
+           int num = (s>=1 && s<stroke->num_points-1)?2:1; // mid points are two points (start+end)
+           if(!dict_contains(d, &p)) {
+               dict_put(d, &p, (void*)(ptroff_t)num);
+           } else {
+               int count = (ptroff_t)dict_lookup(d, &p);
+               dict_del(d, &p);
+               count+=num;
+               dict_put(d, &p, (void*)(ptroff_t)count);
+           }
+       }
     }
     DICT_ITERATE_ITEMS(d, point_t*, p, void*, c) {
         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);
-            return 0;
+            fprintf(stderr, "Point (%d,%d) occurs %d times\n", p->x, p->y, count);
+            dict_destroy(d);
+           assert(count%2 == 0);
         }
     }
+    dict_destroy(d);
     return 1;
 }
 
 void gfxpoly_dump(gfxpoly_t*poly)
 {
-    edge_t* s = poly->edges;
+    int s,t;
     double g = poly->gridsize;
-    while(s) {
-        fprintf(stderr, "(%f,%f) -> (%f,%f)\n", s->a.x*g, s->a.y*g, s->b.x*g, s->b.y*g);
-        s = s->next;
+    fprintf(stderr, "polyon %p (gridsize: %f)\n", poly, poly->gridsize);
+    gfxpolystroke_t*stroke = poly->strokes;
+    for(;stroke;stroke=stroke->next) {
+       fprintf(stderr, "%11p", stroke);
+       if(stroke->dir==DIR_UP) {
+           for(s=stroke->num_points-1;s>=1;s--) {
+               point_t a = stroke->points[s];
+               point_t b = stroke->points[s-1];
+               fprintf(stderr, "%s (%f,%f) -> (%f,%f)%s%s\n", s!=stroke->num_points-1?"           ":"", a.x*g, a.y*g, b.x*g, b.y*g,
+                                                           s==1?"]":"", a.y==b.y?"H":"");
+           }
+       } else {
+           for(s=0;s<stroke->num_points-1;s++) {
+               point_t a = stroke->points[s];
+               point_t b = stroke->points[s+1];
+               fprintf(stderr, "%s (%f,%f) -> (%f,%f)%s%s\n", s?"           ":"", a.x*g, a.y*g, b.x*g, b.y*g,
+                                                           s==stroke->num_points-2?"]":"", a.y==b.y?"H":"");
+           }
+       }
+    }
+}
+
+void gfxpoly_save(gfxpoly_t*poly, const char*filename)
+{
+    FILE*fi = fopen(filename, "wb");
+    fprintf(fi, "%% gridsize %f\n", poly->gridsize);
+    fprintf(fi, "%% begin\n");
+    int s,t;
+    gfxpolystroke_t*stroke = poly->strokes;
+    for(;stroke;stroke=stroke->next) {
+           fprintf(fi, "%g setgray\n", stroke->dir==DIR_UP ? 0.7 : 0);
+       point_t p = stroke->points[0];
+       fprintf(fi, "%d %d moveto\n", p.x, p.y);
+       for(s=1;s<stroke->num_points;s++) {
+           p = stroke->points[s];
+           fprintf(fi, "%d %d lineto\n", p.x, p.y);
+       }
+       fprintf(fi, "stroke\n");
     }
+    fprintf(fi, "showpage\n");
+    fclose(fi);
 }
 
-inline static event_t event_new()
+inline static event_t* event_new()
 {
-    event_t e;
-    memset(&e, 0, sizeof(e));
+    event_t*e = rfx_calloc(sizeof(event_t));
     return e;
 }
+inline static void event_free(event_t*e)
+{
+    free(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);
+        fprintf(stderr, "Horizontal [%d] (%d,%d) -> (%d,%d)\n", (int)e->s1->nr, e->s1->a.x, e->s1->a.y, e->s1->b.x, e->s1->b.y);
     } else if(e->type == EVENT_START) {
-        fprintf(stderr, "event: segment [%d] starts at (%d,%d)\n", e->s1->nr, e->p.x, e->p.y);
+        fprintf(stderr, "event: segment [%d] starts at (%d,%d)\n", (int)e->s1->nr, e->p.x, e->p.y);
     } else if(e->type == EVENT_END) {
-        fprintf(stderr, "event: segment [%d] ends at (%d,%d)\n", e->s1->nr, e->p.x, e->p.y);
+        fprintf(stderr, "event: segment [%d] ends at (%d,%d)\n", (int)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);
+        fprintf(stderr, "event: segment [%d] and [%d] intersect at (%d,%d)\n", (int)e->s1->nr, (int)e->s2->nr, e->p.x, e->p.y);
     } else {
         assert(0);
     }
 }
 
-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;}
+static inline int32_t max32(int32_t v1, int32_t v2) {return v1>v2?v1:v2;}
+static inline int32_t min32(int32_t v1, int32_t v2) {return v1<v2?v1:v2;}
 
-void segment_init(segment_t*s, int x1, int y1, int x2, int y2, windstate_t windstate, int polygon_nr)
+static void segment_dump(segment_t*s)
 {
-    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;
-        s->dir = DIR_UP;
+    fprintf(stderr, "[%d] (%d,%d)->(%d,%d) ", (int)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 fs=%p\n", s->delta.x, s->delta.y, s->k,
+            (double)s->delta.x / s->delta.y, s->fs);
+}
+
+static void segment_init(segment_t*s, int32_t x1, int32_t y1, int32_t x2, int32_t y2, int polygon_nr, segment_dir_t dir)
+{
+    s->dir = dir;
+    if(y1!=y2) {
+       assert(y1<y2);
     } else {
-        /* up/down for horizontal segments is handled by "rotating"
+        /* We need to make sure horizontal segments always go from left to right.
+          "up/down" for horizontal segments is handled by "rotating"
            them 90° anticlockwise in screen coordinates (tilt your head to
-           the right) */
+           the right).
+        */
         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;
@@ -204,14 +311,20 @@ 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
-#ifdef XDEBUG
     static int segment_count=0;
     s->nr = segment_count++;
-#endif
 
+#ifdef CHECKS
+    /* notice: on some systems (with some compilers), for the line 
+       (1073741823,-1073741824)->(1073741823,1073741823)
+       we get LINE_EQ(s->a, s) == 1. 
+       That's why we now clamp to 26 bit.
+    */
     assert(LINE_EQ(s->a, s) == 0);
     assert(LINE_EQ(s->b, s) == 0);
 
@@ -227,98 +340,151 @@ 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
 
+#ifndef DONT_REMEMBER_CROSSINGS
     dict_init2(&s->scheduled_crossings, &ptr_type, 0);
+#endif
 }
 
-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(point_t a, point_t b, int polygon_nr, segment_dir_t dir)
 {
     segment_t*s = (segment_t*)rfx_calloc(sizeof(segment_t));
-    segment_init(s, x1, y1, x2, y2, initial, polygon_nr);
+    segment_init(s, a.x, a.y, b.x, b.y, polygon_nr, dir);
     return s;
 }
-void segment_destroy(segment_t*s)
+
+static void segment_clear(segment_t*s)
 {
+#ifndef DONT_REMEMBER_CROSSINGS
     dict_clear(&s->scheduled_crossings);
+#endif
+}
+static void segment_destroy(segment_t*s)
+{
+    segment_clear(s);
     free(s);
 }
 
-void gfxpoly_enqueue(edge_t*list, heap_t*queue, windstate_t initial, int polygon_nr)
+static void advance_stroke(queue_t*queue, hqueue_t*hqueue, gfxpolystroke_t*stroke, int polygon_nr, int pos)
 {
-    edge_t*l;
-    for(l=list;l;l=l->next) {
-        if(l->a.x == l->b.x &&
-           l->a.y == l->b.y) {
-            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);
+    if(!stroke) 
+       return;
+    segment_t*s = 0;
+    /* we need to queue multiple segments at once because we need to process start events
+       before horizontal events */
+    while(pos < stroke->num_points-1) {
+       assert(stroke->points[pos].y <= stroke->points[pos+1].y);
+       s = segment_new(stroke->points[pos], stroke->points[pos+1], polygon_nr, stroke->dir);
+       s->fs = stroke->fs;
+       pos++;
+       s->stroke = 0;
+       s->stroke_pos = 0;
 #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");
+       /*if(l->tmp)
+           s->nr = l->tmp;*/
+       fprintf(stderr, "[%d] (%d,%d) -> (%d,%d) %s (stroke %p, %d more to come)\n",
+               s->nr, s->a.x, s->a.y, s->b.x, s->b.y,
+               s->dir==DIR_UP?"up":"down", stroke, stroke->num_points - 1 - pos);
+#endif
+       event_t* e = event_new();
+       e->type = s->delta.y ? EVENT_START : EVENT_HORIZONTAL;
+       e->p = s->a;
+       e->s1 = s;
+       e->s2 = 0;
+       
+       if(queue) queue_put(queue, e);
+       else hqueue_put(hqueue, e);
+
+       if(e->type != EVENT_HORIZONTAL) {
+           break;
+       }
+    }
+    if(s) {
+       s->stroke = stroke;
+       s->stroke_pos = pos;
+    }
+}
+
+static void gfxpoly_enqueue(gfxpoly_t*p, queue_t*queue, hqueue_t*hqueue, int polygon_nr)
+{
+    int t;
+    gfxpolystroke_t*stroke = p->strokes;
+    for(;stroke;stroke=stroke->next) {
+       assert(stroke->num_points > 1);
+
+#ifdef CHECKS
+       int s;
+       for(s=0;s<stroke->num_points-1;s++) {
+           assert(stroke->points[s].y <= stroke->points[s+1].y);
+       }
 #endif
-        event_t e = event_new();
-        e.type = s->delta.y ? EVENT_START : EVENT_HORIZONTAL;
-        e.p = s->a;
-        e.s1 = s;
-        e.s2 = 0;
-        heap_put(queue, &e);
+       advance_stroke(queue, hqueue, stroke, polygon_nr, 0);
     }
 }
 
-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);
-    event_t e;
-    e.type = EVENT_END;
-    e.p = s->b;
-    e.s1 = s;
-    e.s2 = 0;
-    heap_put(status->queue, &e);
+    event_t*e = event_new();
+    e->type = EVENT_END;
+    e->p = s->b;
+    e->s1 = s;
+    e->s2 = 0;
+    queue_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
        amazes me every time. -mk */
+#ifdef CHECKS
     assert(s1!=s2);
-
-    /* we probably could precompute these */
-    int32_t minx1 = min32(s1->a.x,s1->b.x);
+    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) {
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: bounding boxes don't intersect\n", s1->nr, s2->nr);
+#endif
         /* bounding boxes don't intersect */
         return;
     }
 
-    if(dict_contains(&s1->scheduled_crossings, s2)) {
+#ifndef DONT_REMEMBER_CROSSINGS
+    if(dict_contains(&s1->scheduled_crossings, (void*)(ptroff_t)s2->nr)) {
         /* 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;
+#ifdef DEBUG
+        fprintf(stderr, "[%d] doesn't intersect with [%d] because: we already scheduled this intersection\n", s1->nr, s2->nr);
+//     DICT_ITERATE_KEY(&s1->scheduled_crossings, void*, x) {
+//         fprintf(stderr, "[%d]<->[%d]\n", s1->nr, (int)(ptroff_t)x);
+//     }
+#endif
+        return; // we already know about this one
     }
+#endif
 
-    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)
@@ -327,20 +493,15 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
 #endif
             return;
         } else {
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: they are parallel to each other\n", s1->nr, s2->nr);
+#endif
             /* lines are parallel */
             return;
         }
     }
+
     double asign2 = LINE_EQ(s1->a, s2);
-    double bsign2 = LINE_EQ(s1->b, s2);
-    if(asign2<0 && bsign2<0) {
-        // segment1 is completely to the left of segment2
-        return;
-    }
-    if(asign2>0 && bsign2>0)  {
-        // segment2 is completely to the left of segment1
-        return;
-    }
     if(asign2==0) {
         // segment1 touches segment2 in a single point (ignored)
 #ifdef DEBUG
@@ -348,6 +509,7 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
 #endif
         return;
     }
+    double bsign2 = LINE_EQ(s1->b, s2);
     if(bsign2==0) {
         // segment1 touches segment2 in a single point (ignored)
 #ifdef DEBUG
@@ -355,16 +517,26 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
 #endif
         return;
     }
-    double asign1 = LINE_EQ(s2->a, s1);
-    double bsign1 = LINE_EQ(s2->b, s1);
-    if(asign1<0 && bsign1<0) {
+
+    if(asign2<0 && bsign2<0) {
         // segment1 is completely to the left of segment2
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: [%d] is completely to the left of [%d]\n", s1->nr, s2->nr, s1->nr, s2->nr);
+#endif
         return;
     }
-    if(asign1>0 && bsign1>0)  {
-        // segment2 is completely to the left of segment1
+    if(asign2>0 && bsign2>0)  {
+        // segment1 is completely to the right of segment2
+#ifndef DONT_REMEMBER_CROSSINGS
+       assert(0);
+#endif
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: [%d] is completely to the left of [%d]\n", s1->nr, s2->nr, s2->nr, s1->nr);
+#endif
         return;
     }
+    
+    double asign1 = LINE_EQ(s2->a, s1);
     if(asign1==0) {
         // segment2 touches segment1 in a single point (ignored)
 #ifdef DEBUG
@@ -372,6 +544,7 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
 #endif
         return;
     }
+    double bsign1 = LINE_EQ(s2->b, s1);
     if(asign2==0) {
         // segment2 touches segment1 in a single point (ignored)
 #ifdef DEBUG
@@ -380,57 +553,93 @@ void schedule_crossing(status_t*status, segment_t*s1, segment_t*s2)
         return;
     }
 
+    if(asign1<0 && bsign1<0) {
+        // segment2 is completely to the left of segment1
+#ifndef DONT_REMEMBER_CROSSINGS
+       assert(0);
+#endif
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: [%d] is completely to the left of [%d]\n", s1->nr, s2->nr, s1->nr, s2->nr);
+#endif
+        return;
+    }
+    if(asign1>0 && bsign1>0)  {
+        // segment2 is completely to the right of segment1
+#ifdef DEBUG
+            fprintf(stderr, "[%d] doesn't intersect with [%d] because: [%d] is completely to the left of [%d]\n", s1->nr, s2->nr, s2->nr, s1->nr);
+#endif
+        return;
+    }
+
+#ifdef DONT_REMEMBER_CROSSINGS
+    /* s2 crosses s1 from *left* to *right*. This is a crossing we already processed- 
+       there's not way s2 would be to the left of s1 otherwise */
+    if(asign1<0 && bsign1>0) return;
+    if(asign2>0 && bsign2<0) return;
+#endif
+
+    assert(!(asign1<0 && bsign1>0));
+    assert(!(asign2>0 && bsign2<0));
+
+    /* 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 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;
+#ifndef DONT_REMEMBER_CROSSINGS
     assert(!dict_contains(status->seen_crossings, &pair));
     dict_put(status->seen_crossings, &pair, 0);
+#endif
+#endif
+#ifdef DEBUG
     fprintf(stderr, "schedule crossing between [%d] and [%d] at (%d,%d)\n", s1->nr, s2->nr, p.x, p.y);
 #endif
 
+#ifndef DONT_REMEMBER_CROSSINGS
     /* we insert into each other's intersection history because these segments might switch
        places and we still want to look them up quickly after they did */
-    dict_put(&s1->scheduled_crossings, s2, 0);
-    dict_put(&s2->scheduled_crossings, s1, 0);
-
-    event_t e = event_new();
-    e.type = EVENT_CROSS;
-    e.p = p;
-    e.s1 = s1;
-    e.s2 = s2;
-    heap_put(status->queue, &e);
+    dict_put(&s1->scheduled_crossings, (void*)(ptroff_t)(s2->nr), 0);
+    dict_put(&s2->scheduled_crossings, (void*)(ptroff_t)(s1->nr), 0);
+#endif
+
+    event_t* e = event_new();
+    e->type = EVENT_CROSS;
+    e->p = p;
+    e->s1 = s1;
+    e->s2 = s2;
+    queue_put(&status->queue, e);
     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;
     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))
         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)
@@ -440,7 +649,7 @@ 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;
@@ -450,29 +659,55 @@ static inline box_t box_new(int x, int y)
     return box;
 }
 
-
 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
+       edgestyle_t*fs = s->fs_out;
+       segment_dir_t dir = s->wind.is_filled?DIR_DOWN:DIR_UP;
+
         // omit horizontal lines
         if(s->pos.y != p.y) {
-            edge_t*e = malloc(sizeof(edge_t));
-            e->a = s->pos;
-            e->b = p;
-            assert(e->a.y != e->b.y);
-            e->next = status->output;
-            status->output = e;
+            point_t a = s->pos;
+            point_t b = p;
+            assert(a.y != b.y);
+
+            gfxpolystroke_t*stroke = status->strokes;
+           /* find a stoke to attach this segment to. It has to have an endpoint
+              matching our start point, and a matching edgestyle */
+           while(stroke) {
+               point_t p = stroke->points[stroke->num_points-1];
+               if(p.x == a.x && p.y == a.y && stroke->fs == fs && stroke->dir == dir)
+                   break;
+               stroke = stroke->next;
+           }
+           if(!stroke) {
+               stroke = rfx_calloc(sizeof(gfxpolystroke_t));
+               stroke->dir = dir;
+               stroke->fs = fs;
+               stroke->next = status->strokes;
+               status->strokes = stroke;
+               stroke->points_size = 2;
+               stroke->points = rfx_calloc(sizeof(point_t)*stroke->points_size);
+               stroke->points[0] = a;
+               stroke->num_points = 1;
+           } else if(stroke->num_points == stroke->points_size) {
+               assert(stroke->fs);
+               stroke->points_size *= 2;
+               stroke->points = rfx_realloc(stroke->points, sizeof(point_t)*stroke->points_size);
+           }
+           stroke->points[stroke->num_points++] = b;
         }
     } else {
 #ifdef DEBUG
@@ -482,12 +717,54 @@ 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)
-*/
+typedef struct _segrange {
+    double xmin;
+    segment_t*segmin;
+    double xmax;
+    segment_t*segmax;
+} segrange_t;
+
+static void segrange_adjust_endpoints(segrange_t*range, int32_t y)
+{
+#define XPOS_EQ(s1,s2,ypos) (XPOS((s1),(ypos))==XPOS((s2),(ypos)))
+    segment_t*min = range->segmin;
+    segment_t*max = range->segmax;
+
+    /* 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)) {
+        max = max->right;
+    }
+    range->segmin = min;
+    range->segmax = max;
+}
+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
+       intersection coordinate), because we need the xpos exactly at the end of
+       this scanline.
+     */
+    double x = XPOS(seg, y);
+    if(!range->segmin || x<range->xmin) {
+        range->segmin = seg;
+        range->xmin = x;
+    }
+}
+static void segrange_test_segment_max(segrange_t*range, segment_t*seg, int32_t y)
+{
+    if(!seg) return;
+    double x = XPOS(seg, y);
+    if(!range->segmax || x>range->xmax) {
+        range->segmax = seg;
+        range->xmax = x;
+    }
+}
+
 /*
    SLOPE_POSITIVE:
       \+     \ +
@@ -497,30 +774,40 @@ 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
-            } else if(seg->delta.x < 0) {
+                // 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 {
+                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) {
+                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);
+            seg = seg->right;
         }
     }
+    segrange_test_segment_min(range, first, y);
+    segrange_test_segment_max(range, last, y);
 }
 /* SLOPE_NEGATIVE:
    |   +   /|  +  /    /
@@ -530,58 +817,170 @@ 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 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
-            } else if(seg->delta.x >= 0) {
+                // 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/ 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;
                     insert_point_into_segment(status, seg, box.right2);
                 } else {
+                    //break;
+                }
+            }
+            seg = seg->left;
+        }
+    }
+    segrange_test_segment_min(range, last, 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
+           assert(seg->b.x == status->xrow->x[0]);
+            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;
                 }
             }
-            seg = actlist_left(status->actlist, seg);
+
+#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)
+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 */
+#ifdef DEBUG
+    fprintf(stderr, "range: [%d]..[%d]\n", SEGNR(range->segmin), SEGNR(range->segmax));
+#endif
+    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 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");
+    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
-        last = s;
-        s = actlist_right(status->actlist, s);
+#ifdef CHECKS
+    /* test sanity: verify 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 = s->right;
+    }
+    s = actlist_rightmost(status->actlist);
+    while(s && s!=range->segmax) {
+        assert(!s->changed);
+        s = s->left;
     }
+    /* in check mode, go through the whole interval so we can test
+       that all polygons where the edgestyle changed also have seg->changed=1 */
+    s = actlist_leftmost(status->actlist);
+    end = 0;
+#endif
+
+    if(end)
+        end = end->right;
+    while(s!=end) {
+#ifndef CHECKS
+        if(s->changed)
+#endif
+        {
+            segment_t* left = actlist_left(status->actlist, s);
+            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);
+            edgestyle_t*fs_old = s->fs_out;
+            s->fs_out = status->windrule->diff(&wind, &s->wind);
+
 #ifdef DEBUG
-    fprintf(stderr, "\n");
+            fprintf(stderr, "[%d] dir=%s wind=%d wind.filled=%s fs_old/new=%s/%s %s\n", s->nr, s->dir==DIR_UP?"up":"down", s->wind.wind_nr, s->wind.is_filled?"fill":"nofill", 
+                   fs_old?"draw":"omit", s->fs_out?"draw":"omit",
+                   fs_old!=s->fs_out?"CHANGED":"");
 #endif
+            assert(!(!s->changed && fs_old!=s->fs_out));
+            s->changed = 0;
 
+#ifdef CHECKS
+            s->fs_out_ok = 1;
+#endif
+        }
+        s = s->right;
+    }
 }
 
 /* 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);
@@ -590,44 +989,46 @@ 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);
-        /*
-           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);
+        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,
                 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);
+        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: {
+            segment_t*s = e->s1;
 #ifdef DEBUG
             event_dump(e);
 #endif
-            intersect_with_horizontal(status, e->s1);
+            intersect_with_horizontal(status, s);
+           advance_stroke(&status->queue, 0, s->stroke, s->polygon_nr, s->stroke_pos);
+            segment_destroy(s);e->s1=0;
             break;
         }
         case EVENT_END: {
@@ -635,18 +1036,23 @@ 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));
             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);
+            segment_t*left = s->left;
+            segment_t*right = s->right;
             actlist_delete(status->actlist, s);
             if(left && right)
                 schedule_crossing(status, left, right);
-            segment_destroy(s);e->s1=0;
+
+           /* schedule segment for xrow handling */
+            s->left = 0; s->right = status->ending_segments;
+            status->ending_segments = s;
+           advance_stroke(&status->queue, 0, s->stroke, s->polygon_nr, s->stroke_pos);
             break;
         }
         case EVENT_START: {
@@ -655,14 +1061,15 @@ 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);
-            segment_t*left = actlist_left(status->actlist, s);
-            segment_t*right = actlist_right(status->actlist, 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 = s->left;
+            segment_t*right = s->right;
             if(left)
                 schedule_crossing(status, left, s);
             if(right)
                 schedule_crossing(status, s, right);
-            schedule_endpoint(status, e->s1);
+            schedule_endpoint(status, s);
             break;
         }
         case EVENT_CROSS: {
@@ -670,36 +1077,44 @@ void event_apply(status_t*status, event_t*e)
 #ifdef DEBUG
             event_dump(e);
 #endif
-            if(actlist_right(status->actlist, e->s1) == e->s2 &&
-               actlist_left(status->actlist, e->s2) == e->s1) {
+            if(e->s1->right == e->s2) {
+               assert(e->s2->left == e->s1);
                 exchange_two(status, e);
             } else {
+               assert(e->s2->left != e->s1);
+#ifdef DEBUG
+               fprintf(stderr, "Ignore this crossing ([%d] not next to [%d])\n", e->s1->nr, e->s2->nr);
+#endif
+#ifndef DONT_REMEMBER_CROSSINGS
                 /* 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);
-                char del2 = dict_del(&e->s2->scheduled_crossings, e->s1);
+                char del1 = dict_del(&e->s1->scheduled_crossings, (void*)(ptroff_t)e->s2->nr);
+                char del2 = dict_del(&e->s2->scheduled_crossings, (void*)(ptroff_t)e->s1->nr);
                 assert(del1 && del2);
-#ifdef DEBUG
+#endif
+#ifdef CHECKS
                 point_t pair;
                 pair.x = e->s1->nr;
                 pair.y = e->s2->nr;
+#ifndef DONT_REMEMBER_CROSSINGS
                 assert(dict_contains(status->seen_crossings, &pair));
                 dict_del(status->seen_crossings, &pair);
 #endif
+#endif
             }
         }
     }
 }
 
-#ifdef DEBUG
-void check_status(status_t*status)
+#ifdef CHECKS
+static void check_status(status_t*status)
 {
     DICT_ITERATE_KEY(status->intersecting_segs, segment_t*, s) {
         if((s->pos.x != s->b.x ||
             s->pos.y != s->b.y) &&
            !dict_contains(status->segs_with_point, s)) {
             fprintf(stderr, "Error: segment [%d] (%sslope) intersects in scanline %d, but it didn't receive a point\n",
-                    s->nr,
+                    SEGNR(s),
                     s->delta.x<0?"-":"+",
                     status->y);
             assert(0);
@@ -708,7 +1123,7 @@ 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)
 {
     /*
           |..|        |...........|                 |           |
@@ -721,140 +1136,248 @@ static void add_horizontals(gfxpoly_t*poly, windrule_t*windrule)
 #ifdef DEBUG
     fprintf(stderr, "========================================================================\n");
 #endif
-    heap_t* queue = heap_new(sizeof(event_t), compare_events_simple);
-    gfxpoly_enqueue(poly->edges, queue, windrule->start(1), 0);
+    hqueue_t hqueue;
+    hqueue_init(&hqueue);
+    gfxpoly_enqueue(poly, 0, &hqueue, 0);
 
     actlist_t* actlist = actlist_new();
-
-    event_t*e = heap_chopmax(queue);
+       
+    event_t*e = hqueue_get(&hqueue);
     while(e) {
-        int y = e->p.y;
-        int x = 0;
-        char fill = 0;
+        int32_t y = e->p.y;
+        int32_t x = 0;
 #ifdef DEBUG
-        actlist_verify_and_dump(actlist, y-1);
+        fprintf(stderr, "HORIZONTALS ----------------------------------- %d\n", y);
+        actlist_dump(actlist, y-1);
 #endif
+#ifdef CHECKS
+        actlist_verify(actlist, y-1);
+#endif
+       edgestyle_t*fill = 0;
+       char dir_up = 0;
+       char dir_down = 0;
+
         do {
+           assert(e->s1->fs);
             if(fill && x != e->p.x) {
+               assert(!dir_up || !dir_down);
+               assert(dir_up || dir_down);
 #ifdef DEBUG
                 fprintf(stderr, "%d) draw horizontal line from %d to %d\n", y, x, e->p.x);
 #endif
-                edge_t*l= malloc(sizeof(edge_t));
-                l->a.y = l->b.y = y;
-                l->a.x = x;
-                l->b.x = e->p.x;
-                l->next = poly->edges;
-                poly->edges = l;
+               assert(x<e->p.x);
+
+                gfxpolystroke_t*stroke = rfx_calloc(sizeof(gfxpolystroke_t));
+               stroke->next = poly->strokes;
+               poly->strokes = stroke;
+
+               stroke->num_points = 2;
+               stroke->points = malloc(sizeof(point_t)*2);
+               stroke->dir = dir_up?DIR_UP:DIR_DOWN;
+               stroke->fs = fill;
+               point_t a,b;
+                a.y = b.y = y;
+               /* we 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)
+                */
+                a.x = e->p.x;
+                b.x = x;
+               stroke->points[0] = a;
+               stroke->points[1] = b;
+#ifdef CHECKS
+               /* the output should always be intersection free polygons, so check this horizontal
+                  line isn't puncturing any segments in the active list */
+               segment_t* start = actlist_find(actlist, b, b);
+               segment_t* s = actlist_find(actlist, a, a);
+               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;
 
-            windstate_t before,after;
+           segment_t*s = e->s1;
+
+            segment_t*left = 0;
             switch(e->type) {
                 case EVENT_START: {
-                    actlist_insert(actlist, e->p, s);
-                    event_t e;
-                    e.type = EVENT_END;
-                    e.p = s->b;
-                    e.s1 = s;
-                    e.s2 = 0;
-                    heap_put(queue, &e);
+                   assert(e->p.x == s->a.x && e->p.y == s->a.y);
+                    actlist_insert(actlist, s->a, s->b, s);
+                    event_t* e = event_new();
+                    e->type = EVENT_END;
+                    e->p = s->b;
+                    e->s1 = s;
+                    e->s2 = 0;
+                    hqueue_put(&hqueue, 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);
+                   if(e->s1->dir==DIR_UP)
+                       dir_up^=1;
+                   else
+                       dir_down^=1;
                     break;
                 }
                 case EVENT_END: {
                     left = actlist_left(actlist, s);
                     actlist_delete(actlist, s);
-
-                    before = s->wind;
-                    after = left?left->wind:windrule->start(1);
+                   advance_stroke(0, &hqueue, s->stroke, s->polygon_nr, s->stroke_pos);
+                   if(e->s1->dir==DIR_DOWN)
+                       dir_up^=1;
+                   else
+                       dir_down^=1;
                     break;
                 }
                 default: assert(0);
             }
 
             x = e->p.x;
-            fill ^= 1;//(before.is_filled != after.is_filled);
+               
+           fill = fill?0:&edgestyle_default;
+#if 0
+           if(windrule==&windrule_evenodd) {
+               if(!!fill != !!fill2) {
+                   segment_dump(s);
+                   event_dump(e);
+                   printf("at y=%d x=%d (hline:%p)\n", e->p.y, x, old_fill);
+                   if(e->type==EVENT_END) {
+                       printf("            %9p\n", s->fs);
+                       printf("               |\n");
+                   }
+                   printf("              %3d %c%2d \n", before1.is_filled, e->type==EVENT_END?'|':' ', after1.is_filled);
+                   printf("%12p -----+----- %p\n", old_fill, fill2);
+                   printf("              %3d %c%2d \n", before2.is_filled, e->type==EVENT_START?'|':' ', after2.is_filled);
+                   if(e->type==EVENT_START) {
+                       printf("                  |\n");
+                       printf("             %9p\n", s->fs);
+                   }
+               }
+               assert(!!fill == !!fill2);
+           }
+#endif
+
 #ifdef DEBUG
-            fprintf(stderr, "%d) event=%s[%d] left:[%d] x:%d before:%d after:%d\n",
+            fprintf(stderr, "%d) event=%s[%d] left:[%d] x:%d\n",
                     y, e->type==EVENT_START?"start":"end",
                     s->nr,
                     left?left->nr:-1,
-                    x,
-                    before.is_filled, after.is_filled);
+                    x);
 #endif
 
             if(e->type == EVENT_END)
                 segment_destroy(s);
 
-            e = heap_chopmax(queue);
+           event_free(e);
+            e = hqueue_get(&hqueue);
         } while(e && y == e->p.y);
 
-        if(fill) {
-            fprintf(stderr, "Error: polygon is bleeding\n");
-            exit(0);
-        }
+#ifdef CHECKS
+       edgestyle_t*bleeding = fill;
+        assert(!bleeding);
+#endif
     }
+
+    actlist_destroy(actlist);
+    hqueue_destroy(&hqueue);
 }
 
-gfxpoly_t* gfxpoly_process(gfxpoly_t*poly, windrule_t*windrule)
+gfxpoly_t* gfxpoly_process(gfxpoly_t*poly1, gfxpoly_t*poly2, windrule_t*windrule, windcontext_t*context)
 {
-    heap_t* queue = heap_new(sizeof(event_t), compare_events);
-
-    gfxpoly_enqueue(poly->edges, queue, windrule->start(1), /*polygon nr*/0);
+    current_polygon = poly1;
 
     status_t status;
     memset(&status, 0, sizeof(status_t));
-    status.num_polygons = 1;
-    status.queue = queue;
+    queue_init(&status.queue);
+    gfxpoly_enqueue(poly1, &status.queue, 0, /*polygon nr*/0);
+    if(poly2) {
+       assert(poly1->gridsize == poly2->gridsize);
+       gfxpoly_enqueue(poly2, &status.queue, 0, /*polygon nr*/1);
+    }
+
     status.windrule = windrule;
+    status.context = context;
     status.actlist = actlist_new();
-#ifdef DEBUG
+
+#ifdef CHECKS
     status.seen_crossings = dict_new2(&point_type);
+    int32_t lasty=-0x80000000;
 #endif
 
     status.xrow = xrow_new();
 
-    event_t*e = heap_chopmax(queue);
+    event_t*e = queue_get(&status.queue);
     while(e) {
+       assert(e->s1->fs);
         status.y = e->p.y;
-#ifdef DEBUG
+#ifdef CHECKS
+       assert(status.y>=lasty);
+       lasty = status.y;
         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 {
             xrow_add(status.xrow, e->p.x);
             event_apply(&status, e);
-            free(e);
-            e = heap_chopmax(queue);
+           event_free(e);
+            e = queue_get(&status.queue);
         } 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);
+        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);
         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);
-    heap_destroy(queue);
+    queue_destroy(&status.queue);
     xrow_destroy(status.xrow);
 
-    gfxpoly_t*p = gfxpoly_new(poly->gridsize);
-    p->edges = status.output;
+    gfxpoly_t*p = (gfxpoly_t*)malloc(sizeof(gfxpoly_t));
+    p->gridsize = poly1->gridsize;
+    p->strokes = status.strokes;
+
+#ifdef CHECKS
+    /* we only add segments with non-empty edgestyles to strokes in
+       recalculate_windings, but better safe than sorry */
+    gfxpolystroke_t*stroke = p->strokes;
+    while(stroke) {
+       assert(stroke->fs);
+       stroke = stroke->next;
+    }
+#endif
 
-    add_horizontals(p, &windrule_evenodd); // output is always even/odd
+    add_horizontals(p, &windrule_evenodd, context); // output is always even/odd
+    //add_horizontals(p, windrule, context);
     return p;
 }
+
+static windcontext_t twopolygons = {2};
+gfxpoly_t* gfxpoly_intersect(gfxpoly_t*p1, gfxpoly_t*p2)
+{
+    return gfxpoly_process(p1, p2, &windrule_intersect, &twopolygons);
+}
+gfxpoly_t* gfxpoly_union(gfxpoly_t*p1, gfxpoly_t*p2)
+{
+    return gfxpoly_process(p1, p2, &windrule_union, &twopolygons);
+}