bless wasm polygon rasterizer for production

wasm/kiri-sla.c

@@ -15,6 +15,10 @@ struct poly {
     Uint16 length; // offset to end of record in bytes
     Uint16 inners; // number of inner polygons
     Uint16 points; // number of points in polygon
+    Uint16 minx;
+    Uint16 maxx;
+    Uint16 miny;
+    Uint16 maxy;
 };
 
 struct point {
@@ -22,6 +26,9 @@ struct point {
     float y;
 };
 
+const Uint8 ph_size = sizeof(struct poly);
+const Uint8 pt_size = sizeof(struct point);
+
 extern void last(float a, float b);
 extern void report(int a, int b);
 
@@ -34,29 +41,28 @@ Uint8 check_cross(Uint32 x, Uint32 y, struct point *p1, struct point *p2) {
     ) ? 1 : 0;
 }
 
-Uint8 check_inside(Uint32 x, Uint32 y, unsigned char *p) {
-    struct poly *poly = (struct poly *)(p + readoff);
+Uint8 is_inside_poly(Uint32 x, Uint32 y, unsigned char *m, Uint32 o) {
+    struct poly *poly = (struct poly *)(m + readoff);
 
     Uint32 nextpoly = readoff + poly->length;
     Uint8 side = 0; // 0=outside, 1=inside
-    Uint8 psize = sizeof(struct point);
 
     // skip post header
-    readoff += sizeof(struct poly);
+    readoff += ph_size;
 
     // save pointer to first point or last comparison
-    struct point *pf = (struct point *)(p + readoff);
+    struct point *pf = (struct point *)(m + readoff);
     struct point *p1 = pf;
     struct point *p2;
 
     // skip past first point
-    readoff += psize;
+    readoff += pt_size;
 
     // read and check point pairs updating `side`
     for (Uint16 i=1; i<poly->points; i++) {
-        p2 = (struct point *)(p + readoff);
+        p2 = (struct point *)(m + readoff);
         // increment read pointe
-        readoff += psize;
+        readoff += pt_size;
         // check current/previous point crossing
         if (check_cross(x, y, p1, p2)) {
             side = 1 - side;
@@ -69,20 +75,75 @@ Uint8 check_inside(Uint32 x, Uint32 y, unsigned char *p) {
         side = 1 - side;
     }
 
-    // check inner polygons only if inside the outer polygon
-    if (side)
-    for (Uint16 i=0; i<poly->inners; i++) {
-        // if inside an inner, then actually outside poly and term
-        if (check_inside(x, y, p + readoff)) {
-            side = 0;
-            break;
+    return side;
+}
+
+void rasterize_poly(unsigned char *m, Uint32 o, Uint32 height) {
+    struct poly *poly = (struct poly *)(m + readoff);
+
+    Uint32 nextpoly = readoff + poly->length;
+
+    // skip post header
+    readoff += ph_size;
+
+    // save pointer to first point or last comparison
+    struct point *pf = (struct point *)(m + readoff);
+    struct point *p1 = pf;
+    struct point *p2;
+
+    // skip past first point
+    readoff += pt_size;
+
+    // point data starts here
+    Uint32 pstart = readoff;
+
+    // scan bounding area of polygon
+    for (Uint32 x=poly->minx; x<poly->maxx; x++) {
+        for (Uint32 y=poly->miny; y<poly->maxy; y++) {
+
+            Uint8 side = 0; // 0=outside, 1=inside
+
+            // re-start at point data offset for each x,y
+            readoff = pstart;
+            p1 = pf;
+
+            // read and check point pairs updating `side`
+            for (Uint16 i=1; i<poly->points; i++) {
+                p2 = (struct point *)(m + readoff);
+                // increment read pointe
+                readoff += pt_size;
+                // check current/previous point crossing
+                if (check_cross(x, y, p1, p2)) {
+                    side = 1 - side;
+                }
+                p1 = p2;
+            }
+
+            // check last/first point crossing
+            if (check_cross(x, y, p1, pf)) {
+                side = 1 - side;
+            }
+
+            // check inner polygons only if inside the outer polygon
+            if (side)
+            for (Uint16 i=0; i<poly->inners; i++) {
+                // if inside an inner, then actually outside poly and term
+                if (is_inside_poly(x, y, m, o)) {
+                    side = 0;
+                    break;
+                }
+            }
+
+            if (side) {
+                Uint32 impos = y + (x * height);
+                (m + o)[impos] = 255;
+            }
+
         }
     }
 
     // update pointer to next polygon
     readoff = nextpoly;
-
-    return side;
 }
 
 EMSCRIPTEN_KEEPALIVE
@@ -90,23 +151,14 @@ Uint32 render(unsigned char *m, Uint32 i, Uint32 o) {
     struct info *info = (struct info *)(m + i);
     Uint32 impos;
     Uint8 inside;
-    Uint32 maxpos = 0;
     Uint32 polypos = (sizeof (struct info)) + i;
 
     memset(m+o, 0, info->width * info->height);
 
-    for (Uint32 x=0; x<info->width; x++) {
-        for (Uint32 y=0; y<info->height; y++) {
-            inside = 0;
-            impos = y + (x * info->height);
-            readoff = polypos;
-            for (Uint32 p=0; p<info->polys; p++) {
-                inside = inside | check_inside(x, y, m);
-            }
-            if (inside) (m + o)[impos] = 255;
-            if (impos > maxpos) maxpos = impos;
-        }
+    readoff = polypos;
+    for (Uint32 p=0; p<info->polys; p++) {
+        rasterize_poly(m, o, info->height);
     }
 
-    return maxpos;
+    return 1;
 }