Simplify.

d3.js

@@ -4793,11 +4793,7 @@ d3 = function() {
     var vb = edge.b;
     if (vb) return true;
     var va = edge.a, x0 = extent[0][0], x1 = extent[1][0], y0 = extent[0][1], y1 = extent[1][1], lSite = edge.l, rSite = edge.r, lx = lSite.x, ly = lSite.y, rx = rSite.x, ry = rSite.y, fx = (lx + rx) / 2, fy = (ly + ry) / 2, fm, fb;
-    if (ry !== ly) {
-      fm = (lx - rx) / (ry - ly);
-      fb = fy - fm * fx;
-    }
-    if (fm == null) {
+    if (ry === ly) {
       if (fx < x0 || fx >= x1) return;
       if (lx > rx) {
         if (!va) va = {
@@ -4818,45 +4814,49 @@ d3 = function() {
           y: y0
         };
       }
-    } else if (fm < -1 || fm > 1) {
-      if (lx > rx) {
-        if (!va) va = {
-          x: (y0 - fb) / fm,
-          y: y0
-        }; else if (va.y >= y1) return;
-        vb = {
-          x: (y1 - fb) / fm,
-          y: y1
-        };
-      } else {
-        if (!va) va = {
-          x: (y1 - fb) / fm,
-          y: y1
-        }; else if (va.y < y0) return;
-        vb = {
-          x: (y0 - fb) / fm,
-          y: y0
-        };
-      }
     } else {
-      if (ly < ry) {
-        if (!va) va = {
-          x: x0,
-          y: fm * x0 + fb
-        }; else if (va.x >= x1) return;
-        vb = {
-          x: x1,
-          y: fm * x1 + fb
-        };
+      fm = (lx - rx) / (ry - ly);
+      fb = fy - fm * fx;
+      if (fm < -1 || fm > 1) {
+        if (lx > rx) {
+          if (!va) va = {
+            x: (y0 - fb) / fm,
+            y: y0
+          }; else if (va.y >= y1) return;
+          vb = {
+            x: (y1 - fb) / fm,
+            y: y1
+          };
+        } else {
+          if (!va) va = {
+            x: (y1 - fb) / fm,
+            y: y1
+          }; else if (va.y < y0) return;
+          vb = {
+            x: (y0 - fb) / fm,
+            y: y0
+          };
+        }
       } else {
-        if (!va) va = {
-          x: x1,
-          y: fm * x1 + fb
-        }; else if (va.x < x0) return;
-        vb = {
-          x: x0,
-          y: fm * x0 + fb
-        };
+        if (ly < ry) {
+          if (!va) va = {
+            x: x0,
+            y: fm * x0 + fb
+          }; else if (va.x >= x1) return;
+          vb = {
+            x: x1,
+            y: fm * x1 + fb
+          };
+        } else {
+          if (!va) va = {
+            x: x1,
+            y: fm * x1 + fb
+          }; else if (va.x < x0) return;
+          vb = {
+            x: x0,
+            y: fm * x0 + fb
+          };
+        }
       }
     }
     edge.a = va;

src/geom/voronoi/clip.js

@@ -36,12 +36,7 @@ function d3_geom_voronoiConnectEdge(edge, extent) {
       fm,
       fb;
 
-  if (ry !== ly) {
-    fm = (lx - rx) / (ry - ly);
-    fb = fy - fm * fx;
-  }
-
-  if (fm == null) {
+  if (ry === ly) {
     if (fx < x0 || fx >= x1) return;
     if (lx > rx) {
       if (!va) va = {x: fx, y: y0};
@@ -52,25 +47,29 @@ function d3_geom_voronoiConnectEdge(edge, extent) {
       else if (va.y < y0) return;
       vb = {x: fx, y: y0};
     }
-  } else if (fm < -1 || fm > 1) {
-    if (lx > rx) {
-      if (!va) va = {x: (y0 - fb) / fm, y: y0};
-      else if (va.y >= y1) return;
-      vb = {x: (y1 - fb) / fm, y: y1};
-    } else {
-      if (!va) va = {x: (y1 - fb) / fm, y: y1};
-      else if (va.y < y0) return;
-      vb = {x: (y0 - fb) / fm, y: y0};
-    }
   } else {
-    if (ly < ry) {
-      if (!va) va = {x: x0, y: fm * x0 + fb};
-      else if (va.x >= x1) return;
-      vb = {x: x1, y: fm * x1 + fb};
+    fm = (lx - rx) / (ry - ly);
+    fb = fy - fm * fx;
+    if (fm < -1 || fm > 1) {
+      if (lx > rx) {
+        if (!va) va = {x: (y0 - fb) / fm, y: y0};
+        else if (va.y >= y1) return;
+        vb = {x: (y1 - fb) / fm, y: y1};
+      } else {
+        if (!va) va = {x: (y1 - fb) / fm, y: y1};
+        else if (va.y < y0) return;
+        vb = {x: (y0 - fb) / fm, y: y0};
+      }
     } else {
-      if (!va) va = {x: x1, y: fm * x1 + fb};
-      else if (va.x < x0) return;
-      vb = {x: x0, y: fm * x0 + fb};
+      if (ly < ry) {
+        if (!va) va = {x: x0, y: fm * x0 + fb};
+        else if (va.x >= x1) return;
+        vb = {x: x1, y: fm * x1 + fb};
+      } else {
+        if (!va) va = {x: x1, y: fm * x1 + fb};
+        else if (va.x < x0) return;
+        vb = {x: x0, y: fm * x0 + fb};
+      }
     }
   }