batch merge new edges

src/core/SkScan_Path.cpp

Index: src/core/SkScan_Path.cpp
diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp
index 804148db360c4d93e2dfb7aae4c45e967940c120..077d9a0a24da321d53ac0f7ed1e98045d8af91fb 100644
--- a/src/core/SkScan_Path.cpp
+++ b/src/core/SkScan_Path.cpp
@@ -61,7 +61,21 @@ static void backward_insert_edge_based_on_x(SkEdge* edge SkDECLAREPARAM(int, cur
     }
 }
 
+#ifndef SK_SUPPORT_LEGACY_INSERT_NEW_EDGES
+// Start from the right side, searching backwards for the point to begin the new edge list
+// insertion, marching forwards from here. The implementation could have started from the left
+// of the prior insertion, and search to the right, or with some additional caching, binary
+// search the starting point. More work could be done to determine optimal new edge insertion.
+static SkEdge* backward_insert_start(SkEdge* prev, SkFixed x) {
+    while (prev->fX > x) {
+        prev = prev->fPrev;
+    }
+    return prev;
+}
+#endif
+
 static void insert_new_edges(SkEdge* newEdge, int curr_y) {
+#ifdef SK_SUPPORT_LEGACY_INSERT_NEW_EDGES
     SkASSERT(newEdge->fFirstY >= curr_y);
 
     while (newEdge->fFirstY == curr_y) {
@@ -69,6 +83,36 @@ static void insert_new_edges(SkEdge* newEdge, int curr_y) {
         backward_insert_edge_based_on_x(newEdge  SkPARAM(curr_y));
         newEdge = next;
     }
+#else
+    if (newEdge->fFirstY != curr_y) {
+        return;
+    }
+    SkEdge* prev = newEdge->fPrev;
+    if (prev->fX <= newEdge->fX) {
+        return;
+    }
+    // find first x pos to insert
+    SkEdge* start = backward_insert_start(prev, newEdge->fX);
+    // insert the lot, fixing up the links as we go
+    do {
+        SkEdge* next = newEdge->fNext;
+        do {
+            if (start->fNext == newEdge) {
+                goto nextEdge;
+            }
+            SkEdge* after = start->fNext;
+            if (after->fX >= newEdge->fX) {
+                break;
+            }
+            start = after;
+        } while (true);
+        remove_edge(newEdge);
+        insert_edge_after(newEdge, start);
+nextEdge:
+        start = newEdge;
+        newEdge = next;
+    } while (newEdge->fFirstY == curr_y);
+#endif
 }
 
 #ifdef SK_DEBUG