tight bounds optimization

src/pathops/SkPathOpsTightBounds.cpp

Index: src/pathops/SkPathOpsTightBounds.cpp
diff --git a/src/pathops/SkPathOpsTightBounds.cpp b/src/pathops/SkPathOpsTightBounds.cpp
index 60f18cfbbc7842c15a212c6d12a14ce451937a55..d748ff538afae063fda7cae7d54fcd346cfa7af7 100644
--- a/src/pathops/SkPathOpsTightBounds.cpp
+++ b/src/pathops/SkPathOpsTightBounds.cpp
@@ -8,6 +8,45 @@
 #include "SkPathOpsCommon.h"
 
 bool TightBounds(const SkPath& path, SkRect* result) {
+    SkPath::RawIter iter(path);
+    SkRect moveBounds = { SK_ScalarMax, SK_ScalarMax, SK_ScalarMin, SK_ScalarMin };
+    bool wellBehaved = true;
+    SkPath::Verb verb;
+    do {
+        SkPoint pts[4];
+        verb = iter.next(pts);
+        switch (verb) {
+            case SkPath::kMove_Verb:
+                moveBounds.fLeft = SkTMin(moveBounds.fLeft, pts[0].fX);
+                moveBounds.fTop = SkTMin(moveBounds.fTop, pts[0].fY);
+                moveBounds.fRight = SkTMax(moveBounds.fRight, pts[0].fX);
+                moveBounds.fBottom = SkTMax(moveBounds.fBottom, pts[0].fY);
+                break;
+            case SkPath::kQuad_Verb:
+            case SkPath::kConic_Verb:
+                if (!wellBehaved) {
+                    break;
+                }
+                wellBehaved &= between(pts[0].fX, pts[1].fX, pts[2].fX);
+                wellBehaved &= between(pts[0].fY, pts[1].fY, pts[2].fY);
+                break;
+            case SkPath::kCubic_Verb:
+                if (!wellBehaved) {
+                    break;
+                }
+                wellBehaved &= between(pts[0].fX, pts[1].fX, pts[3].fX);
+                wellBehaved &= between(pts[0].fY, pts[1].fY, pts[3].fY);
+                wellBehaved &= between(pts[0].fX, pts[2].fX, pts[3].fX);
+                wellBehaved &= between(pts[0].fY, pts[2].fY, pts[3].fY);
+                break;
+            default:
+                break;
+        }
+    } while (verb != SkPath::kDone_Verb);
+    if (wellBehaved) {
+        *result = path.getBounds();
+        return true;
+    }
     SkChunkAlloc allocator(4096);  // FIXME: constant-ize, tune
     SkOpContour contour;
     SkOpContourHead* contourList = static_cast<SkOpContourHead*>(&contour);
@@ -28,7 +67,7 @@ bool TightBounds(const SkPath& path, SkRect* result) {
         return false;
     }
     if (!SortContourList(&contourList, false, false)) {
-        result->setEmpty();
+        *result = moveBounds;
         return true;
     }
     SkOpContour* current = contourList;
@@ -37,5 +76,8 @@ bool TightBounds(const SkPath& path, SkRect* result) {
         bounds.add(current->bounds());
     }
     *result = bounds;
+    if (!moveBounds.isEmpty()) {
+        result->join(moveBounds);
+    }
     return true;
 }