tight bounds optimization

src/pathops/SkPathOpsTightBounds.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkOpEdgeBuilder.h"
 #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);
     SkOpGlobalState globalState(contourList, &allocator  SkDEBUGPARAMS(false)
             SkDEBUGPARAMS(nullptr));
     // turn path into list of segments
     SkScalar scaleFactor = ScaleFactor(path);
     SkPath scaledPath;
     const SkPath* workingPath;
     if (scaleFactor > SK_Scalar1) {
         ScalePath(path, 1.f / scaleFactor, &scaledPath);
         workingPath = &scaledPath;
     } else {
         workingPath = &path;
     }
     SkOpEdgeBuilder builder(*workingPath, contourList, &globalState);
     if (!builder.finish()) {
         return false;
     }
     if (!SortContourList(&contourList, false, false)) {
-        result->setEmpty();
+        *result = moveBounds;
         return true;
     }
     SkOpContour* current = contourList;
     SkPathOpsBounds bounds = current->bounds();
     while ((current = current->next())) {
         bounds.add(current->bounds());
     }
     *result = bounds;
+    if (!moveBounds.isEmpty()) {
+        result->join(moveBounds);
+    }
     return true;
 }