add isRect() check to AAClip, to detect if a soft-clip is really just an irect

tests/AAClipTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAAClip.h"
 #include "SkCanvas.h"
 #include "SkMask.h"
@@ skipping 300 matching lines @@
         clip.setPath(path, NULL, 1 == i);
 
         SkMask mask;
         clip.copyToMask(&mask);
         SkAutoMaskFreeImage freeM(mask.fImage);
 
         REPORTER_ASSERT(reporter, expected == mask);
     }
 }
 
+static void test_really_a_rect(skiatest::Reporter* reporter) {
+    SkRRect rrect;
+    rrect.setRectXY(SkRect::MakeWH(100, 100), 5, 5);
+
+    SkPath path;
+    path.addRRect(rrect);
+
+    SkAAClip clip;
+    clip.setPath(path);
+
+    REPORTER_ASSERT(reporter, clip.getBounds() == SkIRect::MakeWH(100, 100));
+    REPORTER_ASSERT(reporter, !clip.isRect());
+
+    // This rect should intersect the clip, but slice-out all of the "soft" parts,
+    // leaving just a rect.
+    const SkIRect ir = SkIRect::MakeLTRB(10, -10, 50, 90);
+    
+    clip.op(ir, SkRegion::kIntersect_Op);
+
+    REPORTER_ASSERT(reporter, clip.getBounds() == SkIRect::MakeLTRB(10, 0, 50, 90));
+    // the clip recognized that that it is just a rect!
+    REPORTER_ASSERT(reporter, clip.isRect());
+}
+
 #include "SkRasterClip.h"
 
 static void copyToMask(const SkRasterClip& rc, SkMask* mask) {
     if (rc.isAA()) {
         rc.aaRgn().copyToMask(mask);
     } else {
         copyToMask(rc.bwRgn(), mask);
     }
 }
 
@@ skipping 66 matching lines @@
 }
 
 DEF_TEST(AAClip, reporter) {
     test_empty(reporter);
     test_path_bounds(reporter);
     test_irect(reporter);
     test_rgn(reporter);
     test_path_with_hole(reporter);
     test_regressions();
     test_nearly_integral(reporter);
+    test_really_a_rect(reporter);
 }