Fix RRect tranform bug

When a RRect is an oval transforming the rectangle and the radii separately can result in a non-oval result (i.e., due to numerical issues some tiny straight edges may creep in). This CL remedies the situation by computing the new radii directly from the transformed rect.

BUG=skia:2696
R=caryclark@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/354913004

2 files changed, 43 insertions, 4 deletions

diff --git a/src/core/SkRRect.cpp b/src/core/SkRRect.cpp
index 9bb6725dea..10d3d7676b 100644
--- a/src/core/SkRRect.cpp
+++ b/src/core/SkRRect.cpp
@@ -342,6 +342,19 @@ bool SkRRect::transform(const SkMatrix& matrix, SkRRect* dst) const {
     // At this point, this is guaranteed to succeed, so we can modify dst.
     dst->fRect = newRect;
 
+    // Since the only transforms that were allowed are scale and translate, the type
+    // remains unchanged.
+    dst->fType = fType;
+
+    if (kOval_Type == fType) {
+        for (int i = 0; i < 4; ++i) {
+            dst->fRadii[i].fX = SkScalarHalf(newRect.width());
+            dst->fRadii[i].fY = SkScalarHalf(newRect.height());
+        }
+        SkDEBUGCODE(dst->validate();)
+        return true;
+    }
+
     // Now scale each corner
     SkScalar xScale = matrix.getScaleX();
     const bool flipX = xScale < 0;
@@ -377,10 +390,6 @@ bool SkRRect::transform(const SkMatrix& matrix, SkRRect* dst) const {
         SkTSwap(dst->fRadii[kUpperRight_Corner], dst->fRadii[kLowerRight_Corner]);
     }
 
-    // Since the only transforms that were allowed are scale and translate, the type
-    // remains unchanged.
-    dst->fType = fType;
-
     SkDEBUGCODE(dst->validate();)
 
     return true;
diff --git a/tests/RoundRectTest.cpp b/tests/RoundRectTest.cpp
index 0a528a6535..261ec67ca0 100644
--- a/tests/RoundRectTest.cpp
+++ b/tests/RoundRectTest.cpp
@@ -582,6 +582,35 @@ static void test_round_rect_transform(skiatest::Reporter* reporter) {
     }
 }
 
+// Test out the case where an oval already off in space is translated/scaled 
+// further off into space - yielding numerical issues when the rect & radii
+// are transformed separatly
+// BUG=skia:2696
+static void test_issue_2696(skiatest::Reporter* reporter) {
+    SkRRect rrect;
+    SkRect r = { 28443.8594f, 53.1428604f, 28446.7148f, 56.0000038f };
+    rrect.setOval(r);
+
+    SkMatrix xform;
+    xform.setAll(2.44f,  0.0f, 485411.7f,
+                 0.0f,  2.44f,   -438.7f,
+                 0.0f,   0.0f,      1.0f);
+    SkRRect dst;
+
+    bool success = rrect.transform(xform, &dst);
+    REPORTER_ASSERT(reporter, success);
+
+    SkScalar halfWidth = SkScalarHalf(dst.width());
+    SkScalar halfHeight = SkScalarHalf(dst.height());
+
+    for (int i = 0; i < 4; ++i) {
+        REPORTER_ASSERT(reporter, 
+                        SkScalarNearlyEqual(dst.radii((SkRRect::Corner)i).fX, halfWidth));
+        REPORTER_ASSERT(reporter, 
+                        SkScalarNearlyEqual(dst.radii((SkRRect::Corner)i).fY, halfHeight));
+    }
+}
+
 DEF_TEST(RoundRect, reporter) {
     test_round_rect_basic(reporter);
     test_round_rect_rects(reporter);
@@ -591,4 +620,5 @@ DEF_TEST(RoundRect, reporter) {
     test_inset(reporter);
     test_round_rect_contains_rect(reporter);
     test_round_rect_transform(reporter);
+    test_issue_2696(reporter);
 }