commit cea22ae2349502334312bd1d9e10ffa894f70e05
author kolczyk <kolczyk@opera.com> Sat Jul 16 11:52:37 2016 -0700
committer Commit bot <commit-bot@chromium.org> Sat Jul 16 11:52:37 2016 -0700
tree 08fae859e13331b12ee3d5e9ae12d2e65e44a2fd
parent 280d537e2893ee036c5e58e23438b12d30d634ee

Guard SkMatrix::get*Scale[s]() against negative nearly-zero values.

BUG=skia:4718
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2143133005

Review-Url: https://codereview.chromium.org/2143133005

src/core/SkMatrix.cpp

diff --git a/src/core/SkMatrix.cpp b/src/core/SkMatrix.cpp
index 492f3f6..fc69853 100644
--- a/src/core/SkMatrix.cpp
+++ b/src/core/SkMatrix.cpp
@@ -1568,15 +1568,21 @@
             results[1] = apluscdiv2 + x;
         }
     }
-    if (SkScalarIsNaN(results[0])) {
+    if (!SkScalarIsFinite(results[0])) {
         return false;
     }
+    if (results[0] < 0 && results[0] > -SK_ScalarNearlyZero) {
+        results[0] = 0;
+    }
     SkASSERT(results[0] >= 0);
     results[0] = SkScalarSqrt(results[0]);
     if (kBoth_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
-        if (SkScalarIsNaN(results[1])) {
+        if (!SkScalarIsFinite(results[1])) {
             return false;
         }
+        if (results[1] < 0 && results[1] > -SK_ScalarNearlyZero) {
+            results[1] = 0;
+        }
         SkASSERT(results[1] >= 0);
         results[1] = SkScalarSqrt(results[1]);
     }

tests/MatrixTest.cpp

diff --git a/tests/MatrixTest.cpp b/tests/MatrixTest.cpp
index c4eb9c7..414aab2 100644
--- a/tests/MatrixTest.cpp
+++ b/tests/MatrixTest.cpp
@@ -213,11 +213,17 @@
     big.setAll(2.39394089e+36f, 8.85347779e+36f, 9.26526204e+36f,
                3.9159619e+36f, 1.44823453e+37f, 1.51559342e+37f,
                0.f, 0.f, 1.f);
-    REPORTER_ASSERT(reporter, -SK_Scalar1 == perspX.getMinScale());
-    REPORTER_ASSERT(reporter, -SK_Scalar1 == perspX.getMaxScale());
     success = big.getMinMaxScales(scales);
     REPORTER_ASSERT(reporter, !success);
 
+    // skbug.com/4718
+    SkMatrix givingNegativeNearlyZeros;
+    givingNegativeNearlyZeros.setAll(0.00436534f, 0.114138f, 0.37141f,
+                                     0.00358857f, 0.0936228f, -0.0174198f,
+                                     0.f, 0.f, 1.f);
+    success = givingNegativeNearlyZeros.getMinMaxScales(scales);
+    REPORTER_ASSERT(reporter, success && 0 == scales[0]);
+
     SkMatrix perspY;
     perspY.reset();
     perspY.setPerspY(-SK_Scalar1 / 500);