saturate IPoint math, handle NaN in isEmpty

Bug: skia:7507
Change-Id: Ibdb40584effdea70e6499eab1bb64bb4b2260d06
Reviewed-on: https://skia-review.googlesource.com/106972
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>

2 files changed, 19 insertions, 12 deletions

diff --git a/include/core/SkPoint.h b/include/core/SkPoint.h
index 3ccc33e140..2d3a938693 100644
--- a/include/core/SkPoint.h
+++ b/include/core/SkPoint.h
@@ -10,6 +10,7 @@
 
 #include "SkMath.h"
 #include "SkScalar.h"
+#include "../private/SkSafe32.h"
 
 /** \struct SkIPoint16
     SkIPoint holds two 16 bit integer coordinates
@@ -115,8 +116,8 @@ struct SkIPoint {
         @param v  ivector to add
     */
     void operator+=(const SkIVector& v) {
-        fX += v.fX;
-        fY += v.fY;
+        fX = Sk32_sat_add(fX, v.fX);
+        fY = Sk32_sat_add(fY, v.fY);
     }
 
     /** Subtracts ivector v from SkIPoint. Sets SkIPoint to: (fX - v.fX, fY - v.fY).
@@ -124,8 +125,8 @@ struct SkIPoint {
         @param v  ivector to subtract
     */
     void operator-=(const SkIVector& v) {
-        fX -= v.fX;
-        fY -= v.fY;
+        fX = Sk32_sat_sub(fX, v.fX);
+        fY = Sk32_sat_sub(fY, v.fY);
     }
 
     /** Returns true if SkIPoint is equivalent to SkIPoint constructed from (x, y).
@@ -167,7 +168,7 @@ struct SkIPoint {
         @return   ivector from b to a
     */
     friend SkIVector operator-(const SkIPoint& a, const SkIPoint& b) {
-        return {a.fX - b.fX, a.fY - b.fY};
+        return { Sk32_sat_sub(a.fX, b.fX), Sk32_sat_sub(a.fY, b.fY) };
     }
 
     /** Returns SkIPoint resulting from SkIPoint a offset by ivector b, computed as: (a.fX + b.fX, a.fY + b.fY).
@@ -180,7 +181,7 @@ struct SkIPoint {
         @return   SkIPoint equal to a offset by b
     */
     friend SkIPoint operator+(const SkIPoint& a, const SkIVector& b) {
-        return {a.fX + b.fX, a.fY + b.fY};
+        return { Sk32_sat_add(a.fX, b.fX), Sk32_sat_add(a.fY, b.fY) };
     }
 };
 
diff --git a/include/core/SkRect.h b/include/core/SkRect.h
index 5673980d49..ff7715853a 100644
--- a/include/core/SkRect.h
+++ b/include/core/SkRect.h
@@ -849,12 +849,18 @@ struct SK_API SkRect {
     }
 
     /** Returns true if fLeft is equal to or greater than fRight, or if fTop is equal
-        to or greater than fBottom. Call sort() to reverse rectangles with negative
-        width() or height().
-
-        @return  true if width() or height() are zero or negative
-    */
-    bool isEmpty() const { return fLeft >= fRight || fTop >= fBottom; }
+     *  to or greater than fBottom. Call sort() to reverse rectangles with negative
+     *  width() or height().
+     *
+     *  This function also returns true if any of the values are NaN.
+     *
+     *  @return  true if width() or height() are zero or negative
+     */
+    bool isEmpty() const {
+        // We write it as the NOT of a non-empty rect, so we will return true if any values
+        // are NaN.
+        return !(fLeft < fRight && fTop < fBottom);
+    }
 
     /** Returns true if fLeft is equal to or less than fRight, or if fTop is equal
         to or less than fBottom. Call sort() to reverse rectangles with negative