add SkPath::isLine(), similar to isRect()

git-svn-id: http://skia.googlecode.com/svn/trunk@3892 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkPath.h

@@ -221,6 +221,14 @@ public:
                p3.equalsWithinTolerance(p4);
     }
 
+    /**
+     *  Returns true if the path specifies a single line (i.e. it contains just
+     *  a moveTo and a lineTo). If so, and line[] is not null, it sets the 2
+     *  points in line[] to the end-points of the line. If the path is not a
+     *  line, returns false and ignores line[].
+     */
+    bool isLine(SkPoint line[2]) const;
+
     /** Returns true if the path specifies a rectangle. If so, and if rect is
         not null, set rect to the bounds of the path. If the path does not
         specify a rectangle, return false and ignore rect.

src/core/SkPath.cpp

@@ -249,6 +249,24 @@ bool SkPath::isEmpty() const {
     return 0 == fVerbs.count();
 }
 
+bool SkPath::isLine(SkPoint line[2]) const {
+    int verbCount = fVerbs.count();
+    int ptCount = fPts.count();
+    
+    if (2 == verbCount && 2 == ptCount) {
+        const uint8_t* verbs = fVerbs.begin();
+        if (kMove_Verb == verbs[0] && kLine_Verb == verbs[1]) {
+            if (line) {
+                const SkPoint* pts = fPts.begin();
+                line[0] = pts[0];
+                line[1] = pts[1];
+            }
+            return true;
+        }
+    }
+    return false;
+}
+
 /*
  Determines if path is a rect by keeping track of changes in direction
  and looking for a loop either clockwise or counterclockwise.

tests/PathTest.cpp

@@ -425,6 +425,52 @@ static void test_convexity(skiatest::Reporter* reporter) {
     }
 }
 
+static void test_isLine(skiatest::Reporter* reporter) {
+    SkPath path;
+    SkPoint pts[2];
+    const SkScalar value = SkIntToScalar(5);
+
+    REPORTER_ASSERT(reporter, !path.isLine(NULL));
+    
+    // set some non-zero values
+    pts[0].set(value, value);
+    pts[1].set(value, value);
+    REPORTER_ASSERT(reporter, !path.isLine(pts));
+    // check that pts was untouched
+    REPORTER_ASSERT(reporter, pts[0].equals(value, value));
+    REPORTER_ASSERT(reporter, pts[1].equals(value, value));
+
+    const SkScalar moveX = SkIntToScalar(1);
+    const SkScalar moveY = SkIntToScalar(2);
+    SkASSERT(value != moveX && value != moveY);
+
+    path.moveTo(moveX, moveY);
+    REPORTER_ASSERT(reporter, !path.isLine(NULL));
+    REPORTER_ASSERT(reporter, !path.isLine(pts));
+    // check that pts was untouched
+    REPORTER_ASSERT(reporter, pts[0].equals(value, value));
+    REPORTER_ASSERT(reporter, pts[1].equals(value, value));
+
+    const SkScalar lineX = SkIntToScalar(2);
+    const SkScalar lineY = SkIntToScalar(2);
+    SkASSERT(value != lineX && value != lineY);
+
+    path.lineTo(lineX, lineY);
+    REPORTER_ASSERT(reporter, path.isLine(NULL));
+
+    REPORTER_ASSERT(reporter, !pts[0].equals(moveX, moveY));
+    REPORTER_ASSERT(reporter, !pts[1].equals(lineX, lineY));
+    REPORTER_ASSERT(reporter, path.isLine(pts));
+    REPORTER_ASSERT(reporter, pts[0].equals(moveX, moveY));
+    REPORTER_ASSERT(reporter, pts[1].equals(lineX, lineY));
+
+    path.lineTo(0, 0);  // too many points/verbs
+    REPORTER_ASSERT(reporter, !path.isLine(NULL));
+    REPORTER_ASSERT(reporter, !path.isLine(pts));
+    REPORTER_ASSERT(reporter, pts[0].equals(moveX, moveY));
+    REPORTER_ASSERT(reporter, pts[1].equals(lineX, lineY));
+}
+
 // Simple isRect test is inline TestPath, below.
 // test_isRect provides more extensive testing.
 static void test_isRect(skiatest::Reporter* reporter) {
@@ -1315,8 +1361,9 @@ void TestPath(skiatest::Reporter* reporter) {
     bounds.set(0, 0, SK_Scalar1/2, SK_Scalar1/2);
     p.addRect(bounds);
     REPORTER_ASSERT(reporter, !p.isRect(NULL));
-    test_isRect(reporter);
 
+    test_isLine(reporter);
+    test_isRect(reporter);
     test_zero_length_paths(reporter);
     test_direction(reporter);
     test_convexity(reporter);