Rect: Add intersection() method

Resolves: #418

Author: adazem009

include/scratchcpp/rect.h

@@ -38,6 +38,8 @@ class LIBSCRATCHCPP_EXPORT Rect
         bool intersects(const Rect &rect) const;
         bool contains(double x, double y) const;
 
+        static void intersection(const Rect &a, const Rect &b, Rect &dst);
+
     private:
         spimpl::impl_ptr<RectPrivate> impl;
 };

src/rect.cpp

@@ -137,3 +137,12 @@ bool Rect::contains(double x, double y) const
 
     return (x >= impl->left && x <= impl->right && y >= bottom && y <= top);
 }
+
+/*! Saves the intersection of the given rectangles (in Scratch space) to dst. */
+void Rect::intersection(const Rect &a, const Rect &b, Rect &dst)
+{
+    dst.impl->left = std::max(a.impl->left, b.impl->left);
+    dst.impl->right = std::min(a.impl->right, b.impl->right);
+    dst.impl->top = std::min(a.impl->top, b.impl->top);
+    dst.impl->bottom = std::max(a.impl->bottom, b.impl->bottom);
+}

test/rect/rect_test.cpp

@@ -334,3 +334,91 @@ TEST(RectTest, Contains)
     ASSERT_TRUE(rect_ydown.contains(0, -40));
     ASSERT_TRUE(rect_ydown.contains(5, 24));
 }
+
+TEST(RectTest, Intersection)
+{
+    Rect rect1(-50, 25, 150, -75);
+    Rect dst;
+
+    Rect::intersection(rect1, rect1, dst);
+    ASSERT_EQ(dst.left(), rect1.left());
+    ASSERT_EQ(dst.top(), rect1.top());
+    ASSERT_EQ(dst.right(), rect1.right());
+    ASSERT_EQ(dst.bottom(), rect1.bottom());
+
+    // left
+    {
+        Rect rect2(-75, 0, 125, -50);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -50);
+        ASSERT_EQ(dst.top(), 0);
+        ASSERT_EQ(dst.right(), 125);
+        ASSERT_EQ(dst.bottom(), -50);
+    }
+
+    {
+        Rect rect2(-100, 10, -50, -90);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -50);
+        ASSERT_EQ(dst.top(), 10);
+        ASSERT_EQ(dst.right(), -50);
+        ASSERT_EQ(dst.bottom(), -75);
+    }
+
+    // top
+    {
+        Rect rect2(-25, 50, 125, 10);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -25);
+        ASSERT_EQ(dst.top(), 25);
+        ASSERT_EQ(dst.right(), 125);
+        ASSERT_EQ(dst.bottom(), 10);
+    }
+
+    {
+        Rect rect2(-100, 50, 200, 25);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -50);
+        ASSERT_EQ(dst.top(), 25);
+        ASSERT_EQ(dst.right(), 150);
+        ASSERT_EQ(dst.bottom(), 25);
+    }
+
+    // right
+    {
+        Rect rect2(125, 0, 200, -50);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), 125);
+        ASSERT_EQ(dst.top(), 0);
+        ASSERT_EQ(dst.right(), 150);
+        ASSERT_EQ(dst.bottom(), -50);
+    }
+
+    {
+        Rect rect2(150, 10, 200, -90);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), 150);
+        ASSERT_EQ(dst.top(), 10);
+        ASSERT_EQ(dst.right(), 150);
+        ASSERT_EQ(dst.bottom(), -75);
+    }
+
+    // bottom
+    {
+        Rect rect2(-25, -50, 125, -100);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -25);
+        ASSERT_EQ(dst.top(), -50);
+        ASSERT_EQ(dst.right(), 125);
+        ASSERT_EQ(dst.bottom(), -75);
+    }
+
+    {
+        Rect rect2(-100, -75, 200, -100);
+        Rect::intersection(rect1, rect2, dst);
+        ASSERT_EQ(dst.left(), -50);
+        ASSERT_EQ(dst.top(), -75);
+        ASSERT_EQ(dst.right(), 150);
+        ASSERT_EQ(dst.bottom(), -75);
+    }
+}