1 files changed, 30 insertions, 2 deletions
diff --git a/src/common.hpp b/src/common.hpp
index e745ece..d35d1bc 100644
--- a/src/common.hpp
+++ b/src/common.hpp
@@ -13,6 +13,26 @@ struct Pt {
     Pt operator-(Pt o) const { return { x - o.x, y - o.y }; }
     Pt operator*(int k) const { return { x * k, y * k }; }
     Pt operator/(int k) const { return { x / k, y / k }; }
+    Pt& operator+=(Pt o) {
+        x += o.x;
+        y += o.y;
+        return *this;
+    }
+    Pt& operator-=(Pt o) {
+        x -= o.x;
+        y -= o.y;
+        return *this;
+    }
+    Pt& operator*=(Pt o) {
+        x *= o.x;
+        y *= o.y;
+        return *this;
+    }
+    Pt& operator/=(Pt o) {
+        x /= o.x;
+        y /= o.y;
+        return *this;
+    }
     bool operator==(const Pt&) const = default;
 };
 
@@ -25,8 +45,6 @@ inline Pt pt_min(Pt a, Pt b) {
 inline Pt pt_max(Pt a, Pt b) {
     return Pt{ MMAX(a.x, b.x), MMAX(a.y, b.y) };
 }
-#undef MMIN
-#undef MMAX
 
 struct Rect {
     Pt bl, tr;
@@ -46,3 +64,13 @@ inline Rect rect_union(Rect a, Rect b) {
 inline Rect rect_union(Rect a, Pt b) {
     return Rect(pt_min(a.bl, b), pt_max(a.tr, b));
 }
+inline Rect rect_intersect(Rect a, Rect b) {
+    // https://stackoverflow.com/a/19754915
+    int x0 = MMAX(a.bl.x, b.bl.x);
+    int y0 = MMAX(a.bl.y, b.bl.y);
+    int x1 = MMIN(a.tr.x, b.tr.x);
+    int y1 = MMIN(a.tr.y, b.tr.y);
+    return Rect(x0, y0, x1, y1);
+}
+#undef MMIN
+#undef MMAX