Drawing selection and overlapping selections

src/basic/basic.h

@@ -493,6 +493,14 @@ struct Array {
 
     // @copy_paste array slice
 
+    T get_or_default(int64_t i, T default_value = {}) {
+        T result = default_value;
+        if (i >= 0 && i < len) {
+            result = data[i];
+        }
+        return result;
+    }
+
     T pop() {
         Assert(len > 0);
         return data[--len];