optimize PrecipitationRenderer

src/util/CentredMatrix.hpp

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <array>
+#include <stdexcept>
+
+namespace util {
+    template<typename T, int diameter, typename CoordT = int>
+    class CentredMatrix {
+    public:
+        static constexpr CoordT radius = diameter / 2;
+
+        CentredMatrix() {}
+
+        void setCenter(CoordT x, CoordT y) {
+            centerX = x;
+            centerY = y;
+        }
+
+        T& at(CoordT x, CoordT y) {
+            x -= centerX - (diameter - radius);
+            y -= centerY - (diameter - radius);
+            if (x < 0 || y < 0 || x >= diameter || y >= diameter) {
+                throw std::invalid_argument("position is out if matrix");
+            }
+            return arr.at(y * diameter + x);
+        }
+
+        auto begin() {
+            return arr.begin();
+        }
+
+        auto end() {
+            return arr.end();
+        }
+
+        CoordT beginX() const {
+            return centerX - (diameter - radius);
+        }
+
+        CoordT beginY() const {
+            return centerY - (diameter - radius);
+        }
+
+        CoordT endX() const {
+            return centerX + radius;
+        }
+        
+        CoordT endY() const {
+            return centerY + radius;
+        }
+    private:
+        std::array<T, diameter * diameter> arr;
+        CoordT centerX = 0, centerY = 0;
+    };
+}