add macOS implementation

macos/include/filagui/ImGuiMath.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FILAGUI_IMGUIMATH_H_
+#define FILAGUI_IMGUIMATH_H_
+
+#include <imgui.h>
+
+static inline ImVec2 operator+(const ImVec2& lhs, const ImVec2& rhs) {
+    return { lhs.x+rhs.x, lhs.y+rhs.y };
+}
+
+static inline ImVec2 operator-(const ImVec2& lhs, const ImVec2& rhs) {
+    return { lhs.x-rhs.x, lhs.y-rhs.y };
+}
+
+#endif /* FILAGUI_IMGUIMATH_H_ */