common: introduce iterator

+++

auto picture = tvg::Picture::gen();

auto func = [](const tvg::Paint* paint, const tvg::Paint* parent, bool hasChildren) -> int
{
    if (paint->identifier() == Shape::identifier())
        //TODO: override properties.

    //return true to continue, return false to stop.
    return true;
};

picture = tvg::Iteratorv::iterate(move(picture), func);

inc/thorvg.h

@@ -1533,6 +1533,14 @@ public:
     _TVG_DECLARE_PRIVATE(Saver);
 };
 
+
+class TVG_EXPORT Iteratorv final
+{
+public:
+    static std::unique_ptr<Picture> iterate(std::unique_ptr<Picture> picture, int(*func)(const Paint* paint, const Paint* parent, bool hasChildren)) noexcept;
+};
+
+
 /** @}*/
 
 } //namespace

src/lib/meson.build

@@ -30,6 +30,7 @@ source_file = [
    'tvgFill.cpp',
    'tvgGlCanvas.cpp',
    'tvgInitializer.cpp',
+   'tvgIterator.cpp',
    'tvgLinearGradient.cpp',
    'tvgLzw.cpp',
    'tvgLoader.cpp',

src/lib/tvgIterator.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2020-2021 Samsung Electronics Co., Ltd. All rights reserved.
+
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "tvgCommon.h"
+
+/************************************************************************/
+/* Internal Class Implementation                                        */
+/************************************************************************/
+
+
+
+
+/************************************************************************/
+/* External Class Implementation                                        */
+/************************************************************************/
+
+unique_ptr<Picture> Iteratorv::iterate(unique_ptr<Picture> root, int(*func)(const Paint* paint, const Paint* parent, bool hasChild)) noexcept
+{
+    //TODO: Preorder traversal
+
+    return nullptr;
+}