common loader: adds animatable() interface

This interface returns a value indicating
whether the current loader supports animation or not.

src/lib/tvgLoadModule.h

@@ -43,6 +43,8 @@ public:
     //Override this if the vector-format has own resizing policy.
     virtual bool resize(Paint* paint, float w, float h) { return false; }
 
+    virtual bool animatable() { return false; }  //true if this loader supports animation.
+
     virtual bool read() = 0;
     virtual bool close() = 0;
     virtual unique_ptr<Surface> bitmap() { return nullptr; }

src/loaders/lottie/tvgLottieLoader.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2023 the ThorVG project. 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.
+ */
+
+#ifndef _TVG_LOTTIE_LOADER_H_
+#define _TVG_LOTTIE_LOADER_H_
+
+#include "tvgCommon.h"
+#include "tvgFrameModule.h"
+#include "tvgTaskScheduler.h"
+
+class LottieLoader : public LoadModule, public FrameModule, public Task
+{
+public:
+    string filePath;                    //lottie file path
+    const char* content = nullptr;      //lottie file data
+    uint32_t size = 0;                  //lottie data size
+
+    unique_ptr<Scene> root;             //current motion frame
+
+    bool copy = false;                  //"content" is owned by this loader
+
+    LottieLoader();
+    ~LottieLoader();
+
+    //Lottie Loaders
+    using LoadModule::open;
+    bool open(const string& path) override;
+    bool open(const char* data, uint32_t size, bool copy) override;
+    bool resize(Paint* paint, float w, float h) override;
+    bool read() override;
+    bool close() override;
+    unique_ptr<Paint> paint() override;
+
+    bool animatable() override { return true; }
+
+    //Frame Controls
+    bool frame(uint32_t frameNo) override;
+    uint32_t totalFrame() override;
+    uint32_t curFrame() override;
+    double duration() override;
+
+private:
+    bool header();
+    void clear();
+    void run(unsigned tid) override;
+};
+
+
+#endif //_TVG_LOTTIELOADER_H_

src/loaders/svg/tvgSvgLoader.h

@@ -48,6 +48,7 @@ public:
     bool resize(Paint* paint, float w, float h) override;
     bool read() override;
     bool close() override;
+
     unique_ptr<Paint> paint() override;
 
 private:

src/loaders/tvg/tvgTvgLoader.h

@@ -50,6 +50,7 @@ public:
     bool read() override;
     bool close() override;
     bool resize(Paint* paint, float w, float h) override;
+
     unique_ptr<Paint> paint() override;
 
 private: