lottie: Support the slot reverting feature

Implemented the ability to revert Lottie slots by calling override with nullptr.
This functionality allows for the complete reversal of applied slots.

usage:
- `animation->override(nullptr)`

Co-Authored-By: Hermet Park <hermet@lottiefiles.com>

src/bindings/capi/thorvg_capi.h

@@ -2357,7 +2357,7 @@ TVG_API Tvg_Animation* tvg_lottie_animation_new();
 * \brief Override the lottie properties through the slot data. (Experimental API)
 *
 * \param[in] animation The Tvg_Animation object to override the property with the slot.
-* \param[in] slot The lottie slot data in json.
+* \param[in] slot The Lottie slot data in json, or @c nullptr to reset.
 *
 * \return Tvg_Animation A new Tvg_LottieAnimation object.
 * \retval TVG_RESULT_SUCCESS Succeed.

src/loaders/lottie/thorvg_lottie.h

@@ -25,7 +25,7 @@ public:
     /**
      * @brief Override Lottie properties using slot data.
      *
-     * @param[in] slot The Lottie slot data in JSON format.
+     * @param[in] slot The Lottie slot data in JSON format to override, or @c nullptr to reset.
      *
      * @retval Result::Success When succeed.
      * @retval Result::InsufficientCondition In case the animation is not loaded.

src/loaders/lottie/tvgLottieLoader.cpp

@@ -302,8 +302,12 @@ Paint* LottieLoader::paint()
 
 bool LottieLoader::override(const char* slot)
 {
-    if (!slot || !comp || comp->slots.count == 0) return false;
+    if (!comp || comp->slots.count == 0) return false;
 
+    auto success = true;
+
+    //override slots
+    if (slot) {
         //TODO: Crashed, does this necessary?
         auto temp = strdup(slot);
 
@@ -311,19 +315,26 @@ bool LottieLoader::override(const char* slot)
         LottieParser parser(temp, dirName);
 
         auto idx = 0;
-    auto success = true;
         while (auto sid = parser.sid(idx == 0)) {
             for (auto s = comp->slots.begin(); s < comp->slots.end(); ++s) {
                 if (strcmp((*s)->sid, sid)) continue;
-            if (!parser.parse(*s)) success = false;
+                if (!parser.apply(*s)) success = false;
                 break;
             }
             ++idx;
         }
 
         if (idx < 1) success = false;
-
         free(temp);
+        overriden = success;
+
+    //reset slots
+    } else if (overriden) {
+        for (auto s = comp->slots.begin(); s < comp->slots.end(); ++s) {
+            (*s)->reset();
+        }
+        overriden = false;
+    }
     return success;
 }
 

src/loaders/lottie/tvgLottieLoader.h

@@ -44,6 +44,7 @@ public:
 
     char* dirName = nullptr;            //base resource directory
     bool copy = false;                  //"content" is owned by this loader
+    bool overriden = false;             //overridden properties with slots.
 
     LottieLoader();
     ~LottieLoader();

src/loaders/lottie/tvgLottieModel.h

@@ -632,19 +632,89 @@ struct LottieLayer : LottieGroup
 
 struct LottieSlot
 {
-    char* sid;
+    struct Pair {
-    Array<LottieObject*> objs;
+        LottieObject* obj;
-    LottieProperty::Type type;
+        LottieProperty* prop;
+    };
+
+    void assign(LottieObject* target)
+    {
+        //apply slot object to all targets
+        for (auto pair = pairs.begin(); pair < pairs.end(); ++pair) {
+            //backup the original properties before overwriting
+            if (!overriden) {
+                switch (type) {
+                    case LottieProperty::Type::ColorStop: {
+                        pair->prop = new LottieColorStop;
+                        *static_cast<LottieColorStop*>(pair->prop) = static_cast<LottieGradient*>(pair->obj)->colorStops;
+                        break;
+                    }
+                    case LottieProperty::Type::Color: {
+                        pair->prop = new LottieColor;
+                        *static_cast<LottieColor*>(pair->prop) = static_cast<LottieSolid*>(pair->obj)->color;
+                        break;
+                    }
+                    case LottieProperty::Type::TextDoc: {
+                        pair->prop = new LottieTextDoc;
+                        *static_cast<LottieTextDoc*>(pair->prop) = static_cast<LottieText*>(pair->obj)->doc;
+                        break;
+                    }
+                    default: break;
+                }
+            }
+            //FIXME: it overrides the object's whole properties, but it acutally needs a single property of it.
+            pair->obj->override(target);
+        }
+        overriden = true;
+    }
+
+    void reset()
+    {
+        if (!overriden) return;
+
+        for (auto pair = pairs.begin(); pair < pairs.end(); ++pair) {
+            switch (type) {
+                case LottieProperty::Type::ColorStop: {
+                    static_cast<LottieGradient*>(pair->obj)->colorStops.release();
+                    static_cast<LottieGradient*>(pair->obj)->colorStops = *static_cast<LottieColorStop*>(pair->prop);
+                    break;
+                }
+                case LottieProperty::Type::Color: {
+                    static_cast<LottieSolid*>(pair->obj)->color.release();
+                    static_cast<LottieSolid*>(pair->obj)->color = *static_cast<LottieColor*>(pair->prop);
+                    break;
+                }
+                case LottieProperty::Type::TextDoc: {
+                    static_cast<LottieText*>(pair->obj)->doc.release();
+                    static_cast<LottieText*>(pair->obj)->doc = *static_cast<LottieTextDoc*>(pair->prop);
+                    break;
+                }
+                default: break;
+            }
+            delete(pair->prop);
+            pair->prop = nullptr;
+        }
+        overriden = false;
+    }
 
     LottieSlot(char* sid, LottieObject* obj, LottieProperty::Type type) : sid(sid), type(type)
     {
-        objs.push(obj);
+        pairs.push({obj});
     }
 
     ~LottieSlot()
     {
         free(sid);
+        if (!overriden) return;
+        for (auto pair = pairs.begin(); pair < pairs.end(); ++pair) {
+            delete(pair->prop);
         }
+    }
+
+    char* sid;
+    Array<Pair> pairs;
+    LottieProperty::Type type;
+    bool overriden = false;
 };
 
 

src/loaders/lottie/tvgLottieParser.cpp

@@ -478,7 +478,7 @@ void LottieParser::parseProperty(T& prop, LottieObject* obj)
             //append object if the slot already exists.
             for (auto slot = comp->slots.begin(); slot < comp->slots.end(); ++slot) {
                 if (strcmp((*slot)->sid, sid)) continue;
-                (*slot)->objs.push(obj);
+                (*slot)->pairs.push({obj});
                 return;
             }
             comp->slots.push(new LottieSlot(sid, obj, type));
@@ -1250,10 +1250,11 @@ const char* LottieParser::sid(bool first)
 }
 
 
-bool LottieParser::parse(LottieSlot* slot)
+bool LottieParser::apply(LottieSlot* slot)
 {
     enterObject();
 
+    //OPTIMIZE: we can create the property directly, without object
     LottieObject* obj = nullptr;  //slot object
 
     switch (slot->type) {
@@ -1278,10 +1279,7 @@ bool LottieParser::parse(LottieSlot* slot)
 
     if (!obj || Invalid()) return false;
 
-    //apply slot object to all targets
+    slot->assign(obj);
-    for (auto target = slot->objs.begin(); target < slot->objs.end(); ++target) {
-        (*target)->override(obj);
-    }
 
     delete(obj);
 

src/loaders/lottie/tvgLottieParser.h

@@ -36,7 +36,7 @@ public:
     }
 
     bool parse();
-    bool parse(LottieSlot* slot);
+    bool apply(LottieSlot* slot);
     const char* sid(bool first = false);
 
     LottieComposition* comp = nullptr;

src/loaders/lottie/tvgLottieProperty.h

@@ -204,6 +204,7 @@ uint32_t bsearch(T* frames, float frameNo)
 struct LottieProperty
 {
     enum class Type : uint8_t { Point = 0, Float, Opacity, Color, PathSet, ColorStop, Position, TextDoc, Invalid };
+    virtual ~LottieProperty() {}
 };
 
 
@@ -258,7 +259,6 @@ struct LottieGenericProperty : LottieProperty
     T& operator=(const T& other)
     {
         //shallow copy, used for slot overriding
-        delete(frames);
         if (other.frames) {
             frames = other.frames;
             const_cast<T&>(other).frames = nullptr;
@@ -467,7 +467,6 @@ struct LottieColorStop : LottieProperty
     LottieColorStop& operator=(const LottieColorStop& other)
     {
         //shallow copy, used for slot overriding
-        release();
         if (other.frames) {
             frames = other.frames;
             const_cast<LottieColorStop&>(other).frames = nullptr;
@@ -613,7 +612,6 @@ struct LottieTextDoc : LottieProperty
     LottieTextDoc& operator=(const LottieTextDoc& other)
     {
         //shallow copy, used for slot overriding
-        release();
         if (other.frames) {
             frames = other.frames;
             const_cast<LottieTextDoc&>(other).frames = nullptr;