lottie/slot: Introduce reusable Slot API

Introduce Slot APIs for efficient slot data reuse

New APIs:
- uint32_t LottieAnimation::gen(const char* slots)
- Result LottieAnimation::apply(uint32_t id)
- Result LottieAnimation::del(uint32_t id)

Removed API:
- Result override(const char* slot)

src/loaders/lottie/thorvg_lottie.h

@@ -22,17 +22,6 @@ class TVG_API LottieAnimation final : public Animation
 public:
     ~LottieAnimation() override;
 
-    /**
-     * @brief Override Lottie properties using slot data.
-     *
-     * @param[in] slot The Lottie slot data in JSON format to override, or @c nullptr to reset.
-     *
-     * @retval Result::InsufficientCondition In case the animation is not loaded.
-     *
-     * @since 1.0
-     */
-    Result override(const char* slot) noexcept;
-
     /**
     * @brief Specifies a segment by marker. 
     * 
@@ -110,6 +99,56 @@ public:
      */
     Result assign(const char* layer, uint32_t ix, const char* var, float val);
 
+    /**
+     * @brief Creates a new slot based on the given Lottie slot data.
+     *
+     * This function parses the provided JSON-formatted slot data and generates
+     * a new slot for animation control. The returned slot ID can be used to apply
+     * or delete the slot later.
+     *
+     * @param[in] slot A JSON string representing the Lottie slot data.
+     *
+     * @return A unique, non-zero slot ID on success. Returns @c 0 if the slot generation fails.
+     *
+     * @see apply(uint32_t id)
+     * @see del(uint32_t id)
+     *
+     * @since 1.0
+     */
+    uint32_t gen(const char* slot) noexcept;
+
+    /**
+     * @brief Applies a previously generated slot to the animation.
+     *
+     * This function applies the animation parameters defined by a slot.
+     * If the provided slot ID is 0, all previously applied slots will be reset.
+     *
+     * @param[in] id The ID of the slot to apply. Use 0 to reset all slots.
+     *
+     * @retval Result::InvalidArguments If the animation is not loaded or the slot ID is invalid.
+     *
+     * @see gen(const char* slot)
+     *
+     * @since 1.0
+     */
+    Result apply(uint32_t id) noexcept;
+
+    /**
+     * @brief Deletes a previously generated slot.
+     *
+     * This function removes a slot by its ID.
+     *
+     * @param[in] id The ID of the slot to delete. Retrieve the ID from gen().
+     *
+     * @retval Result::InvalidArguments If the animation is not loaded or the slot ID is invalid.
+     *
+     * @note This function should be paired with gen.
+     * @see gen(const char* slot)
+     *
+     * @since 1.0
+     */
+    Result del(uint32_t id) noexcept;
+
     /**
      * @brief Creates a new LottieAnimation object.
      *

src/loaders/lottie/tvgLottieAnimation.cpp

@@ -30,15 +30,39 @@ LottieAnimation::LottieAnimation() = default;
 LottieAnimation::~LottieAnimation() = default;
 
 
-Result LottieAnimation::override(const char* slot) noexcept
+uint32_t LottieAnimation::gen(const char* slot) noexcept
+{
+    auto loader = PICTURE(pImpl->picture)->loader;
+    if (!loader) return 0;
+
+    return static_cast<LottieLoader*>(loader)->gen(slot);
+}
+
+
+Result LottieAnimation::apply(uint32_t id) noexcept
 {
     auto loader = PICTURE(pImpl->picture)->loader;
     if (!loader) return Result::InsufficientCondition;
 
-    if (static_cast<LottieLoader*>(loader)->override(slot)) {
+    if (static_cast<LottieLoader*>(loader)->apply(id)) {
         PAINT(pImpl->picture)->mark(RenderUpdateFlag::All);
         return Result::Success;
     }
+
+    return Result::InvalidArguments;
+}
+
+
+Result LottieAnimation::del(uint32_t id) noexcept
+{
+    auto loader = PICTURE(pImpl->picture)->loader;
+    if (!loader) return Result::InsufficientCondition;
+
+    if (static_cast<LottieLoader*>(loader)->del(id)) {
+        PAINT(pImpl->picture)->mark(RenderUpdateFlag::All);
+        return Result::Success;
+    }
+
     return Result::InvalidArguments;
 }
 

src/loaders/lottie/tvgLottieLoader.cpp

@@ -25,6 +25,7 @@
 #include "tvgLottieModel.h"
 #include "tvgLottieParser.h"
 #include "tvgLottieBuilder.h"
+#include "tvgCompressor.h"
 
 /************************************************************************/
 /* Internal Class Implementation                                        */
@@ -44,7 +45,9 @@ void LottieLoader::run(unsigned tid)
             comp = parser.comp;
         }
         if (parser.slots) {
-            override(parser.slots, true);
+            auto slotcode = gen(parser.slots, true);
+            apply(slotcode, true);
+            del(slotcode, true);
             parser.slots = nullptr;
         }
         builder->build(comp);
@@ -288,45 +291,98 @@ Paint* LottieLoader::paint()
 }
 
 
-bool LottieLoader::override(const char* slots, bool byDefault)
+bool LottieLoader::apply(uint32_t slotcode, bool byDefault)
 {
     if (!ready() || comp->slots.count == 0) return false;
 
-    //override slots
-    if (slots) {
-        //Copy the input data because the JSON parser will encode the data immediately.
-        auto temp = byDefault ? slots : duplicate(slots);
-
-        //parsing slot json
-        LottieParser parser(temp, dirName, builder->expressions());
-        parser.comp = comp;
-
-        auto idx = 0;
-        auto succeed = false;
-        while (auto sid = parser.sid(idx == 0)) {
-            auto applied = false;
-            ARRAY_FOREACH(p, comp->slots) {
-                if (strcmp((*p)->sid, sid)) continue;
-                if (parser.apply(*p, byDefault)) succeed = applied = true;
-                break;
-            }
-            if (!applied) parser.skip();
-            ++idx;
+    bool applied = false;
+    ARRAY_FOREACH(p, comp->slots) {
+        // Reset all slots if slotcode is 0
+        if (slotcode == 0) {
+            (*p)->reset();
+            applied = true;
+            continue;
+        }
+
+        INLIST_FOREACH((*p)->values, q) {
+            if (q->slotcode != slotcode) continue;
+            (*p)->apply(q->prop, byDefault);
+            applied = true;
+            break;
         }
-        tvg::free((char*)temp);
-        rebuild = succeed;
-        overridden |= succeed;
-        return rebuild;
-    //reset slots
-    } else if (overridden) {
-        ARRAY_FOREACH(p, comp->slots) (*p)->reset();
-        overridden = false;
-        rebuild = true;
     }
+
+    if (!applied) return false;
+
+    overridden = slotcode != 0;
+    rebuild = true;
     return true;
 }
 
 
+bool LottieLoader::del(uint32_t slotcode, bool byDefault)
+{
+    if (!ready() || comp->slots.count == 0 || slotcode == 0) return false;
+
+    // Search matching value and remove
+    ARRAY_FOREACH(p, comp->slots) {
+        INLIST_FOREACH((*p)->values, q) {
+            if (q->slotcode != slotcode) continue;
+            if (!byDefault && (*p)->overridden) {
+                (*p)->reset();
+                rebuild = true;
+            }
+            (*p)->values.remove(q);
+            delete(q);
+            break;
+        }
+        if ((*p)->values.empty()) (*p)->overridden = false;
+    }
+
+    return true;
+}
+
+
+uint32_t LottieLoader::gen(const char* slots, bool byDefault)
+{
+    if (!slots || !ready() || comp->slots.count == 0) return 0;
+
+    auto slotcode = djb2Encode(slots);
+    ARRAY_FOREACH(p, comp->slots) {
+        INLIST_FOREACH((*p)->values, q) {
+            if (q->slotcode == slotcode) return slotcode;
+        }
+    }
+
+    auto temp = byDefault ? slots : duplicate(slots);
+
+    //parsing slot json
+    LottieParser parser(temp, dirName, builder->expressions());
+    parser.comp = comp;
+    
+    auto idx = 0;
+    bool generated = false;
+    while (auto sid = parser.sid(idx == 0)) {
+        ARRAY_FOREACH(p, comp->slots) {
+            if (strcmp((*p)->sid, sid)) continue;
+            auto prop = parser.parseSlot(*p);
+
+            if (prop) {
+                (*p)->add(slotcode, prop);
+                generated = true;
+            }
+            break;
+        }
+        ++idx;
+    }
+
+    tvg::free((char*)temp);
+
+    if (!generated) return 0;
+    return slotcode;
+}
+
+
 float LottieLoader::shorten(float frameNo)
 {
     //This ensures that the target frame number is reached.

src/loaders/lottie/tvgLottieLoader.h

@@ -56,7 +56,11 @@ public:
     bool resize(Paint* paint, float w, float h) override;
     bool read() override;
     Paint* paint() override;
-    bool override(const char* slot, bool byDefault = false);
+
+    //Slot APIs
+    uint32_t gen(const char* slot, bool byDefault = false);
+    bool apply(uint32_t slotcode, bool byDefault = false);
+    bool del(uint32_t slotcode, bool byDefault = false);
 
     //Frame Controls
     bool frame(float no) override;

src/loaders/lottie/tvgLottieModel.cpp

@@ -203,7 +203,52 @@ void LottieSlot::reset()
 }
 
 
-void LottieSlot::assign(LottieObject* target, bool byDefault)
+LottieProperty* LottieSlot::property(LottieObject* target)
+{
+    LottieProperty* prop = nullptr;
+    //apply slot object to all targets
+    ARRAY_FOREACH(pair, pairs) {
+        //backup the original properties before overwriting
+        switch (type) {
+            case LottieProperty::Type::Vector: {
+                return new LottieVector(static_cast<LottieTransform*>(target)->position);
+            }
+            case LottieProperty::Type::Scalar: {
+                return new LottieScalar(static_cast<LottieTransform*>(target)->scale);
+            }
+            case LottieProperty::Type::Float: {
+                return new LottieFloat(static_cast<LottieTransform*>(target)->rotation);
+            }
+            case LottieProperty::Type::Opacity: {
+                return new LottieOpacity(static_cast<LottieSolid*>(target)->opacity);
+            }
+            case LottieProperty::Type::Color: {
+                return new LottieColor(static_cast<LottieSolid*>(target)->color);
+            }
+            case LottieProperty::Type::ColorStop: {
+                return new LottieColorStop(static_cast<LottieGradient*>(target)->colorStops);
+            }
+            case LottieProperty::Type::TextDoc: {
+                return new LottieTextDoc(static_cast<LottieText*>(target)->doc);
+            }
+            case LottieProperty::Type::Image: {
+                return new LottieBitmap(static_cast<LottieImage*>(target)->data);
+            }
+            default: break;
+        }
+    }
+
+    return prop;
+}
+
+
+void LottieSlot::add(uint32_t slotcode, LottieProperty* prop)
+{
+    values.back(new Value{nullptr, nullptr, slotcode, prop});
+}
+
+
+void LottieSlot::apply(LottieProperty* prop, bool byDefault)
 {
     auto copy = !overridden && !byDefault;
     auto shallow = pairs.count == 1 ? true : false;
@@ -214,22 +259,22 @@ void LottieSlot::assign(LottieObject* target, bool byDefault)
         switch (type) {
             case LottieProperty::Type::Float: {
                 if (copy) pair->prop = new LottieFloat(static_cast<LottieTransform*>(pair->obj)->rotation);
-                pair->obj->override(&static_cast<LottieTransform*>(target)->rotation, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::Scalar: {
                 if (copy) pair->prop = new LottieScalar(static_cast<LottieTransform*>(pair->obj)->scale);
-                pair->obj->override(&static_cast<LottieTransform*>(target)->scale, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::Vector: {
                 if (copy) pair->prop = new LottieVector(static_cast<LottieTransform*>(pair->obj)->position);
-                pair->obj->override(&static_cast<LottieTransform*>(target)->position, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::Color: {
                 if (copy) pair->prop = new LottieColor(static_cast<LottieSolid*>(pair->obj)->color);
-                pair->obj->override(&static_cast<LottieSolid*>(target)->color, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::Opacity: {
@@ -237,27 +282,28 @@ void LottieSlot::assign(LottieObject* target, bool byDefault)
                     if (pair->obj->type == LottieObject::Type::Transform) pair->prop = new LottieOpacity(static_cast<LottieTransform*>(pair->obj)->opacity);
                     else pair->prop = new LottieOpacity(static_cast<LottieSolid*>(pair->obj)->opacity);
                 }
-                pair->obj->override(&static_cast<LottieSolid*>(target)->opacity, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::ColorStop: {
                 if (copy) pair->prop = new LottieColorStop(static_cast<LottieGradient*>(pair->obj)->colorStops);
-                pair->obj->override(&static_cast<LottieGradient*>(target)->colorStops, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::TextDoc: {
                 if (copy) pair->prop = new LottieTextDoc(static_cast<LottieText*>(pair->obj)->doc);
-                pair->obj->override(&static_cast<LottieText*>(target)->doc, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             case LottieProperty::Type::Image: {
                 if (copy) pair->prop = new LottieBitmap(static_cast<LottieImage*>(pair->obj)->data);
-                pair->obj->override(&static_cast<LottieImage*>(target)->data, shallow, !copy);
+                pair->obj->override(prop, shallow, !copy);
                 break;
             }
             default: break;
         }
     }
+
     if (!byDefault) overridden = true;
 }
 

src/loaders/lottie/tvgLottieModel.h

@@ -26,6 +26,7 @@
 #include "tvgCommon.h"
 #include "tvgStr.h"
 #include "tvgCompressor.h"
+#include "tvgInlist.h"
 #include "tvgRender.h"
 #include "tvgLottieProperty.h"
 #include "tvgLottieRenderPooler.h"
@@ -1058,7 +1059,21 @@ struct LottieSlot
         LottieProperty* prop;
     };
 
-    void assign(LottieObject* target, bool byDefault);
+    struct Value {
+        INLIST_ITEM(Value);
+
+        uint32_t slotcode;
+        LottieProperty* prop;
+
+        ~Value()
+        {
+            delete(prop);
+        }
+    };
+
+    LottieProperty* property(LottieObject* target);
+    void add(uint32_t slotcode, LottieProperty* prop);
+    void apply(LottieProperty* prop, bool byDefault = false);
     void reset();
 
     LottieSlot(LottieLayer* layer, LottieObject* parent, char* sid, LottieObject* obj, LottieProperty::Type type) : context{layer, parent}, sid(sid), type(type)
@@ -1069,6 +1084,7 @@ struct LottieSlot
     ~LottieSlot()
     {
         tvg::free(sid);
+        values.free();
         if (!overridden) return;
         ARRAY_FOREACH(pair, pairs) delete(pair->prop);
     }
@@ -1079,7 +1095,8 @@ struct LottieSlot
     } context;
 
     char* sid;
-    Array<Pair> pairs;
+    Array<Pair> pairs;    // Object-property pairs that can be overridden by this slot
+    Inlist<Value> values; // Available slot values for property overrides
     LottieProperty::Type type;
 
     bool overridden = false;

src/loaders/lottie/tvgLottieParser.cpp

@@ -1539,7 +1539,7 @@ const char* LottieParser::sid(bool first)
 }
 
 
-bool LottieParser::apply(LottieSlot* slot, bool byDefault)
+LottieProperty* LottieParser::parseSlot(LottieSlot* slot)
 {
     enterObject();
 
@@ -1598,14 +1598,13 @@ bool LottieParser::apply(LottieSlot* slot, bool byDefault)
 
     if (!obj || Invalid()) {
         delete(obj);
-        return false;
+        return nullptr;
     }
 
-    slot->assign(obj, byDefault);
-
+    auto prop = slot->property(obj);
     delete(obj);
 
-    return true;
+    return prop;
 }
 
 

src/loaders/lottie/tvgLottieParser.h

@@ -37,8 +37,8 @@ public:
     }
 
     bool parse();
-    bool apply(LottieSlot* slot, bool byDefault);
     const char* sid(bool first = false);
+    LottieProperty* parseSlot(LottieSlot* slot);
     void captureSlots(const char* key);
     void registerSlot(LottieObject* obj, const char* sid, LottieProperty::Type type);