lottie: improve the compatiblity

merge the scene with more accurate condition to allow
the evenodd pathes among the lottie render tree.

src/loaders/lottie/tvgLottieBuilder.cpp

@@ -150,12 +150,8 @@ void LottieBuilder::updateTransform(LottieLayer* layer, float frameNo)
 
     _updateTransform(transform, frameNo, matrix, layer->cache.opacity, layer->autoOrient, tween, exps);
 
-    if (parent) {
-        if (!tvg::identity((const Matrix*) &parent->cache.matrix)) {
-            if (tvg::identity((const Matrix*) &matrix)) layer->cache.matrix = parent->cache.matrix;
-            else layer->cache.matrix = parent->cache.matrix * matrix;
-        }
-    }
+    if (parent) layer->cache.matrix = parent->cache.matrix * matrix;
+
     layer->cache.frameNo = frameNo;
 }
 
@@ -165,25 +161,30 @@ void LottieBuilder::updateTransform(LottieGroup* parent, LottieObject** child, f
     auto transform = static_cast<LottieTransform*>(*child);
     if (!transform) return;
 
+    Matrix m;
     uint8_t opacity;
 
     if (parent->mergeable()) {
-        if (!ctx->transform) ctx->transform = tvg::malloc<Matrix*>(sizeof(Matrix));
+        if (ctx->transform) {
+            _updateTransform(transform, frameNo, m, opacity, false, tween, exps);
+            *ctx->transform *= m;
+        } else {
+            ctx->transform = new Matrix;
             _updateTransform(transform, frameNo, *ctx->transform, opacity, false, tween, exps);
+        }
         return;
     }
 
     ctx->merging = nullptr;
 
-    Matrix matrix;
-    if (!_updateTransform(transform, frameNo, matrix, opacity, false, tween, exps)) return;
+    if (!_updateTransform(transform, frameNo, m, opacity, false, tween, exps)) return;
 
-    ctx->propagator->transform(ctx->propagator->transform() * matrix);
+    ctx->propagator->transform(ctx->propagator->transform() * m);
     ctx->propagator->opacity(MULTIPLY(opacity, PAINT(ctx->propagator)->opacity));
 
     //FIXME: preserve the stroke width. too workaround, need a better design.
     if (SHAPE(ctx->propagator)->rs.strokeWidth() > 0.0f) {
-        auto denominator = sqrtf(matrix.e11 * matrix.e11 + matrix.e12 * matrix.e12);
+        auto denominator = sqrtf(m.e11 * m.e11 + m.e12 * m.e12);
         if (denominator > 1.0f) ctx->propagator->strokeWidth(ctx->propagator->strokeWidth() / denominator);
     }
 }

src/loaders/lottie/tvgLottieBuilder.h

@@ -73,7 +73,7 @@ struct RenderContext
     ~RenderContext()
     {
         propagator->unref(false);
-        tvg::free(transform);
+        delete(transform);
         delete(roundness);
         delete(offset);
     }
@@ -92,6 +92,10 @@ struct RenderContext
             offset = new LottieOffsetModifier(rhs.offset->offset, rhs.offset->miterLimit, rhs.offset->join);
             update(offset);
         }
+        if (rhs.transform) {
+            transform = new Matrix;
+            *transform = *rhs.transform;
+        }
     }
 
     void update(LottieModifier* next)

src/loaders/lottie/tvgLottieModel.cpp

@@ -551,7 +551,7 @@ void LottieGroup::prepare(LottieObject::Type type)
 
         /* Figure out if this group is a simple path drawing.
            In that case, the rendering context can be sharable with the parent's. */
-        if (allowMerge && (child->type == LottieObject::Group || !child->mergeable())) allowMerge = false;
+        if (allowMerge && !child->mergeable()) allowMerge = false;
 
         //Figure out this group has visible contents
         switch (child->type) {

src/loaders/lottie/tvgLottieModel.h

@@ -569,8 +569,7 @@ struct LottieTransform : LottieObject
 
     bool mergeable() override
     {
-        if (!opacity.frames && opacity.value == 255) return true;
-        return false;
+        return true;
     }
 
     LottieProperty* property(uint16_t ix) override