From 5b8c66f5c8326b374649eb800e35af4bf366e5e0 Mon Sep 17 00:00:00 2001
From: Hermet Park <hermet@lottiefiles.com>
Date: Tue, 19 Sep 2023 00:47:43 +0900
Subject: [PATCH] lottie/builder: fix an invalid matting result.

Previously, it ignored the matte when it was out of frames for the sake of optimization.
However, this led to an incorrect matting result.

It should make the scene invisible when the matting is invisible.
---
 src/loaders/lottie/tvgLottieBuilder.cpp | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/loaders/lottie/tvgLottieBuilder.cpp b/src/loaders/lottie/tvgLottieBuilder.cpp
index e5f38b75..bf97150c 100644
--- a/src/loaders/lottie/tvgLottieBuilder.cpp
+++ b/src/loaders/lottie/tvgLottieBuilder.cpp
@@ -799,29 +799,29 @@ static void _updateLayer(LottieLayer* root, LottieLayer* layer, int32_t frameNo)
 
     _updateTransform(layer, frameNo);
 
+    //full transparent scene. no need to perform
+    if (layer->type != LottieLayer::Null && layer->cache.opacity == 0) return;
+
     //Prepare render data
     layer->scene = Scene::gen().release();
 
-    //FIXME: Ignore opacity when Null layer?
-    if (layer->type != LottieLayer::Null) {
-        if (layer->cache.opacity == 0 && !layer->matteSrc) {
-            delete(layer->scene);
-            layer->scene = nullptr;
-            return;
-        }
-        layer->scene->opacity(layer->cache.opacity);
-    }
+    //ignore opacity when Null layer?
+    if (layer->type != LottieLayer::Null) layer->scene->opacity(layer->cache.opacity);
 
     layer->scene->transform(layer->cache.matrix);
 
-    if (layer->matte.target && layer->masks.count > 0) {
-        TVGERR("LOTTIE", "FIXME: Matte + Masking??");
-    }
+    if (layer->matte.target && layer->masks.count > 0) TVGERR("LOTTIE", "FIXME: Matte + Masking??");
 
     //matte masking layer
     if (layer->matte.target) {
         _updateLayer(root, layer->matte.target, frameNo);
         if (layer->matte.target->scene) layer->scene->composite(cast<Scene>(layer->matte.target->scene), layer->matte.type);
+        else if (layer->matte.type == CompositeMethod::AlphaMask || layer->matte.type == CompositeMethod::LumaMask) {
+            //matte target is not exist. alpha blending definitely bring an invisible result
+            delete(layer->scene);
+            layer->scene = nullptr;
+            return;
+        }
     }
 
     _updateMaskings(layer, frameNo);