[skottie] Cleanup: refactor asset lookup to avoid std::function

The main value of current AnimationBuilder::attachAssetRef is to provide
scoping semantics for ref cycle detection.

Refactor using a RAII helper (ScopedAssetRef), and avoid std::function
callbacks.

Change-Id: Idf5327465b8a06313cd9ea89be5f229ddc0aef7f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288617
Reviewed-by: Mike Reed <[email protected]>
Commit-Queue: Florin Malita <[email protected]>

Author: fmalita

modules/skottie/src/Composition.cpp

@@ -18,33 +18,29 @@
 namespace skottie {
 namespace internal {
 
-sk_sp<sksg::RenderNode> AnimationBuilder::attachAssetRef(
-    const skjson::ObjectValue& jlayer,
-    const std::function<sk_sp<sksg::RenderNode>(const skjson::ObjectValue&)>& func) const {
-
+AnimationBuilder::ScopedAssetRef::ScopedAssetRef(const AnimationBuilder* abuilder,
+                                                 const skjson::ObjectValue& jlayer) {
     const auto refId = ParseDefault<SkString>(jlayer["refId"], SkString());
     if (refId.isEmpty()) {
-        this->log(Logger::Level::kError, nullptr, "Layer missing refId.");
-        return nullptr;
+        abuilder->log(Logger::Level::kError, nullptr, "Layer missing refId.");
+        return;
     }
 
-    const auto* asset_info = fAssets.find(refId);
+    const auto* asset_info = abuilder->fAssets.find(refId);
     if (!asset_info) {
-        this->log(Logger::Level::kError, nullptr, "Asset not found: '%s'.", refId.c_str());
-        return nullptr;
+        abuilder->log(Logger::Level::kError, nullptr, "Asset not found: '%s'.", refId.c_str());
+        return;
     }
 
     if (asset_info->fIsAttaching) {
-        this->log(Logger::Level::kError, nullptr,
+        abuilder->log(Logger::Level::kError, nullptr,
                   "Asset cycle detected for: '%s'", refId.c_str());
-        return nullptr;
+        return;
     }
 
     asset_info->fIsAttaching = true;
-    auto asset = func(*asset_info->fAsset);
-    asset_info->fIsAttaching = false;
 
-    return asset;
+    fInfo = asset_info;
 }
 
 CompositionBuilder::CompositionBuilder(const AnimationBuilder& abuilder,

modules/skottie/src/SkottiePriv.h

@@ -19,7 +19,6 @@
 #include "modules/sksg/include/SkSGScene.h"
 #include "src/utils/SkUTF.h"
 
-#include <functional>
 #include <vector>
 
 class SkFontMgr;
@@ -189,8 +188,6 @@ class AnimationBuilder final : public SkNoncopyable {
                                             sk_sp<sksg::RenderNode>) const;
 
     sk_sp<sksg::RenderNode> attachShape(const skjson::ArrayValue*, AttachShapeContext*) const;
-    sk_sp<sksg::RenderNode> attachAssetRef(const skjson::ObjectValue&,
-        const std::function<sk_sp<sksg::RenderNode>(const skjson::ObjectValue&)>&) const;
     const FootageAssetInfo* loadFootageAsset(const skjson::ObjectValue&) const;
     sk_sp<sksg::RenderNode> attachFootageAsset(const skjson::ObjectValue&, LayerInfo*) const;
 
@@ -253,6 +250,24 @@ class AnimationBuilder final : public SkNoncopyable {
         SkISize           fSize;
     };
 
+    class ScopedAssetRef {
+    public:
+        ScopedAssetRef(const AnimationBuilder* abuilder, const skjson::ObjectValue& jlayer);
+
+        ~ScopedAssetRef() {
+            if (fInfo) {
+                fInfo->fIsAttaching = false;
+            }
+        }
+
+        operator bool() const { return !!fInfo; }
+
+        const skjson::ObjectValue& operator*() const { return *fInfo->fAsset; }
+
+    private:
+        const AssetInfo* fInfo = nullptr;
+    };
+
     SkTHashMap<SkString, AssetInfo>                fAssets;
     SkTHashMap<SkString, FontInfo>                 fFonts;
     mutable SkTHashMap<SkString, FootageAssetInfo> fImageAssetCache;

modules/skottie/src/layers/FootageLayer.cpp

@@ -147,10 +147,11 @@ sk_sp<sksg::RenderNode> AnimationBuilder::attachFootageAsset(const skjson::Objec
 
 sk_sp<sksg::RenderNode> AnimationBuilder::attachFootageLayer(const skjson::ObjectValue& jlayer,
                                                              LayerInfo* layer_info) const {
-    return this->attachAssetRef(jlayer,
-        [this, &layer_info] (const skjson::ObjectValue& jimage) {
-            return this->attachFootageAsset(jimage, layer_info);
-        });
+    const ScopedAssetRef footage_asset(this, jlayer);
+
+    return footage_asset
+        ? this->attachFootageAsset(*footage_asset, layer_info)
+        : nullptr;
 }
 
 } // namespace internal

modules/skottie/src/layers/PrecompLayer.cpp

@@ -186,10 +186,11 @@ sk_sp<sksg::RenderNode> AnimationBuilder::attachPrecompLayer(const skjson::Objec
     auto precomp_layer = this->attachExternalPrecompLayer(jlayer, *layer_info);
 
     if (!precomp_layer) {
-        precomp_layer = this->attachAssetRef(jlayer,
-            [this, layer_info] (const skjson::ObjectValue& jcomp) {
-                return CompositionBuilder(*this, layer_info->fSize, jcomp).build(*this);
-            });
+        const ScopedAssetRef precomp_asset(this, jlayer);
+        if (precomp_asset) {
+            precomp_layer =
+                CompositionBuilder(*this, layer_info->fSize, *precomp_asset).build(*this);
+        }
     }
 
     if (requires_time_mapping) {