[skottie] Ignore identity transforms

Some tranform properties are not optional, but many of them are static
identity.  Detect these cases and don't attach SG nodes for them.

Reduces the number of sksg::Matrix nodes by ~18%.

TBR=
Change-Id: Ia51c865d6928e8c48c73b30f6d45541caf334880
Reviewed-on: https://skia-review.googlesource.com/140186
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

2 files changed, 26 insertions, 24 deletions

diff --git a/modules/skottie/src/Skottie.cpp b/modules/skottie/src/Skottie.cpp
index 60009b9bc0..e59ace86ac 100644
--- a/modules/skottie/src/Skottie.cpp
+++ b/modules/skottie/src/Skottie.cpp
@@ -77,20 +77,24 @@ bool LogFail(const skjson::Value& json, const char* msg) {
 
 sk_sp<sksg::Matrix> AttachMatrix(const skjson::ObjectValue& t, AttachContext* ctx,
                                  sk_sp<sksg::Matrix> parentMatrix) {
+    static const VectorValue g_default_vec_0   = {  0,   0},
+                             g_default_vec_100 = {100, 100};
+
     auto matrix = sksg::Matrix::Make(SkMatrix::I(), std::move(parentMatrix));
     auto adapter = sk_make_sp<TransformAdapter>(matrix);
-    auto anchor_attached = BindProperty<VectorValue>(t["a"], &ctx->fAnimators,
+
+    auto bound = BindProperty<VectorValue>(t["a"], &ctx->fAnimators,
             [adapter](const VectorValue& a) {
                 adapter->setAnchorPoint(ValueTraits<VectorValue>::As<SkPoint>(a));
-            });
-    auto position_attached = BindProperty<VectorValue>(t["p"], &ctx->fAnimators,
+            }, g_default_vec_0);
+    bound |= BindProperty<VectorValue>(t["p"], &ctx->fAnimators,
             [adapter](const VectorValue& p) {
                 adapter->setPosition(ValueTraits<VectorValue>::As<SkPoint>(p));
-            });
-    auto scale_attached = BindProperty<VectorValue>(t["s"], &ctx->fAnimators,
+            }, g_default_vec_0);
+    bound |= BindProperty<VectorValue>(t["s"], &ctx->fAnimators,
             [adapter](const VectorValue& s) {
                 adapter->setScale(ValueTraits<VectorValue>::As<SkVector>(s));
-            });
+            }, g_default_vec_100);
 
     const auto* jrotation = &t["r"];
     if (jrotation->is<skjson::NullValue>()) {
@@ -98,30 +102,20 @@ sk_sp<sksg::Matrix> AttachMatrix(const skjson::ObjectValue& t, AttachContext* ct
         // we can still make use of rz.
         jrotation = &t["rz"];
     }
-    auto rotation_attached = BindProperty<ScalarValue>(*jrotation, &ctx->fAnimators,
+    bound |= BindProperty<ScalarValue>(*jrotation, &ctx->fAnimators,
             [adapter](const ScalarValue& r) {
                 adapter->setRotation(r);
-            });
-    auto skew_attached = BindProperty<ScalarValue>(t["sk"], &ctx->fAnimators,
+            }, 0.0f);
+    bound |= BindProperty<ScalarValue>(t["sk"], &ctx->fAnimators,
             [adapter](const ScalarValue& sk) {
                 adapter->setSkew(sk);
-            });
-    auto skewaxis_attached = BindProperty<ScalarValue>(t["sa"], &ctx->fAnimators,
+            }, 0.0f);
+    bound |= BindProperty<ScalarValue>(t["sa"], &ctx->fAnimators,
             [adapter](const ScalarValue& sa) {
                 adapter->setSkewAxis(sa);
-            });
-
-    if (!anchor_attached &&
-        !position_attached &&
-        !scale_attached &&
-        !rotation_attached &&
-        !skew_attached &&
-        !skewaxis_attached) {
-        LogFail(t, "Could not parse transform");
-        return nullptr;
-    }
+            }, 0.0f);
 
-    return matrix;
+    return bound ? matrix : nullptr;
 }
 
 sk_sp<sksg::RenderNode> AttachOpacity(const skjson::ObjectValue& jtransform, AttachContext* ctx,
diff --git a/modules/skottie/src/SkottieAnimator.h b/modules/skottie/src/SkottieAnimator.h
index c4464e3138..23bd9aa500 100644
--- a/modules/skottie/src/SkottieAnimator.h
+++ b/modules/skottie/src/SkottieAnimator.h
@@ -22,7 +22,15 @@ template <typename T>
 bool BindProperty(const skjson::Value&,
                   sksg::AnimatorList*,
                   std::function<void(const T&)>&&,
-                  const T* noop = nullptr);
+                  const T* default_igore = nullptr);
+
+template <typename T>
+bool BindProperty(const skjson::Value& jv,
+                  sksg::AnimatorList* animators,
+                  std::function<void(const T&)>&& apply,
+                  const T& default_ignore) {
+    return BindProperty(jv, animators, std::move(apply), &default_ignore);
+}
 
 } // namespace skottie