[skottie] "hold" keyframe support

TBR=

Change-Id: I5388bc5a5d24b3bbe3962b2da646719e95efe858
Reviewed-on: https://skia-review.googlesource.com/99281
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

2 files changed, 39 insertions, 15 deletions

diff --git a/experimental/skottie/SkottieAnimator.cpp b/experimental/skottie/SkottieAnimator.cpp
index 6568d1b183..da00beb2fe 100644
--- a/experimental/skottie/SkottieAnimator.cpp
+++ b/experimental/skottie/SkottieAnimator.cpp
@@ -48,16 +48,20 @@ bool KeyframeIntervalBase::parse(const Json::Value& k, KeyframeIntervalBase* pre
         prev->fT1 = fT0;
     }
 
-    // default is linear lerp
-    static constexpr SkPoint kDefaultC0 = { 0, 0 },
-                             kDefaultC1 = { 1, 1 };
-    const auto c0 = ParsePoint(k["i"], kDefaultC0),
-               c1 = ParsePoint(k["o"], kDefaultC1);
-
-    if (c0 != kDefaultC0 || c1 != kDefaultC1) {
-        fCubicMap = skstd::make_unique<SkCubicMap>();
-        // TODO: why do we have to plug these inverted?
-        fCubicMap->setPts(c1, c0);
+    fHold = ParseBool(k["h"], false);
+
+    if (!fHold) {
+        // default is linear lerp
+        static constexpr SkPoint kDefaultC0 = { 0, 0 },
+                                 kDefaultC1 = { 1, 1 };
+        const auto c0 = ParsePoint(k["i"], kDefaultC0),
+                   c1 = ParsePoint(k["o"], kDefaultC1);
+
+        if (c0 != kDefaultC0 || c1 != kDefaultC1) {
+            fCubicMap = skstd::make_unique<SkCubicMap>();
+            // TODO: why do we have to plug these inverted?
+            fCubicMap->setPts(c1, c0);
+        }
     }
 
     return true;
@@ -65,6 +69,12 @@ bool KeyframeIntervalBase::parse(const Json::Value& k, KeyframeIntervalBase* pre
 
 float KeyframeIntervalBase::localT(float t) const {
     SkASSERT(this->isValid());
+
+    // 'hold' pins to v0
+    if (fHold) {
+        return 0;
+    }
+
     auto lt = (t - fT0) / (fT1 - fT0);
 
     if (fCubicMap) {
diff --git a/experimental/skottie/SkottieAnimator.h b/experimental/skottie/SkottieAnimator.h
index 4ab877ecaf..c03449d11a 100644
--- a/experimental/skottie/SkottieAnimator.h
+++ b/experimental/skottie/SkottieAnimator.h
@@ -29,7 +29,7 @@ public:
     float t0() const { return fT0; }
     float t1() const { return fT1; }
 
-    bool isValid() const { return fT0 < fT1; }
+    bool isValid() const { return fT0 < fT1 || fHold; }
     bool contains(float t) const { return t >= fT0 && t <= fT1; }
 
 protected:
@@ -40,6 +40,8 @@ protected:
     // through the cubic (if applicable).
     float localT(float t) const;
 
+    bool isHold() const { return fHold; }
+
 private:
     // Initialized for non-linear interpolation.
     std::unique_ptr<SkCubicMap> fCubicMap;
@@ -47,6 +49,8 @@ private:
     // Start/end times.
     float                       fT0 = 0,
                                 fT1 = 0;
+
+    bool                        fHold = false;
 };
 
 // Describes a keyframe interpolation interval (v0@t0) -> (v1@t1).
@@ -56,10 +60,20 @@ public:
     bool parse(const Json::Value& k, KeyframeInterval* prev) {
         SkASSERT(k.isObject());
 
-        return this->INHERITED::parse(k, prev) &&
-            ValueTraits<T>::Parse(k["s"], &fV0) &&
-            ValueTraits<T>::Parse(k["e"], &fV1) &&
-            ValueTraits<T>::Cardinality(fV0) == ValueTraits<T>::Cardinality(fV1) &&
+        if (!this->INHERITED::parse(k, prev) ||
+            !ValueTraits<T>::Parse(k["s"], &fV0)) {
+            return false;
+        }
+
+        if (this->isHold()) {
+            // Hold v1 == v0.
+            fV1 = fV0;
+        } else if (!ValueTraits<T>::Parse(k["e"], &fV1)) {
+            return false;
+        }
+
+
+        return ValueTraits<T>::Cardinality(fV0) == ValueTraits<T>::Cardinality(fV1) &&
             (!prev || ValueTraits<T>::Cardinality(fV0) == ValueTraits<T>::Cardinality(prev->fV0));
     }