Add function to recursively calculate duration of a blend tree

The resulting duration is independent of which animators the blend
tree is associated with so this can be implemented as a simple set
of virtual functions in the concrete classes.

The value node simply returns the duration of the contained clip; the
additive node returns the duration of the base node; and the lerp node
lerps the durations of the start and end nodes.

Change-Id: Ib6edea3fa495885493fa72d44437fea5a8c5a446
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
Reviewed-by: Mike Krus <mike.krus@kdab.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/animation/backend/lerpclipblend.cpp b/src/animation/backend/lerpclipblend.cpp
index 7e10a5174..7b1efbf50 100644
--- a/src/animation/backend/lerpclipblend.cpp
+++ b/src/animation/backend/lerpclipblend.cpp
@@ -85,6 +85,17 @@ void LerpClipBlend::initializeFromPeer(const Qt3DCore::QNodeCreatedChangeBasePtr
     m_blendFactor = cloneData.blendFactor;
 }
 
+double LerpClipBlend::duration() const
+{
+    ClipBlendNode *startNode = clipBlendNodeManager()->lookupNode(m_startClipId);
+    const double startNodeDuration = startNode ? startNode->duration() : 0.0;
+
+    ClipBlendNode *endNode = clipBlendNodeManager()->lookupNode(m_endClipId);
+    const double endNodeDuration = endNode ? endNode->duration() : 0.0;
+
+    return blend(startNodeDuration, endNodeDuration);
+}
+
 } // Animation
 
 } // Qt3DAnimation