Hello !

I have a performance issue when trying to fade out a SkeletonGraphic via code.
To do that, I am using the SkeletonGraphic.color property, inherited from UnityEngine.UI.Graphic.color, and modify its alpha.
My first question is : is it the correct way to do it ? (or should I use a CanvasGroup on top, or another method...)

When profiling, I was surprised by the long time processing Canvas.SendWillRenderCanvases, in particular, CanvasUpdate.PreRender.

After debugging, I eventually understood that :

1. Setting the color property marks the vertices of the Graphic component as dirty :

   public virtual Color color { get { return m_Color; } set { if (SetPropertyUtility.SetColor(ref m_Color, value)) SetVerticesDirty(); } } // from UnityEngine.UI.Graphic.cs

2. The dirty SkeletonGraphic will be rebuilt during the Canvas Update (cf. "SpineCanvasRebuild" screenshot)

3. When rebuilding, the SkeletonGraphic will (re)Update its mesh.

   // From SkeletonGraphic.cs
   public override void Rebuild (CanvasUpdate update) {
      base.Rebuild(update);
      if (canvasRenderer.cull) return;
      if (update == CanvasUpdate.PreRender) UpdateMesh(keepRendererCount: true);
      if (allowMultipleCanvasRenderers) canvasRenderer.Clear();
   }

For my use case, this is redundant : the mesh is already updated in SkeletonGraphic.LateUpdate(), I don't want to reupdate it in the same frame as it was already quite expensive ^^"

So I tried setting the color not via the color property, but directly in the skeleton using skeleton.A or skeleton.SetColor().

Unfortunately, SkeletonGraphic eventually uses this Graphic.color property I'm dreading :

public void UpdateMesh (bool keepRendererCount = false) {
   if (!this.IsValid) return;

   // !!!
   skeleton.SetColor(this.color); // !!! The culprit !!!
   // !!!

   var currentInstructions = this.currentInstructions;
   if (!this.allowMultipleCanvasRenderers) {
      UpdateMeshSingleCanvasRenderer();
   } else {
      UpdateMeshMultipleCanvasRenderers(currentInstructions, keepRendererCount);
   }

   if (OnMeshAndMaterialsUpdated != null)
      OnMeshAndMaterialsUpdated(this);
}

Do you have any recommendation ? How can I achieve my effect, possibly without modifying the Spine Unity runtime ?

Thanks in advance

One way I see to prevent this would be to temporarily limit the updateMode to "OnlyAnimationStatus", while I do my alpha fading.

But I'd be happy to hear other solutions