Linked meshes multiply deformation applied through a slider

[misaki-eymard]

Description:
When many linked meshes use the same mesh attachment as their source mesh, deformation applied to the source mesh through a slider is multiplied.

The amount of deformation increases depending on the number of linked meshes that reference the same source mesh.

Expected behavior:
Even when many linked meshes use the same mesh attachment as their source mesh, deformation applied to the source mesh through a slider should be applied to each linked mesh by exactly the same amount when the slider mix is set to 100.

Steps to reproduce:

1. Download the attached .zip file: 1082-linked-mesh-count-increases-slider-deformation.zip

2. Open the Spine project in Spine 4.3.23. The skeleton contains a simple pentagonal mesh, as shown below:

3. Switch to Animate mode and view the slider animation. Notice that the pentagonal mesh is compressed and becomes narrower due to a deform key:

4. Next, view the animation named animation. This animation applies the slider with its mix set to 100 and uses frame keys to move the slider. However, instead of merely being compressed, the pentagonal mesh is deformed so far that it expands toward the opposite side:

If some of the linked meshes in the Linked meshes slot are deleted, reducing the total number of linked meshes, the amount of deformation changes.

Version where this issue was observed:
4.3.23

This issue was reported via email:
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