Cancel painting teleports to the same block

[roccodev]

In 1.8 (and presumably below?), teleporting a painting to the same block, or too close to its current entity coordinates causes it to calculate the wrong block coordinates and move a block out.

This issue can be reproduced in a Paper 26.2 server. Since this commit, entities will broadcast a teleport packet every time a new player is tracked. I don't think teleport is normally sent for paintings otherwise (unless you /tp them far enough away)

Note: This depends on ViaVersion/ViaBackwards#1313 to get accurate entity coordinates from the upstream protocols.

For reference, in EntityPainting:

@SideOnly(Side.CLIENT)
public void setPositionAndRotation2(double x, double y, double z, float yaw, float pitch, int posRotationIncrements, boolean p_180426_10_) {
    BlockPos blockpos = this.hangingPosition.add(x - this.posX, y - this.posY, z - this.posZ);
    this.setPosition((double)blockpos.getX(), (double)blockpos.getY(), (double)blockpos.getZ());
}

However, setPosition immediately overwrites the entity coordinates, and only performs the painting recalculation if the attached block is different:

public void setPosition(double x, double y, double z) {
    this.posX = x;
    this.posY = y;
    this.posZ = z;
    // ^ The entity coordinates aren't supposed to be the block coordinates (in 1.8)
    
    BlockPos blockpos = this.hangingPosition;
    this.hangingPosition = new BlockPos(x, y, z);

    if (!this.hangingPosition.equals(blockpos))
    {
        // This recalculates the entity coordinates
        // ...but only if the painting moved to a different block
        this.updateBoundingBox();
        // ...
    }
}

I couldn't reproduce the issue in 1.9, which makes me think it's a 1.8 issue, though I haven't looked at its code.

Here is the bug in action, by the way:

out.mp4