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Unity2020 Graphic 小坑

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最近项目升级了2020.3，Graphic这边多给了一个Raycast Padding的设置。
我们有在用一些完全空白的图片来接受UI的点击响应，同时也有一些用图片接收点击的按钮。

但很坑爹的是，我发现无论怎么设置Raycast Padding的值，场景预览中都没有显示框框，所以我其实是完全不知道这玩意儿到底怎么用的。
搜索一下才知道原来是padding的数值是负数的时候才是往外扩张。

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public class RaycastTarget : Graphic
{
    // Additionally, If you need a Raycast target that is not a rectangle, you can implement bool Raycast(Vector2 sp, Camera eventCamera) method from Graphic.
    public override void SetMaterialDirty() { return; }
    public override void SetVerticesDirty() { return; }
    /// Probably not necessary since the chain of calls `Rebuild()`->`UpdateGeometry()`->`DoMeshGeneration()`->`OnPopulateMesh()` won't happen; so here really just as a fail-safe.
    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();
        return;
    }

#if UNITY_EDITOR

    private void OnDrawGizmos()
    {
        if (!this.enabled)
            return
        RectTransform rectTransform = this.transform as RectTransform;
        Color wireColor = Color.yellow;
        if (this.isActiveAndEnabled)
            wireColor.a *= 0.7f
        // Padding to be applied to the masking
        // X = Left, Y = Bottom, Z = Right, W = Top
        // if you wanna make it bigger, then the all value shouble be negative
        Vector4 padding = this.raycastPadding * -1.0f;
        Matrix4x4 localToWorld = rectTransform.localToWorldMatrix
        Vector3 topLeft = SomeUtils.GetOffsetLocalPosition(rectTransform, SomeUtils.UIOffsetType.TopLeft);
        Vector3 topRight = SomeUtils.GetOffsetLocalPosition(rectTransform, SomeUtils.UIOffsetType.TopRight);
        Vector3 bottomLeft = SomeUtils.GetOffsetLocalPosition(rectTransform, SomeUtils.UIOffsetType.BottomLeft);
        Vector3 bottomRight = SomeUtils.GetOffsetLocalPosition(rectTransform, SomeUtils.UIOffsetType.BottomRight)
        topLeft = localToWorld.MultiplyPoint(topLeft + (Vector3.left * padding.x) + (Vector3.up * padding.w));
        topRight = localToWorld.MultiplyPoint(topRight + (Vector3.right * padding.z) + (Vector3.up * padding.w));
        bottomLeft = localToWorld.MultiplyPoint(bottomLeft + (Vector3.left * padding.x) + (Vector3.down * padding.y));
        bottomRight = localToWorld.MultiplyPoint(bottomRight + (Vector3.right * padding.z) + (Vector3.down * padding.y))
        Color tempColor = Gizmos.color;
        Gizmos.color = wireColor
        Gizmos.DrawLine(topLeft, topRight);
        Gizmos.DrawLine(topLeft, bottomLeft);
        Gizmos.DrawLine(bottomRight, topRight);
        Gizmos.DrawLine(bottomRight, bottomLeft);
        Gizmos.color = tempColor
    }

#endif

}

空白raycast target的可以在Gizmo里画，但是Image本身的不是那么好画，因为无法直接覆写原本的Editor。
一个笨办法就是做一个自己的Iamge然后也在Gizmo里画。
但其实这个是Graphic的property 不知道怎么做通用解决方案。