NGUI的UIPanel双层裁剪

有时候有这样的需求，在一个滚动的列表里面，item中又有滚动列表，也就是UIPanel的嵌套裁剪。

而NGUI中，子UIPanel不会被父UIPanel正常裁剪，需要改造一下。

首先，在UIPanel中，增加一个parentClipPanel成员

//UIPanel.cs

[Serializefield]
public UIPanel parentClipPanel;

然后改造一下UIDrawCall的OnWillRenderObject函数

//UIDrawCall.cs


void OnWillRenderObject()
{
    ...
    if(urrentPanel.hasClipping)
    {
        float angle =0f;
        Vector4 cr = currentPanel.drawCallClipRange;

        
        if(currentPanel.parentClipPanel != null && currentPanel.parentClipPanel != panel && currentPanel.parentClipPanel.hasClipping)
        {
            //限制不能超过父Panel的裁剪区域
            Vector4 parentCR = currentPanel.parentClipPanel.drawCallClipRange;
            Vector3 pos = currentPanel.parentClipPanel.cachedTransform.InverseTransformPoint(panel.cachedTransform.position);
            parentCR.x -= pos.x;
            parentCR.y -= pos.y;

            float pXMin = parentCR.x - parentCR.z;
            float pXMax = parentCR.x + parentCR.z;
            float pYMin = parentCR.y - parentCR.w;
            float pYMax = parentCR.y + parentCR.w;
            float xMin = cr.x - cr.z;
            if (xMin < pXMin)
            {
                xMin = pXMin;
            }

            float xMax = (cr.x + cr.z);
            if (xMax > pXMax)
            {
                xMax = pXMax;
            }

            float yMin = (cr.y - cr.w);
            if (yMin < pYMin)
            {
                yMin = pYMin;
            }

            float yMax = (cr.y + cr.w);
            if (yMax > pYMax)
            {
                yMax = pYMax;
            }
            //重现计算中心点
            cr.x = (xMin + xMax) / 2;
            cr.y = (yMin + yMax) / 2;
            cr.z = (xMax - xMin) / 2;
            cr.w = (yMax - yMin) / 2;
        }
    
        //Clipping regions past the first one need additional math
        ...
    }
    ...
}

然后再改一下UIPanelInspetor

//UIPanelInspector.cs

protected override bool ShouldDrawProperties()
{
    ...
    if(mPanel.clipping == UIDrawCall.Clipping.softClip)
    {
        ...
        NGUIEditorTools.DrawProperty("应用父Panel裁剪",serializedobjet,"parentClipPanel",GUILayout.MinWidth(100f));
    }
}

然后，当有UIPanel嵌套裁剪的时候，只需要把子UIPanel的parentClipPanel设为父UIPanel即可。