初学者求教这段C++代码的意思

菜鸟求教这段C++代码的意思
TRect CR;
void __fastcall TMainForm::SeriesAfterAdd(TChartSeries *Sender, int ValueIndex)
{
HRGN ClipRgn = CreateRectRgnIndirect(&CR);
SelectClipRgn(static_cast<TChart *>(Sender->ParentChart)->Canvas->ReferenceCanvas->Handle, ClipRgn);
DeleteObject(ClipRgn);
}

bool __fastcall TMainForm::SeriesBeforeAdd(TChartSeries *Sender)
{
TCanvas *cav = static_cast<TChart *>(Sender->ParentChart)->Canvas->ReferenceCanvas;
CR = cav->ClipRect;
TRect rc = static_cast<TChart *>(Sender->ParentChart)->ChartRect;
IntersectClipRect(cav->Handle,
                  rc.Left+1,
                  rc.Top+1,
                  rc.Right,
                  rc.Bottom);

return true;
}
------解决方案--------------------
IntersectClipRect
函数功能：该函数创建了一个新的剪切区域，该区域是当前剪切区域和一个特定矩形的交集。 

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