PtInRegion判断一个点是不是在四边形内，代码错哪了

PtInRegion判断一个点是不是在四边形内，代码哪里错了 - C++ Builder / Windows SDK/API
用的API函数PtInRegion判断的

C/C++ code

   float x1 = StrToFloat(Edit1->Text),y1 = StrToFloat(Edit2->Text),         x2 = StrToFloat(Edit3->Text),y2 = StrToFloat(Edit4->Text),         x3 = StrToFloat(Edit5->Text),y3 = StrToFloat(Edit6->Text),         x4 = StrTofloat(Edit7->Text),y4 = StrToFloat(Edit8->Text),         x = StrToFloat(Edit9->Text),y = StrtoFloat(Edit10->Text);   POINT p[3];   p[0].x = x1;  p[0].y = y1;   p[1].x = x2;  p[1].y = y2;   p[2].x = x3;  p[2].y = y3;   p[3].x = x4;  p[3].y = y4;   HRGN hRgn = CreatePolygonRgn(p,4,ALTERNATE);   bool a = PtInRegion(hRgn,x,y);   ShowMessage(a);