SuperStrict

Graphics(800,600,0)

Local G_Timer:TTimer=CreateTimer(50)

Local X1:Int,Y1:Int,X2:Int,Y2:Int,X3:Int,Y3:Int,X4:Int,Y4:Int
X1=200;Y1=100
X3=150;Y3=10
X4=150;Y4=200

Repeat
	
	X2=MouseX()
	Y2=MouseY()
	
	DrawLine(X1,Y1,X2,Y2)
	DrawLine(X3,Y3,X4,Y4)
	
	DrawText(LinesIntersect(X1,Y1,X2,Y2,X3,Y3,X4,Y4),10,580)
	
	DrawText("Punkt 1: "+X1+","+Y1,10,500)
	DrawText("Punkt 2: "+X2+","+Y2,10,520)
	DrawText("Punkt 3: "+X3+","+Y3,10,540)
	DrawText("Punkt 4: "+X4+","+Y4,10,560)
	
	Flip 0
	WaitTimer(G_Timer)
	Cls
Until (KeyHit(KEY_ESCAPE) Or AppTerminate())
End

Function LinesIntersect:Int(X1:Int,Y1:Int,X2:Int,Y2:Int,X3:Int,Y3:Int,X4:Int,Y4:Int)
	Local DX1:Int=X2-X1,DX2:Int=X4-X3
	Local DY1:Int=Y2-Y1,DY2:Int=Y4-Y3
	Local DX:Int=X1-X3,DY:Int=Y1-Y3
	
	Local Det:Int=DX2*DY1-DY2*DX1
	
	If (Det<>0)
		Local DetInv:Float=1.0/Float(Det)'Inverse of determinant of the system of linear equations given by the intersection of the two lines
		Local DetS:Int=DX*DY2-DX2*DY
		Local DetT:Int=DX*DY1-DX1*DY
		Local s:Float=Float(DetS)*DetInv,t:Float=Float(DetT)*DetInv
		DrawText("s="+s+" t="+t,10,480)
		If ((0<=s) And (1>=s))
			If ((0<=t) And (1>=t))
				Return True
			End If
		End If
	End If
	Return False
End Function