void AddMiddleArrowHead(TCurlyLine *cl);


void feynman_ComptonPion(void)
{
	TCanvas *c1 = new TCanvas("c1", "", 600, 600);
	c1->Range(-1.0, -1.0, +1.0, +1.0);
	
	gStyle->SetLineWidth(6);
	
#if 1
	// Draw with time going from left to right
	TCurlyLine *gamma1 = new TCurlyLine(0.0, 0.0, +0.7, +0.7);
	gamma1->SetWavy();
	gamma1->SetWaveLength(0.08);
	gamma1->Draw();

	TCurlyLine *gamma2 = new TCurlyLine(-0.7, +0.7, 0.0, 0.0);
	gamma2->SetWavy();
	gamma2->SetWaveLength(0.08);
	gamma2->Draw();

	AddMiddleArrowHead(gamma1);
	AddMiddleArrowHead(gamma2);

	TArrow *pip = new TArrow(-0.7, -0.7, 0.0, 0.0, 0.05, "->-");
	pip->Draw();

	TArrow *pim = new TArrow(0.0, 0.0, +0.7, -0.7, 0.05, "->-");
	pim->Draw();
	
	TEllipse *exchange = new TEllipse(0.0, 0.0, 0.1, 0.1);
	exchange->SetFillColor(kCyan);
//	TLine *exchange = new TLine(0.0, -0.2, 0.0, +0.2);
	exchange->Draw();
	
	TLatex t;
	t.SetTextAlign(22);
	t.SetTextSize(0.2);

	t.DrawLatex(-0.830, +0.80, "#gamma");
	t.DrawLatex(-0.860, -0.80, "#pi^{#pm}");
	t.DrawLatex(+0.830, +0.80, "#gamma");
	t.DrawLatex(+0.830, -0.80, "#pi^{#pm}");

#else
	// Draw with time going from bottom to top
	TCurlyLine *gamma1 = new TCurlyLine(-0.9, -0.9, -0.2, 0.0);
	gamma1->SetWavy();
	gamma1->SetWaveLength(0.08);
	gamma1->Draw();
	
	TCurlyLine *gamma2 = new TCurlyLine(+0.2, 0.0, +0.9, +0.9);
	gamma2->SetWavy();
	gamma2->SetWaveLength(0.08);
	gamma2->Draw();

	//AddMiddleArrowHead(gamma1);
	//AddMiddleArrowHead(gamma2);
	
	TArrow *pi1 = new TArrow(+0.9, -0.9, +0.2, 0.0, 0.05, "->-");
	pi1->Draw();
	
	TArrow *pi2 = new TArrow(-0.2, 0.0, -0.9, +0.9, 0.05, "->-");
	pi2->Draw();
	
	TLine *exchange = new TLine(-0.2, 0.0, +0.2, 0.0);
	exchange->Draw();
	
	TLatex t;
	t.SetTextSize(0.2);
	
	t.DrawLatex(-0.951, -0.771, "#gamma");
	t.DrawLatex(+0.759, -0.712, "#pi*");
	t.DrawLatex(-0.805, +0.784, "#pi");
	t.DrawLatex(+0.618, +0.75, "#gamma");
#endif

	c1->SaveAs("feynman_ComptonPion.png");
	c1->SaveAs("feynman_ComptonPion.pdf");
}

void AddMiddleArrowHead(TCurlyLine *cl)
{
	double xmid = (cl->GetStartX() + cl->GetEndX())/2.0;
	double ymid = (cl->GetStartY() + cl->GetEndY())/2.0;
	double dX = (cl->GetEndX() - cl->GetStartX())/1000.0;
	double dY = (cl->GetEndY() - cl->GetStartY())/1000.0;
	
	xmid += 10.0*dX;
	ymid += 10.0*dY;

	TArrow *arrow = new TArrow(xmid, ymid, xmid+dX, ymid+dY, 0.05, "->-");
	arrow->Draw();
	
	
	
}