fix the aspect ratio of plots

[kratsg]

See:

• https://root.cern.ch/phpBB3/viewtopic.php?f=3&t=22969&p=101346#p101346
• https://root.cern.ch/phpBB3/viewtopic.php?f=3&t=22969&p=101341#p101341
• https://root.cern.ch/phpBB3/viewtopic.php?f=12&t=21203
• https://root.cern.ch/phpBB3/viewtopic.php?t=17131
• https://root.cern.ch/root/roottalk/roottalk02/1068.html

[kratsg]

void DrawTextWithAngle()
{
   auto *C = gPad->GetCanvas();
   Double_t RM = C->GetRightMargin();
   Double_t LM = C->GetLeftMargin();
   Double_t TM = C->GetTopMargin();
   Double_t BM = C->GetBottomMargin();
   Double_t W = Double_t(C->GetWw()*(1.-LM-RM));
   Double_t H = Double_t(C->GetWh()*(1.-TM-BM));

   Double_t A = (180.*TMath::ATan(H/W))/(TMath::Pi());

   auto *t = new TText(0.3,0.3,Form("This text is parallel to the line the angle is %f degrees",A));
   t->SetTextAngle(A);
   t->Paint();
}

void textangle()
{
   auto *C = new TCanvas("C","C", 1600, 1200);
   C->SetRightMargin(0.16);

   auto *h = new TH2F("h","h",20,0.,2500.,20,0.,2500);
   h->Fill(1000.,1000.,123.);
   h->Fill(1500.,1000.,1230.);
   h->Draw("col");
   h->Draw("text45 same");
   auto *l = new TLine(0.,0.,2300.,2300.);
   l->Draw();
   gPad->Update();

   auto *ex = new TExec("ex","DrawTextWithAngle();");
   ex->Draw();
}

macro should allow us to fix up the angle.