#include "TApplication.h"
#include "TGFrame.h"
#include "TRootEmbeddedCanvas.h"
#include "TCanvas.h"
#include "TVirtualPad.h"
#include "TTimer.h"
#include "Riostream.h"

void SetMargins(TVirtualPad *pad)
{
  // keep square frame
  double h = pad->GetWh();
  double w = pad->GetWw();
  double topMargin, botMargin, leftMargin, rightMargin;

  if (w > h) {
    topMargin = 0.1;
    botMargin = 0.1;
    const double rightMarginRatio = 0.6;

    double spaceW = (w - h * (1. - topMargin - botMargin)) / w;
    rightMargin = spaceW * rightMarginRatio;
    leftMargin = spaceW * (1. - rightMarginRatio);

  } else {
    leftMargin = 0.1;
    rightMargin = 0.1;
    const double topMarginRatio = 0.5;
    
    double spaceH = (h - w * (1. - leftMargin - rightMargin)) / h;
    topMargin = spaceH * topMarginRatio;
    botMargin = spaceH * (1. - topMarginRatio);
  }
    
  pad->SetTopMargin(topMargin);
  pad->SetBottomMargin(botMargin);
  pad->SetLeftMargin(leftMargin);
  pad->SetRightMargin(rightMargin);
  pad->GetCanvas()->Modified();
  pad->GetCanvas()->Update();
}

void HandleResizing(Event_t *e)
{
   if (e->fType == kConfigureNotify) {
      std::cout << "window resized !" << std::endl;
      TTimer::SingleShot(50, 0, 0, "SetMargins(=gPad)");
   }
}

void TestMargins()
{
   TGMainFrame * w = new TGMainFrame (gClient->GetRoot(), 600, 400);
   TRootEmbeddedCanvas *ec = new TRootEmbeddedCanvas("Ecanvas1", w, 600, 400);
   w->AddFrame(ec, new TGLayoutHints(kLHintsExpandX | kLHintsExpandY));
   
   w->Connect("CloseWindow()", "TApplication", gApplication, "Terminate()");
   w->DontCallClose();
   w->Connect("ProcessedEvent(Event_t*)", 0, 0, "HandleResizing(Event_t*)");
   
   w->SetWindowName("Example Macro");
   w->MapSubwindows();
   w->MapWindow();

   ec->GetCanvas()->cd();
   gPad->DrawFrame(-100, -100, 100, 100);
   SetMargins(gPad);
}