TCanvas *c1 = nullptr;
TRootCanvas *imp = nullptr;

void print_sizes(const char *header)
{
   printf("\n%s\n", header);

   printf("Window size %d x %d\n", c1->GetWindowWidth(), c1->GetWindowHeight());

   printf("Window pos %d x %d\n", c1->GetWindowTopX(), c1->GetWindowTopY());

   printf("Canvas size %d x %d\n", c1->GetWw(), c1->GetWh());

   if (imp)
      printf("Canvas imp size %d x %d\n", imp->GetCwidth(), imp->GetCheight());

}

void realsize()
{
   const int width = 700, height = 700;


   c1 = new TCanvas("c1", "c1", width, height);

   imp = dynamic_cast<TRootCanvas *> (c1->GetCanvasImp());

   print_sizes("Create canvas");

   c1->SetWindowSize(width, height);

   print_sizes(Form("c1->SetWindowSize(%d, %d)", width, height));


   c1->SetWindowSize(width + (width - c1->GetWw()), height + (height - c1->GetWh()));

   print_sizes(Form("c1->SetWindowSize(%d + (%d - c1->GetWw()), %d + (%d - c1->GetWh()))", width, width, height, height));

   auto hist = new TH2I("test","test", 50, 0., 50., 50, 0., 50.);

   for (int i = 0; i < 50; i++)
      hist->Fill(i, 25, 100);
   hist->Draw("");

   c1->Update();

   print_sizes("c1->Update()");
}