function ListSelectCB(list)
{
   f = document.mainform;

   if ( list.name == 'sitelist' )
   {
      f.site.value = list[list.selectedIndex].value;
      f.action = "#imagetable";
      f.submit();
   }
}

function ImageCB(task)
{
   var f = document.mainform;
   var i = f.sitelist.selectedIndex;

   if (task == 'dec') { i = (i == 0) ? i : -- i; }
   if (task == 'inc') { i = (i < f.sitelist.length - 1) ? ++ i : i; }

   f.site.value = f.sitelist[i].value;
   f.action = "#imagetable";
   f.submit();
}

function ImageYrHrCB()
{
   var f = document.mainform;

   var i = f.sitelist.selectedIndex;
   f.site.value = f.sitelist[i].value;

   yrval = f.yrlist[f.yrlist.selectedIndex].value;

   if ( yrval != 'all' && ! yrval.match(/^[0-9]{4}$/) ) { return; }

   if ( yrval == 'all' )
   {
      f.ts_img.src = f.ts_dir.value+'/'+f.site.value+'_plot_residuals.png';
      document.getElementById('ts_pdflink').href = f.ts_dir.value+'/'+f.site.value+'_plot_residuals.pdf';
      f.sh_img.src = f.sh_dir.value+'/'+f.site.value+'_seasonal_hist.png';
      document.getElementById('sh_pdflink').href = f.sh_dir.value+'/'+f.site.value+'_seasonal_hist.pdf';
   }
   else
   {
      f.ts_img.src = f.ts_dir.value+'/'+f.site.value+'_plot_residuals_'+yrval+'.png';
      document.getElementById('ts_pdflink').href = f.ts_dir.value+'/'+f.site.value+'_plot_residuals_'+yrval+'.pdf';
      f.sh_img.src = f.sh_dir.value+'/'+f.site.value+'_seasonal_hist_'+yrval+'.png';
      document.getElementById('sh_pdflink').href = f.sh_dir.value+'/'+f.site.value+'_seasonal_hist_'+yrval+'.pdf';
   }
}

function SetBtns()
{
   var f = document.mainform;
   var i = f.sitelist.selectedIndex;

   f.prevbtn.disabled = false;
   f.nextbtn.disabled = false;
   if ( i == 0 ) { f.prevbtn.disabled = true; }
   if ( i == f.sitelist.length - 1 ) { f.nextbtn.disabled = true; }
}