var last_id = null;
var first_no = 1;
var nbre_img = 20;
var tot_img = 22;

function show_block(id_block){
	if(last_id != null && last_id != id_block){
		close_block(last_id);
	}
	last_id=id_block;
	open_block(id_block);
}
function open_block(id_block){
	elem = document.getElementById(id_block);
	if(elem.style.display == 'none' || elem.style.display == ''){
		elem.style.display = 'block';
	}else{
		close_block(id_block);
	}
}
function close_block(id_block){
	elem = document.getElementById(id_block);
	elem.style.display = 'none';
}

function next_v(){
	first_no++;
	if(first_no>tot_img-nbre_img+1) first_no = tot_img-nbre_img+1;
	
	for(var i=1; i<=tot_img; i++){
		elem = document.getElementById("imgtd"+i);
		if(i>=first_no && i<first_no+nbre_img){
			elem.style.display = 'table-cell';
		}else{
			elem.style.display = 'none';
		}
	}
	elem = document.getElementById("flg");
	if(first_no>1){
		elem.style.display = 'table-cell';
	}else{
		elem.style.display = 'none';
	}
	elem = document.getElementById("fld");
	if(first_no+nbre_img<=tot_img){
		elem.style.display = 'table-cell';
	}else{
		elem.style.display = 'none';
	}
}
function prev_v(){
	first_no--;
	if(first_no<1) first_no = 1;
	
	for(var i=1; i<=tot_img; i++){
		elem = document.getElementById("imgtd"+i);
		if(i>=first_no && i<first_no+nbre_img){
			elem.style.display = 'table-cell';
		}else{
			elem.style.display = 'none';
		}
	}
	elem = document.getElementById("flg");
	if(first_no>1){
		elem.style.display = 'table-cell';
	}else{
		elem.style.display = 'none';
	}
	elem = document.getElementById("fld");
	if(first_no+nbre_img<=tot_img){
		elem.style.display = 'table-cell';
	}else{
		elem.style.display = 'none';
	}
}