function confirm_delete ()
{
    return confirm ('Skutečně nenávratně smazat položku?');
}

function hide_element (id)
{
    var obj;
    obj     = document.getElementById (id);
    obj.style.display = 'none';
}

function val_search_menu (minlength)
{
    var obj;
    obj     = document.getElementById ('menu_hledat');
    if (obj.value.length < minlength)
    {
        alert ("Příliš krátký výraz!\nHledám slova dlouhá alespoň " + minlength + " znaky.");
        obj.focus ();
        return false;
    }
    return true;
}

function val_search_form (form, minlength)
{
    var obj, error, temp, temp1, temp2, temp3, temp4;
    error = false;
    if (form.elements.f_q.value.length < minlength)
    {
        temp = form.elements.f_q.value;
        obj = document.getElementById ('td_q');
        obj.innerHTML = '<span class="hlaska"><em class="hlaska-error">Hledám slova dlouhá alespoň ' + minlength + ' znaky.</em></span><br />' + obj.innerHTML;
        form.elements.f_q.value = temp;
        error = true;
    }
    if (!form.elements.f_nov.checked && !form.elements.f_gal.checked && !form.elements.f_fot.checked && !form.elements.f_sek.checked)
    {
        temp1 = form.elements.f_nov.checked;
        temp2 = form.elements.f_sek.checked;
        temp3 = form.elements.f_gal.checked;
        temp4 = form.elements.f_fot.checked;
        obj = document.getElementById ('td_s');
        obj.innerHTML = '<span class="hlaska"><em class="hlaska-error">Musíte zadat alespoň jednu sekci, ve které hledat.</em></span><br />' + obj.innerHTML;
        form.elements.f_nov.checked = temp1;
        form.elements.f_sek.checked = temp2;
        form.elements.f_gal.checked = temp3;
        form.elements.f_fot.checked = temp4;
        error = true;
    }
    if (error)
        return false;
    else
        return true;
}

function toggle_active (id_toggle, id_par)
{
    var obj, par;
    obj = document.getElementById (id_toggle);
    par = document.getElementById (id_par);
    if (par.checked == true)
        obj.disabled = false;
    else
        obj.disabled = true;
}

function isIE()
{
    return (document.all && !isOpera()
        && navigator.appName == 'Microsoft Internet Explorer') ?
        true : false;
}

function isOpera()
{
    return (window.opera) ? true : false;
}

function getEl(id)
{
    return document.getElementById(id);
}

function getElTags(tag)
{
    return document.getElementsByTagName(tag);
}

function showAll (id, button)
{
    var obj, but;
    obj = getEl(id);
    but = getEl(button);
    obj.style.height = 'auto';
    but.style.display = 'none';
    return false;
}