I want the map to show the Netherlands only - zooming

Question

This is my init function to load the map, I want it to show only the Netherlands, zooming in should be possible but zooming out should'nt. I searched all over, but I can't find a proper explanation on how to do this.
var config = {
zoom: 14,
zoomStart: 8,
centerPoint: new OpenLayers.LonLat(622044.536098, 6797086.3022847),
strokeColor: "#941B80",
strokeColor_allloc: "#575757",
strokeOpacity: 0.8,
strokeOpacity_allloc: 0.9,
strokeWeight: 2,
trackWeight: 5,
fillColor: "#941B80",
fillColor_allloc: "#575757",
fillOpacity: 0.25,
fillOpacity_allloc: 0.40,
pointRadius: 5,
fontColor: "black",
fontSize: 10,
fontFamily: "Arial",
scaleFactor: 1000000,
extent: new OpenLayers.Bounds(-5037508, -5037508, 5037508, 5037508.34),
units: 'm',
resolution: 156543.0339,
displayProjection: new OpenLayers.Projection("EPSG:4326"),
projection: new OpenLayers.Projection("EPSG:900913"),
controls: [
new OpenLayers.Control.Navigation(), new OpenLayers.Control.PanZoomBar(), new OpenLayers.Control.Attribution()],
copyright: 'Map data © 2010 CC-BY-SA<br />OpenStreetMap.org contributors',
numZoomLevels: 10,
numberPlateTail: new OpenLayers.Size(117.333, 42),
numberPlate: new OpenLayers.Size(117.333, 25),
iconSize: new OpenLayers.Size(32, 37)
};
var myLayers = {
base: new OpenLayers.Layer.OSM('', '', {
attribution: config.copyright,
transitionEffect: 'resize',
layers: 'basic'
}, {
isBaseLayer: true
}),
vector: new OpenLayers.Layer.Vector('Vormen aan/uit', {
styleMap: my_style,
renderers: ['Canvas', 'SVG', 'VML']
}),
allloc_vector: new OpenLayers.Layer.Vector('Vormen aan/uit', {
styleMap: my_style,
renderers: ['Canvas', 'SVG', 'VML']
}),
markers: new OpenLayers.Layer.Markers('Markers')
};
init: function (canvas) {
this.canvas = canvas;
$('#' + canvas).append('<input type="button" class="button" value="Volledig scherm" onclick="tbMap.toggleFs();" />');
this.map = new OpenLayers.Map(this.canvas, {
controls: config.controls,
displayProjection: config.displayProjection,
Projection: config.projection,
maxExtent: config.extent,
maxResolution: config.resolution,
units: config.units,
numZoomLevels: config.numZoomLevels,
theme: null
});
tbMap.zoom();
this.map.addLayers([myLayers.base, myLayers.vector]);
this.map.setCenter(config.centerPoint, config.zoomStart);
},
zoom: function () {
OpenLayers.Control.Navigation.prototype.counter = 0;
//Inzoomgevoeligheid
OpenLayers.Control.Navigation.prototype.wheelUp = function (evt) {
this.counter++;
if (this.counter > 2) {
this.counter = 0;
this.wheelChange(evt, 1);
}
};
//Uitzoomgevoeligheid
OpenLayers.Control.Navigation.prototype.wheelDown = function (evt) {
this.counter--;
if (this.counter < -2) {
this.counter = 0;
this.wheelChange(evt, -1);
}
};
},

Answer 1

You can set the config attribute maxExtent. Using your existing bounds in your config it would look like this,
maxExtent : new OpenLayers.Bounds(-5037508, -5037508, 5037508, 5037508.34)
you would add this to the map config when you initialise.
you might also want to look at restrictedExtent
Hope this helps

Answer 2

Maybe can help you:
/**
*
* #type {int}
* #constant
*/
var MAX_ZOOM_LEVEL = 6;
/**
* The OpenLayers object that sets the map extent to the Europe scale
* #type {OpenLayers.Bounds}
* #var
*/
var europeGoogleExtent = new OpenLayers.Bounds(-4931105.5677773, 2641663.6973633, 8570731.1060977, 12425603.316113);
Zoom in?
//triggered after a zoom completes
mp.events.register('zoomend', this, checkZoom);
function checkZoom() {
var zoom = mp.getZoom();
if(MAX_ZOOM_LEVEL >= zoom ) {
J('#dialog').html('You reached the maximum zoom level. <strong>The spatial accuracy is of the order of X km.</strong>');
J('#dialog').attr('title', 'Warning message');
J('#dialog').dialog({
height: 140,
modal: true
});
} else {
return true;
}
}
//Loading the initial extent
if (!mp.getCenter()) {
if (document.getElementById('userMapExtent').value != '') {
var sExtent = document.getElementById('userMapExtent').value.split(',');
mp.zoomToExtent(new OpenLayers.Bounds(sExtent[0], sExtent[1], sExtent[2], sExtent[3]), true);
} else {
mp.zoomToExtent(europeGoogleExtent);
}
}