KML layer in Openlayers doesn't work on localhost

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I have strange problem with rendering KML file in OpenLayers. It seems to be easy, but it\'s not. I\'ve started with an example from here OpenLayers example . I wanted to ad

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故里飘歌

2021-01-03 04:28
This thread is old but I know it will still be looked at.

Try setting the projection when creating the KML layer. That worked for me.
```
    var kmllayer = new OpenLayers.Layer.Vector("KML", {
            projection: map.displayProjection,
```
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野的像风

2021-01-03 04:29
The reason that your local copy of sundials.kml won't render is that you're using OpenLayers.Protocol.HTTP, which won't load an address of the kind file://directory/file.kml.

But I've no idea why your posted code doesn't render. I'm currently wrestling with the same problem. All I can tell you is what else doesn't work.

The Openlayers documentation explains how a GML layer can be used to load a KML layer. Unfortunately, the code snippet they give in the documentation doesn't match their actual example, which uses a Vector layer just like most of their other KML (and GML) examples.

I copied the example code anyway, but changed the Vector layer to var layer = new OpenLayers.Layer.GML("GML", "gml/polygon.xml");, as per the documentation. Then I made local copies of Openlayers.js, polygon.xml and the .css stylesheets, and changed the urls to point to my local copies. So everything is local.
```
<!DOCTYPE html> 
<html> 
    <head> 
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"> 
        <meta name="apple-mobile-web-app-capable" content="yes"> 
        <title>GML Doesn't Render</title> 
        <link rel="stylesheet" href="defaultstyle.css" type="text/css"> 
        <link rel="stylesheet" href="examplesstyle.css" type="text/css"> 
        <script src="OpenLayers.js"></script> 
        <script type="text/javascript">
            var map;

            function init(){
                map = new OpenLayers.Map('map');
                var wms = new OpenLayers.Layer.WMS(
                    "OpenLayers WMS", "http://vmap0.tiles.osgeo.org/wms/vmap0",
                    {layers: 'basic'}
                );

                var layer = new OpenLayers.Layer.GML("GML", "gml/polygon.xml");

                map.addLayers([wms, layer]);
                map.zoomToExtent(new OpenLayers.Bounds(
                    -3.92, 44.34, 4.87, 49.55
                ));
            }
        </script> 
    </head> 
    <body onload="init()"> 
        <div id="map" class="smallmap"></div> 
    </body> 
</html> 
```
It doesn't work.

I also tried the suggestion from the documentation:
```
var layer = new OpenLayers.Layer.GML("KML", "kml/lines.kml", {
   format: OpenLayers.Format.KML,
   formatOptions: {
       'extractStyles': true
   }
});
```
It doesn't work.

There is even a specific example of loading "locally stored GML vector data on a basemap". It uses the same code as the documentation, so, needless to say, it doesn't work. I can't hyperlink to it because I haven't enough reputation yet to make three hyperlinks, but you can find it if you search the examples for "GML".

Openlayers has a security feature to make it difficult to load data and javascript from wildly different locations (and a workaround called "proxyhost" if you really have to do this). But I can't see how that would get involved when all the urls point to the localhost.

Please be gentle, this is my first post!

EDIT: It turns out that a) it's a browser security feature, not OpenLayers, and b) it doesn't allow a script on the localhost to load any other file on the localhost, even if you're offline. Chrome/Chromium has a command-line parameter -allow-file-access-from-files. Using this parameter, the above examples work. Other workarounds (Google them) seem tricky.
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