[OpenLayers-Users] Multiple linestrings originating from the same point disappear when zooming

[Pierre GIRAUD]

For your information, your code is correct and I think I've found what
part of the OpenLayers' code is involved in this weird behavior.
I'll try to find out a fix or at least a workaround for this issue. If
your interested in fixing this too, you can have a look at the SVG
renderer (lib/OpenLayers/Renderer/SVG.js) and in particular at
getShortString(), inValidRange() and MAX_PIXEL.

I plan to fill a bug report, but don't hesitate to do so if your quicker.

Hum, I was unable to reproduce the issue under IE with your example.

Regards,
Pierre


On Jan 18, 2008 5:23 PM, cmose <cjmose at gmail.com> wrote:
>
> I have several lineStrings on a vector layer that originate from the same
> lat/lon coordinate. As you zoom in on the map, the lineStrings randomly
> disappear, e.g,. if you start out with 6 lines originating from the same
> point, as you zoom in on the map lines will randomly disappear until there
> are <6 lines left.
>
> I've verified this behavior using a modified version of vector-features.html
> from the examples directory. I don't have anywhere to host my example but
> here is my modified script declaration from vector-features.html:
>
>     <script src="../lib/OpenLayers.js" type="text/javascript"></script>
>     <script type="text/javascript">
>         var map;
>
>         function init(){
>             map = new OpenLayers.Map('map');
>             var layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
>                     "http://labs.metacarta.com/wms/vmap0", {layers: 'basic'}
> );
>             map.addLayer(layer);
>
>             /*
>              * Layer style
>              */
>             // we want opaque external graphics and non-opaque internal
> graphics
>             var layer_style = OpenLayers.Util.extend({},
> OpenLayers.Feature.Vector.style['default']);
>             layer_style.fillOpacity = 0.2;
>             layer_style.graphicOpacity = 1;
>
>             /*
>              * Blue style
>              */
>             var style_blue = OpenLayers.Util.extend({}, layer_style);
>             style_blue.strokeColor = "blue";
>             style_blue.fillColor = "blue";
>
>             /*
>              * Green style
>              */
>             var style_green = {
>                 strokeColor: "#00FF00",
>                 strokeWidth: 2,
>                 pointRadius: 4,
>                 pointerEvents: "visiblePainted"
>             };
>
>             /*
>              * Mark style
>              */
>             var style_mark = OpenLayers.Util.extend({},
> OpenLayers.Feature.Vector.style['default']);
>             // each of the three lines below means the same, if only one of
>             // them is active: the image will have a size of 24px, and the
>             // aspect ratio will be kept
>             // style_mark.pointRadius = 12;
>             // style_mark.graphicHeight = 24;
>             // style_mark.graphicWidth = 24;
>
>             // if graphicWidth and graphicHeight are both set, the aspect
> ratio
>             // of the image will be ignored
>             style_mark.graphicWidth = 24;
>             style_mark.graphicHeight = 20;
>             style_mark.graphicXOffset = -(style_mark.graphicWidth/2);  //
> this is the default value
>             style_mark.graphicYOffset = -style_mark.graphicHeight;
>             style_mark.externalGraphic = "../img/marker.png";
>
>             var vectorLayer = new OpenLayers.Layer.Vector("Simple Geometry",
> {style: layer_style});
>                 var point = OpenLayers.Geometry.Point;
>                 var ls = OpenLayers.Geometry.LineString;
>                 var vector = OpenLayers.Feature.Vector;
>                 var lines = [];
>                 var features = [];
>
>                 lines.push(new ls([new point(1,50), new point(75,60)]));
>                 lines.push(new ls([new point(1,50), new point(-60,-30)]));
>                 lines.push(new ls([new point(1,50), new point(40,89)]));
>                 lines.push(new ls([new point(1,50), new point(-150,-55)]));
>                 lines.push(new ls([new point(1,50), new point(-30,-25)]));
>                 lines.push(new ls([new point(1,50), new point(-5,-10)]));
>
>                 for(var i=0;i<lines.length;i++){
>                         features.push(new vector(lines[i], null, style_green));
>                 }
>
>             map.addLayer(vectorLayer);
>             map.setCenter(new OpenLayers.LonLat(1,50), 5);
>             vectorLayer.addFeatures(features);
>         }
>     </script>
>
> The map is initialized with a zoom level of 5. Once you get to 8 one of the
> 6 lines disappears, leaving you with 5. Zoom level 9 removes all but one
> line. Zoom level 10 removes all lines.
>
> I haven't traced the issue beyond drawFeature() in Vector.js. I've tested
> the example in Firefox thus far but in my app I'm getting the same behavior
> in ff and ie.
>
> Any ideas?
> --
> View this message in context: http://www.nabble.com/Multiple-linestrings-originating-from-the-same-point-disappear-when-zooming-tp14952551p14952551.html
> Sent from the OpenLayers Users mailing list archive at Nabble.com.
>
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