Upon further review, I was not setting the srs() of the layer. However, doing
this did not solve the problem.
After digging a while, the problem only seems to occur whenever the dynamic
layer is empty. When I first add the layer, and it contains no points, the
zoom_all function does not appear to work correctly. However, once a point
is added to the dynamic layer, zoom_all() works fine.
Here is the code I am using to create the layer:
feature_type_style lstyle;
point_datasource *ps = new point_datasource();
datasource_ptr ds(ps);
// create the point rule
rule_type point_rule;
// add image using point_rule.append()
...
// add the rule to the feature style
lstyle.add_rule(point_rule);
// insert style to the map
map->insert_style(styleName, lstyle);
// create the layer
Layer lyr(layerName);
lyr.set_datasource(ds);
lyr.add_style(styleName);
lyr.set_srs("+proj=latlong +datum=WGS84");
map->addLayer(lyr);
Dane Springmeyer-4 wrote:
>
>
> On Oct 18, 2010, at 8:37 AM, mjb1999 wrote:
>
>>
>> I am writing a small Mapnik viewer application using c++, much like the
>> viewer demo application.
>
> Curious, is there a reason you are not using/extending the viewer? Are you
> using a different GUI framework than QT?
>
>> I load a map from an XML file and I display it on
>> screen.
>>
>> In this application, I give the user the option to view the entire map in
>> the window. I use the zoom_all() function to accomplish this, and it
>> works
>> fine. However, I also add a point_datasource() layer that dynamically
>> shows
>> a GPS position. When I do this, the zoom_all() function no longer works
>> as
>> expected. The map area is much larger than I would expect.
>>
>
> Okay, interesting. Are the point datasource geometries in the same
> coordinate system as your map? Are you remembering to set the proper srs
> for the layer you are adding the point datasource to?
>
>> I am thinking that my problem is that I do not specify the extent of the
>> dynamic layer when I create it, but I am not sure how to do this.
>
> Point Datasource inherits from the Memory Datasource (which you could use
> directly). But, either way the extent *should* be calculated for you
> automatically when the datasource.envelope() is called for the layer. For
> the memory datasource that happens here:
>
> http://trac.mapnik.org/browser/trunk/src/memory_datasource.cpp#L31
>
> The code looks fine to me on first glance, but you may be seeing a bug.
> Please let me know what you find and if you can narrow it to a small
> testcase.
>
> Dane
>
> _______________________________________________
> Mapnik-users mailing list
> [email protected]
> https://lists.berlios.de/mailman/listinfo/mapnik-users
>
>
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