The commit is to fix a problem that dynamic visibility settings don't work for layers in a MapGroup, also there has been an issue logged long time ago. Fixes #1289

Reproducible steps:

1. in DemoMap.exe
2. Create a Group
3. add a layer with line shape, named as "layerInAGroup", move the layer into created Group
4. set Dynamic Visibility Scale for the "layerInAGroup"
5. zoom in or zoom out the map, the "layerInAGroup" never show up

The root of this issue is that there is some logic error to determine the layer in a MapGroup is visible by testing the "IsVisible", "UseDynamicVisibility", "DynamicVisibilityMode" and "DynamicVisibilityWidth"

public void DrawRegions(MapArgs args, List<Extent> regions, bool selected)
{
    if (Layers == null) return;
    foreach (IMapLayer layer in Layers)
    {
        if (!layer.IsVisible) continue;
        if (layer.UseDynamicVisibility && ((layer.DynamicVisibilityMode == DynamicVisibilityMode.ZoomedIn && MapFrame.ViewExtents.Width > layer.DynamicVisibilityWidth) || MapFrame.ViewExtents.Width < layer.DynamicVisibilityWidth))
        {
             continue; // skip the layer if we are zoomed in or out too far.
        }
        layer.DrawRegions(args, regions, selected);
    }
}

The fix is simple, there is already a method Layer::VisibleAtExtent wrappered the above logic and it is correct. Use the method directly in the MapGroup::DrawRegions method.

Checklist

• I have included examples or tests
• I have updated the change log
• I am listed in the CONTRIBUTORS file
• I have cleaned up the commit history (use rebase and squash)

Changes proposed in this pull request: