Add a minzoom option

This only affects what's written to overviewerConfig.js.  That is, it
does not change the amount of tiles rendered (it's exactly analogous to
maxzom)

Closes #994

docs/config.rst

@@ -540,6 +540,18 @@ values. The valid configuration keys are listed below.
 
     **Default:** Automatically set to most detailed zoom level
 
+``minzoom``
+    This specifies the minimum zoom allowed by the zoom control on the web page.  For
+    example, setting this to 2 will disable the two most-zoomed out levels.
+
+    .. note::
+
+            This does not change the number of zoom levels rendered, but allows
+            you to have control over the number of zoom levels accessible via the
+            slider control.
+
+    **Default:** 0 (zero, which does not disable any zoom levels)
+
 ``showlocationmarker``
     Allows you to specify whether to show the location marker when accessing a URL
     with coordinates specified.

overviewer.py

@@ -479,7 +479,7 @@ dir but you forgot to put quotes around the directory, since it contains spaces.
 
         # only pass to the TileSet the options it really cares about
         render['name'] = render_name # perhaps a hack. This is stored here for the asset manager
-        tileSetOpts = util.dict_subset(render, ["name", "imgformat", "renderchecks", "rerenderprob", "bgcolor", "defaultzoom", "imgquality", "optimizeimg", "rendermode", "worldname_orig", "title", "dimension", "changelist", "showspawn", "overlay", "base", "poititle", "maxzoom", "showlocationmarker"])
+        tileSetOpts = util.dict_subset(render, ["name", "imgformat", "renderchecks", "rerenderprob", "bgcolor", "defaultzoom", "imgquality", "optimizeimg", "rendermode", "worldname_orig", "title", "dimension", "changelist", "showspawn", "overlay", "base", "poititle", "maxzoom", "showlocationmarker", "minzoom"])
         tileSetOpts.update({"spawn": w.find_true_spawn()}) # TODO find a better way to do this
         tset = tileset.TileSet(w, rset, assetMrg, tex, tileSetOpts, tileset_dir)
         tilesets.append(tset)

overviewer_core/settingsDefinition.py

@@ -86,6 +86,7 @@ renders = Setting(required=True, default=util.OrderedDict(),
             "poititle": Setting(required=False, validator=validateStr, default="Markers"),
             "customwebassets": Setting(required=False, validator=validateWebAssetsPath, default=None),
             "maxzoom": Setting(required=False, validator=validateInt, default=None),
+            "minzoom": Setting(required=False, validator=validateInt, default=0),
             "manualpois": Setting(required=False, validator=validateManualPOIs, default=[]),
             "showlocationmarker": Setting(required=False, validator=validateBool, default=True),
             # Remove this eventually (once people update their configs)

overviewer_core/tileset.py

@@ -517,7 +517,6 @@ class TileSet(object):
         
         d = dict(name = self.options.get('title'),
                 zoomLevels = self.treedepth,
-                minZoom = 0,
                 defaultZoom = self.options.get('defaultzoom'),
                 maxZoom = self.options.get('maxzoom', self.treedepth) if self.options.get('maxzoom', self.treedepth) >= 0 else self.treedepth+self.options.get('maxzoom'),
                 path = self.options.get('name'),
@@ -531,6 +530,7 @@ class TileSet(object):
                 poititle = self.options.get("poititle"),
                 showlocationmarker = self.options.get("showlocationmarker")
                 )
+        d['minZoom'] = min(max(0, self.options.get("minzoom", 0)), d['maxZoom'])
 
         if isOverlay:
             d.update({"tilesets": self.options.get("overlay")})