Switching map types preserves location.

.gitignore

@@ -2,4 +2,5 @@ GooMPy.egg-info
 build
 dist
 mapscache
+*.swp
 

example.py

@@ -23,12 +23,13 @@
 
 from goompy import GooMPy
 
-LATITUDE  =  37.7913838
-LONGITUDE = -79.44398934
-
 WIDTH = 800
 HEIGHT = 500
 
+LATITUDE  =  37.7913838
+LONGITUDE = -79.44398934
+ZOOM = 15
+MAPTYPE = 'roadmap'
 
 class UI(Tk):
 
@@ -62,9 +63,8 @@ def __init__(self):
 
         maptype_index = 0
         self.radiovar.set(maptype_index)
-        self.maptype = self.maptypes[maptype_index]
 
-        self.zoomlevel = 15
+        self.goompy = GooMPy(WIDTH, HEIGHT, LATITUDE, LONGITUDE, ZOOM, MAPTYPE)
 
         self.restart()
 
@@ -82,7 +82,6 @@ def zoom(self, sign):
 
     def reload(self):
 
-        self.goompy = GooMPy(WIDTH, HEIGHT, LATITUDE, LONGITUDE, self.zoomlevel, self.maptype)
         self.coords = None
         self.redraw()
 
@@ -98,7 +97,8 @@ def restart(self):
     def add_radio_button(self, text, index):
 
         maptype = self.maptypes[index]
-        Radiobutton(self.radiogroup, text=maptype, variable=self.radiovar, value=index, command=lambda:self.usemap(maptype)).grid(row=0, column=index)
+        Radiobutton(self.radiogroup, text=maptype, variable=self.radiovar, value=index, 
+                command=lambda:self.usemap(maptype)).grid(row=0, column=index)
 
     def click(self, event):
 
@@ -129,7 +129,7 @@ def redraw(self):
 
     def usemap(self, maptype):
 
-        self.maptype = maptype
+        self.goompy.useMaptype(maptype)
         self.restart()
 
     def check_quit(self, event):

goompy/.gitignore

@@ -1 +1,2 @@
 *.pyc
+*.swp

goompy/__init__.py

@@ -140,36 +140,24 @@ def __init__(self, width, height, latitude, longitude, zoom, maptype, radius_met
 
         self.zoom = zoom
         self.maptype = maptype
+        self.radius_meters = radius_meters
 
         self.winimage = _new_image(self.width, self.height)
 
-        self.bigimage, self.northwest, self.southeast = fetchTiles(latitude, longitude,  zoom, maptype, radius_meters)
+        self._fetch()
 
         self.leftx  = self._center(self.width)
         self.uppery = self._center(self.height)
 
         self._update()
 
-    def _center(self, dim):
-
-        return (self.bigimage.size[0] - dim) / 2
-
-    def _update(self):
-
-        self.winimage.paste(self.bigimage, (-self.leftx, -self.uppery))
-
     def getImage(self):
         '''
         Returns the current image as a PIL.Image object.
         '''
 
         return self.winimage
 
-    def _constrain(self, oldval, diff, dimsize):
-
-        newval = oldval + diff
-        return newval if newval > 0 and newval < self.bigimage.size[0]-dimsize else oldval
-
     def move(self, dx, dy):
         '''
         Moves the view by the specified pixels dx, dy.
@@ -179,3 +167,33 @@ def move(self, dx, dy):
         self.uppery = self._constrain(self.uppery, dy, self.height)
         self._update()
 
+    def useMaptype(self, maptype):
+
+        self.maptype = maptype
+
+        self._fetch()
+
+        self._update()
+
+    def useZoom(self, zoom):
+
+        None
+
+    def _fetch(self):
+
+        self.bigimage, self.northwest, self.southeast = fetchTiles(self.lat, self.lon, self.zoom, self.maptype, self.radius_meters)
+
+    def _center(self, dim):
+
+        return (self.bigimage.size[0] - dim) / 2
+
+    def _update(self):
+
+        self.winimage.paste(self.bigimage, (-self.leftx, -self.uppery))
+
+    def _constrain(self, oldval, diff, dimsize):
+
+        newval = oldval + diff
+        return newval if newval > 0 and newval < self.bigimage.size[0]-dimsize else oldval
+
+