move clip_altitudes and altitudes management to SVGEngine

src/c3nav/mapdata/render/engines/base.py

@@ -4,7 +4,6 @@ from functools import lru_cache
 from typing import Optional
 
 from shapely.geometry import JOIN_STYLE, box
-from shapely.ops import unary_union
 
 
 class FillAttribs:
@@ -48,10 +47,6 @@ class RenderEngine(ABC):
 
         self.background_rgb = tuple(int(background[i:i + 2], 16)/255 for i in range(1, 6, 2))
 
-        # keep track which area of the image has which altitude currently
-        self.altitudes = {}
-        self.last_altitude = None
-
     @abstractmethod
     def get_png(self) -> bytes:
         # render the image to png.
@@ -67,17 +62,6 @@ class RenderEngine(ABC):
             return (*(i/255 for i in color[:3]), color[3] if alpha is None else alpha)
         raise ValueError('invalid color string!')
 
-    def clip_altitudes(self, new_geometry, new_altitude=None):
-        # register new geometry with an altitude
-        # a geometry with no altitude will reset the altitude information of its area as if nothing was ever there
-        if self.last_altitude is not None and self.last_altitude > new_altitude:
-            raise ValueError('Altitudes have to be ascending.')
-
-        if new_altitude in self.altitudes:
-            self.altitudes[new_altitude] = unary_union([self.altitudes[new_altitude], new_geometry])
-        else:
-            self.altitudes[new_altitude] = new_geometry
-
     def add_geometry(self, geometry, fill: Optional[FillAttribs] = None, stroke: Optional[StrokeAttribs] = None,
                      altitude=None, height=None, shape_cache_key=None):
         # draw a shapely geometry with a given style

src/c3nav/mapdata/render/engines/svg.py

@@ -11,8 +11,9 @@ from django.core import checks
 from PIL import Image
 from shapely.affinity import translate
 from shapely.geometry import LineString, Polygon
-
 # import gobject-inspect, cairo and rsvg if the native rsvg SVG_RENDERER should be used
+from shapely.ops import unary_union
+
 from c3nav.mapdata.render.engines.base import FillAttribs, RenderEngine, StrokeAttribs
 
 if settings.SVG_RENDERER == 'rsvg':
@@ -53,6 +54,10 @@ class SVGEngine(RenderEngine):
         # keep track of created blur filters to avoid duplicates
         self.blurs = set()
 
+        # keep track which area of the image has which altitude currently
+        self.altitudes = {}
+        self.last_altitude = None
+
         self._create_geometry_cache = {}
 
     def get_xml(self, buffer=False):
@@ -196,6 +201,17 @@ class SVGEngine(RenderEngine):
         shadow = self._create_geometry(shadow_geom, attribs)
         self.g += shadow
 
+    def clip_altitudes(self, new_geometry, new_altitude=None):
+        # register new geometry with an altitude
+        # a geometry with no altitude will reset the altitude information of its area as if nothing was ever there
+        if self.last_altitude is not None and self.last_altitude > new_altitude:
+            raise ValueError('Altitudes have to be ascending.')
+
+        if new_altitude in self.altitudes:
+            self.altitudes[new_altitude] = unary_union([self.altitudes[new_altitude], new_geometry])
+        else:
+            self.altitudes[new_altitude] = new_geometry
+
     def _add_geometry(self, geometry, fill: Optional[FillAttribs] = None, stroke: Optional[StrokeAttribs] = None,
                       altitude=None, height=None, shape_cache_key=None):
         geometry = self.buffered_bbox.intersection(geometry.geom)