Merge pull request #1812 from tilezen/zerebubuth/1730-water-labels-st…

…rike-back

Update min zoom of water label points.

integration-test/1730-further-water-layer-name-dropping.py

@@ -172,3 +172,52 @@ def test_no_label_boundary(self):
                 'name': type(None),
                 'name:fr': type(None),
             })
+
+
+class WaterLabelZoomAdjustmentTest(FixtureTest):
+
+    def test_label_lake_athabasca_z5(self):
+        import dsl
+
+        z, x, y = (5, 6, 9)
+
+        self.generate_fixtures(
+            dsl.way(1, dsl.box_area(z, x, y, 31390412728.710949), {
+                'featurecla': u'Lake',
+                'label': u'Lake Athabasca',
+                'min_label': 3.7,
+                'min_zoom': 2.0,
+                'name': u'Lake Athabasca',
+                'name_abb': u'L. Athabasca',
+                'name_de': u'Athabascasee',
+                'name_en': u'Lake Athabasca',
+                'name_es': u'Lago Athabasca',
+                'name_fr': u'lac Athabasca',
+                'name_hu': u'Atabaszk-tó',
+                'name_it': u'Athabasca',
+                'name_ja': u'アサバスカ湖',
+                'name_nl': u'Athabascameer',
+                'name_pl': u'Athabaska',
+                'name_pt': u'Lago Athabasca',
+                'name_ru': u'Атабаска',
+                'name_sv': u'Athabascasjön',
+                'name_tr': u'Athabasca Gölü',
+                'name_zh': u'阿薩巴斯卡湖',
+                'ne_id': u'1159106863',
+                'scalerank': 2,
+                'source': u'naturalearthdata.com',
+                'wdid_score': 4,
+                'wikidataid': u'Q272463',
+            }),
+        )
+
+        # we should get a label placement point, and its zoom should have been
+        # adjusted. we should also have all the names at this point.
+        self.assert_has_feature(
+            z, x, y, 'water', {
+                'kind': 'lake',
+                'label_placement': True,
+                'min_zoom': 5,
+                'name': str,
+                'name:de': str,
+            })

queries.yaml

@@ -777,35 +777,6 @@ post_process:
       where: >-
         kind == 'lake'
 
-  # some water polygon features are too small to need a label - and if we label
-  # them then the label is often so prominent that it hides the polygon it's
-  # for! see the images here for examples of this:
-  # https://github.com/tilezen/vector-datasource/issues/1477#issuecomment-447162484
-  #
-  # therefore, we want to remove the name properties from those small water
-  # polygon features before we extract the label placements in a following step.
-  - fn: vectordatasource.transform.drop_names
-    params:
-      source_layer: water
-      start_zoom: 4
-      end_zoom: 16
-      geom_types: [Polygon, MultiPolygon]
-      where: >-
-        area < {
-            4:  40000000000,
-            5:  10000000000,
-            6:   5000000000,
-            7:    400000000,
-            8:    200000000,
-            9:    100000000,
-            10:    10000000,
-            11:     4000000,
-            12:      750000,
-            13:      100000,
-            14:       50000,
-            15:       10000,
-        }.get(zoom)
-
   - fn: vectordatasource.transform.handle_label_placement
     params:
       layers:
@@ -817,6 +788,40 @@ post_process:
       label_where: >-
         'name' in properties
 
+  # some water polygon features are too small to need a label - and if we label
+  # them then the label is often so prominent that it hides the polygon it's
+  # for! see the images here for examples of this:
+  # https://github.com/tilezen/vector-datasource/issues/1477#issuecomment-447162484
+  #
+  # we want to reset min_zoom on these features and screen them out if they
+  # don't meet minimum sizes per zoom.
+  - fn: vectordatasource.transform.update_min_zoom
+    params:
+      source_layer: water
+      start_zoom: 4
+      end_zoom: 16
+      # the inclusion of "None" in the list might seem odd, but None compares
+      # numerically smaller than any integer, so acts as a default for this
+      # table.
+      min_zoom: >-
+        [min_zoom for min_zoom, area_threshold in [
+            (4,  40000000000),
+            (5,  10000000000),
+            (6,   5000000000),
+            (7,    400000000),
+            (8,    200000000),
+            (9,    100000000),
+            (10,    10000000),
+            (11,     4000000),
+            (12,      750000),
+            (13,      100000),
+            (14,       50000),
+            (15,       10000),
+            (16,        None),
+        ] if area >= area_threshold][0]
+      where: >-
+        kind == 'lake' and label_placement
+
   - fn: vectordatasource.transform.handle_label_placement
     params:
       layers:

vectordatasource/transform.py

@@ -8627,3 +8627,55 @@ def remap_viewpoint_kinds(shape, props, fid, zoom):
             props[key] = _REMAP_VIEWPOINT_KIND.get(props[key])
 
     return (shape, props, fid)
+
+
+def update_min_zoom(ctx):
+    """
+    Update the min zoom for features matching the Python fragment "where"
+    clause. If none is provided, update all features.
+
+    The new min_zoom is calculated by evaluating a Python fragment passed
+    in through the "min_zoom" parameter. This is evaluated in the context
+    of the features' parameters, plus a zoom variable.
+
+    If the min zoom is lower than the current min zoom, the current one is
+    kept. If the min zoom is increased, then it's checked against the
+    current zoom and the feature dropped if it's not in range.
+    """
+
+    params = _Params(ctx, 'update_min_zoom')
+    layer_name = params.required('source_layer')
+    start_zoom = params.optional('start_zoom', typ=int, default=0)
+    end_zoom = params.optional('end_zoom', typ=int)
+    min_zoom = params.required('min_zoom')
+    where = params.optional('where')
+
+    layer = _find_layer(ctx.feature_layers, layer_name)
+    zoom = ctx.nominal_zoom
+
+    if zoom < start_zoom or \
+       (end_zoom is not None and zoom >= end_zoom):
+        return None
+
+    min_zoom = compile(min_zoom, 'queries.yaml', 'eval')
+    if where:
+        where = compile(where, 'queries.yaml', 'eval')
+
+    new_features = []
+    for shape, props, fid in layer['features']:
+        local = defaultdict(lambda: None)
+        local.update(props)
+        local['zoom'] = zoom
+
+        if where and eval(where, {}, local):
+            new_min_zoom = eval(min_zoom, {}, local)
+            if new_min_zoom > props.get('min_zoom'):
+                props['min_zoom'] = new_min_zoom
+                if new_min_zoom >= zoom + 1 and zoom < 16:
+                    # DON'T add feature - it's masked by min zoom.
+                    continue
+
+        new_features.append((shape, props, fid))
+
+    layer['features'] = new_features
+    return layer