Issue #63: add ghost icons.

Add keys with lifecycle prefixes to MapCSS with ghost icons (icons with
low opacity).

roentgen/mapcss.py

@@ -2,39 +2,80 @@
 MapCSS scheme creation.
 """
 from pathlib import Path
-from typing import Dict, List
+from typing import Dict, List, Optional
 
 import logging
 from colour import Color
 
 from roentgen.grid import IconCollection
 from roentgen.icon import ShapeExtractor
-from roentgen.scheme import Scheme
+from roentgen.osm_reader import STAGES_OF_DECAY
+from roentgen.scheme import Scheme, Matcher
 
 
-def construct_selectors(scheme: Scheme, icon_directory_name: str) -> str:
-    """
-    Construct icon selectors for MapCSS 0.2 scheme.
-    """
-    selectors: Dict[str, List[str]] = {}
-    for matcher in scheme.node_matchers:
-        if matcher.shapes and not matcher.location_restrictions:
-            # TODO: support location restrictions
-            selectors[matcher.get_mapcss_selector()] = [
-                (x if isinstance(x, str) else x["shape"])
-                for x in matcher.shapes
-            ]
+class MapCSSWriter:
+    def __init__(
+        self,
+        scheme: Scheme,
+        icon_directory_name: str,
+        add_icons_for_lifecycle: bool,
+    ):
+        self.add_icons_for_lifecycle = add_icons_for_lifecycle
+        self.icon_directory_name = icon_directory_name
 
-    s: str = ""
-    for selector in selectors:
-        for target in ["node", "area"]:
-            s += (
-                target + selector + " {\n"
-                f'    icon-image: "{icon_directory_name}/'
-                + "___".join(selectors[selector])
-                + '.svg";\n}\n'
-            )
-    return s
+        self.matchers: Dict[Matcher, List[str]] = {}
+        for matcher in scheme.node_matchers:
+            if matcher.shapes and not matcher.location_restrictions:
+                self.matchers[matcher] = [
+                    (x if isinstance(x, str) else x["shape"])
+                    for x in matcher.shapes
+                ]
+
+    def add_selector(
+        self,
+        target: str,
+        matcher: Matcher,
+        prefix: str = "",
+        opacity: Optional[float] = None,
+    ) -> str:
+        selector = (
+            target + matcher.get_mapcss_selector(prefix) + " {\n"
+            f'    icon-image: "{self.icon_directory_name}/'
+            + "___".join(self.matchers[matcher])
+            + '.svg";\n'
+        )
+        if opacity is not None:
+            selector += f"    icon-opacity: {opacity:.2f};\n"
+        selector += "}\n"
+        return selector
+
+    def write(self, output_file) -> None:
+        """
+        Construct icon selectors for MapCSS 0.2 scheme.
+        """
+        with Path("data/roentgen_icons_part.mapcss").open() as input_file:
+            output_file.write(input_file.read())
+
+        output_file.write("\n")
+
+        for matcher in self.matchers:
+            for target in ["node", "area"]:
+                output_file.write(self.add_selector(target, matcher))
+
+        if not self.add_icons_for_lifecycle:
+            return
+
+        for index, stage_of_decay in enumerate(STAGES_OF_DECAY):
+            opacity: float = 0.6 - 0.4 * index / (len(STAGES_OF_DECAY) - 1)
+            for matcher in self.matchers:
+                if len(matcher.tags) > 1:
+                    continue
+                for target in ["node", "area"]:
+                    output_file.write(
+                        self.add_selector(
+                            target, matcher, stage_of_decay, opacity
+                        )
+                    )
 
 
 def write_mapcss() -> None:
@@ -58,12 +99,10 @@ def write_mapcss() -> None:
     collection.draw_icons(
         icons_with_outline_path, color=Color("black"), outline=True
     )
-    with Path("data/roentgen_icons_part.mapcss").open() as input_file:
-        header = input_file.read()
-
+    mapcss_writer: MapCSSWriter = MapCSSWriter(
+        scheme, icon_directory_name, True
+    )
     with (directory / "roentgen_icons.mapcss").open("w+") as output_file:
-        output_file.write(header)
-        output_file.write("\n")
-        output_file.write(construct_selectors(scheme, icon_directory_name))
+        mapcss_writer.write(output_file)
 
     logging.info(f"MapCSS 0.2 scheme is written to {directory}.")

roentgen/osm_reader.py

@@ -23,6 +23,18 @@ KILOMETERS_PATTERN = re.compile("^(?P<value>\\d*\\.?\\d*)\\s*km$")
 MILES_PATTERN = re.compile("^(?P<value>\\d*\\.?\\d*)\\s*mi$")
 
 
+STAGES_OF_DECAY: List[str] = [
+    "disused",
+    "abandoned",
+    "ruins",
+    "demolished",
+    "removed",
+    "razed",
+    "destroyed",
+    "was",  # is not actually a stage of decay
+]
+
+
 def parse_float(string: str) -> Optional[float]:
     """
     Parse string representation of a float or integer value.

roentgen/scheme.py

@@ -69,6 +69,17 @@ def is_matched_tag(
     return MatchingType.NOT_MATCHED
 
 
+def get_selector(key: str, value: str, prefix: str = "") -> str:
+    """Get MapCSS 0.2 selector for one key."""
+    if prefix:
+        key = f"{prefix}:{key}"
+    if value == "*":
+        return f"[{key}]"
+    if '"' in value:
+        return f"[{key}='{value}']"
+    return f'[{key}="{value}"]'
+
+
 class Matcher:
     """
     Tag matching.
@@ -120,21 +131,13 @@ class Matcher:
 
         return matched
 
-    def get_mapcss_selector(self) -> str:
+    def get_mapcss_selector(self, prefix: str = "") -> str:
         """
         Construct MapCSS 0.2 selector from the node matcher.
 
         See https://wiki.openstreetmap.org/wiki/MapCSS/0.2
         """
-        def get_selector(key: str, value: str) -> str:
-            """Get MapCSS 0.2 selector for one key."""
-            if value == "*":
-                return f"[{key}]"
-            if '"' in value:
-                return f"[{key}='{value}']"
-            return f'[{key}="{value}"]'
-
-        return "".join([get_selector(x, y) for (x, y) in self.tags.items()])
+        return "".join([get_selector(x, y, prefix) for (x, y) in self.tags.items()])
 
 
 class NodeMatcher(Matcher):