document icons property for (combo) fields, closes #56

CHANGELOG.md

@@ -13,7 +13,9 @@
 * :warning: Rename field type `cycleway` to `directionalCombo` ([#79])
 * Introduce new `date` field type ([#76])
 * Allow the `Röntgen` icon set to be used for icons ([#75])
+* Allow to specify icons for values of combo fields ([#56])
 
+[#56]: https://github.com/ideditor/schema-builder/issues/56
 [#75]: https://github.com/ideditor/schema-builder/issues/75
 [#76]: https://github.com/ideditor/schema-builder/issues/76
 [#79]: https://github.com/ideditor/schema-builder/issues/79

README.md

@@ -656,6 +656,30 @@ For `identifier` fields, the permalink URL of the external record. It must conta
 
 For `identifier` fields, the regular expression that valid values are expected to match to be linkable.
 
+##### `icons`
+
+For combo fields, the `icons` object might contain the name of icons which represent the different values of the field.
+
+Combo field types can accept key-label pairs in the `options` value of the `strings` property.
+
+```js
+{
+    "key": "crossing:markings",
+    "type": "combo",
+    "label": "Crossing Markings",
+    "icons": {
+        "zebra": "iD-crossing_markings-zebra",
+        "lines": "iD-crossing_markings-lines",
+        …
+    }
+}
+```
+
+##### `iconsCrossReferences`
+
+An optional property to reference to the icons of another field, indicated  by using that field's name contained in brackets, like `{field}`. This is for example useful when there are multiple variants of fields for the same tag, which should all use the same icons.
+
+
 ## Contributing
 
 iD's [code of conduct](https://github.com/openstreetmap/iD/blob/release/CODE_OF_CONDUCT.md) and

schemas/field.json

@@ -244,6 +244,14 @@
             "description": "The manner and context in which the field is used",
             "type": "string",
             "enum": ["preset", "changeset", "manual", "group"]
+        },
+        "icons": {
+            "description": "For combo fields: Name of icons which represents different values of this field",
+            "type": "object"
+        },
+        "iconsCrossReference": {
+            "description": "A field can reference icons of another by using that field's identifier contained in brackets, like {field}.",
+            "type": "string"
         }
     },
     "additionalProperties": false,