global-state expression #1044

maplibre/maplibre-style-spec#1044

- new expression `global-state` that retrieves a property value from the new root property state
  https://maplibre.org/maplibre-style-spec/expressions/#global-state

- new root property `state`, where the default value can be set
  https://maplibre.org/maplibre-style-spec/root/#state

Author: Natalia Kowalczyk

src/style-spec/reference/v8.json

@@ -48,6 +48,26 @@
       "doc": "Default pitch, in degrees. Zero is perpendicular to the surface, for a look straight down at the map, while a greater value like 60 looks ahead towards the horizon. The style pitch will be used only if the map has not been positioned by other means (e.g. map options or user interaction).",
       "example": 50
     },
+    "state": {
+      "type": "state",
+      "default": {},
+      "doc": "An object used to define default values when using the [`global-state`](https://maplibre.org/maplibre-style-spec/expressions/#global-state) expression.",
+      "example": {
+        "chargerType": {
+          "default": ["CCS", "CHAdeMO", "Type2"]
+        },
+        "minPreferredChargingSpeed": {
+          "default": 50
+        }
+      },
+      "sdk-support": {
+        "basic functionality": {
+          "js": "https://github.com/maplibre/maplibre-gl-js/issues/4964",
+          "android": "https://github.com/maplibre/maplibre-native/issues/3302",
+          "ios": "https://github.com/maplibre/maplibre-native/issues/3302"
+        }
+      }
+    },
     "light": {
       "type": "light",
       "doc": "The global light source.",
@@ -1293,8 +1313,8 @@
         },
         {
           "symbol-placement": [
-              "line",
-              "line-center"
+            "line",
+            "line-center"
           ]
         }
       ],
@@ -1816,10 +1836,10 @@
       "requires": [
         "text-field",
         {
-            "symbol-placement": [
-                "line",
-                "line-center"
-            ]
+          "symbol-placement": [
+            "line",
+            "line-center"
+          ]
         }
       ],
       "sdk-support": {
@@ -1907,10 +1927,10 @@
           "text-rotation-alignment": "map"
         },
         {
-            "symbol-placement": [
-                "line",
-                "line-center"
-            ]
+          "symbol-placement": [
+            "line",
+            "line-center"
+          ]
         }
       ],
       "sdk-support": {
@@ -2554,6 +2574,24 @@
           }
         }
       },
+      "global-state": {
+        "doc": "Retrieves a property value from global state that can be set with platform-specific APIs. Defaults can be provided using the [`state`](https://maplibre.org/maplibre-style-spec/root/#state) root property. Returns `null` if no value nor default value is set for the retrieved property.",
+        "group": "Lookup",
+        "example": {
+          "syntax": {
+            "method": ["string"],
+            "result": "value"
+          },
+          "value": ["global-state", "someProperty"]
+        },
+        "sdk-support": {
+          "basic functionality": {
+            "js": "https://github.com/maplibre/maplibre-gl-js/issues/4964",
+            "android": "https://github.com/maplibre/maplibre-native/issues/3302",
+            "ios": "https://github.com/maplibre/maplibre-native/issues/3302"
+          }
+        }
+      },
       "to-string": {
         "doc": "Converts the input value to a string. If the input is `null`, the result is `\"\"`. If the input is a boolean, the result is `\"true\"` or `\"false\"`. If the input is a number, it is converted to a string as specified by the [\"NumberToString\" algorithm](https://tc39.github.io/ecma262/#sec-tostring-applied-to-the-number-type) of the ECMAScript Language Specification. If the input is a color, it is converted to a string of the form `\"rgba(r,g,b,a)\"`, where `r`, `g`, and `b` are numerals ranging from 0 to 255, and `a` ranges from 0 to 1. Otherwise, the input is converted to a string in the format specified by the [`JSON.stringify`](https://tc39.github.io/ecma262/#sec-json.stringify) function of the ECMAScript Language Specification.",
         "group": "Types",
@@ -3722,7 +3760,9 @@
       },
       "expression": {
         "interpolated": false,
-        "parameters": ["zoom"]
+        "parameters": [
+          "zoom"
+        ]
       },
       "property-type": "data-constant"
     }
@@ -5232,10 +5272,10 @@
       "type": "enum",
       "values": {
         "map": {
-            "doc": "The hillshade illumination is relative to the north direction."
+          "doc": "The hillshade illumination is relative to the north direction."
         },
         "viewport": {
-            "doc": "The hillshade illumination is relative to the top of the viewport."
+          "doc": "The hillshade illumination is relative to the top of the viewport."
         }
       },
       "default": "viewport",