add translate-anchor property

include/llmr/style/properties.hpp

@@ -31,6 +31,11 @@ enum class Property {
     Linear = 4
 };
 
+enum class TranslateAnchor : uint8_t {
+    Map = 1,
+    Viewport = 2
+};
+
 namespace functions {
 
 float null(float z, const std::vector<float>&);
@@ -121,6 +126,7 @@ struct FillProperties {
 struct TextClass {
     FunctionProperty enabled = true;
     std::array<FunctionProperty, 2> translate = {{ 0, 0 }};
+    TranslateAnchor translateAnchor = TranslateAnchor::Map;
     Color color = {{ 0, 0, 0, 1 }};
     Color halo = {{ 1, 1, 1, 0.75 }};
     FunctionProperty haloRadius = 0.25f;
@@ -133,6 +139,7 @@ struct TextClass {
 struct TextProperties {
     bool enabled = true;
     std::array<float, 2> translate = {{ 0, 0 }};
+    TranslateAnchor translateAnchor = TranslateAnchor::Map;
     Color color = {{ 0, 0, 0, 1 }};
     Color halo = {{ 1, 1, 1, 0.75 }};
     float haloRadius = 0.25f;

src/style/style.cpp

@@ -97,6 +97,7 @@ void Style::cascade(float z) {
             text.enabled = layer.enabled.evaluate<bool>(z);
             text.translate = {{ layer.translate[0].evaluate<float>(z),
                                 layer.translate[1].evaluate<float>(z) }};
+            text.translateAnchor = layer.translateAnchor;
             text.color = layer.color;
             text.size = layer.size.evaluate<float>(z);
             text.halo = layer.halo;

src/style/style_parser.cpp

@@ -523,6 +523,18 @@ PointClass StyleParser::parsePointClass(JSVal value) {
     return klass;
 }
 
+TranslateAnchor parseTranslateAnchor(JSVal anchor) {
+    if (anchor.IsString()) {
+        std::string a { anchor.GetString(), anchor.GetStringLength() };
+        if (a == "viewport") {
+            return TranslateAnchor::Viewport;
+        } else {
+            return TranslateAnchor::Map;
+        }
+    } else {
+        throw Style::exception("translate anchor must be a string");
+    }
+}
 
 TextClass StyleParser::parseTextClass(JSVal value) {
     TextClass klass;
@@ -536,6 +548,10 @@ TextClass StyleParser::parseTextClass(JSVal value) {
         klass.translate = std::array<FunctionProperty, 2> {{ values[0], values[1] }};
     }
 
+    if (value.HasMember("translate-anchor")) {
+        klass.translateAnchor = parseTranslateAnchor(value["translate-anchor"]);
+    }
+
     if (value.HasMember("color")) {
         klass.color = parseColor(value["color"]);
     }