[core] Add minzoom to GeoJSONOptions

include/mbgl/style/conversion/geojson_options.hpp

@@ -14,6 +14,16 @@ struct Converter<GeoJSONOptions> {
     optional<GeoJSONOptions> operator()(const V& value, Error& error) const {
         GeoJSONOptions options;
 
+        const auto minzoomValue = objectMember(value, "minzoom");
+        if (minzoomValue) {
+            if (toNumber(*minzoomValue)) {
+                options.minzoom = static_cast<uint8_t>(*toNumber(*minzoomValue));
+            } else {
+                error = { "GeoJSON source minzoom value must be a number" };
+                return {};
+            }
+        }
+
         const auto maxzoomValue = objectMember(value, "maxzoom");
         if (maxzoomValue) {
             if (toNumber(*maxzoomValue)) {

include/mbgl/style/sources/geojson_source.hpp

@@ -12,6 +12,7 @@ namespace style {
 
 struct GeoJSONOptions {
     // GeoJSON-VT options
+    uint8_t minzoom = 0;
     uint8_t maxzoom = 18;
     uint16_t buffer = 128;
     double tolerance = 0.375;

src/mbgl/style/sources/geojson_source_impl.cpp

@@ -71,7 +71,7 @@ GeoJSONSource::Impl::Impl(const Impl& other, const GeoJSON& geoJSON)
 GeoJSONSource::Impl::~Impl() = default;
 
 Range<uint8_t> GeoJSONSource::Impl::getZoomRange() const {
-    return { 0, options.maxzoom };
+    return { options.minzoom, options.maxzoom };
 }
 
 GeoJSONData* GeoJSONSource::Impl::getData() const {

test/style/conversion/geojson_options.test.cpp

@@ -33,6 +33,7 @@ TEST(GeoJSONOptions, RetainsDefaults) {
     GeoJSONOptions defaults;
 
     // GeoJSON-VT
+    ASSERT_EQ(converted.minzoom, defaults.minzoom);
     ASSERT_EQ(converted.maxzoom, defaults.maxzoom);
     ASSERT_EQ(converted.buffer, defaults.buffer);
     ASSERT_EQ(converted.tolerance, defaults.tolerance);
@@ -61,6 +62,7 @@ TEST(GeoJSONOptions, FullConversion) {
     GeoJSONOptions converted = *convert<GeoJSONOptions>(raw, error);
 
     // GeoJSON-VT
+    ASSERT_EQ(converted.minzoom, 0);
     ASSERT_EQ(converted.maxzoom, 1);
     ASSERT_EQ(converted.buffer, 2);
     ASSERT_EQ(converted.tolerance, 3);