[core] Add runtime API for setting tile prefetch delta for Source

New setPrefetchZoomDelta(optional<uint8_t> delta) method allow overriding
default tile prefetch setting that is defined by the Map instance. The
method can be moved to generic style specification if found to be useful
for gl-js engine.

2 files changed, 11 insertions, 1 deletions

diff --git a/src/mbgl/annotation/annotation_source.cpp b/src/mbgl/annotation/annotation_source.cpp
index 7a137f1881..318241a914 100644
--- a/src/mbgl/annotation/annotation_source.cpp
+++ b/src/mbgl/annotation/annotation_source.cpp
@@ -14,6 +14,10 @@ AnnotationSource::Impl::Impl()
     : Source::Impl(SourceType::Annotations, AnnotationManager::SourceID) {
 }
 
+const AnnotationSource::Impl& AnnotationSource::impl() const {
+    return static_cast<const Impl&>(*baseImpl);
+}
+
 void AnnotationSource::loadDescription(FileSource&) {
     loaded = true;
 }
@@ -26,4 +30,8 @@ bool AnnotationSource::supportsLayerType(const mbgl::style::LayerTypeInfo* info)
     return !std::strcmp(info->type, "line") || !std::strcmp(info->type, "symbol") || !std::strcmp(info->type, "fill");
 }
 
+Mutable<Source::Impl> AnnotationSource::createMutable() const noexcept {
+    return staticMutableCast<Source::Impl>(makeMutable<Impl>(impl()));
+}
+
 } // namespace mbgl
diff --git a/src/mbgl/annotation/annotation_source.hpp b/src/mbgl/annotation/annotation_source.hpp
index 0379426b3e..de432202a0 100644
--- a/src/mbgl/annotation/annotation_source.hpp
+++ b/src/mbgl/annotation/annotation_source.hpp
@@ -12,13 +12,15 @@ public:
     class Impl;
     const Impl& impl() const;
 
+protected:
+    Mutable<Source::Impl> createMutable() const noexcept final;
+
 private:
     void loadDescription(FileSource&) final;
     bool supportsLayerType(const mbgl::style::LayerTypeInfo*) const override;
     mapbox::base::WeakPtr<Source> makeWeakPtr() override {
         return weakFactory.makeWeakPtr();
     }
-    Mutable<Impl> mutableImpl() const;
     mapbox::base::WeakPtrFactory<Source> weakFactory {this};
 };