[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.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mbgl/style/source.cpp b/src/mbgl/style/source.cpp
index e7701b8bec..644a31dace 100644
--- a/src/mbgl/style/source.cpp
+++ b/src/mbgl/style/source.cpp
@@ -31,6 +31,18 @@ void Source::setObserver(SourceObserver* observer_) {
     observer = observer_ ? observer_ : &nullObserver;
 }
 
+void Source::setPrefetchZoomDelta(optional<uint8_t> delta) noexcept {
+    if (getPrefetchZoomDelta() == delta) return;
+    auto newImpl = createMutable();
+    newImpl->setPrefetchZoomDelta(std::move(delta));
+    baseImpl = std::move(newImpl);
+    observer->onSourceChanged(*this);
+}
+
+optional<uint8_t> Source::getPrefetchZoomDelta() const noexcept {
+    return baseImpl->getPrefetchZoomDelta();
+}
+
 void Source::dumpDebugLogs() const {
     Log::Info(Event::General, "Source::id: %s", getID().c_str());
     Log::Info(Event::General, "Source::loaded: %d", loaded);