[core] Add setMaxOverscaleFactorForParentTiles

3 files changed, 36 insertions, 0 deletions

diff --git a/src/mbgl/style/source.cpp b/src/mbgl/style/source.cpp
index 644a31dace..51a3c80089 100644
--- a/src/mbgl/style/source.cpp
+++ b/src/mbgl/style/source.cpp
@@ -43,6 +43,18 @@ optional<uint8_t> Source::getPrefetchZoomDelta() const noexcept {
     return baseImpl->getPrefetchZoomDelta();
 }
 
+void Source::setMaxOverscaleFactorForParentTiles(optional<uint8_t> overscaleFactor) noexcept {
+    if (getMaxOverscaleFactorForParentTiles() == overscaleFactor) return;
+    auto newImpl = createMutable();
+    newImpl->setMaxOverscaleFactorForParentTiles(std::move(overscaleFactor));
+    baseImpl = std::move(newImpl);
+    observer->onSourceChanged(*this);
+}
+
+optional<uint8_t> Source::getMaxOverscaleFactorForParentTiles() const noexcept {
+    return baseImpl->getMaxOverscaleFactorForParentTiles();
+}
+
 void Source::dumpDebugLogs() const {
     Log::Info(Event::General, "Source::id: %s", getID().c_str());
     Log::Info(Event::General, "Source::loaded: %d", loaded);
diff --git a/src/mbgl/style/source_impl.cpp b/src/mbgl/style/source_impl.cpp
index 7f6f633eda..98433a8c86 100644
--- a/src/mbgl/style/source_impl.cpp
+++ b/src/mbgl/style/source_impl.cpp
@@ -1,8 +1,19 @@
 #include <mbgl/style/source_impl.hpp>
+#include <mbgl/util/constants.hpp>
+#include <mbgl/util/logging.hpp>
 
 namespace mbgl {
 namespace style {
 
+namespace {
+void WarnIfOverscaleFactorCapsPrefetchDelta(const optional<uint8_t>& overscale, const optional<uint8_t>& prefetch) {
+    const uint8_t prefetchDelta = std::max<uint8_t>(util::DEFAULT_PREFETCH_ZOOM_DELTA, prefetch.value_or(0u));
+    if (overscale && *overscale < prefetchDelta) {
+        Log::Warning(Event::Style, "Parent tile overscale factor will cap prefetch delta to %d", int(*overscale));
+    }
+}
+} // namespace
+
 Source::Impl::Impl(SourceType type_, std::string id_)
     : type(type_),
       id(std::move(id_)) {
@@ -10,11 +21,21 @@ Source::Impl::Impl(SourceType type_, std::string id_)
 
 void Source::Impl::setPrefetchZoomDelta(optional<uint8_t> delta) noexcept {
     prefetchZoomDelta = std::move(delta);
+    WarnIfOverscaleFactorCapsPrefetchDelta(maxOverscaleFactor, prefetchZoomDelta);
 }
 
 optional<uint8_t> Source::Impl::getPrefetchZoomDelta() const noexcept {
     return prefetchZoomDelta;
 }
 
+void Source::Impl::setMaxOverscaleFactorForParentTiles(optional<uint8_t> overscaleFactor) noexcept {
+    maxOverscaleFactor = std::move(overscaleFactor);
+    WarnIfOverscaleFactorCapsPrefetchDelta(maxOverscaleFactor, prefetchZoomDelta);
+}
+
+optional<uint8_t> Source::Impl::getMaxOverscaleFactorForParentTiles() const noexcept {
+    return maxOverscaleFactor;
+}
+
 } // namespace style
 } // namespace mbgl
diff --git a/src/mbgl/style/source_impl.hpp b/src/mbgl/style/source_impl.hpp
index d2c5d54d10..af8435537a 100644
--- a/src/mbgl/style/source_impl.hpp
+++ b/src/mbgl/style/source_impl.hpp
@@ -22,10 +22,13 @@ public:
     virtual optional<std::string> getAttribution() const = 0;
     void setPrefetchZoomDelta(optional<uint8_t> delta) noexcept;
     optional<uint8_t> getPrefetchZoomDelta() const noexcept;
+    void setMaxOverscaleFactorForParentTiles(optional<uint8_t> overscaleFactor) noexcept;
+    optional<uint8_t> getMaxOverscaleFactorForParentTiles() const noexcept;
 
     const SourceType type;
     const std::string id;
     optional<uint8_t> prefetchZoomDelta;
+    optional<uint8_t> maxOverscaleFactor;
 
 protected:
     Impl(SourceType, std::string);