1 files changed, 20 insertions, 13 deletions

diff --git a/src/mbgl/renderer/layers/render_background_layer.cpp b/src/mbgl/renderer/layers/render_background_layer.cpp
index b633ad0671..d5ba8c879f 100644
--- a/src/mbgl/renderer/layers/render_background_layer.cpp
+++ b/src/mbgl/renderer/layers/render_background_layer.cpp
@@ -14,25 +14,30 @@ namespace mbgl {
 
 using namespace style;
 
-RenderBackgroundLayer::RenderBackgroundLayer(Immutable<style::BackgroundLayer::Impl> _impl)
-    : RenderLayer(std::move(_impl)),
-      unevaluated(impl().paint.untransitioned()) {
+inline const BackgroundLayer::Impl& impl(const Immutable<style::Layer::Impl>& impl) {
+    return static_cast<const style::BackgroundLayer::Impl&>(*impl);
 }
 
-const style::BackgroundLayer::Impl& RenderBackgroundLayer::impl() const {
-    return static_cast<const style::BackgroundLayer::Impl&>(*baseImpl);
+RenderBackgroundLayer::RenderBackgroundLayer(Immutable<style::BackgroundLayer::Impl> _impl)
+    : RenderLayer(makeMutable<BackgroundLayerProperties>(std::move(_impl))),
+      unevaluated(impl(baseImpl).paint.untransitioned()) {
 }
 
+RenderBackgroundLayer::~RenderBackgroundLayer() = default;
+
 void RenderBackgroundLayer::transition(const TransitionParameters &parameters) {
-    unevaluated = impl().paint.transitioned(parameters, std::move(unevaluated));
+    unevaluated = impl(baseImpl).paint.transitioned(parameters, std::move(unevaluated));
 }
 
 void RenderBackgroundLayer::evaluate(const PropertyEvaluationParameters &parameters) {
-    evaluated = unevaluated.evaluate(parameters);
-    crossfade = parameters.getCrossfadeParameters();
-
-    passes = evaluated.get<style::BackgroundOpacity>() > 0 ? RenderPass::Translucent
-                                                           : RenderPass::None;
+    auto properties = makeMutable<BackgroundLayerProperties>(
+        staticImmutableCast<BackgroundLayer::Impl>(baseImpl),
+        parameters.getCrossfadeParameters(),
+        unevaluated.evaluate(parameters));
+
+    passes = properties->evaluated.get<style::BackgroundOpacity>() > 0 ? RenderPass::Translucent
+                                                                       : RenderPass::None;
+    evaluatedProperties = std::move(properties);
 }
 
 bool RenderBackgroundLayer::hasTransition() const {
@@ -40,7 +45,7 @@ bool RenderBackgroundLayer::hasTransition() const {
 }
 
 bool RenderBackgroundLayer::hasCrossfade() const {
-    return crossfade.t != 1;
+    return static_cast<const BackgroundLayerProperties&>(*evaluatedProperties).crossfade.t != 1;
 }
 
 void RenderBackgroundLayer::render(PaintParameters& parameters, RenderSource*) {
@@ -81,7 +86,8 @@ void RenderBackgroundLayer::render(PaintParameters& parameters, RenderSource*) {
             getID()
         );
     };
-
+    const auto& evaluated = static_cast<const BackgroundLayerProperties&>(*evaluatedProperties).evaluated;
+    const auto& crossfade = static_cast<const BackgroundLayerProperties&>(*evaluatedProperties).crossfade;
     if (!evaluated.get<BackgroundPattern>().to.empty()) {
         optional<ImagePosition> imagePosA = parameters.imageManager.getPattern(evaluated.get<BackgroundPattern>().from);
         optional<ImagePosition> imagePosB = parameters.imageManager.getPattern(evaluated.get<BackgroundPattern>().to);
@@ -123,6 +129,7 @@ void RenderBackgroundLayer::render(PaintParameters& parameters, RenderSource*) {
 }
 
 optional<Color> RenderBackgroundLayer::getSolidBackground() const {
+    const auto& evaluated = static_cast<const BackgroundLayerProperties&>(*evaluatedProperties).evaluated;
     if (!evaluated.get<BackgroundPattern>().from.empty()) {
         return nullopt;
     }