[core][tile|static mode] Introduce MapOptions::keepRenderData() flag

Render orchestrator stores the render data between render frames if this flag is set.

3 files changed, 13 insertions, 2 deletions

diff --git a/src/mbgl/renderer/render_orchestrator.cpp b/src/mbgl/renderer/render_orchestrator.cpp
index 7fb6eff29c..5851da98eb 100644
--- a/src/mbgl/renderer/render_orchestrator.cpp
+++ b/src/mbgl/renderer/render_orchestrator.cpp
@@ -141,6 +141,13 @@ std::unique_ptr<RenderTree> RenderOrchestrator::createRenderTree(
     if (!isMapModeContinuous) {
         // Reset zoom history state.
         zoomHistory.first = true;
+        if (!updateParameters->keepRenderData && stillImageRequest != updateParameters->stillImageRequest) {
+            sourceImpls = makeMutable<std::vector<Immutable<style::Source::Impl>>>();
+            layerImpls = makeMutable<std::vector<Immutable<style::Layer::Impl>>>();
+            renderSources.clear();
+            renderLayers.clear();
+            stillImageRequest = updateParameters->stillImageRequest;
+        }
     }
 
     if (LayerManager::annotationsEnabled) {
diff --git a/src/mbgl/renderer/render_orchestrator.hpp b/src/mbgl/renderer/render_orchestrator.hpp
index 4983538749..7ede688dd7 100644
--- a/src/mbgl/renderer/render_orchestrator.hpp
+++ b/src/mbgl/renderer/render_orchestrator.hpp
@@ -126,6 +126,7 @@ private:
 
     const bool backgroundLayerAsColor;
     bool contextLost = false;
+    const void* stillImageRequest = nullptr;
 
     // Vectors with reserved capacity of layerImpls->size() to avoid reallocation
     // on each frame.
diff --git a/src/mbgl/renderer/update_parameters.hpp b/src/mbgl/renderer/update_parameters.hpp
index 8dd256329a..fbdebc4197 100644
--- a/src/mbgl/renderer/update_parameters.hpp
+++ b/src/mbgl/renderer/update_parameters.hpp
@@ -41,9 +41,12 @@ public:
     const uint8_t prefetchZoomDelta;
     
     // For still image requests, render requested
-    const bool stillImageRequest;
-    
+    const void* stillImageRequest;
+
     const bool crossSourceCollisions;
+
+    // If set, the render data from the previous render calls is kept.
+    const bool keepRenderData;
 };
 
 } // namespace mbgl