[default] headless frontend - allow access to the transform state

platform/default/mbgl/gl/headless_frontend.cpp

@@ -1,6 +1,8 @@
 #include <mbgl/gl/headless_frontend.hpp>
 #include <mbgl/renderer/renderer.hpp>
+#include <mbgl/renderer/update_parameters.hpp>
 #include <mbgl/map/map.hpp>
+#include <mbgl/map/transform_state.hpp>
 #include <mbgl/util/run_loop.hpp>
 
 namespace mbgl {
@@ -83,4 +85,12 @@ PremultipliedImage HeadlessFrontend::render(Map& map) {
     return result;
 }
 
+optional<TransformState> HeadlessFrontend::getTransformState() const {
+    if (updateParameters) {
+        return updateParameters->transformState;
+    } else {
+        return {};
+    }
+}
+
 } // namespace mbgl

platform/default/mbgl/gl/headless_frontend.hpp

@@ -14,6 +14,7 @@ class Scheduler;
 class Renderer;
 class RendererBackend;
 class Map;
+class TransformState;
 
 class HeadlessFrontend : public RendererFrontend {
 public:
@@ -34,6 +35,8 @@ public:
     PremultipliedImage readStillImage();
     PremultipliedImage render(Map&);
 
+    optional<TransformState> getTransformState() const;
+
 private:
     Size size;
     float pixelRatio;