3 files changed, 19 insertions, 6 deletions
diff --git a/platform/default/include/mbgl/gfx/headless_backend.hpp b/platform/default/include/mbgl/gfx/headless_backend.hpp
index 325422323a..5167e6a465 100644
--- a/platform/default/include/mbgl/gfx/headless_backend.hpp
+++ b/platform/default/include/mbgl/gfx/headless_backend.hpp
@@ -15,11 +15,13 @@ namespace gfx {
 // of readStillImage.
 class HeadlessBackend : public gfx::Renderable {
 public:
+    enum class SwapBehaviour { NoFlush, Flush };
+
     // Factory.
-    static std::unique_ptr<HeadlessBackend>
-    Create(const Size size = { 256, 256 },
-           const gfx::ContextMode contextMode = gfx::ContextMode::Unique) {
-        return Backend::Create<HeadlessBackend, Size, gfx::ContextMode>(size, contextMode);
+    static std::unique_ptr<HeadlessBackend> Create(const Size size = {256, 256},
+                                                   SwapBehaviour swapBehavior = SwapBehaviour::NoFlush,
+                                                   const gfx::ContextMode contextMode = gfx::ContextMode::Unique) {
+        return Backend::Create<HeadlessBackend, Size, SwapBehaviour, gfx::ContextMode>(size, swapBehavior, contextMode);
     }
 
     virtual PremultipliedImage readStillImage() = 0;
diff --git a/platform/default/include/mbgl/gfx/headless_frontend.hpp b/platform/default/include/mbgl/gfx/headless_frontend.hpp
index 8f7a7bf202..353452123d 100644
--- a/platform/default/include/mbgl/gfx/headless_frontend.hpp
+++ b/platform/default/include/mbgl/gfx/headless_frontend.hpp
@@ -1,11 +1,12 @@
 #pragma once
 
+#include <mbgl/gfx/headless_backend.hpp>
 #include <mbgl/map/camera.hpp>
 #include <mbgl/renderer/renderer_frontend.hpp>
-#include <mbgl/gfx/headless_backend.hpp>
 #include <mbgl/util/async_task.hpp>
 #include <mbgl/util/optional.hpp>
 
+#include <atomic>
 #include <memory>
 
 namespace mbgl {
@@ -17,10 +18,12 @@ class TransformState;
 class HeadlessFrontend : public RendererFrontend {
 public:
     HeadlessFrontend(float pixelRatio_,
+                     gfx::HeadlessBackend::SwapBehaviour swapBehviour = gfx::HeadlessBackend::SwapBehaviour::NoFlush,
                      gfx::ContextMode mode = gfx::ContextMode::Unique,
                      const optional<std::string> localFontFamily = {});
     HeadlessFrontend(Size,
                      float pixelRatio_,
+                     gfx::HeadlessBackend::SwapBehaviour swapBehviour = gfx::HeadlessBackend::SwapBehaviour::NoFlush,
                      gfx::ContextMode mode = gfx::ContextMode::Unique,
                      const optional<std::string> localFontFamily = {});
     ~HeadlessFrontend() override;
@@ -29,6 +32,7 @@ public:
     void update(std::shared_ptr<UpdateParameters>) override;
     void setObserver(RendererObserver&) override;
 
+    double getFrameTime() const;
     Size getSize() const;
     void setSize(Size);
 
@@ -45,6 +49,7 @@ public:
 
     PremultipliedImage readStillImage();
     PremultipliedImage render(Map&);
+    void renderOnce(Map&);
 
     optional<TransformState> getTransformState() const;
 
@@ -52,6 +57,7 @@ private:
     Size size;
     float pixelRatio;
 
+    std::atomic<double> frameTime;
     std::unique_ptr<gfx::HeadlessBackend> backend;
     util::AsyncTask asyncInvalidate;
 
diff --git a/platform/default/include/mbgl/gl/headless_backend.hpp b/platform/default/include/mbgl/gl/headless_backend.hpp
index 8aefb5ff6c..b77f1b756f 100644
--- a/platform/default/include/mbgl/gl/headless_backend.hpp
+++ b/platform/default/include/mbgl/gl/headless_backend.hpp
@@ -10,13 +10,17 @@ namespace gl {
 
 class HeadlessBackend final : public gl::RendererBackend, public gfx::HeadlessBackend {
 public:
-    HeadlessBackend(Size = { 256, 256 }, gfx::ContextMode = gfx::ContextMode::Unique);
+    HeadlessBackend(Size = {256, 256},
+                    SwapBehaviour = SwapBehaviour::NoFlush,
+                    gfx::ContextMode = gfx::ContextMode::Unique);
     ~HeadlessBackend() override;
     void updateAssumedState() override;
     gfx::Renderable& getDefaultRenderable() override;
     PremultipliedImage readStillImage() override;
     RendererBackend* getRendererBackend() override;
 
+    void swap();
+
     class Impl {
     public:
         virtual ~Impl() = default;
@@ -37,6 +41,7 @@ private:
 private:
     std::unique_ptr<Impl> impl;
     bool active = false;
+    SwapBehaviour swapBehaviour = SwapBehaviour::NoFlush;
 };
 
 } // namespace gl