1 files changed, 59 insertions, 0 deletions
diff --git a/include/mbgl/gl/renderer_backend.hpp b/include/mbgl/gl/renderer_backend.hpp
new file mode 100644
index 0000000000..7ef8759477
--- /dev/null
+++ b/include/mbgl/gl/renderer_backend.hpp
@@ -0,0 +1,59 @@
+#pragma once
+
+#include <mbgl/gfx/renderer_backend.hpp>
+#include <mbgl/util/image.hpp>
+#include <mbgl/util/size.hpp>
+#include <mbgl/util/util.hpp>
+
+namespace mbgl {
+namespace gl {
+
+class Context;
+using ProcAddress = void (*)();
+using FramebufferID = uint32_t;
+
+class RendererBackend : public gfx::RendererBackend {
+public:
+    RendererBackend();
+    ~RendererBackend() override;
+
+    // Returns the backend's context which manages OpenGL state.
+    Context& getGLContext();
+
+    // Called prior to rendering to update the internally assumed OpenGL state.
+    virtual void updateAssumedState() = 0;
+
+protected:
+    std::unique_ptr<gfx::Context> createContext() override;
+
+    // Called with the name of an OpenGL extension that should be loaded. RendererBackend implementations
+    // must call the API-specific version that obtains the function pointer for this function,
+    // or a null pointer if unsupported/unavailable.
+    virtual ProcAddress getExtensionFunctionPointer(const char*) = 0;
+
+    // Reads the color pixel data from the currently bound framebuffer.
+    PremultipliedImage readFramebuffer(const Size&);
+
+    // A constant to signal that a framebuffer is bound, but with an unknown ID.
+    static constexpr const FramebufferID ImplicitFramebufferBinding =
+        std::numeric_limits<FramebufferID>::max();
+
+    // Tells the renderer that OpenGL state has already been set by the windowing toolkit.
+    // It sets the internal assumed state to the supplied values.
+    void assumeFramebufferBinding(FramebufferID fbo);
+    void assumeViewport(int32_t x, int32_t y, const Size&);
+    void assumeScissorTest(bool);
+
+    // Returns true when assumed framebuffer binding hasn't changed from the implicit binding.
+    bool implicitFramebufferBound();
+
+public:
+    // Triggers an OpenGL state update if the internal assumed state doesn't match the
+    // supplied values.
+    void setFramebufferBinding(FramebufferID fbo);
+    void setViewport(int32_t x, int32_t y, const Size&);
+    void setScissorTest(bool);
+};
+
+} // namespace gl
+} // namespace mbgl