Selectable renderer implementation (#1247)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/mbgl/gfx/renderer_backend.hpp

@@ -44,8 +44,10 @@ public:
     /// Returns a reference to the default surface that should be rendered on.
     virtual Renderable& getDefaultRenderable() = 0;
 
+#if MLN_DRAWABLE_RENDERER
     /// One-time shader initialization
     virtual void initShaders(gfx::ShaderRegistry&, const ProgramParameters&) = 0;
+#endif
 
 protected:
     virtual std::unique_ptr<Context> createContext() = 0;

include/mbgl/gfx/texture2d.hpp

@@ -11,8 +11,6 @@ class Size;
 
 namespace gfx {
 
-constexpr int32_t MaxActiveTextureUnits = 8;
-
 class Context;
 class UploadPass;
 class TextureResource;

include/mbgl/gl/renderer_backend.hpp

@@ -22,8 +22,10 @@ public:
     /// Called prior to rendering to update the internally assumed OpenGL state.
     virtual void updateAssumedState() = 0;
 
+#if MLN_DRAWABLE_RENDERER
     /// One-time shader initialization
     void initShaders(gfx::ShaderRegistry&, const ProgramParameters& programParameters) override;
+#endif
 
 protected:
     std::unique_ptr<gfx::Context> createContext() override;

include/mbgl/renderer/renderer_frontend.hpp

@@ -1,6 +1,8 @@
 #pragma once
 
+#if MLN_DRAWABLE_RENDERER
 #include <mbgl/gfx/drawable.hpp>
+#endif
 
 #include <memory>