[core] refactor RendererBackend

2 files changed, 58 insertions, 2 deletions

diff --git a/include/mbgl/gfx/backend_scope.hpp b/include/mbgl/gfx/backend_scope.hpp
index b92334ae0f..ae42123e97 100644
--- a/include/mbgl/gfx/backend_scope.hpp
+++ b/include/mbgl/gfx/backend_scope.hpp
@@ -1,11 +1,10 @@
 #pragma once
 
 namespace mbgl {
+namespace gfx {
 
 class RendererBackend;
 
-namespace gfx {
-
 class BackendScope {
 public:
     // There are two types of scopes: Creating an "Implicit" scope tells Mapbox GL that the
diff --git a/include/mbgl/gfx/renderer_backend.hpp b/include/mbgl/gfx/renderer_backend.hpp
new file mode 100644
index 0000000000..032c7021da
--- /dev/null
+++ b/include/mbgl/gfx/renderer_backend.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <mbgl/util/util.hpp>
+
+#include <memory>
+#include <mutex>
+
+namespace mbgl {
+namespace gfx {
+
+class Context;
+class Renderable;
+class BackendScope;
+
+// TODO: Rename to "Device"
+class RendererBackend {
+protected:
+    explicit RendererBackend();
+
+public:
+    virtual ~RendererBackend();
+    RendererBackend(const RendererBackend&) = delete;
+    RendererBackend& operator=(const RendererBackend&) = delete;
+
+    // Returns the device's context.
+    Context& getContext();
+
+    // Returns a reference to the default surface that should be rendered on.
+    virtual Renderable& getDefaultRenderable() = 0;
+
+protected:
+    virtual std::unique_ptr<Context> createContext() = 0;
+
+    // Called when the backend's GL context needs to be made active or inactive. These are called,
+    // as a matched pair, exclusively through BackendScope, in two situations:
+    //
+    //   1. When releasing GL resources during Renderer destruction
+    //      (Including calling CustomLayerHost::deinitialize during RenderCustomLayer destruction)
+    //   2. When renderering through Renderer::render()
+    //      (Including calling CustomLayerHost::initialize for newly added custom layers and
+    //       CustomLayerHost::deinitialize on layer removal)
+    virtual void activate() = 0;
+    virtual void deactivate() = 0;
+
+protected:
+    std::unique_ptr<Context> context;
+    std::once_flag initialized;
+
+    friend class BackendScope;
+};
+
+MBGL_CONSTEXPR bool operator==(const RendererBackend& a, const RendererBackend& b) {
+    return &a == &b;
+}
+
+} // namespace gfx
+} // namespace mbgl