1 files changed, 34 insertions, 0 deletions
diff --git a/include/mbgl/map/backend.hpp b/include/mbgl/map/backend.hpp
new file mode 100644
index 0000000000..e4a5634b88
--- /dev/null
+++ b/include/mbgl/map/backend.hpp
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <mbgl/map/change.hpp>
+
+namespace mbgl {
+
+class Map;
+
+class Backend {
+public:
+    virtual ~Backend() = default;
+
+    // Called when the backend's GL context needs to be made active or inactive. These are called,
+    // as a matched pair, in four situations:
+    //
+    //   1. When releasing GL resources during Map destruction
+    //   2. When calling a CustomLayerInitializeFunction, during Map::addLayer
+    //   3. When calling a CustomLayerDeinitializeFunction, during Map::removeLayer
+    //   4. When rendering for Map::renderStill
+    //
+    // They are *not* called for Map::render; it is assumed that the correct context is already
+    // activated prior to calling Map::render.
+    virtual void activate() = 0;
+    virtual void deactivate() = 0;
+
+    // Called when the map needs to be rendered; the backend should call Map::render() at some point
+    // in the near future. (Not called for Map::renderStill() mode.)
+    virtual void invalidate() = 0;
+
+    // Notifies a watcher of map x/y/scale/rotation changes.
+    virtual void notifyMapChange(MapChange change);
+};
+
+} // namespace mbgl