1 files changed, 66 insertions, 0 deletions
diff --git a/src/mbgl/renderer/backend_scope.cpp b/src/mbgl/renderer/backend_scope.cpp
new file mode 100644
index 0000000000..fafeaabb39
--- /dev/null
+++ b/src/mbgl/renderer/backend_scope.cpp
@@ -0,0 +1,66 @@
+#include <mbgl/renderer/backend_scope.hpp>
+#include <mbgl/renderer/renderer_backend.hpp>
+#include <mbgl/util/thread_local.hpp>
+
+#include <cassert>
+
+namespace mbgl {
+
+static util::ThreadLocal<BackendScope> currentScope;
+
+BackendScope::BackendScope(RendererBackend& backend_, ScopeType scopeType_)
+    : priorScope(currentScope.get()),
+      nextScope(nullptr),
+      backend(backend_),
+      scopeType(scopeType_) {
+    if (priorScope) {
+        assert(priorScope->nextScope == nullptr);
+        priorScope->nextScope = this;
+        priorScope->deactivate();
+    }
+
+    activate();
+
+    currentScope.set(this);
+}
+
+BackendScope::~BackendScope() {
+    assert(nextScope == nullptr);
+    deactivate();
+
+    if (priorScope) {
+        priorScope->activate();
+        currentScope.set(priorScope);
+        assert(priorScope->nextScope == this);
+        priorScope->nextScope = nullptr;
+    } else {
+        currentScope.set(nullptr);
+    }
+}
+
+void BackendScope::activate() {
+    if (scopeType == ScopeType::Explicit &&
+            !(priorScope && this->backend == priorScope->backend) &&
+            !(nextScope && this->backend == nextScope->backend)) {
+        // Only activate when set to Explicit and
+        // only once per RenderBackend
+        backend.activate();
+        activated = true;
+    }
+}
+
+void BackendScope::deactivate() {
+    if (activated &&
+        !(nextScope && this->backend == nextScope->backend)) {
+        // Only deactivate when set to Explicit and
+        // only once per RenderBackend
+        backend.deactivate();
+        activated = false;
+    }
+}
+
+bool BackendScope::exists() {
+    return currentScope.get();
+}
+
+} // namespace mbgl