[core] Refactor HeadlessFrontend/Backend: GL separation and factory (#14692)

Refactor out HeadlessFrontend and HeadlessBackend gl independent code to gfx.
Define gl::HeadlessBackend as subclass, instantiated by gfx::HeadlessBackend static factory method.
GL dependent tests are still using gl::HeadlessBackend directly (not through gfx).

1 files changed, 16 insertions, 0 deletions

diff --git a/platform/default/src/mbgl/gfx/headless_backend.cpp b/platform/default/src/mbgl/gfx/headless_backend.cpp
new file mode 100644
index 0000000000..f3eded8dcb
--- /dev/null
+++ b/platform/default/src/mbgl/gfx/headless_backend.cpp
@@ -0,0 +1,16 @@
+#include <mbgl/gfx/headless_backend.hpp>
+
+namespace mbgl {
+namespace gfx {
+
+HeadlessBackend::HeadlessBackend(Size size_)
+    : mbgl::gfx::Renderable(size_, nullptr) {
+}
+
+void HeadlessBackend::setSize(Size size_) {
+    size = size_;
+    resource.reset();
+}
+
+} // namespace gfx
+} // namespace mbgl