layers: provide a layers-only vector

Signed-off-by: Marcus Fritzsch <marcus_fritzsch@mentor.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/layers.cpp b/src/layers.cpp
index f475556..0d01080 100644
--- a/src/layers.cpp
+++ b/src/layers.cpp
@@ -30,10 +30,16 @@ struct result<struct surface_id_to_layer_map> to_surface_id_to_layer_map(
    try {
       surface_id_to_layer_map stl{};
       auto m = j["mappings"];
+      stl.layers.reserve(m.size());
       std::transform(
          std::cbegin(m), std::cend(m),
          std::inserter(stl.mapping, stl.mapping.end()),
-         [](nlohmann::json const &j) { return surface_id_to_layer(j); });
+         [&stl](nlohmann::json const &j) {
+            auto k = surface_id_to_layer(j);
+            stl.layers.push_back(unsigned(k.layer_id));
+            return k;
+         });
+      // XXX need to sort layers?
       for (auto i : stl.mapping) {
          if (i.name.empty()) {
             return Err<struct surface_id_to_layer_map>(