Fix MapSnapshotter build failure on Windowsupstream/anderco-win-snapshot

MSVC implementation of std::promise is buggy and only works with types
that can be default-constructed. Wrap LatLngBounds in such a struct to
avoid a compilation failure in the instantiation of ask() inside
MapSnapshotter::getRegion() since that would create a
std::promise<LanLngBounds>.

1 files changed, 17 insertions, 4 deletions

diff --git a/platform/default/src/mbgl/map/map_snapshotter.cpp b/platform/default/src/mbgl/map/map_snapshotter.cpp
index 705a791af9..0c94eadc33 100644
--- a/platform/default/src/mbgl/map/map_snapshotter.cpp
+++ b/platform/default/src/mbgl/map/map_snapshotter.cpp
@@ -12,6 +12,17 @@
 
 namespace mbgl {
 
+/*
+ * MSVC implementation of std::promise is buggy and only works with types that can be default-constructed.
+ * Wrap LatLngBounds in such a struct to avoid a compilation failure in the instantiation of ask() inside
+ * MapSnapshotter::getRegion() since that would create a std::promise<LanLngBounds>.
+ */
+struct RegionWrapper {
+    explicit RegionWrapper() : region(LatLngBounds::unbounded()) {}
+
+    LatLngBounds region;
+};
+
 class MapSnapshotter::Impl {
 public:
     Impl(const std::pair<bool, std::string> style,
@@ -35,7 +46,7 @@ public:
     CameraOptions getCameraOptions() const;
 
     void setRegion(LatLngBounds);
-    LatLngBounds getRegion() const;
+    RegionWrapper getRegion() const;
 
     void snapshot(ActorRef<MapSnapshotter::Callback>);
 
@@ -157,8 +168,10 @@ void MapSnapshotter::Impl::setRegion(LatLngBounds region) {
     map.jumpTo(map.cameraForLatLngs(latLngs, insets));
 }
 
-LatLngBounds MapSnapshotter::Impl::getRegion() const {
-    return map.latLngBoundsForCamera(getCameraOptions());
+RegionWrapper MapSnapshotter::Impl::getRegion() const {
+    RegionWrapper region;
+    region.region = map.latLngBoundsForCamera(getCameraOptions());
+    return region;
 }
 
 MapSnapshotter::MapSnapshotter(const std::pair<bool, std::string> style,
@@ -215,7 +228,7 @@ void MapSnapshotter::setRegion(const LatLngBounds& bounds) {
 }
 
 LatLngBounds MapSnapshotter::getRegion() const {
-    return impl->actor().ask(&Impl::getRegion).get();
+    return impl->actor().ask(&Impl::getRegion).get().region;
 }
 
 } // namespace mbgl