Fix updateViewGroupOffline() so that it doesn't hang

Cesium3DTilesSelection/src/Tileset.cpp

@@ -333,16 +333,19 @@ const ViewUpdateResult& Tileset::updateViewGroupOffline(
 
   // TODO: fix the fading for offline case
   // (https://github.com/CesiumGS/cesium-native/issues/549)
+  this->_asyncSystem.dispatchMainThreadTasks();
   this->updateViewGroup(viewGroup, frustums, 0.0f);
   while (viewGroup.getPreviousLoadProgressPercentage() < 100.0f) {
     this->_externals.pAssetAccessor->tick();
+    this->_asyncSystem.dispatchMainThreadTasks();
     this->loadTiles();
 
     // If there are no frustums, we'll never make any progress. So break here to
     // avoid getting stuck in an endless loop.
     if (frustums.empty())
       break;
 
+    this->_asyncSystem.dispatchMainThreadTasks();
     this->updateViewGroup(viewGroup, frustums, 0.0f);
   }
 
@@ -371,9 +374,12 @@ const ViewUpdateResult& Tileset::updateViewGroupOffline(
 }
 
 const ViewUpdateResult&
+
 Tileset::updateView(const std::vector<ViewState>& frustums, float deltaTime) {
+  this->_asyncSystem.dispatchMainThreadTasks();
   const ViewUpdateResult& result =
       this->updateViewGroup(this->_defaultViewGroup, frustums, deltaTime);
+  this->_asyncSystem.dispatchMainThreadTasks();
   this->loadTiles();
   return result;
 }

Cesium3DTilesSelection/test/TestTilesetSelectionAlgorithm.cpp

@@ -567,6 +567,13 @@ TEST_CASE("Test replace refinement for render") {
     }
   }
 
+  SUBCASE(
+      "updateViewGroupOffline does its own dispatching of main thread tasks "
+      " so it doesn't get stuck") {
+    ViewState viewState = zoomToTileset(tileset);
+    tileset.updateViewGroupOffline(tileset.getDefaultViewGroup(), {viewState});
+  }
+
   SUBCASE(
       "updateViewGroupOffline does not get stuck in an endless loop when no "
       "frustums are given") {