add removeEverything() function

Author: nmwsharp

include/polyscope/polyscope.h

@@ -63,6 +63,10 @@ void frameTick();
 // Do shutdown work and de-initialize Polyscope
 void shutdown(bool allowMidFrameShutdown = false);
 
+// Remove all structures / quantities / groups / slice planes / callbacks / etc, as if Polyscope was just initialized.
+// (But does _not_ reset option & config settings, nor de-initialize the render engine)
+void removeEverything();
+
 // Returns true if the user has tried to exit the window at the OS level, e.g clicking the close button. Useful for
 // deciding when to exit your control loop when using frameTick()
 bool windowRequestsClose();

src/polyscope.cpp

@@ -1208,6 +1208,18 @@ bool isHeadless() {
   return false;
 }
 
+void removeEverything() {
+  removeAllStructures();
+  removeAllGroups();
+  removeAllSlicePlanes();
+  removeAllTransformationGizmos();
+  clearMessages();
+  state::userCallback = nullptr;
+  state::filesDroppedCallback = nullptr;
+  options::configureImGuiStyleCallback = configureImGuiStyle; // restore defaults
+  options::prepareImGuiFontsCallback = loadBaseFonts;
+}
+
 void shutdown(bool allowMidFrameShutdown) {
   checkInitialized();
 
@@ -1220,16 +1232,7 @@ void shutdown(bool allowMidFrameShutdown) {
     writePrefsFile();
   }
 
-  // Clear out all structures and other scene objects
-  removeAllStructures();
-  removeAllGroups();
-  removeAllSlicePlanes();
-  removeAllTransformationGizmos();
-  clearMessages();
-  state::userCallback = nullptr;
-  state::filesDroppedCallback = nullptr;
-  options::configureImGuiStyleCallback = configureImGuiStyle; // restore defaults
-  options::prepareImGuiFontsCallback = loadBaseFonts;
+  removeEverything();
 
   // Shut down the render engine
   render::engine->shutdown();

src/view.cpp

@@ -424,6 +424,7 @@ float computeRelativeMotionScale() {
     return state::lengthScale;
   }
   }
+  return -1.; // should be unreachable
 }
 
 void projectCenterToBeValidForView() {