add windowRequestsClose()

include/polyscope/polyscope.h

@@ -62,6 +62,10 @@ void frameTick();
 // Do shutdown work and de-initialize Polyscope
 void shutdown();
 
+// 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();
+
 // === Global variables ===
 namespace state {
 

src/polyscope.cpp

@@ -926,6 +926,14 @@ void show(size_t forFrames) {
 
 void unshow() { unshowRequested = true; }
 
+bool windowRequestsClose() {
+  if (render::engine && render::engine->windowRequestsClose()) {
+    return true;
+  }
+
+  return false;
+}
+
 void shutdown() {
 
   // TODO should we make an effort to destruct everything here?