wasm improvements

implementations/Crafter.Graphics-Window.cpp

@@ -715,6 +715,17 @@ void Window::StartSync() {
     #endif
 }
 
+void Window::StayAlive() {
+    // Native has no equivalent of the browser's "return from main but keep
+    // the instance alive" trick — the process simply ends. The event loop
+    // IS what keeps a native window alive, so the only correct native
+    // behaviour is StartSync's loop. Delegating keeps a single source that
+    // compiles identically on both targets: an app can call StayAlive
+    // unconditionally and get the cheap path in the browser without a
+    // #ifdef at the call site.
+    StartSync();
+}
+
 void Window::StartUpdate() {
     lastFrameBegin = std::chrono::high_resolution_clock::now();
     updating = true;
@@ -1571,6 +1582,23 @@ void Window::StartSync() {
     std::_Exit(0);
 }
 
+void Window::StayAlive() {
+    // As StartSync, minus the rAF loop.
+    //
+    // The _Exit(0) is the part that keeps the instance alive: it skips
+    // __wasm_call_dtors so every statically allocated object (event
+    // listeners, HtmlElementPtr handles, the Window itself) survives, and
+    // runtime.js catches the resulting __wasi_proc_exit via a sentinel.
+    // The frame loop is a separate concern, and a page that only renders
+    // DOM has no use for it — a rAF tick that runs forever to do nothing
+    // costs battery on every open tab.
+    //
+    // Use this for event-driven DOM pages; use StartSync when something
+    // actually animates or draws. As with StartSync, no caller code after
+    // this point ever runs.
+    std::_Exit(0);
+}
+
 void Window::StartUpdate() {
     lastFrameBegin = std::chrono::high_resolution_clock::now();
     updating = true;