Fix for resize events when building with ASSERTIONS (#21362)

Building with ASSERTIONS is failing the safe heap checks when e.detail is undefined.

Author: cwoffenden

site/source/docs/api_reference/html5.h.rst

@@ -596,7 +596,7 @@ Struct
 
   .. c:member:: long detail
 
-    Specifies additional detail/information about this event.
+    For resize and scroll events this is always zero.
 
   .. c:member:: int documentBodyClientWidth
     int documentBodyClientHeight
@@ -616,7 +616,7 @@ Struct
   .. c:member:: int scrollTop
     int scrollLeft
 
-    The page scroll position.
+    The page scroll position (rounded down to the nearest pixel).
 
 
 Callback functions

src/library_html5.js

@@ -710,15 +710,15 @@ var LibraryHTML5 = {
 #else
       var uiEvent = JSEvents.uiEvent;
 #endif
-      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.detail, 'e.detail', 'i32') }}};
+      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.detail, '0', 'i32') }}}; // always zero for resize and scroll
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.documentBodyClientWidth, 'b.clientWidth', 'i32') }}};
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.documentBodyClientHeight, 'b.clientHeight', 'i32') }}};
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.windowInnerWidth, 'innerWidth', 'i32') }}};
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.windowInnerHeight, 'innerHeight', 'i32') }}};
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.windowOuterWidth, 'outerWidth', 'i32') }}};
       {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.windowOuterHeight, 'outerHeight', 'i32') }}};
-      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.scrollTop, 'pageXOffset', 'i32') }}};
-      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.scrollLeft, 'pageYOffset', 'i32') }}};
+      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.scrollTop, 'pageXOffset | 0', 'i32') }}}; // scroll offsets are float
+      {{{ makeSetValue('uiEvent', C_STRUCTS.EmscriptenUiEvent.scrollLeft, 'pageYOffset | 0', 'i32') }}};
 #if PTHREADS
       if (targetThread) __emscripten_run_callback_on_thread(targetThread, callbackfunc, eventTypeId, uiEvent, userData);
       else