diff options
| -rw-r--r-- | src/library_browser.js | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/library_browser.js b/src/library_browser.js index f3363e51..bf8444bd 100644 --- a/src/library_browser.js +++ b/src/library_browser.js @@ -478,8 +478,17 @@ mergeInto(LibraryManager.library, { // in the coordinates. var rect = Module["canvas"].getBoundingClientRect(); var x, y; + + //Neither .scrollX or .pageXOffset are defined in a spec, but + //we prefer .scrollX because it is currently in a spec draft. + //(see: http://www.w3.org/TR/2013/WD-cssom-view-20131217/) var scrollX = ((window.scrollX !== undefined) ? window.scrollX : window.pageXOffset); var scrollY = ((window.scrollY !== undefined) ? window.scrollY : window.pageYOffset); + #if ASSERTIONS + //If this assert lands, it's likely because the browser doesn't support scrollX or pageXOffset + //and we have no viable fallback. + assert((scrollX !== undefined) && (scrollY !== undefined), 'Unable to retrieve scroll position, mouse positions likely broken.'); + #endif if (event.type == 'touchstart' || event.type == 'touchend' || event.type == 'touchmove') { |