diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/library_browser.js | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/src/library_browser.js b/src/library_browser.js index b368c6ac..e0f53052 100644 --- a/src/library_browser.js +++ b/src/library_browser.js @@ -478,19 +478,30 @@ 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 = ((typeof window.scrollX !== 'undefined') ? window.scrollX : window.pageXOffset); + var scrollY = ((typeof 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((typeof scrollX !== 'undefined') && (typeof scrollY !== 'undefined'), 'Unable to retrieve scroll position, mouse positions likely broken.'); +#endif if (event.type == 'touchstart' || event.type == 'touchend' || event.type == 'touchmove') { var t = event.touches.item(0); if (t) { - x = t.pageX - (window.scrollX + rect.left); - y = t.pageY - (window.scrollY + rect.top); + x = t.pageX - (scrollX + rect.left); + y = t.pageY - (scrollY + rect.top); } else { return; } } else { - x = event.pageX - (window.scrollX + rect.left); - y = event.pageY - (window.scrollY + rect.top); + x = event.pageX - (scrollX + rect.left); + y = event.pageY - (scrollY + rect.top); } // the canvas might be CSS-scaled compared to its backbuffer; |