michael@0: /* Any copyright is dedicated to the Public Domain.
michael@0:  * http://creativecommons.org/publicdomain/zero/1.0/ */
michael@0: 
michael@0: function is_hidden(aElement) {
michael@0:   var style = aElement.ownerDocument.defaultView.getComputedStyle(aElement, "");
michael@0:   if (style.display == "none")
michael@0:     return true;
michael@0:   if (style.visibility != "visible")
michael@0:     return true;
michael@0: 
michael@0:   // Hiding a parent element will hide all its children
michael@0:   if (aElement.parentNode != aElement.ownerDocument)
michael@0:     return is_hidden(aElement.parentNode);
michael@0: 
michael@0:   return false;
michael@0: }
michael@0: 
michael@0: function is_element_visible(aElement, aMsg) {
michael@0:   isnot(aElement, null, "Element should not be null, when checking visibility");
michael@0:   ok(!is_hidden(aElement), aMsg);
michael@0: }
michael@0: 
michael@0: function is_element_hidden(aElement, aMsg) {
michael@0:   isnot(aElement, null, "Element should not be null, when checking visibility");
michael@0:   ok(is_hidden(aElement), aMsg);
michael@0: }
michael@0: 
michael@0: function open_preferences(aCallback) {
michael@0:   gBrowser.selectedTab = gBrowser.addTab("about:preferences");
michael@0:   let newTabBrowser = gBrowser.getBrowserForTab(gBrowser.selectedTab);
michael@0:   newTabBrowser.addEventListener("Initialized", function () {
michael@0:     newTabBrowser.removeEventListener("Initialized", arguments.callee, true);
michael@0:     aCallback(gBrowser.contentWindow);
michael@0:   }, true);
michael@0: }