3 files changed, 10 insertions, 3 deletions
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 5f88882d1..aef570109 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -4380,6 +4380,8 @@ pref("dom.webnotifications.enabled", true);
 
 // Alert animation effect, name is disableSlidingEffect for backwards-compat.
 pref("alerts.disableSlidingEffect", false);
+// The immediate duration of the alert, in milliseconds.
+pref("alerts.durationImmediate", 20000);
 
 // DOM full-screen API.
 pref("full-screen-api.enabled", false);
diff --git a/toolkit/components/alerts/resources/content/alert.css b/toolkit/components/alerts/resources/content/alert.css
index e6c1a14eb..37140a911 100644
--- a/toolkit/components/alerts/resources/content/alert.css
+++ b/toolkit/components/alerts/resources/content/alert.css
@@ -3,7 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #alertBox[animate] {
-  animation-duration: 4s;
   animation-fill-mode: both;
   animation-name: alert-animation;
 }
diff --git a/toolkit/components/alerts/resources/content/alert.js b/toolkit/components/alerts/resources/content/alert.js
index e97c0c23d..a9450f883 100644
--- a/toolkit/components/alerts/resources/content/alert.js
+++ b/toolkit/components/alerts/resources/content/alert.js
@@ -85,7 +85,12 @@ function prefillAlertInfo() {
 }
 
 function onAlertLoad() {
-  const ALERT_DURATION_IMMEDIATE = 4000;
+  const ALERT_DURATION_IMMEDIATE_MIN = 4000;
+  const ALERT_DURATION_IMMEDIATE_MAX = 60000;
+  var alertDurationImmediate = Services.prefs.getIntPref("alerts.durationImmediate");
+  alertDurationImmediate = alertDurationImmediate >= ALERT_DURATION_IMMEDIATE_MIN
+      && alertDurationImmediate <= ALERT_DURATION_IMMEDIATE_MAX
+      ? alertDurationImmediate : ALERT_DURATION_IMMEDIATE_MIN;
   let alertTextBox = document.getElementById("alertTextBox");
   let alertImageBox = document.getElementById("alertImageBox");
   alertImageBox.style.minHeight = alertTextBox.scrollHeight + "px";
@@ -103,7 +108,7 @@ function onAlertLoad() {
   window.addEventListener("XULAlertClose", function() { window.close(); });
 
   if (Services.prefs.getBoolPref("alerts.disableSlidingEffect")) {
-    setTimeout(function() { window.close(); }, ALERT_DURATION_IMMEDIATE);
+    setTimeout(function() { window.close(); }, alertDurationImmediate);
     return;
   }
 
@@ -114,6 +119,7 @@ function onAlertLoad() {
       window.close();
     }
   }, false);
+  alertBox.style.animationDuration = Math.round(alertDurationImmediate / 1000).toString() + "s";
   alertBox.setAttribute("animate", true);
 
   if (gAlertListener) {