Index: chrome/common/extensions/docs/static/event_pages.html |
diff --git a/chrome/common/extensions/docs/static/event_pages.html b/chrome/common/extensions/docs/static/event_pages.html |
index 723f99ebd368e675f154534ba37ddf62257ed280..4956a5075eaf6a24e4b61ce1274f11380219ee46 100644 |
--- a/chrome/common/extensions/docs/static/event_pages.html |
+++ b/chrome/common/extensions/docs/static/event_pages.html |
@@ -58,6 +58,14 @@ popup windows) are closed. |
</p> |
<p> |
+You can observe the lifetime of your event page by clicking |
+on "View Background Pages" in Chrome's Wrench menu, or by |
+opening Chrome's task manager. You can see when your event |
+page loads and unloads by observing when an entry for your |
+extension appears in the list of processes. |
+</p> |
+ |
+<p> |
Once the event page has been idle a short time |
(a few seconds), the |
<code><a href="runtime.html#event-onSuspend">chrome.runtime.onSuspend</a></code> |
@@ -65,3 +73,51 @@ event is dispatched. The event page has a few more seconds to handle this |
event before it is forcibly unloaded. Note that once the event is dispatched, |
new activity will not keep the event page open. |
</p> |
+ |
+<h2 id="transition">Convert background page to event page</h2> |
+<p> |
+Follow this checklist to convert your extension's |
+(persistent) background page to an event page. |
+ |
+<ol> |
+ <li>Add <code>"persistent": false</code> to your manifest as shown above. |
+ |
+ <li>Register to receive any events your extension is interested in |
+ each time the event page is loaded. The event page will be loaded once |
+ for each new version of your extension. After that it will only be |
+ loaded to deliver events you have registered for. |
+ |
+ <li>If you need to do some initialization when your extension is |
+ installed or upgraded, listen to the |
+ <code><a href="runtime.html#event-onInstalled">chrome.runtime.onInstalled</a></code> |
+ event. |
+ |
+ <li>If you need to keep runtime state in memory throughout a browser |
+ session, use the <a href="storage.html">storage API</a> or |
+ IndexedDB. Since the event page does not stay loaded for long, you |
+ can no longer rely on global variables for runtime state. |
+ |
+ <li>Listen to the |
+ <code><a href="runtime.html#event-onSuspend">chrome.runtime.onSuspend</a></code> |
+ event if you need to do last second cleanup before your event page |
+ is shut down. However, we recommend persisting periodically instead. |
+ That way if your extension crashes without receiving |
+ <code>onSuspend</code>, no data will typically be lost. |
+ |
+ <li>If your extension uses <code>window.setTimeout()</code> or |
+ <code>window.setInterval()</code>, switch to using the |
+ <a href="alarms.html">alarms API</a> instead. DOM-based timers won't |
+ be honored if the event page shuts down. |
+ |
+ <li>If your extension uses, |
+ <code><a href="extension.html#method-getBackgroundPage">chrome.extension.getBackgroundPage()</a></code>, |
+ switch to |
+ <code><a href="runtime.html#method-getBackgroundPage">chrome.runtime.getBackgroundPage()</a></code> |
+ instead. The newer method is asynchronous so that it can start the event |
+ page if necessary before returning it. |
+ |
+ <li>If you're using <a href="messaging.html">message passing</a>, be sure |
+ to close unused message ports. The event page will not shut down until all |
+ message ports are closed. |
+</ol> |
+</p> |