gecko-dev/toolkit/components/thumbnails/BackgroundPageThumbs.jsm

392 lines
14 KiB
JavaScript

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
const EXPORTED_SYMBOLS = [
"BackgroundPageThumbs",
];
const DEFAULT_CAPTURE_TIMEOUT = 30000; // ms
const DESTROY_BROWSER_TIMEOUT = 60000; // ms
const FRAME_SCRIPT_URL = "chrome://global/content/backgroundPageThumbsContent.js";
const TELEMETRY_HISTOGRAM_ID_PREFIX = "FX_THUMBNAILS_BG_";
// possible FX_THUMBNAILS_BG_CAPTURE_DONE_REASON_2 telemetry values
const TEL_CAPTURE_DONE_OK = 0;
const TEL_CAPTURE_DONE_TIMEOUT = 1;
// 2 and 3 were used when we had special handling for private-browsing.
const TEL_CAPTURE_DONE_CRASHED = 4;
const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
const HTML_NS = "http://www.w3.org/1999/xhtml";
const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
Cu.import("resource://gre/modules/PageThumbs.jsm");
Cu.import("resource://gre/modules/Services.jsm");
const BackgroundPageThumbs = {
/**
* Asynchronously captures a thumbnail of the given URL.
*
* The page is loaded anonymously, and plug-ins are disabled.
*
* @param url The URL to capture.
* @param options An optional object that configures the capture. Its
* properties are the following, and all are optional:
* @opt onDone A function that will be asynchronously called when the
* capture is complete or times out. It's called as
* onDone(url),
* where `url` is the captured URL.
* @opt timeout The capture will time out after this many milliseconds have
* elapsed after the capture has progressed to the head of
* the queue and started. Defaults to 30000 (30 seconds).
*/
capture: function (url, options={}) {
if (!PageThumbs._prefEnabled()) {
if (options.onDone)
schedule(() => options.onDone(url));
return;
}
this._captureQueue = this._captureQueue || [];
this._capturesByURL = this._capturesByURL || new Map();
tel("QUEUE_SIZE_ON_CAPTURE", this._captureQueue.length);
// We want to avoid duplicate captures for the same URL. If there is an
// existing one, we just add the callback to that one and we are done.
let existing = this._capturesByURL.get(url);
if (existing) {
if (options.onDone)
existing.doneCallbacks.push(options.onDone);
// The queue is already being processed, so nothing else to do...
return;
}
let cap = new Capture(url, this._onCaptureOrTimeout.bind(this), options);
this._captureQueue.push(cap);
this._capturesByURL.set(url, cap);
this._processCaptureQueue();
},
/**
* Asynchronously captures a thumbnail of the given URL if one does not
* already exist. Otherwise does nothing.
*
* @param url The URL to capture.
* @param options An optional object that configures the capture. See
* capture() for description.
*/
captureIfMissing: function (url, options={}) {
// The fileExistsForURL call is an optimization, potentially but unlikely
// incorrect, and no big deal when it is. After the capture is done, we
// atomically test whether the file exists before writing it.
PageThumbsStorage.fileExistsForURL(url).then(exists => {
if (exists.ok) {
if (options.onDone)
options.onDone(url);
return;
}
this.capture(url, options);
}, err => {
if (options.onDone)
options.onDone(url);
});
},
/**
* Ensures that initialization of the thumbnail browser's parent window has
* begun.
*
* @return True if the parent window is completely initialized and can be
* used, and false if initialization has started but not completed.
*/
_ensureParentWindowReady: function () {
if (this._parentWin)
// Already fully initialized.
return true;
if (this._startedParentWinInit)
// Already started initializing.
return false;
this._startedParentWinInit = true;
// Create an html:iframe, stick it in the parent document, and
// use it to host the browser. about:blank will not have the system
// principal, so it can't host, but a document with a chrome URI will.
let hostWindow = Services.appShell.hiddenDOMWindow;
let iframe = hostWindow.document.createElementNS(HTML_NS, "iframe");
iframe.setAttribute("src", "chrome://global/content/mozilla.xhtml");
let onLoad = function onLoadFn() {
iframe.removeEventListener("load", onLoad, true);
this._parentWin = iframe.contentWindow;
this._processCaptureQueue();
}.bind(this);
iframe.addEventListener("load", onLoad, true);
hostWindow.document.documentElement.appendChild(iframe);
this._hostIframe = iframe;
return false;
},
/**
* Destroys the service. Queued and pending captures will never complete, and
* their consumer callbacks will never be called.
*/
_destroy: function () {
if (this._captureQueue)
this._captureQueue.forEach(cap => cap.destroy());
this._destroyBrowser();
if (this._hostIframe)
this._hostIframe.remove();
delete this._captureQueue;
delete this._hostIframe;
delete this._startedParentWinInit;
delete this._parentWin;
},
/**
* Creates the thumbnail browser if it doesn't already exist.
*/
_ensureBrowser: function () {
if (this._thumbBrowser)
return;
let browser = this._parentWin.document.createElementNS(XUL_NS, "browser");
browser.setAttribute("type", "content");
browser.setAttribute("remote", "true");
// Size the browser. Make its aspect ratio the same as the canvases' that
// the thumbnails are drawn into; the canvases' aspect ratio is the same as
// the screen's, so use that. Aim for a size in the ballpark of 1024x768.
let [swidth, sheight] = [{}, {}];
Cc["@mozilla.org/gfx/screenmanager;1"].
getService(Ci.nsIScreenManager).
primaryScreen.
GetRectDisplayPix({}, {}, swidth, sheight);
let bwidth = Math.min(1024, swidth.value);
// Setting the width and height attributes doesn't work -- the resulting
// thumbnails are blank and transparent -- but setting the style does.
browser.style.width = bwidth + "px";
browser.style.height = (bwidth * sheight.value / swidth.value) + "px";
this._parentWin.document.documentElement.appendChild(browser);
// an event that is sent if the remote process crashes - no need to remove
// it as we want it to be there as long as the browser itself lives.
browser.addEventListener("oop-browser-crashed", () => {
Cu.reportError("BackgroundThumbnails remote process crashed - recovering");
this._destroyBrowser();
let curCapture = this._captureQueue.length ? this._captureQueue[0] : null;
// we could retry the pending capture, but it's possible the crash
// was due directly to it, so trying again might just crash again.
// We could keep a flag to indicate if it previously crashed, but
// "resetting" the capture requires more work - so for now, we just
// discard it.
if (curCapture && curCapture.pending) {
curCapture._done(null, TEL_CAPTURE_DONE_CRASHED);
// _done automatically continues queue processing.
}
// else: we must have been idle and not currently doing a capture (eg,
// maybe a GC or similar crashed) - so there's no need to attempt a
// queue restart - the next capture request will set everything up.
});
browser.messageManager.loadFrameScript(FRAME_SCRIPT_URL, false);
this._thumbBrowser = browser;
},
_destroyBrowser: function () {
if (!this._thumbBrowser)
return;
this._thumbBrowser.remove();
delete this._thumbBrowser;
},
/**
* Starts the next capture if the queue is not empty and the service is fully
* initialized.
*/
_processCaptureQueue: function () {
if (!this._captureQueue.length ||
this._captureQueue[0].pending ||
!this._ensureParentWindowReady())
return;
// Ready to start the first capture in the queue.
this._ensureBrowser();
this._captureQueue[0].start(this._thumbBrowser.messageManager);
if (this._destroyBrowserTimer) {
this._destroyBrowserTimer.cancel();
delete this._destroyBrowserTimer;
}
},
/**
* Called when the current capture completes or fails (eg, times out, remote
* process crashes.)
*/
_onCaptureOrTimeout: function (capture) {
// Since timeouts start as an item is being processed, only the first
// item in the queue can be passed to this method.
if (capture !== this._captureQueue[0])
throw new Error("The capture should be at the head of the queue.");
this._captureQueue.shift();
this._capturesByURL.delete(capture.url);
// Start the destroy-browser timer *before* processing the capture queue.
let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
timer.initWithCallback(this._destroyBrowser.bind(this),
this._destroyBrowserTimeout,
Ci.nsITimer.TYPE_ONE_SHOT);
this._destroyBrowserTimer = timer;
this._processCaptureQueue();
},
_destroyBrowserTimeout: DESTROY_BROWSER_TIMEOUT,
};
/**
* Represents a single capture request in the capture queue.
*
* @param url The URL to capture.
* @param captureCallback A function you want called when the capture
* completes.
* @param options The capture options.
*/
function Capture(url, captureCallback, options) {
this.url = url;
this.captureCallback = captureCallback;
this.options = options;
this.id = Capture.nextID++;
this.creationDate = new Date();
this.doneCallbacks = [];
if (options.onDone)
this.doneCallbacks.push(options.onDone);
}
Capture.prototype = {
get pending() {
return !!this._msgMan;
},
/**
* Sends a message to the content script to start the capture.
*
* @param messageManager The nsIMessageSender of the thumbnail browser.
*/
start: function (messageManager) {
this.startDate = new Date();
tel("CAPTURE_QUEUE_TIME_MS", this.startDate - this.creationDate);
// timeout timer
let timeout = typeof(this.options.timeout) == "number" ?
this.options.timeout :
DEFAULT_CAPTURE_TIMEOUT;
this._timeoutTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
this._timeoutTimer.initWithCallback(this, timeout,
Ci.nsITimer.TYPE_ONE_SHOT);
// didCapture registration
this._msgMan = messageManager;
this._msgMan.sendAsyncMessage("BackgroundPageThumbs:capture",
{ id: this.id, url: this.url });
this._msgMan.addMessageListener("BackgroundPageThumbs:didCapture", this);
},
/**
* The only intended external use of this method is by the service when it's
* uninitializing and doing things like destroying the thumbnail browser. In
* that case the consumer's completion callback will never be called.
*/
destroy: function () {
// This method may be called for captures that haven't started yet, so
// guard against not yet having _timeoutTimer, _msgMan etc properties...
if (this._timeoutTimer) {
this._timeoutTimer.cancel();
delete this._timeoutTimer;
}
if (this._msgMan) {
this._msgMan.removeMessageListener("BackgroundPageThumbs:didCapture",
this);
delete this._msgMan;
}
delete this.captureCallback;
delete this.doneCallbacks;
delete this.options;
},
// Called when the didCapture message is received.
receiveMessage: function (msg) {
tel("CAPTURE_SERVICE_TIME_MS", new Date() - this.startDate);
// A different timed-out capture may have finally successfully completed, so
// discard messages that aren't meant for this capture.
if (msg.json.id == this.id)
this._done(msg.json, TEL_CAPTURE_DONE_OK);
},
// Called when the timeout timer fires.
notify: function () {
this._done(null, TEL_CAPTURE_DONE_TIMEOUT);
},
_done: function (data, reason) {
// Note that _done will be called only once, by either receiveMessage or
// notify, since it calls destroy here, which cancels the timeout timer and
// removes the didCapture message listener.
let { captureCallback, doneCallbacks, options } = this;
this.destroy();
if (typeof(reason) != "number")
throw new Error("A done reason must be given.");
tel("CAPTURE_DONE_REASON_2", reason);
if (data && data.telemetry) {
// Telemetry is currently disabled in the content process (bug 680508).
for (let id in data.telemetry) {
tel(id, data.telemetry[id]);
}
}
let done = () => {
captureCallback(this);
for (let callback of doneCallbacks) {
try {
callback.call(options, this.url);
}
catch (err) {
Cu.reportError(err);
}
}
};
if (!data) {
done();
return;
}
PageThumbs._store(this.url, data.finalURL, data.imageData, true)
.then(done, done);
},
};
Capture.nextID = 0;
/**
* Adds a value to one of this module's telemetry histograms.
*
* @param histogramID This is prefixed with this module's ID.
* @param value The value to add.
*/
function tel(histogramID, value) {
let id = TELEMETRY_HISTOGRAM_ID_PREFIX + histogramID;
Services.telemetry.getHistogramById(id).add(value);
}
function schedule(callback) {
Services.tm.mainThread.dispatch(callback, Ci.nsIThread.DISPATCH_NORMAL);
}