1338004 - [meta] Headless browsing mode

Status: RESOLVED FIXED

(Firefox :: Headless, defect)

Description

[Brendan Dahl [:bdahl]]

This will be the tracking bug for headless browsing. The first overall goal of headless browsing is to make automated testing of Firefox less painful for developers. One of the first steps towards this will be to support a headless mode in Firefox that can run slimer.js on linux without an X server. 

The initial plan is to have either a command line flag or environment variable that starts Firefox in a mode that doesn’t call into gtk and creates enough stubs for pages to load and be rendered by a software renderer. 

In a previous effort to make Firefox headless (bug 446591) a completely new headless widget and shell were created. The new approach will be slightly different in that headless won’t be it’s own shell/widget, but instead a mode that is supported by all platforms. The benefits of this approach are: any Firefox becomes testable, headless Firefox will closely match release versions, binaries are already being built and distributed, and this will hopefully align with work Chrome is doing (making cross browser testing easier).

Comment 1

[Brendan Dahl [:bdahl]]

Attachment: Prototype headless browser mode.

Comment 2

[Brendan Dahl [:bdahl]]

Attachment: Prototype headless browser mode.

Comment 3

[Brendan Dahl [:bdahl]]

Comment on attachment 8840239 [details] [diff] [review]
Prototype headless browser mode.

Hey Jeff,
I've got some basics tests working and I'll have another patch that introduces a headless mode for xpcshell tests. Overall, I've found myself creating a few stubs and having to scatter around some checks to avoid calling into gdk/X. I'm not crazy about sprinkling these 'ifs', but I'm not seeing a better way since a lot of the calls are in only one small spot in a class and stubbing the whole class to avoid it would cause a lot of duplication. I'm looking for some general feedback if this approach is looking acceptable.

Some other notes/todos:
 - I haven't got full Firefox running in headless mode yet, I've been focusing on slimerjs (which works).
 - Need to get window resizing working
 - Add support for a headless flavor of xpcshell tests (and maybe mochitest)
 - Add --headless flag for FF
 - Sort out popup and new windows

Comment 4

[Jeff Muizelaar [:jrmuizel]]

(In reply to Brendan Dahl [:bdahl] from comment #3)
> Comment on attachment 8840239 [details] [diff] [review]
> Prototype headless browser mode.

I've only taken a very quick look. But it seems reasonable. You should replace getenv("MOZ_HEADLESS") with gfxPlatform::IsHeadless() or something like that.

Comment 5

[Brendan Dahl [:bdahl]]

Attachment: Add headless flavor of xpcshell tests.

Comment 6

[Brendan Dahl [:bdahl]]

Comment on attachment 8842596 [details] [diff] [review]
Add headless flavor of xpcshell tests.

Hi Ted,
It looks like you're a peer/owner of all the overlapping pieces for this patch. Let me know if there's someone better or if you want me to break out some of the changes.

Try run:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=9d9769cc03563fe680cbe9974af48d53026f9e35

Comment 7

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8840239 [details] [diff] [review]
Prototype headless browser mode.

Review of attachment 8840239 [details] [diff] [review]:
-----------------------------------------------------------------

Yeah, this doesn't seem so ugly and has some potentially for cleaning up.

Comment 8

[(not currently active) Ted Mielczarek]

I dunno if you've seen info on the equivalent work that's happening in Chromium, but it could be informative:
https://chromium.googlesource.com/chromium/src/+/lkgr/headless/README.md
https://bugs.chromium.org/p/chromium/issues/detail?id=546953

I'll review this patch soon, exciting to see someone working on this again! I love the plan to make it work with our stock Firefox builds--that makes it a lot more useful. I think having Marionette built-in helps shortcut a lot of the issues around embedding that previous efforts hit, since you ought to be able to just run a headless instance and drive it via Marionette.

Comment 9

[Brendan Dahl [:bdahl]]

(In reply to Ted Mielczarek [:ted.mielczarek] from comment #8)
> I dunno if you've seen info on the equivalent work that's happening in
> Chromium, but it could be informative:

Yeah, I've been following some of their progress. It looks like they also plan support webdriver, so in the future it may be much easier to write cross browser headless tests.

Comment 10

[(not currently active) Ted Mielczarek]

Comment on attachment 8842596 [details] [diff] [review]
Add headless flavor of xpcshell tests.

Review of attachment 8842596 [details] [diff] [review]:
-----------------------------------------------------------------

I wonder whether we actually need a separate test manifest type + mach command and all that. If the harness just needs to execute xpcshell with `MOZ_HEADLESS=1`, what if we just allowed xpcshell tests to specify `headless = true` in the xpcshell.ini manifest, like:
```
[test_foo.js]
headless = true
```

That seems like it'd work just as well and not require as much other fiddling. You could implement support for that by doing something like  `headless = test_object.get('headless', false)` here:
https://dxr.mozilla.org/mozilla-central/rev/8d026c60151005ad942e3d4389318fe28a0c8c54/testing/xpcshell/runxpcshelltests.py#1322

Then pass the `headless` var down to the test execution and set the env vars appropriately. If you want to run the headless tests only on Linux for now you could special-case that there as well.

If you really feel that these tests ought to run as a separate test job, you could use a subsuite for this in the test manifest. We use that for some other test types, but it'd let us keep the tests in regular xpcshell test manifests, just run them as separate jobs.

Comment 11

[Brendan Dahl [:bdahl]]

Attachment: Add headless mode xpcshell tests.

Comment 12

[Brendan Dahl [:bdahl]]

Comment on attachment 8844245 [details] [diff] [review]
Add headless mode xpcshell tests.

That approach is much easier! I had started down a similar path before, but I seem to have misunderstood and thought that multiple xpcshell tests ran per process and thought I'd have to do grouping anyway.

Having a separate headless xcpshell group does have a few advantages such as breaking up tests and eventually being able to run them on a truly headless environment. However, just having a headless attribute is much simper for now.

Comment 13

[(not currently active) Ted Mielczarek]

Comment on attachment 8844245 [details] [diff] [review]
Add headless mode xpcshell tests.

Review of attachment 8844245 [details] [diff] [review]:
-----------------------------------------------------------------

That's much simpler! :)

Comment 14

[Brendan Dahl [:bdahl]]

Attachment: Add headless browser mode.

Supports creating a windowless browser on Linux without an X server. Most of the
changes are just adding branches to avoid calls in to GTK which calls
into X. Some of the bigger additions were adding a separate headless look and
feel and a headless screen manager. These were added since there
were many calls into GTK and in the future we can re-use these on other
platforms.

Comment 15

[Brendan Dahl [:bdahl]]

Attachment: Support re-sizing a windowless browser.

Comment 16

[Brendan Dahl [:bdahl]]

Comment on attachment 8846115 [details] [diff] [review]
Support re-sizing a windowless browser.

I'm not quite sure the proper way to support resizing a windowless browser. This approach seemed the cleanest, but there are other ways too. 

Originally, I didn't have the changes to the widget code and only called window->SetSize in WebBrowserChrome2Stub::SetDimensions, but this didn't cause the window to actually be resized. To fix it, I added the IsPuppetWidget to basically cause mAttachedToParent to be set to true which in turn causes us to follow the code path in http://searchfox.org/mozilla-central/rev/b035220d0f939559f4f8cf7b9079bc12f6adfc35/layout/base/nsDocumentViewer.cpp#1997 which calls nsViewManager::SetWindowDimensions with the proper dimensions. Alternatively, in WebBrowserChrome2Stub::SetDimensions I could  get the presshell, prescontext, and viewmanager and call nsViewManager::SetWindowDimensions directly. Or maybe there's a even better way?

Comment 17

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8846115 [details] [diff] [review]
Support re-sizing a windowless browser.

Review of attachment 8846115 [details] [diff] [review]:
-----------------------------------------------------------------

::: layout/base/nsDocumentViewer.cpp
@@ +4291,5 @@
>    if (!containerItem)
>      return false;
>  
>    // We always attach when using puppet widgets
> +  if (nsIWidget::UsePuppetWidgets() || mParentWidget->IsPuppetWidget())

When is nsIWidget::UsePuppetWidgets() false but mParentWidget->IsPuppetWidget() true?

Comment 18

[Brendan Dahl [:bdahl]]

(In reply to Jeff Muizelaar [:jrmuizel] from comment #17)
> When is nsIWidget::UsePuppetWidgets() false but
> mParentWidget->IsPuppetWidget() true?

This can happen when we create a windowless browser in the parent process (http://searchfox.org/mozilla-central/rev/ca7015fa45b30b29176fbaa70ba0a36fe9263c38/xpfe/appshell/nsAppShellService.cpp#523). Alternatively, I could change UsePuppetWidgets() to do XRE_IsContentProcess() || gfxPlatform::IsHeadless()

Comment 19

[Brendan Dahl [:bdahl]]

The comment above could still be a fix, but as I've started fixing tests in the slimer js test suite it's looking like creating a separate HeadlessWidget will be cleaner than abusing the PuppetWidget. Most of the code paths in PuppetWidget are safe and don't call to the tab child if it doesn't exist, but there are still a few that can crash (also I don't think the PuppetWidget was really designed to be used this way). So far in the HeadlessWidget I've had to implement just a few methods to get most things working. Any thoughts on this approach instead?

Comment 20

[Jeff Muizelaar [:jrmuizel]]

Yes, please. Let's use a HeadlessWidget.

Comment 21

[Brendan Dahl [:bdahl]]

Attachment: Support re-sizing a windowless browser.

Comment 22

[Brendan Dahl [:bdahl]]

Attachment: Support re-sizing a windowless browser.

Comment 23

[Brendan Dahl [:bdahl]]

Comment on attachment 8852313 [details] [diff] [review]
Support re-sizing a windowless browser.

One thing I wasn't sure on is if I need to do anything during the HeadlessWidget::Invalidate.

Comment 24

[Brendan Dahl [:bdahl]]

Attachment: Add headless browser mode.

Supports creating a windowless browser on Linux without an X server. Most of the
changes are just adding branches to avoid calls in to GTK which calls
into X. Some of the bigger additions were adding a separate headless look and
feel and a headless screen manager. These were added since there
were many calls into GTK and in the future we can re-use these on other
platforms.

Comment 25

[Brendan Dahl [:bdahl]]

Comment on attachment 8853151 [details] [diff] [review]
Add headless browser mode.

As discussed on IRC with jmuizelaar, did some clean up removing 'ns' prefix and moved things into mozilla::widget namespace. Carrying r+ forward.

Comment 26

[Brendan Dahl [:bdahl]]

Attachment: Add headless browser mode. (for checkin)

Supports creating a windowless browser on Linux without an X server. Most of the
changes are just adding branches to avoid calls in to GTK which calls
into X. Some of the bigger additions were adding a separate headless widget
which implements just enough to render a page. A headless look and
feel were also added since there are many calls into GTK in the platform
specific one.

Comment 27

[Brendan Dahl [:bdahl]]

The new patch is the squash of the above reviewed patches and resolving merge conflicts from the removal of ScreenManager.

Try run:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=e86ed1de993f3c704021d880d4572428de2ac3be

Comment 28

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/23674d708903
Add headless browser mode. r=jrmuizel, r=ted

Comment 29

[Kris Maglione [:kmag]]

This change breaks xpcshell tests that create windowless browsers when I run them locally:

#0  0x00002aaab04818f9 in ?? () from /usr/lib/libgtk-3.so.0
#1  0x00002aaab03292a8 in ?? () from /usr/lib/libgtk-3.so.0
#2  0x00002aaab033dcf4 in ?? () from /usr/lib/libgtk-3.so.0
#3  0x00002aaab032a5ec in ?? () from /usr/lib/libgtk-3.so.0
#4  0x00002aaab033dbdc in ?? () from /usr/lib/libgtk-3.so.0
#5  0x00002aaab033dc74 in ?? () from /usr/lib/libgtk-3.so.0
#6  0x00002aaab032af52 in ?? () from /usr/lib/libgtk-3.so.0
#7  0x00002aaab1f0133f in g_type_create_instance () from /usr/lib/libgobject-2.0.so.0
#8  0x00002aaab1ee320b in ?? () from /usr/lib/libgobject-2.0.so.0
#9  0x00002aaab1ee4c1d in g_object_newv () from /usr/lib/libgobject-2.0.so.0
#10 0x00002aaab1ee53d4 in g_object_new () from /usr/lib/libgobject-2.0.so.0
#11 0x00002aaab0345ffa in ?? () from /usr/lib/libgtk-3.so.0
#12 0x00002aaab05154e7 in ?? () from /usr/lib/libgtk-3.so.0
#13 0x00002aaab1f0133f in g_type_create_instance () from /usr/lib/libgobject-2.0.so.0
#14 0x00002aaab1ee320b in ?? () from /usr/lib/libgobject-2.0.so.0
#15 0x00002aaab1ee511e in g_object_new_valist () from /usr/lib/libgobject-2.0.so.0
#16 0x00002aaab1ee53c1 in g_object_new () from /usr/lib/libgobject-2.0.so.0
#17 0x00002aaaad256468 in CreateScrollbarWidget (aWidgetType=MOZ_GTK_BUTTON, aOrientation=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:57
#18 CreateWidget (aWidgetType=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:550
#19 0x00002aaaad25d2dd in GetWidget (aWidgetType=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:628
#20 GetWidgetRootStyle (aNodeType=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:769
#21 0x00002aaaad25d36b in CreateChildCSSNode (aName=0x2aaaaeaaa25e "contents", aParentNodeType=2990728240) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:782
#22 0x00002aaaad2574bf in GetCssNodeStyleInternal (aNodeType=MOZ_GTK_SCROLLBAR_CONTENTS_VERTICAL) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:818
#23 CreateChildCSSNode (aParentNodeType=MOZ_GTK_SCROLLBAR_CONTENTS_VERTICAL, aName=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:782
#24 GetCssNodeStyleInternal (aNodeType=MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:822
#25 0x00002aaaad256ed5 in ClaimStyleContext (aNodeType=MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL, aDirection=GTK_TEXT_DIR_NONE, aStateFlags=GTK_STATE_FLAG_NORMAL, aFlags=<optimized out>) at /home/kris/code/mozilla-central/widget/gtk/WidgetStyleCache.cpp:1131
#26 0x00002aaaad26c726 in nsLookAndFeel::EnsureInit (this=0x2aaabcc18090) at /home/kris/code/mozilla-central/widget/gtk/nsLookAndFeel.cpp:1175
#27 0x00002aaaad26c3d4 in nsLookAndFeel::NativeGetColor (this=0x2aaabcc18090, aID=mozilla::LookAndFeel::ColorID::eColorID_WindowBackground, aColor=@0x2aaac35da9a0: 0) at /home/kris/code/mozilla-central/widget/gtk/nsLookAndFeel.cpp:226
#28 0x00002aaaad23fc55 in nsXPLookAndFeel::GetColorImpl (this=0x2aaabcc18090, aID=mozilla::LookAndFeel::ColorID::eColorID_WindowBackground, aUseStandinsForNativeColors=false, aResult=<optimized out>) at /home/kris/code/mozilla-central/widget/nsXPLookAndFeel.cpp:822
#29 0x00002aaaadedb3f1 in nsWebBrowser::Create (this=0x2aaac35da880) at /home/kris/code/mozilla-central/toolkit/components/browser/nsWebBrowser.cpp:1208
#30 0x00002aaaaddc4fe2 in nsAppShellService::CreateWindowlessBrowser (this=<optimized out>, aIsChrome=<optimized out>, aResult=0x7fffffff84a8) at /home/kris/code/mozilla-central/xpfe/appshell/nsAppShellService.cpp:539

I'm not sure why it appears to work on inbound.

Comment 30

[Mike Hommey [:glandium]]

Could be a difference in the version of Gtk. IIRC the test machines are on Ubuntu 12.04.

Comment 31

[Brendan Dahl [:bdahl]]

I'm also able to reproduce the failures locally. I thought I had successfully run several of the windowless browser tests locally (maybe they passed for the same reason try is working?). 

I was curious if maybe some of the tests were disabled on linux, but looks like they're running: js/xpconnect/tests/unit/test_nuke_sandbox_event_listeners.js in https://public-artifacts.taskcluster.net/cq7Igmc6TjK0BSJDPhwW7w/0/public/logs/live_backing.log

I'll look into this more when tomorrow when I have physical access to my linux desktop.

Comment 32

[Brendan Dahl [:bdahl]]

Btw: If you need a quick fix revert nsappshellservice	
from:
  nsCOMPtr<nsIWidget> widget = nsIWidget::CreateHeadlessWidget();
to
  nsCOMPtr<nsIWidget> widget = nsIWidget::CreatePuppetWidget(nullptr);

Comment 33

[Kris Maglione [:kmag]]

Yup, already did. That's how I confirmed that this was the cause.

Comment 34

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/23674d708903

Comment 35

[Daniele "Mte90" Scasciafratte]

Just a question from an enthusiastic of this feature.
It is available in Nightly?
What is the parameter? --headless?
Maybe a documentation on MDN will be helpful :-D

Comment 36

[ziyunfei]

(In reply to Daniele "Mte90" Scasciafratte from comment #35)
> Just a question from an enthusiastic of this feature.
> It is available in Nightly?
> What is the parameter? --headless?
> Maybe a documentation on MDN will be helpful :-D

MOZ_HEADLESS=1 /path/firefox

Comment 37

[woprandi]

I'm trying this mode for automatic testing but I doesn't get anything in stdout

Comment 38

[Myk Melez [:myk] [@mykmelez]]

(In reply to woprandi from comment #37)
> I'm trying this mode for automatic testing but I doesn't get anything in
> stdout

This is a meta-bug, so its comments aren't a good place to report issues with headless mode. For that, please file a new bug in the Firefox :: Headless component:

https://bugzilla.mozilla.org/enter_bug.cgi?product=Firefox&component=Headless

Comment 39

[Chris Mills [:cmills]]

Documented:

https://developer.mozilla.org/en-US/Firefox/Headless_mode
https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options#-headless

I've also created an examples repo:

https://github.com/mdn/headless-examples

And added a note to the Fx rel notes:

https://developer.mozilla.org/en-US/Firefox/Releases/55#Other (for Linux)
https://developer.mozilla.org/en-US/Firefox/Releases/56#Other (for Win/Mac)

Comment 40

[Michał Gołębiowski-Owczarek [:mgol]]

(In reply to Chris Mills (Mozilla, MDN editor) [:cmills] from comment #39)
> https://developer.mozilla.org/en-US/Firefox/Releases/55#Other (for Linux)
> https://developer.mozilla.org/en-US/Firefox/Releases/56#Other (for Win/Mac)

From what I see in the code the flag is `--headless`, not `-headless` as documented under those URLs. Am I missing something?

Comment 41

[(not currently active) Ted Mielczarek]

(In reply to Michał Gołębiowski-Owczarek [:mgol] from comment #40)
> From what I see in the code the flag is `--headless`, not `-headless` as
> documented under those URLs. Am I missing something?

Our commandline parser allows either -arg or --arg. It's a little silly but not important enough to change and break people.

Comment 42

[Henrik Skupin [:whimboo][⌚️UTC+1]]

(In reply to Ted Mielczarek [:ted.mielczarek] from comment #41)
> Our commandline parser allows either -arg or --arg. It's a little silly but
> not important enough to change and break people.

Just as info beside... as we experienced with Marionette the double hyphen causes problems on Windows. See https://hg.mozilla.org/mozilla-central/rev/cd8a44efa422 for the necessary changes.

Comment 43

[Andreas Tolfsen ❲:ato❳]

(In reply to Michał Gołębiowski-Owczarek [:mgol] from comment #40)
> (In reply to Chris Mills (Mozilla, MDN editor) [:cmills] from comment #39)
> > https://developer.mozilla.org/en-US/Firefox/Releases/55#Other (for Linux)
> > https://developer.mozilla.org/en-US/Firefox/Releases/56#Other (for Win/Mac)
> 
> From what I see in the code the flag is `--headless`, not `-headless` as
> documented under those URLs. Am I missing something?

You should prefer the single hyphen -headless, as --headless will
not work on Windows.

Comment 44

[Andreas Tolfsen ❲:ato❳]

(In reply to Chris Mills (Mozilla, MDN editor) [:cmills] from
comment #39)

> https://developer.mozilla.org/en-US/Firefox/Headless_mode

In this article you say:

> Next, set the MOZ_HEADLESS environment variable to 1, so that the
> test will be run in headless mode:
> 
>> process.env.MOZ_HEADLESS = "1";

Ideally you should use the moz:firefoxOptions object to set {"args":
["-headless"]}, as it is documented in the geckodriver README:
https://github.com/mozilla/geckodriver/blob/master/README.md

There are a number of MOZ_* prefixed environment variables we
don’t want average users to use.

Comment 45

[Myk Melez [:myk] [@mykmelez]]

(In reply to Andreas Tolfsen ‹:ato› from comment #44)
> Ideally you should use the moz:firefoxOptions object to set {"args":
> ["-headless"]}, as it is documented in the geckodriver README:
> https://github.com/mozilla/geckodriver/blob/master/README.md

The geckodriver README explains how to specify a moz:firefoxOptions object for geckodriver, but it doesn't explain how to do that using selenium-webdriver, which is the API that Chris's article uses.

selenium-webdriver lets you specify command-line arguments, but it isn't obvious how.  I browsed its docs <http://seleniumhq.github.io/selenium/docs/api/javascript/module/selenium-webdriver/index.html>, read its source code <https://github.com/SeleniumHQ/selenium/tree/master/javascript/node/selenium-webdriver>, and spent some time debugging an example script before finally figuring out how it works:

```
const binary = new firefox.Binary(firefox.Channel.NIGHTLY);
binary.addArguments("--headless");
const options = new firefox.Options().setBinary(binary);

const driver = new Builder()
.forBrowser('firefox')
.setFirefoxOptions(options)
.build();
```

> There are a number of MOZ_* prefixed environment variables we
> don’t want average users to use.

I agree, but I also think we don't want users to jump through hoops to configure Firefox to run headlessly.  I filed Selenium issue #4591 <https://github.com/SeleniumHQ/selenium/issues/4591> to add a headless() method to the Options class, so you can configure headless more simply:

const driver = new Builder()
.forBrowser('firefox')
.setFirefoxOptions(new firefox.Options().headless())
.build();

Note: Chrome's implementation of the Options class already has such a method, plus a setArguments() method that allows you to set arbitrary arguments directly on the Options class (so you don't have to instantiate a separate Binary object).

Comment 46

[Chris Mills [:cmills]]

(In reply to Myk Melez [:myk] [@mykmelez] from comment #45)
> (In reply to Andreas Tolfsen ‹:ato› from comment #44)
> > Ideally you should use the moz:firefoxOptions object to set {"args":
> > ["-headless"]}, as it is documented in the geckodriver README:
> > https://github.com/mozilla/geckodriver/blob/master/README.md
> 
> The geckodriver README explains how to specify a moz:firefoxOptions object
> for geckodriver, but it doesn't explain how to do that using
> selenium-webdriver, which is the API that Chris's article uses.
> 
> selenium-webdriver lets you specify command-line arguments, but it isn't
> obvious how.  I browsed its docs
> <http://seleniumhq.github.io/selenium/docs/api/javascript/module/selenium-
> webdriver/index.html>, read its source code
> <https://github.com/SeleniumHQ/selenium/tree/master/javascript/node/selenium-
> webdriver>, and spent some time debugging an example script before finally
> figuring out how it works:
> 
> ```
> const binary = new firefox.Binary(firefox.Channel.NIGHTLY);
> binary.addArguments("--headless");
> const options = new firefox.Options().setBinary(binary);
> 
> const driver = new Builder()
> .forBrowser('firefox')
> .setFirefoxOptions(options)
> .build();
> ```
> 
> > There are a number of MOZ_* prefixed environment variables we
> > don’t want average users to use.
> 
> I agree, but I also think we don't want users to jump through hoops to
> configure Firefox to run headlessly.  I filed Selenium issue #4591
> <https://github.com/SeleniumHQ/selenium/issues/4591> to add a headless()
> method to the Options class, so you can configure headless more simply:
> 
> const driver = new Builder()
> .forBrowser('firefox')
> .setFirefoxOptions(new firefox.Options().headless())
> .build();
> 
> Note: Chrome's implementation of the Options class already has such a
> method, plus a setArguments() method that allows you to set arbitrary
> arguments directly on the Options class (so you don't have to instantiate a
> separate Binary object).

Thanks for the help here Myk. I've updated the article to use the improved version (and not the MOZ_HEADLESS variable), and accepted your PRs ;-)

Comment 47

[Greg Lindahl]

Can someone edit bug # 1453229 to have component Headless and be dependent on this metabug? I don't have the privs to edit it.

Comment 48

[Brendan Dahl [:bdahl]]

I'm going to close this bug as the bulk of the work is done now. New bugs can just be filed in Firefox->Headless component.