Block Element doesn't appear in the context menu of a tab under specific circumstances

[ghost]

Prerequisites

• I verified that this is not a filter issue
  • Filter issues MUST be reported at filter issue tracker
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uBlockOrigin
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
• I tried to reproduce the issue when...
  • uBlock Origin is the only extension
  • uBlock Origin with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uBlock Origin
• I checked the documentation to understand that the issue I report is not a normal behavior

Description

Sometimes if you right click and accidently click open a new Window instead of a new tab for a link and if you happen to quickly close that new Window and thereafter right click to open the context menu on the already opened tab, Block Element will not appear, so this is more of a visual issue under the above mentioned circumstances.

A specific URL where the issue occurs

https://www.google.com/

Steps to Reproduce

1. Close all opened tabs and windows and browse to google.com in a new tab.
2. Right click on Gmail and select Open link in a new Window which will spawn a new Window, so quickly close it(as fast as you can) before it loads.
3. Now back on the already opened tab of google.com, right click to open the context menu and notice Block Element is missing.

Expected behavior:

Block Element would appear when context menu of the tab is opened.

Actual behavior:

Block Element is missing from the context menu.

Supporting Evidence

Chrome 70

https://i.gyazo.com/27e5e60c750d0794ab1ff232ec94d57a.mp4

Firefox 63

https://i.gyazo.com/b3cc16d203426f59e2e718a8e0837b2b.mp4

Your environment

• uBlock Origin version: 1.16.15b6
• Browser Name and version: Chrome 70/Firefox 63
• Operating System and version: Win 10 x64 1807 build

PS

It was difficult to reproduce on Firefox, so it may take you some tries. I have attached videos as supporting evidence so as to provide some visual aide in reproduction.

[uBlock-user]

Also happens when you open a tab by middle click.

STR

• Browse to google.com and middle click on Gmail, as soon a new tab opens, click it on the tab and close the tab quickly as you can.

• Back on the google.com tab right click and find Block Element missing from the context menu.

[u-RraaLL]

After opening a link in a new tab, be it via the context menu or via middle-clicking, uBO's context-menu item will never appear if the connection is interrupted. Even by uBO itself.

STR:

1. Add ||reddit.com^|$document to "My filters".
2. Open uBO's sub.
3. Middle-Click the link to reddit's home.
4. Right-click anywhere on the page.
5. See no context menu item for uBO.
6. Repeat 4-5 as long as you want.
7. Switch the tab or refresh the page to bring back the context menu.

ubo-context-menu-bug-2022-07-17_13.45.47.mp4

This is a new browser profile with uBO just installed and updated.

The missing context menu also occurs on lagging websites. I'm guessing before the initial response from the website reaches the browser. So immediately after opening a new tab on any website - normally not an issue since that'll usually last only under/about 1s, but if a website/server is lagging, it can take up to a minute. Or more, if the connection fails.
One such website is https://rmz.cr, but the lagging occurs at random times so it's not that easy to reproduce.

But whether the connection is lagging or blocked by uBO, the issue is probably the same.

~~
Originally posted as a comment to my (related?) issue #2085, but this one seems like a better place. That issue is tagged as a FF only bug, but this is reproducible on both FF and Chrome.

The only difference between them I've noticed is that if I use picker via the popup and close it, the context menu item will come back on Chrome, while it won't on FF.

The main problem with the disappearing item when the connection in the new tab is interrupted remains in both.

[uBlock-user]

@u-RraaLL cannot reproduce on Firefox 127, can you now ?

[u-RraaLL]

Seems to be fixed now. On FF and Chrome both.

[uBlock-user]

Context menu entry do not appear when iframe src = about:blank

STR --

• Become advanced user and add the following rules in my rules -

* * 3p block, * * 3p-frame block, * * 3p-script block and animehub.ac static.anmedm.com * noop

• Browse to https://animehub.ac/animehub.to

• Right click on the top right rectangular box and see that context menu entry doesn't appear and the iframe src is about:blank

Sometimes contextmenu entry may appear if an empty iframe has not loaded...

[garry-ut99]

Context menu entry do not appear when iframe src = about:blank

That's already another separate issue, a duplicate of:

• No context menu entry for data:* iframes (banners) #283

[gorhill]

top right rectangular box

I don't see such thing.

[uBlock-user]

I don't see such thing.

[gorhill]

[uBlock-user]

Does disabling cosmetic filtering make it appear ?

My bad. Hide placeholders of blocked elements setting was disabled on my end.

[gorhill]

Hide placeholders of blocked elements setting was disabled

Still works fine in Chromium, but not in Firefox. I stepped through the code and uBO does tell Firefox to add a "Block element..." item to the menu, but the browser is not doing it, so this appears to be a Firefox-specific quirk.

[uBlock-user]

but not in Firefox.

Yes, that is true, do you intend to address that with a fix ?

[gorhill]

Not really, it's Firefox not enforcing uBO's context menu entries, I currently don't have the time to track down the issue in Firefox's code base for such a small issue.

[garry-ut99]

Are you sure that it's Firefox specifc, because the issue can be reproduced on Chromium too: in browser inspector pane, by changing manually the iframe's src attribute to: src="about:blank" (or to src=""), then uBO menu doesn't appear anymore in that frame.

[gorhill]

The src was not about:blank in the reported case:

For the about:blank case, using '<all_urls>' instead at this line seems to work. This still doesn't solve the reported case above for Firefox, which is expected since the src is not about:blank.

[uBlock-user]

The src was not about:blank in the reported case:

src becomes about:blank if you follow the STR + disable Hide placeholders of blocked elements setting which is the situation I reported in #151 (comment)

[gorhill]

The screenshot I posted is the result of following your steps, using Firefox 129.0. I don't see about:blank, I see https://discordapp.com/widget?id=556038524151791616&theme=dark

[uBlock-user]

The screenshot I posted

That is correct, inspector does show the original iframe src, but if you right click on the white box and click on This Frame > followed by View Frame Info, you will see this --

Instead of View Frame Info, you can also click on View Frame Source and verify the same.

[gorhill]

you will see this

Very well. The proposed change to '<all_urls>' still doesn't make a difference in Firefox, so there is something specific to Firefox which prevents the context menu entry from appearing no matter what.

[garry-ut99]

Context menu appears in uBO 1.46.1b18 (and earlier), but not in uBO uBO 1.46.1rc0 (and later)
Caused by this commit in (uBO 1.46.1rc0): gorhill/uBlock@8f2e7ae: [Prevent context menu entries on non-HTTP documents]

---

Besides some things I noticed in uBO 1.46.0:

A) Even despite a double context menu appears after click inside the iframe
(because content inside/below ##iframe is targeted), clicking either:
[1] uBlock Origin ==> Block Element or
[2] uBlock Origin ==> Block Element in iFrame
results in nothing: Element Picker doesn't appear

B) After clicking in iframe's border/corner, where only a single context menu appear
(because ##iframe itself is targeted):
Block Element and then after clicking it, then it works: Element Picker appears

C) Now, what is also interesting:
[1] is that after doing B), suddenly A)[1] is fixed (but not [2]) and works fine: Element Picker appears, until the page is reloaded.
[2] also intertesting is that setting manually the iframe's src to about:blank in browser inspector pane also fixes A)[1] the same way like above

VIDEO - the sequence of actions in video is the following:

• A[2]
• A[1] (Element Picker doesn't appear)
• B (it has fixed A[1]]
• A[1] (Element Picker does appear)

D) Now:
[1] Element Picker appears when invoked from both A[1] & A[2] in case of a normal iframe,
[2] but I don't know whether a lack of appearance of Element Picker in A[1] & A[2] in case of an empty about:blank iframe is expected or not,
[3] and why B or C[1] fixes A[1]
[4] but since it does, it suggets that at least A[1] should work even in an empty about:blank iframe
[5] of course it might be that both of A should work (or none)
[6] unless that is just some random conicidence that B or C[1] fixes A[1]

[uBlock-user]

@gorhill https://fc-lc.xyz/ltio is a case where I don't have to disable Hide placeholders of blocked elements and do any special repro requirements and yet context menu won't appear in the embedded iframe(right click in the centre above the blue button) whose source is about:blank

[garry-ut99]

Moreover, unlike in the previous case from my last comment, this time, on https://fc-lc.xyz/ltio , on uBO 1.46.0:

• (A[1]) uBlock Origin ==> Block Element : works since the beginning (Element Picker appears)
• (A[2]) uBlock Origin ==> Block Element in iFrame : Element Picker still doesn't appear

[gorhill]

Please provide browser name for when you state it works/doesn't works.

[garry-ut99]

(As for me) The same result for both Firefox/Chromium. (that's why I didn't mention browser name, but I understand you just want to make sure).

[gorhill]

a case where I don't have to disable Hide placeholders of blocked elements

When I change this line to:

documentUrlPatterns: [ '<all_urls>' ],

It solves the issue in Chromium. It does not solve the issue in Firefox. To solve the issue in Firefox, I need to completely remove the line, but then this brings back this issue -- which I argue is a Firefox issue, but nevertheless I do not want to bring it back.

The workaround is trivial : use the Enter element picker mode from the popup panel or use assigned keyboard shortcut if any to enter element picker mode.

Since I can't fix the issue in Firefox, I consider it's not worth to make any change and advise to use the workaround.

[uBlock-user]

Will using *://*/* make any difference in Firefox ?

[gorhill]

*://*/* does not match about:blank.

[uBlock-user]

I don't suppose about://*/* is considered valid, is it ?

[garry-ut99]

Doesn't work either. Besides, AdGuard's and AdBlocker Ultimate's context menus work on about:blank, but suffer #1093 as a side-effect.