493715 - Random render issues: "generated code" shows the extra code that is actually rendered while "view source" shows right code

Status: UNCONFIRMED

(Core :: Layout, defect)

Description

[Jose R. Cabanes]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.10) Gecko/2009042708 Fedora/3.0.10-1.fc9 Firefox/3.0.10
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10

The URL I posted above is rendered correctly in all browsers I tested, included Firefox 2, and even Firefox 3. But sometimes, randomly, Firefox 3 shows the page broken. I've attached an image where the broken part can be seen (it is in the calendar). The week of the calendar broken will be different on different machines.

When the bug manifests, looking at "generated code", there is some code that is repeated (why?) and that is what is brokening the page. Absurdily enough, "view source code" shows the right code.

Even weirder, I've seen the bug happen a lot more in fast machines than in slow machines or in busy machines.

It seems that the bug is more likely to happen if prior to load the offending page, a page with lots of Javascripts and Flashes is loaded.


Reproducible: Sometimes

Steps to Reproduce:
1. Go to http://mortimer.zentense.com/bug/events.html (it will show right)
2. Click on the red top-left logo and see if calendar is correctly rendered
3. Repeat step 2 until the bug reproduces
4. If you cannot reproduce it, try to load a flash-intensive page in another tab, close it, and then try step 2 again, or try in another machine.
Actual Results:  
If the bug manifests calendar will show broken and one or more weeks will be rendered vertically instead of horizontally, as seen in the attached image.

Expected Results:  
The page rendered as expected.

Bug never seen on Linux Firefox. Untested on MacOs. Seen in all Windows 3.x Firefox (since 3.0 to 3.0.10)

The bug never seen on LAN. It seems that latencies and CPU speed affect the behaviour of this bug.

Comment 1

[Jose R. Cabanes]

Attachment: This image shows what happens when the bug manifests

This image shows what happens when the bug manifests

Comment 2

[Jose R. Cabanes]

Bug also seen on MacOS

Comment 3

[Ria Klaassen (not reading all bugmail)]

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.11pre) Gecko/2009051205 GranParadiso/3.0.11pre

I can't reproduce the issue. Maybe additional steps to reproduce?

Comment 4

[Jose R. Cabanes]

Ok, let's try this link:

http://mortimer.zentense.com/webapp/events
User: amnesia
Pass: test123

It's the same page, but server-side generated (a servlet). The one I posted was a static version of the same page. The bug can be seen on both, but on the dynamic one it's much easier to reproduce this problem.

Comment 5

[Ria Klaassen (not reading all bugmail)]

Alas, I'm not able to reproduce it; maybe someone else.

Comment 6

[Jose R. Cabanes]

Step 1: Go to http://mortimer.zentense.com/webapp/events
Step 2: Click on Events on main menu (try it several times if needed)
Step 3: Select a week on calendar (try the same week  several times if needed)

Comment 7

[Ria Klaassen (not reading all bugmail)]

Nope :). 
Have you tried running Firefox in safe-mode and with a new profile?
http://support.mozilla.com/en-US/kb/Safe+Mode
http://support.mozilla.com/en-US/kb/Basic+Troubleshooting#Make_a_new_profile

Comment 8

[Jose R. Cabanes]

From the last URL and procedure I am able to consistently reproduce the bug on all the Windows XP I have available.

I've tried in safe mode and I reproduced it as expected (as I was not using any extension on some machines).

I've tried to create a new profile and the bug has been also reproduced. 

What I do is go to http://mortimer.zentense.com/webapp/events, and then click (just once) on Events on main menu (for loading the same page), and voila, calendar shows broken.

But for what I've seen this bug is very, very weird... so probably just it won't manifest on your machine... I have exactly the same app in another server in the office, and when connecting to that server, the bug cannot be seen... so it is not easy to catch: only happens when some unknown conditions are met.

Comment 9

[Jose R. Cabanes]

Also seen in firefox in 3.5 beta 4

Comment 10

[vargoxyz]

(In reply to comment #5)
> Alas, I'm not able to reproduce it; maybe someone else.

I can't reproduce it too.

Comment 11

[Jose R. Cabanes]

I've tried in another machine. Now with Firefox 2.0.0.20. And again calendar showed broken sometimes, not always, and it brakes in several different ways (not always being broken the same way) :-(

I've seen this in 4 different machines, 3 XPs and 1 Mac OSX, in 2 different places. Only happens with Firefox, and only with production server (mortimer) as the same page rendered from development server works fine in all Firefox. 

There is something wrong, but I have no idea of what it is, but is really weird and random. Probably I will try to make up the calendar in another way and see what happens.

I would be happy if I am the only person in the world that can reproduce this bug... :-). But I had a similar issue a while ago, in another application. It was just showing the same behaviour, but in another page with an AJAX request (some code randomly repeated in Firefox brokening the page). This was also seen by some customers, but in that case never was seen in Firefox 2. Now it is. Again the problem was only observed randomly on production server, never on development one. So latencies seem important for this thing to happen.

Of course I know that if the bug cannot be reproduced, it cannot be fixed. It is what I say to a customer when they state that something is wrong: tell me how to reproduce it and then I'll fix it.

I will add additional information if I discover something new that may bring some light to this...

Comment 12

[Jose R. Cabanes]

Attachment: Other manifestation of the bug

Comment 13

[Jose R. Cabanes]

Bug spontaneously confirmed by one of our customers (he says see it a lot)... so far seen in 5 machines, from 3 different locations and 4 different connections.

Maybe this helps. When bug shows, the generated code is (comments added by me right now):

<!-- This is a right week -->
  <a href="events?week=41" class="week">
    <div class="">4</div>
    <div class="">5</div>
    <div class="">6</div>
    <div class="">7</div>
    <div class="">8</div>
    <div class="">9</div>
    <div class="">10</div>
    <div style="clear: left;"></div>
  </a>


<!-- This is a broken week. See extra code. It should be as previous one-->
  <a href="events?week=42" class="week">
    </a><div class=""><a href="events?week=42" class="week">11</a></div>

<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">12</a></div>
<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">13</a></div>
<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">14</a></div>
<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">15</a></div>
<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">16</a></div>
<a href="events?week=42" class="week">    </a><div class=""><a href="events?week=42" class="week">17</a></div>

<a href="events?week=42" class="week">    </a><div style="clear: left;"></div>
<a href="events?week=42" class="week">  </a>

The first week is right. The second week displays broken (vertically). For some reason FF repeats href tag on each day. I tried to put comments but then it began to repeat comments and calendar broke in a different way. 

   Looking at source code (not generated code) always shows the right code. I've seen this behaviour even with the static HTML I posted as original URL bug so it does not seem a server-side problem (using Apache as server) and if it was a server-side problem, why only can be seen on Apache?

   Maybe is not a layout problem as layout is right given the generated source code. The question is: why the extra code? 

   Amazing and annoying that bug cannot be seen there while customers are seeing it spontaneously, so when web will be launched other users will see it as well, and that is ugly. Murphy is not on our side...

I think that I cannot give more details on this. I appreciate your patiente. It's a pitty that this effort will be worth nothing if bug cannot be confirmed there, but well... at least I have tried as hard as I have could and I know that debugging a complex piece of software as FF is absolutely not an easy task.

Comment 14

[Jose R. Cabanes]

Also seen in Linux. Just once. But it also happened in Linux.

Comment 15

[Jose R. Cabanes]

I've done a new version of the web. Not any relevant change in the calendar beyond some adjustments to CSS, but now is quite harder for me to reproduce the bug, but still happens sometimes. 

As you have experienced, I've realized that in some machines (maybe most of them?) the bug just won't manifest. 

Unable to determine what makes this to happen in some machines, this bug seems will be unconfirmed for long. Too subtle and hard to catch.

Comment 16

[Tupohlav]

Hello, I use a link to my discord invite on my website https://minecraftclue.com . However, I wish it was possible to add some js code with a button in place of the link, similar to torrent links. Anyone out there who can explain this?