LaTeX Is LaTeX Preview Working Properly?

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LaTeX preview functionality has been recently updated, allowing users to see graphical representations of their LaTeX code in posts. However, some users are experiencing issues where previews display incorrect cached images instead of the intended LaTeX output. This problem appears to be linked to browser settings and user accounts, with varying experiences reported across different platforms. A workaround suggested involves adding dummy LaTeX images to force the generation of new previews. The developer has implemented code to delete stale images, aiming to resolve these caching issues.
chroot
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Hey all,

Just wanted to let you know I finished installing the code that enables LaTeX preview. Try it out and let me know if you find any bugs.

- Warren
 
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Geez, that must've been really hard to fix. :P
 
I = I_S (e^\frac{qV}{kT} -1)

Thanks chroot! That really is a big help in posting replies. :biggrin:
 
good day... good day :P

nice work chroot!
 
-Job- said:
Geez, that must've been really hard to fix. :P

:rolleyes: Yeah... whew, I'm beat.

- Warren
 
{\rm\HUGE\color{red} JOY!}
 
Since the recent update, I just noticed that my blog/journal entries with attempts at \LaTeX now show graphic images... of the form "preview9587-0.png"... which are images from other LaTeX posts or previews of mine. They used to show the red "LaTeX image generation failed..." graphic. So, it seems that we are one step closer to LaTeX in the blog/journals... which might be a good place to place easier-to-find tutorials or notes... with no time limits on editing.. and no possible interference from other posters [but, of course, subject to approval by the mentors].
 
robphy,

I don't really have any intention of supporting LaTeX in blogs. What you're seeing is actually a bug: if the code is run inside anything other than a normal post, it assumes it's in a preview. That apparently wasn't a good plan...

- Warren
 
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  • #10
chroot said:
robphy,

I don't really have any intention of supporting LaTeX in blogs. What you're seeing is actually a bug: if the code is run inside anything other than a normal post, it assumes it's in a preview. That apparently wasn't a good plan...

- Warren

ok. i see.
But Thanks again for fixing the LaTeX preview! :smile::smile::smile::smile::smile::smile:
 
  • #11
Thanks Warren.

\nabla \times \mathbf{H} = \mathbf{J} + \frac{\partial \mathbf{D}} {\partial t}

\oint_C \mathbf{H} \cdot \mathrm{d}\mathbf{l} = \int_S \mathbf{J} \cdot \mathrm{d} \mathbf{A} +<br /> \int_S \frac{\partial\mathbf{D}}{\partial t} \cdot \mathrm{d} \mathbf{A}

Does this mean I can LaTeX all I want? How'd you get around the issues that were preventing you from doing it in the first place?
 
  • #12
When couldn't you use LaTeX all you wanted?

I got around the issues by scouring the vB code for an hour or two and finding the right places to put my hooks. It was actually really easy to find a reasonable way to do it. I'm sorry I didn't do it a long time ago. :frown:

- Warren
 
  • #13
\chi\varpi\varpi\lambda.
 
  • #14
\kappa oo\lambda or\chi \omega\omega\lambda? :biggrin:
 
  • #15
\varsigma o o \lambda

P.S. (yes, \iota\tau works)
P.P.S. so does inline :approve:
 
  • #16
Awesome, thanks!

2 + 2 = 4
 
  • #17
\begin{equation}\label{Eq2101}
m \ddot x (t) = R(t) - m \cdot g \cdot \sin \theta _E
\end{equation}
 
  • #18
LaTeX in previews is not working for me. Since no one else is reporting this problem, is it some setting on my browser (IE 8) I need to configure or something with the cookie I have do?
The following should look like the fraction 2/3 formatted nicely, but what I see when I preview it is an integral sign.
<br /> \frac{2}{3}<br />
 
  • #19
Now that I've posted it, the LaTeX code renders correctly, but it didn't in the preview.
Any ideas?
 
  • #20
Mark, yes, LaTex doesn't always display properly in preview mode.

FYI:

DrGreg said:
Previewing a message seems to show incorrect cached images instead of generating a new Latex image. No problem when you actually post the message.

Redbelly98 said:
Yes, this was a problem even before the recent LaTex issues of 1 or 2 weeks ago. I guess there is no easy fix, or it would have been fixed already, and so we just live with it.

This is one reason why I avoid LaTex unless absolutely necessary, and instead copy-and-paste the symbols linked to in my sig. If you just need to use the occasional Greek letter, the copy-and-paste route is definitely preferable.

It's worth mentioning that we have LaTex mainly (perhaps entirely?) due to the efforts of one of the PF volunteer staffmembers, chroot.

Regards,

Mark
 
  • #21
Up until the recent problem with the hard drive failure (I think that was the problem), LaTeX preview worked perfectly for me. I'm glad to see that it works now when you submit your post, but being able to preview it is a nice feature when you're working with definite integrals or matrices or the like.
Mark
 
  • #22
I may be a little slow, so apologies if this has been asked and answered already. I don't see the LaTex button in the Advanced Reply or New Topic windows anymore. Am I missing it?
 
  • #23
It depends what forum you're in berkeman. Its not available in all of them.
 
  • #24
Kurdt said:
It depends what forum you're in berkeman. Its not available in all of them.

Hah! That's it Kurdt, thanks.

The thread that confused me is currently posted in Computer Science / Math Software, and there is no LaTex sigma available there:

https://www.physicsforums.com/showthread.php?t=312053

But you're correct, I see it in EE and in the Homework Help forums. I had held off moving the post at the link above until I could figure out (whenever the OP responds to my question) where to move it. I tried to refer to the LaTex button in my post, but noticed that it wasn't available as I was making my reply.

Thanks for clarifying this for me. Makes sense now.
 
  • #25
I just made a couple of posts, and LaTeX preview didn't work. :confused:
 
  • #26
It still doesn't work, even after clearing my browser cache, deleting cookies etc. Does it work for the rest of you?!
 
  • #27
Fredrik said:
It still doesn't work, even after clearing my browser cache, deleting cookies etc. Does it work for the rest of you?!
It's working for me (Firefox 3, Fedora 10).
 
  • #28
test \Omega \omega

worked in preview for me. IE7 on Vista (yuck)
 
  • #29
LaTeX previews are not working for me. When I preview the code below I get the first four LaTeX images from this post (starting with the one I quoted from Strangerep's post). I have tried this from three different computers and I get the same result every time. It doesn't matter if I use Firefox or IE, or if I use XP or Vista. This is definitely tied to my user account somehow.

\int

\sum

3+3

x

By the way, when I wrote #5 in that thread, I messed up some tex or itex tag and got a very weird result. The last paragraph ended up outside the rectangular area where the post is supposed to be. It was below the "report" button. Something is really weird here. (That post went back to normal when I fixed the broken tags).
 
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  • #30
I know that Greg or chroot had explained this before. From what I remember, it has to do with LaTex code causing a new image to be generated. This is a CPU-intensive process, or perhaps it had to do with the images taking up hard drive space. At any rate, generation of new fresh images is not done everytime a post with LaTex code is viewed. That's why old or wrong LaTex images sometimes show up.

Refreshing a post should force new, correct images to be generated. But refreshing a preview does not do this, apparently.

At least this is my understanding. Greg definitely prefers we not use LaTex for simple things like Greek characters, superscripts, and subscripts that can be done easily without LaTex.
 
  • #31
That's definitely not the problem I have. It fails every time, no matter what browser or computer(!) I use. I never had those intermittent problems that you have described before. (At least I think it was you, but I may remember it wrong).
 
  • #32
Aren't images which are used more than once generated once? For example, if I type \lambda once and then \lambda again, it generates, stores and inserts two separate images?

[edit]Apparently it does... that's weird[/edit]
 
  • #33
Fredrik said:
That's definitely not the problem I have. It fails every time, no matter what browser or computer(!) I use. I never had those intermittent problems that you have described before. (At least I think it was you, but I may remember it wrong).

I'm not sure if my description was completely accurate either, just going from memory of something that was posted last summer.

A work-around might be to write "editing in progress" at the top of a post, then submit it. Proofread, edit, and save as needed. When you're done, remove the "editing in progress" sign.

I've been frustrated with LaTex often enough that I try to avoid it. Not really possible all the time (such as in the post you linked to) though.

CompuChip said:
Aren't images which are used more than once generated once? For example, if I type https://www.physicsforums.com/latex_images/21/2192470-0.png once and then https://www.physicsforums.com/latex_images/21/2192470-1.png again, it generates, stores and inserts two separate images?

[edit]Apparently it does... that's weird[/edit]

Yup, those are two separate images with different URL's:
https://www.physicsforums.com/latex_images/21/2192470-0.png
and
https://www.physicsforums.com/latex_images/21/2192470-1.png
 
Last edited by a moderator:
  • #34
Redbelly98 said:
A work-around might be to write "editing in progress" at the top of a post, then submit it. Proofread, edit, and save as needed. When you're done, remove the "editing in progress" sign.

I've been frustrated with LaTex often enough that I try to avoid it. Not really possible all the time (such as in the post you linked to) though.
Most of my posts are like that, so avoiding LaTeX isn't really an option for me. The "editing in progress" trick is only good enough for posts that have very little LaTeX content. So if this problem can't be solved, I would either have to get a new account or stop posting.

I'm writing this on a fourth computer, and I still get the same images when I preview. It's not the latest images or anything like that, but always the images from the post I linked to. I just did some more testing and noticed that if I put more than 15 LaTeX images in my post, only the first 15 are messed up in the preview. The 16th is displayed fine. Maybe I'll use that as a workaround for a while. :smile:
 
  • #35
Fredrik said:
Most of my posts are like that, so avoiding LaTeX isn't really an option for me. The "editing in progress" trick is only good enough for posts that have very little LaTeX content. So if this problem can't be solved, I would either have to get a new account or stop posting.

I'm writing this on a fourth computer, and I still get the same images when I preview. It's not the latest images or anything like that, but always the images from the post I linked to. I just did some more testing and noticed that if I put more than 15 LaTeX images in my post, only the first 15 are messed up in the preview. The 16th is displayed fine. Maybe I'll use that as a workaround for a while. :smile:

I'm having exactly the same problem as Fredrik, except for me the number is not 15 but 2. Always. And the 2 corrupted images I see are always the same images every time. They are two equations that I once generated some time ago (probably the first Latex I created after it got reenabled after the disk problems).

I suspect that something went wrong in the past, some images got cached (on the server) in such a way that the cached images take precedence over freshly generated Latex in previews. Different users have a different number of "badly cached" images. For me it's 2, for Fredrik it's 15, for many lucky souls it's zero.

So a workaround is to stick a load of dummy latex images at the top of your post while previewing, remembering to delete them again before posting.
 
  • #36
Okay guys, I added a bit of code that actively deletes stale preview images before generating new ones. That hopefully means the images will no longer be cached (by any entity -- our server, intervening proxy servers, or the browsers themselves).

Let me know if anything changes for you. Since some of you have this problem no matter what computer you use, etc., I'm worried there's actually a caching proxy server upstream of you, even if it's usually transparent.

- Warren
 
  • #37
chroot said:
Okay guys, I added a bit of code that actively deletes stale preview images before generating new ones. That hopefully means the images will no longer be cached (by any entity -- our server, intervening proxy servers, or the browsers themselves).

Let me know if anything changes for you. Since some of you have this problem no matter what computer you use, etc., I'm worried there's actually a caching proxy server upstream of you, even if it's usually transparent.

- Warren
The problem seems to be fixed, for me at least. Thank you!
 
  • #38
chroot said:
Okay guys, I added a bit of code that actively deletes stale preview images before generating new ones.
...
Let me know if anything changes for you.
Thank you. It's working fine for me now.
 
  • #39
I just noticed another problem. Maybe it's only when I preview. I'll have to post this to find out. If I write f'(x), it appears as f single − quote(x).

f&#039;(x)

Nope, it looks fine when I post it.
 
  • #40
Fredrik said:
I just noticed another problem. Maybe it's only when I preview. I'll have to post this to find out. If I write f'(x), it appears as f single − quote(x).

f&#039;(x)

Nope, it looks fine when I post it.

Fredrik,

Fixed that one too. All should be well in LaTeX-land now.

- Warren
 
  • #41
Thank you. We're lucky to have you here. :smile:
 
  • #42
mattmns said:
2 + 2 = 4
2 + 2 = 5 :smile:
 
  • #43
Unit said:
2 + 2 = 5 :smile:

That is true, modulo one.
 
  • #44
\sum(A+BX_{i}-Y_{i})^2=0

\mbox{just practising}
 
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  • #45
I've just given up on trying to post an answer because in preview all of my Latex stuff is showing images from a previous post ages ago and refuses to show the stuff I've entered today. I've cleared the browser cache and restarted it before trying again and that didn't help. What else can I try? For example, the following expression is displaying in preview as v2/r which I used in a post some weeks ago:

<br /> \frac{d\mathbf{p}}{dt} = \frac{E}{c^2} \mathbf{g} \left ( 1 + \frac{v^2}{c^2} \right )<br />

Edit: When I submitted this one, the LaTeX now appears as a broken image marker.
 
  • #46
Johnathan: You need to use lowercase letters for the tex tags.

Is it just me, or do we now have to refresh after every preview to get the correct latex expression to show up? :confused:
 
  • #47
There's an ongoing problem with LaTeX used in blogs and PMs. The image files in this case have "preview" URL, and you often get the wrong image. The problem is described also in thread [post=2590434]TEX broken?[/post].

I've just checked and the problem is still there.
 
  • #48
I'm not sure if you posted that to report a problem, or if it was a reply to me. I'm aware of the need to click reply and preview, to get the LaTeX to look OK when you receive a PM. But that's not what I was talking about. I've been making a bunch of posts today, and every time, the LaTeX is messed up when I preview. (Older images are displayed). It doesn't help to just click preview again. I have to click my browser's refresh button, and then the resend button that shows up. And if I make any little change, I have to repeat the procedure.
 
  • #49
Latex preview is working fine for me, but I see old images for latex in private messages and profile visitor messages.
 
  • #50
dx said:
Latex preview is working fine for me, but I see old images for latex in private messages and profile visitor messages.

LaTeX has never worked in PMs and PVMs
 

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