Fixing Latex Issues Post-Upgrade on Physics Forums

[Fredrik]

https://www.physicsforums.com/threads/matrix-representations-of-linear-transformations.694922/ was somehow messed up by the upgrade. I am able to edit the post myself, so I can probably fix it. But I would like to understand what's going on. About half-way through the post, everything goes nuts. If I choose to "edit" or "reply", I see stuff like this:

We will denote the matrix of S with respect to (C,D) by .
\begin{align}Sg_1 &=S(1,0,0)=(-1,0) =-1h_1+0h_2\\
Sg_2 &=S(0,1,0) =(0,2)=0h_1+2h_2\\
Sg_3 &=S(0,0,1) =(3,0)=3h_1+0h_2\\
&=\begin{pmatrix}(Sg_1)_1 & (Sg_2)_1 & (Sg_3)_1\\ (Sg_1)_2 & (Sg_2)_2 & (Sg_3)_2\end{pmatrix} =\begin{pmatrix}-1 & 0 & 3\\ 0 & 2 & 0 \end{pmatrix}.
\end{align}

That's a copy-and-paste from the edit window. However, if I paste this into a notepad window, and then copy-and-paste it from there, this is the result:

We will denote the matrix of S with respect to (C,D) by .
\begin{align}Sg_1 &=S(1,0,0)=(-1,0) =-1h_1+0h_2\\
Sg_2 &=S(0,1,0) =(0,2)=0h_1+2h_2\\
Sg_3 &=S(0,0,1) =(3,0)=3h_1+0h_2\\
&=\begin{pmatrix}(Sg_1)_1 & (Sg_2)_1 & (Sg_3)_1\\ (Sg_1)_2 & (Sg_2)_2 & (Sg_3)_2\end{pmatrix} =\begin{pmatrix}-1 & 0 & 3\\ 0 & 2 & 0 \end{pmatrix}.
\end{align}

So the code isn't wrong, or at least the part that Notepad can handle isn't, except for that period that isn't supposed to be there. (The period is probably an editing mistake from me from when I wrote this). But there's a line through the code?! Why? And how come that line shows up in the edit window as well as in the published version?

Did any other posts with LaTeX get messed up?

Also (this is an unrelated problem), is everyone else seeing that what I'm seeing? In some of the matrices, only the bottom half of the parentheses are visible. They show up if I highlight the matrix with my mouse, and then click somewhere to remove the highlight. But if I scroll down so that I don't see the matrices anymore, and then scroll back up, the first one is messed up again. I've been having this issue since, I don't know, about a week before the upgrade? Something changed about the LaTeX then. We got a bigger font or something.

 

[gneill]

I've also noted that the symbols and characters look as though they are being rendered by a crude raster scan compared to the smoother rendering of the previous forum's LaTeX mechanism. Integral signs in particular.

$$\int_{-\infty}^{+\infty} f(x) \; dx $$

Just in case the issue is resolved in the future, here's a screen capture showing the above in all its jagged glory:

 

[Fredrik]

I've also noted that the symbols and characters look as though they are being rendered by a crude raster scan compared to the smoother rendering of the previous forum's LaTeX mechanism. Integral signs in particular.

$$\int_{-\infty}^{+\infty} f(x) \; dx $$

That integral looks fine to me. Here's a picture of what it looks like to me:

Cool, I could do that without using img tags.

 

[gneill]

Hmm. Very odd. I wonder what's different for you and me? My browser is Firefox.

I added an image of what I'm seeing to my previous post.

 

[Fredrik]

Weird. I'm using Firefox too.

 

[Borek]

But I would like to understand what's going on.

[ S ] (no spaces) is interpreted as an opening strikethrough tag.

 

[D H]

\int_{-\infty}^{\infty} f(x)\,dx

This previews terribly, but it looks rather nice with OSX/Safari. This, on the other hand, looks awful:

View attachment 73394

Edit

Okay, that didn't work. You'll have to take my word for it that the image posted by Fredrik looks awful. Jaggies galore.

 

[gneill]

Weird. I'm using Firefox too.

Okay, not so weird after all. It seems it's my old version of Firefox that's the culprit. Checked it out on another machine with an up-to-date browser and it rendered nicely.

 

[Fredrik]

[ S ] (no spaces) is interpreted as an opening strikethrough tag.

I don't see that anywhere in my post. I tried copying the text from the edit window to a Notepad window and then searching for it there, but there were no matches.

Edit: Wait, I get it. The sentence with the weird period at the end must have ended with

by [S].

And now that looks like "by .", with the period being the first strikethrough character. This raises the question of whether it's possible to get the tag to reappear so I can edit it. I think I have seen the option to choose between a rich text editor and a plain text editor somewhere, but I don't seem to get that choice when I try to edit that post.

 

[Borek]

I switched my quick reply editor from rich text to just text somewhere in my personal preferences, as far as I can tell now all edit windows I see use plain text. YMMV

You may have to switch all occurrences of [ S] to latex, and even then to \[S\].

 

[Fredrik]

Thanks Borek. I made a mistake. There is a simple way to get those tags to appear. The symbol that looks like a piece of paper with some text on it switches to the BB Code editor. I will fix that FAQ post today.

 

[Mark44]

Thanks Borek. I made a mistake. There is a simple way to get those tags to appear. The symbol that looks like a piece of paper with some text on it switches to the BB Code editor. I will fix that FAQ post today.

The paper icon that Fredrik mentioned is in the upper right corner. To its left is the "Remove formatting" icon.

 

[Fredrik]

I switched my quick reply editor from rich text to just text somewhere in my personal preferences, as far as I can tell now all edit windows I see use plain text. YMMV

You may have to switch all occurrences of [ S] to latex, and even then to \[S\].

Switching to LaTeX didn't help, and typing \[ wouldn't have helped, because that's the code to start an unnumbered equation on a new line (i.e. it's the same as $$). What did help was to switch to LaTeX and add a space:

##[ S]##

I would say that my FAQ post was messed up by two separate issues: The first one is that BB Code tags don't have to be closed. For example, if you type

[i]hello

somewhere in your post, the rest of it will be in italics. The second issue is that BB Code tags inside LaTeX formulas are not ignored.

If possible, I would like both of these things changed. I don't think it's a good thing that people don't have to close BB Code tags.

Finding these issues was made more difficult by a third issue. When I edited the post, it was impossible to get any LaTeX to show up in the preview. I clicked "edit", and then the "BB Code Editor" button in the upper right corner. Then I made the changes I wanted to make, and tried to find a way to preview. Clicking "more options" gave me a preview button. That button gave me some sort of preview where no LaTeX was rendered.

 

[Borek]

I don't think it's a good thing that people don't have to close BB Code tags.

I am afraid all forum engines I know do the same - they automatically close all the opened tags at the end of the post. It is especially irritating in chemistry, where we often use [ B] as concentration of some substance B (like in for the reaction A+B -> C, reaction rate is given by k[A][ B]).

The second issue is that BB Code tags inside LaTeX formulas are not ignored.

That's because these are two different, independent systems, each knowing nothing about the other.