xhtml sim freezes when "About..." in PhET menu is selected

[stemilymill]

Win10 Firefox and Chrome. For https://github.com/phetsims/qa/issues/721.

Clicking or selecting with keyboard nav "About..." in the PhET menu freezes the sim. This happens in every dev/rc version I've tested, but not in dev/rc versions of other recent sims (fourier, pH scale, etc)

https://user-images.githubusercontent.com/85511101/138527854-a9c03998-9a16-47b4-bb42-76a9133fbf13.mp4

Troubleshooting information: !!!!! DO NOT EDIT !!!!! Name: ‪Balloons and Static Electricity‬ URL: https://phet-dev.colorado.edu/html/balloons-and-static-electricity/1.5.0-rc.2/phet/xhtml/balloons-and-static-electricity_all.xhtml Version: 1.5.0-rc.2 2021-10-11 21:55:48 UTC Features missing: touch Flags: pixelRatioScaling User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:93.0) Gecko/20100101 Firefox/93.0 Language: en-US Window: 1408x668 Pixel Ratio: 1.3636363636363635/1 WebGL: WebGL 1.0 GLSL: WebGL GLSL ES 1.0 Vendor: Mozilla (ANGLE (Intel(R) HD Graphics Direct3D11 vs_5_0 ps_5_0)) Vertex: attribs: 16 varying: 30 uniform: 4096 Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32) Max viewport: 32767x32767 OES_texture_float: true Dependencies JSON: {}

[KatieWoe]

I didn't see this in the published version of Fourier, so it looks like this may be specific to BASE somehow.

[Nancy-Salpepi]

This is also happens with Mac iOS 11.6 + chrome. Console error

:

[jbphet]

I've done some investigation into this, and have learned the following:

• This problem is not specific to this sim. It occurs in any sim that has the <br> tag (line break) in the credits. More on this later.
• This is not a new problem. I looked through the code base and found that the John Travoltage sim, among many others, uses the <br> tag, so I tested its current XHTML version at https://phet-dev.colorado.edu/html/john-travoltage/1.6.1/phet/xhtml/john-travoltage_all.xhtml, and it exhibits the same problem. I went back several versions and found that the version at https://phet-dev.colorado.edu/html/john-travoltage/1.5.12/phet/xhtml/ has the problem too, and it was published on 10/25/2019 (whoa, that's exactly two years ago...crazy), so this problem has existed for at least two years.
• The exception is being thrown because having the <br> tag in the string makes this invalid XML, which is true (I guess - I don't really have much expertise on XML, but I think every tag needs to be closed). The question is, why does it have to be valid XML?
• I could temporarily fix this in this sim by simply removing all occurrences of tag in the credits. The only downside is that our word wrap algorithm will break first and last names across lines, but that's only cosmetic.
• The code that is causing the problem is in PDOMUtils.setTextContent.

I think I will go ahead and remove the <br> tags from the credits in the 1.5 branch and then move this issue to the appropriate common code repo and assignee.

[jbphet]

I've fixed this in the 1.5 branch by removing the <br> tags in the credits strings, and it seems to have done the trick. There are a couple of line breaks in between first and last names as shown in the screenshot, but I think we can live with this.

I am not going to fix this on master, but will log a common code issue, since we should be able to use these tags like this.

[KatieWoe]

Looks good on Win 11, rc.3