We shouldn't be able to make sheetnames bigger then 31 characters.

[jappeace]

The reason is that excell claims the worksheet "may contain a virus" if it detects this.
Excell validator explain this:

File: xlsx/avy.xlsx
Error: The attribute 'name' has invalid value 'Gross written premium (calendar years)'. The actual length is greater than the MaxLength value. The length must be smaller than or equal to 31.
ContentType: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml
XPath: /x:workbook[1]/x:sheets[1]/x:sheet[1]

[vrom911]

Additionally to that, here are all the conditions on the sheet names:

• the name you entered does not exceed 31 characters.
• the name does not contain any of the following characters: : \ / ? * [ or ]
• the name is not blank.

We could introduce "safe" function like createSafeSheetName for these checks.

[L0neGamer]

I believe that the above conditions are not enough.

From testing, it seems that the sheet names treat emoji such as 🎬 as if they are multiple characters, presumably because it is multiple code points for whatever encoding is being used. As such, it is not sufficient to simply count unicode characters.