FileMaker has trouble with symbol fonts.
For More Information see: Webdings
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
What I do is use the shareware program: Paint.net to turn font characters from Wingding, Webdings or Symbol into a transparent gif. These can be inserted into a button object and you can specfiy a different icon for "hover" as a way to show that the icon can be clicked. You can put a second copy of the gif colored grey behind the actual button and use "hide object when" to hide the actual button, revealing the grey "button". This not only produces a "disabled button", but you do not have to put your script inside an If block that does nothing when the button should be disabled as a way to keep it from doing anything when a user clicks/taps a "disabled" button.
Thanks for the prompt reply! I've actually being doing what you suggested, using "hide object when" (my new favorite FM feature) so far. Trouble is, I have a lot of buttons, different hiding criteria for different user types, and it's getting a bit complex. Hence my desire to use a symbol font. I found a few icon fonts online. One, called FontAwesome (https://fortawesome.github.io/Font-Awesome/), seems to work in FileMaker. The other one, IcoMoo (https://icomoon.io/app/), does not, at least not for me. Thanks for the links. I'm going to review them now.
Yes, but wouldn't that "different criteria" be just as complex when using conditional formatting to turn the text grey?
And now you have three additional and undesirable issues:
Each button's script must be enclosed in an if block to keep it from doing anything when the button is "disabled".
Any "hover" feature such as turning the mouse cursor into a hand or hover state formatting in the inspector equally affects the button whether enabled or disabled--which pretty much forces you to disable any such feature for your button.
Like "hover", if the user clicks a disabled button, it's appearance changes in response to the mouse down (pressed state) identically whether the button is or is not disabled.
You are correct in that I'd be trading one type of complexity for another. Having to manage a stack of images/buttons with different hiding criteria on a layout is more annoying to me than opening one script, or one conditional formatting window, and making changes as needed. I have a lot grouped objects with hiding criteria, and some of those contain objects with their own hiding criteria. Etc. It's just unwieldy.
For some of my more complex hiding calcs, I've started using a calculated field in the table and simply reference the field in the "hide object when" inspector field. That way, when the hiding criteria changes for some reason (which, on my project it has, since this is a make-it-up-as-we-go-along situation...ugh), it's a lot easier to just open the field definitions and change the calc than drill down into my layout, ungrouping things, etc. Personal preference I guess.
But your points are well taken and I appreciate the link to the symbol font thread. Seems like images and hiding are the way to go.
That stack should only need consist of two items and a single "hide object when" expression can control visibility based on multiple criteria.