How do I get the width of text on a disabled TMP text?

I want to draw a line under the width of my text, like this:


In the screenshot above, I'm using this code on my TMP object:

lineScaler.x = GetTextWidth(Text);

However, when the TMP is disabled (I'm hiding it because it's "scrolled" out of visibility), the GetTextWidth(Text) is always zero, even when I do Text.ForceMeshUpdate() first. So my line is way too small.

So I tried using

lineScaler.x = Text.preferredWidth;

But then the line is the width of .... well, I'm not really sure what the width is. But it's something with margins that are wider than the text:


This, however, returns the same value whether the Text is enabled or disabled.

How do I get the TextWidth like in the first picture even when the TMP object is disabled?


I'm using Unity 2018.3 and TMP 1.3.0 from the Package Manager.