How to detect my font is correctly rendered at browsers ?

Has there any way to detect my font was correctly rendered at browsers ?

To clarify my question , my API server was send Unicode Myanmar texts as response and I setted them as values of input boxes (textboxes,textareas etc). But when I was changed my browser's font to **ZawGyi Font** , I can't see correctly the texts of my input boxes.

I can't receive the the browser's active font, so I would like to detect when the **Unicode** texts are not correctly displayed and I would like to convert them as **ZawGyi** text values.

Any suggestions would be really appreciated. Thanks