Finding out the appropriate texture size for a font

In my program I have a texture array where I want to cache the rasterized
bitmaps for the characters. This texture array will need to be big enough
to accommodate the widest and tallest characters in the font. How do I
calculate the appropriate size for this texture. I'm using
`FT_Set_Pixel_Size` to size the characters but the width and height of the
rendered bitmaps is often bigger than the provided size, which matches what
the documentation of this function says. It also says I need to use
`FT_Request_Size` but I'm unable to understand how to use it. How can I
implement what I need?

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Best Regards
Sagar Tiwari