XTextWidth(3) XLIB FUNCTIONS XTextWidth(3)

XTextWidth, XTextWidth16 - compute text width

int XTextWidth(XFontStruct *font_struct, _Xconst char *string, int count);

int XTextWidth16(XFontStruct *font_struct, _Xconst XChar2b *string, int count);

Specifies the character count in the specified string.
Specifies the font used for the width computation.
Specifies the character string.

The XTextWidth and XTextWidth16 functions return the width of the specified 8-bit or 2-byte character strings.

XLoadFont(3), XTextExtents(3)
Xlib - C Language X Interface

libX11 1.8.10 X Version 11