how to change the text background color?

[zhl8223]

[vallentin]

Do you mean as in drawing a colored rectangle behind the text? If so, then the library itself does not support that (yet?).

Instead you'd have to "manually", issue the needed draw calls to draw a rectangle behind the text beforehand. You can use the functions gltGetTextWidth and gltGetTextHeight to query the bounds of the text, for the rectangle.