Currently there are two types of fonts.
Variable width fonts (where each character can have its own width)
fixed width fonts (where all characters are the same width).
The information you are seeing is from a variable width font and is in a comment.
It is merely informational. It describes the code values of first character the last lastvalue
and how many characters are actually used in the font.
I’d have to go look at the font generation tool to make sure but the reason the have the “used chars”
information is the variable fonts can have “holes” in it.
i.e. not all the characters between the first and last font characters are required to have
So when some characters dont’ have definitions, there is a “hole” in the font and the number
of “used chars” between first and last will not be equal to last - first
so that is why there is a “used chars” in the comment.
If you want to play around with creating fonts, I recommend using the glcdfont creator tool.
It is a java gui tool that can create font header files for you from fronts that are installed
on your operating system. It does all the work for you.
You can find information about it in the included html documentation.
If you want create your own by hand you will need to look closer at the actual font data format.
Unfortunately right now there is no real documentation on the data format.
Here is a general overview:
The font data format currently consists of a 6 byte header that describes the font data format.
If the first two bytes are zero it is a fixed font if not it is variable.
The width and height bytes describe the rendered width and height of the font.
(The library uses 1 extra pixel below and to the right of these values for inter character gaps).
The pixel data is stored in the data bytes in the same order as the glcd data pages.
Vertically lsb to msb within each byte.
Then for each 8 pixels it goes from left to right in incrementing data bytes.
So the pixel data is top to bottom per byte and left to right per 8 pixels
then when fonts are taller than 8 pixels, the format continues on the next lower