Crate bmfont_rs

Expand description

BMFont parsing library.

Manipulate, import and export BMFont files in text, binary, XML formats, and more.

Overview

This crate provides building, manipulation, import, and export functions for BMFont descriptor files.

The core data object is the Font. This struct holds, in its entirety, the data contained within a BMFont descriptor file. When paired with the associated texture bitmap file/s, we have the information required to render the font in question.

Due to the numerous graphics backends and usage requirements, this crate does not attempt to offer a universal rendering solution.

This crate contains no unsafe code. Also, unless specified by compilation switches, it doesn’t pull in any external dependencies.

Basic usage

The modules are organized around the core BMFont file formats:

text : text format
binary : binary format
xml : XML format, requires: --features xml

Each module is provides a number of import from_... and export: to_... functions.

To use:

Select the desired BMFont format you want to work with.
Select the appropriate from/ to methods based on the data structures you want to work with.

Example: import a BMFont text format file.

use std::io;
use std::io::prelude::*;
use std::fs;

fn main() -> bmfont_rs::Result<()> {
    let mut buf = fs::read("font.fnt")?;
    let font = bmfont_rs::text::from_bytes(&buf)?;
    println!("{:?}", font);
    Ok(())
}

Example: export a BMFont text format file.

use std::io;
use std::io::prelude::*;
use std::fs::File;

fn main() -> bmfont_rs::Result<()> {
    let font = bmfont_rs::Font::default();
    let mut writer = File::create("font.fnt")?;
    bmfont_rs::text::to_writer(&mut writer, &font)?;
    Ok(())
}

Advanced usage - broken files

Unfortunately, there exist several BMFont tools that output broken files. Either they do not comply with the BMFont standard as written or contain other errors. When attempting to load these files, bmfont_rs will emit an error describing the problem.

We may be able to work around or ignore some of these problems using the LoadSettings struct. Simply build the LoadSettings instance using the desired behavior switches and pass it into the ext form of the load function.

If you encounter a BMFont file that appears to work with other tools, but not bmfont_rs then kindly open a ticket. It may be possible to add the correct behavior switch in future versions of bmfont_rs.

Example: import a BMFont text file with incorrect character counts.

use std::io;
use std::io::prelude::*;
use std::fs;

fn main() -> bmfont_rs::Result<()> {
    let src = fs::read_to_string("font.txt")?;
    let settings = bmfont_rs::LoadSettings::default().ignore_counts();
    let font = bmfont_rs::text::from_str_ext(&src, &settings)?;
    println!("{:?}", font);
    Ok(())
}

Rendering fonts

The render.rs example, demonstrates a simple way to render font text to an image. Substituting your own graphics backend should not be too difficult.

To view the example’s output and for details on how to run it, kindly refer to the repository README.

Due to the numerous graphics back-ends and usage requirements, this crate makes no attempt at offering a universal rendering solution.

Serde

Font implements Serde’s serialize and deserialize traits. These are feature gated and require: --features serde.

JSON

The json.rs example demonstrates this.

For details on how to run the example, kindly refer to the repository README.

JSON is not natively supported. However, as we do support Serde, we can easily cobble together support with Serde JSON.

By default our Serde serializers map boolean types to JSON boolean types: true and false. However, at least one JSON BMFont parser expects integer boolean types: 1 and 0. To facilitate the latter we can pass --features serde_boolint, which casts boolean values to integers and vice versa.