display_modpack/font_api/API.md

# Font Lib API
This document describes Font Lib API. Font Lib creates textures for font display on entities.

## Settings
### default_font
Name of the font to be used when no font is given. The font should be registered.

If no default\_font given or if default\_font given but not registered, the first registered font will be used as default.

## Provided methods

### font_api.get_default_font_name()
Returns de default font name.

### font_api.register_font(font_name, font_def)
Register a new font.
**font_name**: Name of the font to register. If registering different sizes of the same font, add size in the font name (e.g. times_10, times_12...).
**font_def**: Font definition table (see **Font definition table** below).

### font_api.on_display_update(pos, objref)
Standard on_display_update entity callback.

**pos**: Node position

**objref**: Object reference of entity

Node should have a corresponding display_entity with size, resolution and maxlines fields and optionally halign, valign and color fields.

### Font definition table
Font definition table used by **font_api.register_font** and **font\_api.Font:new** may/can contain following elements:

* **height** (required): Font height in pixels (all font textures should have the same height) .
* **widths** (required): Array of character widths in pixels, indexed by UTF codepoints.
* **margintop** (optional): Margin (in texture pixels) added on top of each char texture.
* **marginbottom** (optional): Margin (in texture pixels) added at bottom of each char texture.
* **linespacing** (optional): Spacing (in texture pixels) between each lines.

**margintop**, **marginbottom** and **linespacing** can be negative numbers (default 0) and are to be used to adjust various font styles to each other.

Font must have a char 0 which will be used to display any unknown char.

All textures corresponding to the indexes in widths array should be present in textures directory with a name matching the pattern :

> font\_**{font_name}**_**{utf_code}**.png

**{font\_name}**: Name of the font as given in the first argument

**{utf\_code}**: UTF code of the char in 4 hexadecimal digits

Example : font_courrier_0041.png is for the "A" char in the "courrier" font.

To ease that declaration (specially to build the **widths** array), a shell is provided to build a {font\_name}.lua file from the texture files (see provided tools).

## Provided tools

Still in early stage of development, these tools are helpers to create font mods.

### make_font_texture.sh

This scripts takes a .ttf file as input and create one .png file per char, that can be used as font texture. Launch it from your future font mod directory. 

__Advice__

This script works much better with pixels font, providing the correct height. There is no antialiasing at all, vector fonts and bad heights gives very ugly results.

__Syntax__

**make\_font\_texture.sh {fontfile} {fontname} {fontsize}**

**{fontfile}**: A TTF font file to use to create textures.
**{fontname}**: The font name to be used in font_api (should be simple, with no spaces).
**{fontsize}**: Font height to be rendered.

### make_font_lua.sh

This script analyses textures in textures directory and creates a font\_{font\_name}.lua files with a call to register_font with images information. Launch it from your future font mod directory.

Once the font\_{font\_name}.lua created, it can be included by a init.lua file or directly renamed to init.lua if you are creating a simple font mod.

__Syntax__

**make\_font_lua.sh {fontname}**

**{fontname}**: The font name to be used in font_api (same as given to make\_font\_texture.sh)

### An exemple generating a font mod

    mkdir font_myfont
    cd font_myfont
    /<path_to_font_api>/tools/make_font_texture.sh myfont.ttf myfont 12
    /<path_to_font_api>/tools/make_font_lua.sh myfont
    mv font_myfont.lua init.lua

## Font class
A font usable with font API. This class is supposed to be for internal use but who knows.

### font\_api.Font:new(def)
Create a new font object. 

**def** is a table containing font definition. See **Font definition table** above.

### font:get_char_width(char)
Returns the width of char **char** in texture pixels.

**char**: Unicode codepoint of char.

### font:get_height(nb_of_lines)
Returns line(s) height. Takes care of top and bottom margins and line spacing.

**nb_of_lines**: Number of lines in the text.

### font:get_width(line)

Returns the width of a text line. Beware, if line contains any new line char, they are ignored.

**line**: Line of text which the width will be computed.

### font:make_line_texture(line, texturew, x, y)
Create a texture for a text line.

**line**: Line of text to be rendered in texture.

**texturew**: Width of the texture (extra text is not rendered).

**x**: Starting x position in texture.

**y**: Vertical position of the line in texture.

### font:make_text_texture(text, texturew, textureh, maxlines, halign, valign, color)
Builds texture for a multiline colored text.

**text**: Text to be rendered.

**texturew**: Width of the texture (extra text will be truncated).

**textureh**: Height of the texture.

**maxlines**: Maximum number of lines.

**halign**: Horizontal text align ("left"/"center"/"right") (optional).

**valign**: Vertical text align ("top"/"center"/"bottom") (optional).

**color**: Color of the text (optional).