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minetest-mm/mods/display_modpack/font_api/API.md
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2020-11-15 20:25:38 +01:00

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Font API

This document describes Font API. Font API 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.

Use font_api with display_api (to display text on nodes)

Base setup

Font_api offers a direct integration with display_api to display text on nodes.

First of all, create a display node with an entity. To do this, refer to API.md in display_api mod, in particular "Howto register a display node".

The only requirement then is to connect the on_display_update callback of the display entity to font_api.on_display_update:

minetest.register_node("mymod:test_text_node", {
	...
	paramtype2 = "facedir",
	...
	groups = { display_api = 1, ... },
	...
	display_entities = {
		["mymod:text"] = {
			depth = -0.5 - display_api.entity_spacing,
			on_display_update = font_api.on_display_update },
	}
	...
	on_place = display_api.on_place,
	on_construct = display_api.on_construct,
	on_destruct = display_api.on_destruct,
	on_rotate = display_api.on_rotate,
	...
})

At this step, your node already displays text form "display_text" (by default) node meta. If you want to store your text into another meta data field, add a meta_text field to display entity definition.

But it uses defaults (default font, default size, default color). Likely you need something more.

Style your text

Font style and size can be chosen by adding some more entries to the display_entities definition table.

Font size

Font size can be defined in various ways (maybe more in the future). Start with a number of lines, and font_api will make it fit to the entity size.

  • maxlines or lines: Number of maximum lines of text to be displayed. The font height will be adjusted accordingly.

Then specify the char width. Two methods available:

  • aspect_ratio: Defines the aspect ratio of chars. Works with all fonts. Should not be used if columns is specified.
    • columns: Only if using a fixed width font, specifies the number of columns to display.

Font style

  • font_name: name of the font to use. Should correspond to a registered font (from a font mod). If not specified or font not found, default font is used.
  • color: color to be used (default black).
  • halign: Horizontal alignment: "left", "center" or "right" (default "center").
  • valign: Vertical alignement: "top", "middle" or "bottom" (default "middle").

Example

Using blue //botic// font, three lines height, aligned top left. Text stored in "text" node meta.

minetest.register_node("mymod:test_text_node", {
	...
	...
	display_entities = {
		["mymod:text"] = {
			depth = -0.5 - display_api.entity_spacing,
			on_display_update = font_api.on_display_update
			meta_text = "text",
			font_name = "botic",
			color = "#0000FF",
			maxlines = 3,
			aspect_ratio = 0.5,
			halign = "left",
			valign = "top",
			},
	}
	...
})

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 attributes around a single char:
Font attributes on a char

Font attributes effects on several lines:
Font attributes on lines

Additional requirements

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(codepoint)

Returns the width of char codepoint in texture pixels.

  • codepoint: 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:renter(text, texturew, textureh, style)

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 (extra text will be truncated).
  • style: A table with style indications:
    • lines or maxlines: Maximum number of lines (default none).
    • halign: Horizontal text align: "left"/"center"/"right" (default "center")
    • valign: Vertical text align: "top"/"middle"/"bottom" (default "middle")
    • color: Color of the text (default black)