Shape libaries¶
Most pieces in a game in Otter will be from a shape library.
Introduction; general structure¶
A shape library is a set of named pieces. Mostly, it defines their appearance.
Shape library pieces can have more or more sides (faces), and they can also have an occulted view which is used when the identity of the piece is to be hidden (possibly from only some of the players).
For example:
Playing cards have two faces: one is the front, which identifies the card, and the other is the back, which is a generic card back. Cards also have an occulted view: again, the back.
Chess pieces usually have only one face. The Knight has two faces, because it is not symmetrical: the first face looks to the right, and the other face to the left. Chess pieces can be occulted, but when they are occulted they reveal their shape but not their colour. The occulted view of a chess piece is a grey version of the piece.
A library has a library name. This is a string. For a library in
a bundle, it’s the LIB
part of the filename
libraries/LIB.toml
.
Each piece in a library has an item name. Item names are unique
within a library. The item name is used within Otter to refer to the
piece (for example, with otter library-add
).
Pieces in shape libraries cannot have “behaviours”: they can’t do anything “special” like react to being moved or clicked on. Pieces with special functionality do exist, but they are built into Otter. (See Piece Specs for all the kinds of piece.)
A library consists of a catalogue, and a set of image files
which contain the actual appearances. When a library is in a bundle
the catalogue is libraries/LIB.toml
and the image files are in a
directory libraries/LIB.toml
. The layout of Otter’s builtin
libraries is similar.
Image files¶
Otter supports uploading of SVG and PNG files. They should be in the
directory library/LIB
, named after the item. (See Files entry
for details of how to specify the file names.)
Image files should be small — ideally a handful of kilobytes, or less. SVG images should be of modest complexity.
Large image files don’t just upload slowly; they also make the game perform poorly when playing. This is because the image files are frequently (re)transmitted by the server to each client.
It is not normally necessary to specify images in great detail: they
take only a small space on the players’ screens, so the resolution
does not need to be awesome. As an example, the playing cards in the
builtin cards-oxymoron
library are image files of just 73x97
pixels.
Catalogue¶
The catalogue defines what pieces the library contains. For each piece it defines each face looks like, how big it is on the screen, whether and how the piece can be occulted, and what source image files are to be used to display it.
The catalogue is a TOML file.
The file should have a toplevel key format
, specifying which
version of the Otter data formats the file was written to.
This document describes format=1
.
See Bundle compatibility.
The catalogue’s main contents is a dictionary
groups
, mapping each group name to a sub-dict of parameters:
Each catalogue is organised into named groups. Each group defines some pieces. It specifies various parameters, and also gives a list of indvidual image files which should be processed according to those parameters.
For example:
[group.dried]
outline = "Circle"
size = [14]
orig_size = [64, 48]
centre = [32,24]
files = """
dried-lemon - a dried lemon
"""
This defines a group dried
, with parameters such as size
and
outline
. The files
entry defines the list of pieces.
The group names are not visible when using the library, but they can
be used within the library using the inherit
feature.
The builtin catalogues also have a toplevel dict scraper
, which
controls how the builtin shape data is processed during the build, and
how it is to be updated. (Downloads are never automatically run
during the build. If you updated the catalougue in a way that means
files should be re-downloaded, you should re-run ./media-scraper
library/LIB.toml
.)
Files entry¶
Each group has an entry files
. This is a string, which is treated
as a series of lines (so it is best to use the TOML multi-line string
syntax).
Each line of which has (normally) three fields (the leading ones
terminated by whitespace). #
comment lines are supported and
blank lines are ignored.
Each non-empty non-comment line in files
specifies a single piece,
like this:
ITEM-SPEC SRC DESCRIPTION...
The item name of the piece will be ITEM-SPEC
sandwiched
between the item_prefix
and item_suffix
parameters (see
below).
The image filename is derived from SRC
or the item name, as
follows: library/LIB/SRC.svg
or .png
. If SRC
is -
then the item name is used for SRC
. (Builtin libraries: these
support SVG only; and the SRC
is not used at runtime, or when
loading shapes — rather, only when scraping or building.)
DESCRIPTION
is the description, a string which will be used to
describe the piece (eg in in-game log messages). In English, it
should contain an article. Eg, the black queen
, a white pawn
.
It will be HTML-escaped, so it should be plain text, not HTML.
It is also possible to specify additional data for each piece by
adding fields to each line in files
. This is done by adding a
line at the start starting with :
listing the extra fields, and
then additng one additional whitespace separated value before the
description on each data line. Values given for unknown field are
ignored.
Currently the extra fields supported are:
sort
: Specifies the sort key. See thesort
group parameter.x...
: Can be referenced by templates in “Magic” items.
The values for these extra fields come just before the
DWSCRIPTION
, after the other whitespace-delimited fields, in the
same order as specified in the :
heading line.
Item names¶
Item names do not need to be unique within a game, but there are places where a piece is found just by the item name, so pieces should have the same item name (only) if they are in some sense equivalent.
Item names are conventionally structured using a hierarchical name
with -
between the components.
The item name is a string but may contain only ASCII alphanumerics,
plain ASCII spaces, and the punctuation characters -._
. Do not
put /
or _
in item names. /
is forbidden and _
can
interfere with the template substitution system.
See the existing examples to see what item names usually look like.
Parameters¶
These are the entries which can appear in each group.GROUP
dictionary:
Mandatory parameters¶
files
: The list of pieces to define, one per line. See Files entry. [multi-line string]outline
[dictionary]: Defines the outline of the piece, which is used for drawing “haloes” around the piece, indicating selection and movement.outline
[string]: Abbreviated way of specifyingoutline = { shape: ... }
. The shape mkust be specified, either viaoutline = "Shape"
or by settingoutline.shape
.outline.shape
["Circle"
or"Rect"
]: Ifoutline
isCircle
, and the the nominal size (calculated from all the other parameters) has different width and height, the larger of the width and height is used (ellipses are not supported).outline.size
: nominal size of the piece, used for calculating the size of “haloes”. Note that this is not the szie of the “haloes”; it is the (nominal) size of the piece image itself: the “haloes” indicating selection etc. will be somewhat larger. [1- or 2-element array of numbers: width and height; default: calculated from the piece’ssize
andscale
]outline.scale
: Adjusts the nominal size of the outline, multiplying it by this factor. Not meaningful together withoutline.size
. [number; default1.0
]
Important parameters¶
inherit
: Causes this group to inherit every parameter (exceptfiles
) from the group named byinherit
(recursively, if applicable). [string: group name]When inheritance is happening, there is of course a difference between leaving a value unspecified, and specifying it to have the usual default value: the latter would override any inherited setting.
item_prefix
,item_suffix
. Prepended and appended toITEM-SPEC
infiles
to produce the item name. [strings]
Geometry parameters¶
centre
: The centre of the image, measured from the top left in the image’s own internal units. If not supplied, calculated from the size. [2-element array]
size
: The size at which the piece will show up in the game, in nominal game coordinate units. The supplied SVG will be reiszed from its internall specified witdth and height, to that specified. If the aspect ratio does not match the supplied image,scale
controls the behaviour. (Specifying only one value forsize
means a square of that size.) [1- or 2-element array of numbers: width and height]For reference: the builtin library’s chess pieces are 9.5 units; the builtin playing cards are 9.65, 17.125.
scale
[string]: Specifies what to do if the SVG’s own size does not have the same aspect ratio as a sspecifiedsize
:
"fit"
: the image is placed within the specifiedsize
;"cover"
: the image is placed around the specifiedsize
;"stretch"
: the image is distorted to become exactlysize
.
scale
[number]: Specifies that the image SVG should be rescaledby this amount. This use of
scale
cannot be combined withsize
.
Parameters for defining faces¶
flip
: Whether this piece can “flip”. If true, the piece will have two faces, one of which is a mirror image of the other. The default face will be un-reflected version; the other face is the same image, but flipped left-to-right. [boolean]It doesn’t make sense to enable this for pieces with a symmetrical appearance. (It is a bad idea to have the game contain state which is not visible to the players.) Not compatible with
back
.
back
: [Piece spec]. The back of this piece looks like some other piece (typically, another library item such as a card back). If specified, the piece will have two faces: the one implied by itsfiles
entry, and a 2nd face looking likeback
. If you want to make the piece be occultable, you must also specifyocculted
.back
is not compatible withflip
.
“Magic” items¶
The shape library primarily defines inert image pieces. But it is also possible to define, as part of a library, a non-inert behaviour to go with an image. (These could be defined directly, in game spec files, but library items are more convenient to reuse, since the necessary parameters do not need to be recapitulated for each use.)
Magic items are produced by a magic
section in the group. This is
applied once for each item (ie, once for each entry in files
).
The magic
section generates an additional item in the library for
each ordinary item defined by the group via its files
.
The magic item is typically defined using a non-library piece spec type, and usually references the corresponding ordinary (base) item.
The magic section in the group may contain:
magic.item_prefix
,magic.item_suffix
[strings, default""
]. Defines the magic item name. The item name to define is assembled the same way as the base image item name, only with these prefix and suffix instead of the main ones in the group.template
. Template which will generate TOML defining the magic piece. The string value has variables${...}
expanded, and is then reparsed as a new piece of nested TOML. The resulting dictionary must be a valid Piece Spec Substitution variables are (in precedence order):
${CVAR}
, the value ofcolours.COLOUR.substs.CVAR
for the currentCOLOUR
, and for eachSVAR
defined there.${SVAR}
, the value ofmagic.substs.SVAR
for each anySVAR
defined there.${x...}
, values of extra fields in thefiles
list (but only those starting with anx
).${image}
a TOML in-line dictionary for the piece spec for the base item. (The substitution references the containing library by name, so it is possible that later-loaded libraries might intercept this reference.)${colour}
, the recolouring name from thecolours
group parameter.substs
: Extra substitutions for the template.
Other group parameters¶
sort
. The sort key. Used for item sorting in hands. When the user asks to sort their hand, all the items in it are sorted according to (primarily) simply this sort key, interpreted lexicographically. [string]The sort key should generally contain all of the information in the item name; if the item name contains an element referring to style or aesthetic, that should appear at the end of the sort key (if at all).
If neither the group parameter, nor the
files
extra fieldsort
, are specified, the item name is used as the sort key.If both are specified, the group parameter is used as a template:
_s
is replaced by thesort
extra field from thefiles
list;_c
is replaced by the colour, if applicable.
colors
[dictionary]. If specified and non-empty, specifies that this group should be instantiated multiple times, for different colours.For each entry in the
colours
dict, a separate piece is generated for each item in thefiles
list. The keys of thecolours
are recolouring names, and the values are sub-tables.Every effective item name (i.e., after the
item_prefix
anditem_suffix
have been added) must contain the substring_c
exactly once, and every item description must contain the substring${colour}
exactly once._c
in the item name will be replaced with the value of the recoluring’sabbrev
, and${colour}
with the recolouring name (the key of thecolours
dict).For libraries in bundles, a separate image file must be supplied for each recolouring. If
SRC
is not-
, it also must contain_c
which will be substitued withabbrev
to find the colour-specific image file.For builtin libraries, the Otter build system will do the recolouring automatically at build time; each recolouring should have a
map
entry which is a sub-sub-dict mapping input colours (strings in#rrggbb
format) to output colours.
desc_template
[string: template]: : If specified, provides a template for the description, to allow formulaic descriptions of pieces in this group. The string specified bydesc_template
must contain${desc}
exactly once; that will be replaced with the description calculated according to the other rules. (${desc}
substitution happens after${colour}
substitution.)
occulted
[dict, contents depend onocculted.method
]. If specified, these pieces be occulted. For example, when a player has them in their hand and the hand is active and owned by them, only the occulted view (eg, the back of a playing card) will be shown.occulted
is a dict whose other contents depend on itsmethod
entry, which must be a string:
"ByColour"
: Occult by displaying a particular recolouring of this piece. The sub-entryocculted.colour
names a recolouring - one of the keys of thecolours
group parameter. When the piece is occulted it will show that colour, instead of its actual colour. In the description,${colour}
will be elided rather than substituted (along with up to one of any spaces either side of it).
"ByBack"
: Occult by displaying the back of this piece, as specified by theback
group parameter. Theocculted
dict must also contain a sub-entryilk
, a string. Pieces which have the sameilk
display identically when occulted, even if the different piece definitions imply different backs. (Whichever pieces are first loaded define what the backs of a particular ilk look like.)For pieces that are like cards, the ilk should be different for cards which have different backs in the game. Generally, standard playing cards should all specify
card-back
.