Configuration: Overview

The way the output is formatted and some behavioural aspects of the reference implementation are configurable via configuration files.

ChordPro configuration files are JSON files. However, since JSON can be tedious and error prone to maintain, ChordPro uses a special relaxed version of JSON: Really Relaxed JSON (RRJSON).

RRJSON files have filenames with extension .json and can be created and modified using any convenient text editor.

As an example, compare the variants of the following identical definitions. First strict JSON:

{
  "diagrams" : {
    "auto"   :  true,
    "show"   :  "all",
    "sorted" :  false
  },
  "dates" : {
    "today" : {
      "format" : "%A, %B %e, %Y"
    }
  },
  "tuning" : [ "E2", "A2", "D3", "G3", "B3", "E4" ]
}

Note that there are no comments, and there may be no commas after false and the closing ].

// Relaxed JSON
{
  diagrams : {
    auto   :  false,
    show   :  all
    sorted :  false,
  },
  dates : {
    today : {
      format: /* for diagnostics */ "%A, %B %e, %Y"
    },
  },
  tuning : [ E2 A2 D3 G3 B3 E4 ],
}

Relaxed JSON has comments, doesn’t require most of the quotes, and doesn’t care much about the commas.

// Really Relaxed JSON
diagrams {
  auto   :  false
  show   :  all
  sorted :  false
}
dates.today.format: "%A, %B %e, %Y"
tuning : [ E2 A2 D3 G3 B3 E4 ]

No need for the outer braces, no need for colons before braces, and keys of nested data can be combined into a compact, period-separated format. It is not only much shorter, but also much easier to write and maintain.

In this documentation we will preferably use RRJSON format, although the stricter JSON format can be still be seen in several places for legacy reasons.

Converting configuration files

Config files in JSON, RJSON, RRJSON and PRP formats can easily be converted to RRJSON format:

chordpro --convert-config=myconf.json --output=newconf.json

As an additional benefit, the converted config will have comments. For example, this trivial config:

settings.chordnames=strict

becomes, after conversion:

// Configuration for ChordPro
// 
// This is a really relaxed JSON document, see
// https://metacpan.org/pod/JSON::Relaxed#REALLY-RELAXED-EXTENSIONS

// General settings, often changed by configs and command line.
settings.chordnames : strict

// End of Config.

Standard configuration files

ChordPro tries to read several configuration files and combines their contents to form the actual configuration. ChordPro always starts with the built-in default configuration. Then all configuration files are processed in order, and their contents are merged into the existing configuration. So all settings accumulate. Configuration files do not need to be complete (i.e., contain all settings), it is often sufficient to only include the settings that must be changed. See for example the preset configurations modern1 and nashville, that only contains a few changes.

In the examples below the symbol ~ denotes the user’s home directory. Windows users may need to change the forward slashes to backward slashes.

  1. On systems that support it, a system-wide configuration file is read. On Linux systems, this is /etc/chordpro.json.

  2. A user specific configuration file is read from either:

    $XDG_CONFIG_HOME/chordpro/chordpro.json

    or:

    ~/.config/chordpro/chordpro.json
    ~/.chordpro/chordpro.json
    Note that if you have a ~/.config directory ChordPro expects the configs to be there and the latter alternative will be ignored.

  3. A project specific configuration file is read from the current directory, either:

    chordpro.json
    .chordpro.json

    Instead of a project specific configuration file you can specify arbitrary configuration files.

    • In the GUI, select Preferences... from the Edit menu.
      Using the configuration dropdown list, choose Custom.
      Click ... for a file dialog to choose the desired configuration file.
    • On the command line, pass the name of the configuration file with --config, for example --config=myconfig.json.

  4. A song specific configuration file is read if it exists. The name of the configuration file is the same as the song file name, with the extension replaced by prp or json (in that order).

    Note that the scope of the song specific configuration file is the song only. Every song will start with an initial config that results from steps 1 through 3, and then its song specific configuration file if it exists.

    Important A song specific configuration file may not contain an "include" or "tuning" item.

How config files are combined

The config files are processed in order, and their contents are merged. In general, a config setting from a later file replaces the value from previous files. There are a few exceptions: instrument definitions, hashes and arrays.

Merging instrument definitions

Instrument definitions, in particular the settings "tuning", "notes" and "chords", are handled differently. These are processed immediately after parsing a configuration file and then the setting is removed from the configuration.

For example, assume "chords_italian.json" defines a number of chords using italian (latin) note names and "chords_german.json" defines some chords using german note names. Then the following sequence of configuration files will work as expected:

notes:latin           (built-in, enable latin note names)
chords_italian.json   (defines chords with latin note names)
notes:german          (built-in, enable german note names)
chords_german.json    (defines chords with german note names)

Merging hash valued items

Hashes are merged by key. For example, assume:

{ "settings" : { "titles" : "center", "columns" : 1 } }

when merged with:

{ "settings" : { "columns" : 2 } }

the result will be:

{ "settings" : { "titles" : "center", "columns" : 2 } }

Merging array values items

Arrays are either overwritten or appended/prepended. This is controlled by the first element of the new array. If this first element is the string "append" then the new contents are appended, if it is "prepend" then the new contents are prepended. Otherwise the new contents replace the existing contents.

For example:

{ "keys" : [ "title", "subtitle" ] }

when merged with:

{ "keys" : [ "composer" ] }

will result in:

{ "keys" : [ "composer" ] }

If, however, this was merged with:

{ "keys" : [ "append", "composer" ] }

the result would have been:

{ "keys" : [ "title", "subtitle", "composer" ] }

Likewise, use "prepend" to prepend items.

How the config can be adjusted

ChordPro supports two methods to make simple adjustments to the config at runtime.

  • The command line option define:
--define diagrams.auto=true
  • The magic {+ ...} directive in a song:
{+diagrams.auto:true}

In either method a key and a value is specified. In the above examples, the key is diagrams.auto and the value is true.

Note that not all config items can be adjusted this way.

Property files

ChordPro also provides support for PRP files. These were an early attempt at providing easier maintainble configs. PRP files have a number of shortcomings, in particular with regard to array data. Although still supported, please use the newer RRJSON format instead. As you may have noticed this is very close to the PRP format. The main difference is that non-trivial strings must be quoted. For example, in PRP:

toc.title : Table of Contents
toc.line: %{line}

These must be changed to:

toc.title : "Table of Contents"
toc.line: "%{line}"