engravingDefaults

The "engravingDefaults" structure contains key/value pairs defining recommended defaults for line widths etc., as follows, with all measurements expressed in staff spaces:

Key name	Description
"textFontFamily"	An array containing the text font family (or families, in descending order of preference) that are ideally paired with this music font; this list may also use the generic font family values defined in CSS, i.e. serif, sans-serif, cursive, fantasy, and monospace. Generic font family names should be listed after specific font families.
"staffLineThickness"	The thickness of each staff line
"stemThickness"	The thickness of a stem
"beamThickness"	The thickness of a beam
"beamSpacing"	The distance between the inner edge of the primary and outer edge of subsequent secondary beams
"legerLineThickness"	The thickness of a leger line (normally somewhat thicker than a staff line)
"legerLineExtension"	The amount by which a leger line should extend either side of a notehead, scaled proportionally with the notehead's size, e.g. when scaled down as a grace note
"slurEndpointThickness"	The thickness of the end of a slur
"slurMidpointThickness"	The thickness of the mid-point of a slur (i.e. its thickest point)
"tieEndpointThickness"	The thickness of the end of a tie
"tieMidpointThickness"	The thickness of the mid-point of a tie
"thinBarlineThickness"	The thickness of a thin barline, e.g. a normal barline, or each of the lines of a double barline
"thickBarlineThickness"	The thickness of a thick barline, e.g. in a final barline or a repeat barline
"dashedBarlineThickness"	The thickness of a dashed barline
"dashedBarlineDashLength"	The length of the dashes to be used in a dashed barline
"dashedBarlineGapLength"	The length of the gap between dashes in a dashed barline
"barlineSeparation"	The default distance between multiple thin barlines when locked together, e.g. between two thin barlines making a double barline, measured from the right-hand edge of the left barline to the left-hand edge of the right barline.
"thinThickBarlineSeparation"	The default distance between a pair of thin and thick barlines when locked together, e.g. between the thin and thick barlines making a final barline, or between the thick and thin barlines making a start repeat barline.
"repeatBarlineDotSeparation"	The default horizontal distance between the dots and the inner barline of a repeat barline, measured from the edge of the dots to the edge of the barline.
"bracketThickness"	The thickness of the vertical line of a bracket grouping staves together
"subBracketThickness"	The thickness of the vertical line of a sub-bracket grouping staves belonging to the same instrument together
"hairpinThickness"	The thickness of a crescendo/diminuendo hairpin
"octaveLineThickness"	The thickness of the dashed line used for an octave line
"pedalLineThickness"	The thickness of the line used for piano pedaling
"repeatEndingLineThickness"	The thickness of the brackets drawn to indicate repeat endings
"arrowShaftThickness"	The thickness of the line used for the shaft of an arrow
"lyricLineThickness"	The thickness of the lyric extension line to indicate a melisma in vocal music
"textEnclosureThickness"	The thickness of a box drawn around text instructions (e.g. rehearsal marks)
"tupletBracketThickness"	The thickness of the brackets drawn either side of tuplet numbers
"hBarThickness"	The thickness of the horizontal line drawn between two vertical lines, known as the H-bar, in a multi-bar rest

Below is a dummy "engravingDefaults" structure, with some of the values filled in:

{
  ...
  "engravingDefaults": {
    "textFontFamily" : [ "Academico", "Century Schoolbook", "serif" ],
    "staffLineThickness": 0.1,
    "stemThickness": 0.1,
    "beamThickness": 0.5,
    "beamSpacing": 0.25,
    "legerLineThickness": 0.2,
    "legerLineExtension": 0.2,
    ...
  },
  ...
}