File size: 4,294 Bytes
af6912c |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 |
// abc_beam_element.js: Definition of the BeamElem class.
// Most elements on the page are related to a particular absolute element -- notes, rests, bars, etc. Beams, however, span multiple elements.
// This means that beams can't be laid out until the absolute elements are placed. There is the further complication that the stems for beamed
// notes can't be laid out until the beams are because we don't know how long they will be until we know the slope of the beam and the horizontal
// spacing of the absolute elements.
//
// So, when a beam is detected, a BeamElem is created, then all notes belonging to that beam are added to it. These notes are not given stems at that time.
// Then, after the horizontal layout is complete, all of the BeamElem are iterated to set the beam position, then all of the notes that are beamed are given
// stems. After that, we are ready for the drawing step.
// There are three phases: the setup phase, when new elements are being discovered, the layout phase, when everything is calculated, and the drawing phase,
// when the object is not changed, but is used to put the elements on the page.
//
// Setup phase
//
var BeamElem = function BeamElem(stemHeight, type, flat, firstElement) {
// type is "grace", "up", "down", or undefined. flat is used to force flat beams, as it commonly found in the grace notes of bagpipe music.
this.type = "BeamElem";
this.isflat = !!flat;
this.isgrace = !!(type && type === "grace");
this.forceup = !!(this.isgrace || (type && type === "up"));
this.forcedown = !!(type && type === "down");
this.elems = []; // all the AbsoluteElements that this beam touches. It may include embedded rests.
this.total = 0;
this.average = 6; // use middle line as start for average.
this.allrests = true;
this.stemHeight = stemHeight;
this.beams = []; // During the layout phase, this will become a list of the beams that need to be drawn.
if (firstElement && firstElement.duration) {
this.duration = firstElement.duration;
if (firstElement.startTriplet) {
this.duration *= firstElement.tripletMultiplier;
}
this.duration = Math.round(this.duration * 1000) / 1000;
} else
this.duration = 0;
};
BeamElem.prototype.setHint = function () {
this.hint = true;
};
BeamElem.prototype.runningDirection = function (abcelem) {
var pitch = abcelem.averagepitch;
if (pitch === undefined) return; // don't include elements like spacers in beams
this.total = Math.round(this.total + pitch);
if (!this.count)
this.count = 0;
this.count++
};
BeamElem.prototype.add = function (abselem) {
var pitch = abselem.abcelem.averagepitch;
if (pitch === undefined) return; // don't include elements like spacers in beams
if (!abselem.abcelem.rest)
this.allrests = false;
abselem.beam = this;
this.elems.push(abselem);
this.total = Math.round(this.total + pitch);
if (this.min === undefined || abselem.abcelem.minpitch < this.min) {
this.min = abselem.abcelem.minpitch;
}
if (this.max === undefined || abselem.abcelem.maxpitch > this.max) {
this.max = abselem.abcelem.maxpitch;
}
};
BeamElem.prototype.addBeam = function (beam) {
this.beams.push(beam);
};
BeamElem.prototype.setStemDirection = function () {
// Have to figure this out before the notes are placed because placing the notes also places the decorations.
this.average = calcAverage(this.total, this.count);
if (this.forceup) {
this.stemsUp = true;
} else if (this.forcedown) {
this.stemsUp = false;
} else {
var middleLine = 6; // hardcoded 6 is B
this.stemsUp = this.average < middleLine; // true is up, false is down;
}
delete this.count;
this.total = 0;
};
BeamElem.prototype.calcDir = function () {
this.average = calcAverage(this.total, this.elems.length);
if (this.forceup) {
this.stemsUp = true;
} else if (this.forcedown) {
this.stemsUp = false;
} else {
var middleLine = 6; // hardcoded 6 is B
this.stemsUp = this.average < middleLine; // true is up, false is down;
}
var dir = this.stemsUp ? 'up' : 'down';
for (var i = 0; i < this.elems.length; i++) {
for (var j = 0; j < this.elems[i].heads.length; j++) {
this.elems[i].heads[j].stemDir = dir;
}
}
};
function calcAverage(total, numElements) {
if (!numElements)
return 0;
return total / numElements;
}
module.exports = BeamElem;
|