Class: HeadMusic::Notation::LilyPond::RenderPlan

Inherits:
Object
  • Object
show all
Defined in:
lib/head_music/notation/lily_pond/render_plan.rb

Overview

The computed musical facts a Writer needs to serialize a composition: the token for every placement and the key/time signatures in force at each measure. Construction eagerly computes everything that can raise on unmappable keys, durations, or alterations, so a RenderPlan that builds successfully cannot fail assembly on those grounds.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(composition) ⇒ RenderPlan

Returns a new instance of RenderPlan.



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 11

def initialize(composition)
  @composition = composition
  precompute_eager_data
end

Instance Attribute Details

#composition ⇒ Object (readonly)

Returns the value of attribute composition.



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 9

def composition
  @composition
end

Instance Method Details

#bar_numbers ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 16

def bar_numbers
  composition.earliest_bar_number..composition.latest_bar_number
end

#chord_token(placement) ⇒ Object (private) 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 89

def chord_token(placement)
  body = "<#{placement.pitches.sort.map { |pitch| PitchWriter.token(pitch) }.join(" ")}>"
  placement.rhythmic_value.tied_chain.map { |link| "#{body}#{DurationWriter.token(link)}" }.join("~ ")
end

#effective_meter(bar_number) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 41

def effective_meter(bar_number)
  change_bar = measure_time_changes.keys.select { |number| number <= bar_number }.max
  change_bar ? measure_time_changes[change_bar] : composition.meter
end

#first_measure_key ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 32

def first_measure_key
  @first_measure_key ||=
    measure_key_changes[bar_numbers.first] || KeyMapper.token(composition.key_signature)
end

#first_measure_meter ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 37

def first_measure_meter
  @first_measure_meter ||= effective_meter(bar_numbers.first)
end

#measure_key_changes ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 20

def measure_key_changes
  @measure_key_changes ||= bar_numbers.zip(composition.bars).filter_map { |bar_number, bar|
    [bar_number, KeyMapper.token(bar.key_signature)] if bar.key_signature
  }.to_h
end

#measure_time_changes ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 26

def measure_time_changes
  @measure_time_changes ||= bar_numbers.zip(composition.bars).filter_map { |bar_number, bar|
    [bar_number, bar.meter] if bar.meter
  }.to_h
end

#note_token(placement) ⇒ Object (private) 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 84

def note_token(placement)
  pitch_token = PitchWriter.token(placement.pitch)
  placement.rhythmic_value.tied_chain.map { |link| "#{pitch_token}#{DurationWriter.token(link)}" }.join("~ ")
end

#placements_by_bar(voice) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 46

def placements_by_bar(voice)
  @placements_by_bar ||= {}
  @placements_by_bar[voice] ||= voice.placements.group_by { |placement| placement.position.bar_number }
end

#precompute_eager_data ⇒ Object (private)

Everything that can raise on unmappable keys, durations, or alterations is computed here so it raises at construction, before the Writer assembles output.



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 62

def precompute_eager_data
  first_measure_key
  first_measure_meter
  measure_key_changes
  measure_time_changes
  tokens_by_placement
end

#rest_token(placement) ⇒ Object (private) 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 80

def rest_token(placement)
  placement.rhythmic_value.tied_chain.map { |link| "r#{DurationWriter.token(link)}" }.join(" ")
end

#token(placement) ⇒ Object (private)

A tied chain within a placement joins its links with the tie mark; a chain of rests emits consecutive untied rests, and a tied chord repeats the whole chord.



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 73

def token(placement)
  return rest_token(placement) if placement.rest?
  return chord_token(placement) if placement.chord?

  note_token(placement)
end

#tokens_by_placement ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/render_plan.rb', line 51

def tokens_by_placement
  @tokens_by_placement ||= composition.voices.flat_map(&:placements).to_h do |placement|
    [placement, token(placement)]
  end
end