Class: Fontisan::Variable::DeltaApplicator

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/variable/delta_applicator.rb

Overview

Main orchestrator for delta application in variable fonts

Coordinates the entire delta application pipeline:

  1. Normalizes user coordinates to design space
  2. Calculates region scalars based on normalized coordinates
  3. Applies glyph outline deltas via GlyphDeltaProcessor
  4. Applies metric deltas via MetricDeltaProcessor

This is the primary interface for applying variation deltas to fonts.

Examples:

Apply deltas at specific coordinates

applicator = DeltaApplicator.new(font)
result = applicator.apply({ "wght" => 700, "wdth" => 100 })
# => { normalized_coords: {...}, region_scalars: [...],
#      glyph_deltas: {...}, metric_deltas: {...} }

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(font, config = {}) ⇒ DeltaApplicator

Initialize the delta applicator

Parameters:

  • font (TrueTypeFont, OpenTypeFont) —

    Font object

  • config (Hash) (defaults to: {}) —

    Optional configuration overrides



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# File 'lib/fontisan/variable/delta_applicator.rb', line 42

def initialize(font, config = {})
  @font = font
  @config = load_config.merge(config)

  # Load variation tables
  @fvar = load_table("fvar")
  @gvar = load_table("gvar")
  @hvar = load_table("HVAR")
  @vvar = load_table("VVAR")
  @mvar = load_table("MVAR")

  # Initialize components
  initialize_components
end

Instance Attribute Details

#axis_normalizer ⇒ AxisNormalizer (readonly)

Returns Axis normalizer.

Returns:



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# File 'lib/fontisan/variable/delta_applicator.rb', line 27

def axis_normalizer
  @axis_normalizer
end

#config ⇒ Hash (readonly)

Returns Configuration settings.

Returns:

  • (Hash) —

    Configuration settings



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# File 'lib/fontisan/variable/delta_applicator.rb', line 24

def config
  @config
end

#glyph_delta_processor ⇒ GlyphDeltaProcessor (readonly)

Returns Glyph delta processor.

Returns:



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# File 'lib/fontisan/variable/delta_applicator.rb', line 33

def glyph_delta_processor
  @glyph_delta_processor
end

#metric_delta_processor ⇒ MetricDeltaProcessor (readonly)

Returns Metric delta processor.

Returns:



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# File 'lib/fontisan/variable/delta_applicator.rb', line 36

def metric_delta_processor
  @metric_delta_processor
end

#region_matcher ⇒ RegionMatcher (readonly)

Returns Region matcher.

Returns:



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# File 'lib/fontisan/variable/delta_applicator.rb', line 30

def region_matcher
  @region_matcher
end

Instance Method Details

#advance_width_delta(glyph_id, user_coords) ⇒ Integer

Get advance width delta for a glyph

Parameters:

  • glyph_id (Integer) —

    Glyph ID

  • user_coords (Hash<String, Numeric>) —

    User coordinates

Returns:

  • (Integer) —

    Advance width delta



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# File 'lib/fontisan/variable/delta_applicator.rb', line 150

def advance_width_delta(glyph_id, user_coords)
  normalized_coords = @axis_normalizer.normalize(user_coords)
  region_scalars = @region_matcher.match(normalized_coords)

  @metric_delta_processor.advance_width_delta(glyph_id, region_scalars)
end

#apply(user_coords) ⇒ Hash

Apply deltas at specified user coordinates

Parameters:

  • user_coords (Hash<String, Numeric>) —

    User coordinates

Returns:

  • (Hash) —

    Delta application results



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# File 'lib/fontisan/variable/delta_applicator.rb', line 61

def apply(user_coords)
  # Validate we have required tables
  unless @fvar
    raise ArgumentError,
          "Font does not have fvar table (not a variable font)"
  end

  # Step 1: Normalize coordinates
  normalized_coords = @axis_normalizer.normalize(user_coords)

  # Step 2: Calculate region scalars
  region_scalars = @region_matcher.match(normalized_coords)

  # Step 3: Prepare result structure
  result = {
    user_coords: user_coords,
    normalized_coords: normalized_coords,
    region_scalars: region_scalars,
    glyph_deltas: {},
    metric_deltas: {},
    font_metrics: {},
  }

  # Step 4: Apply font-level metrics if MVAR present
  if @metric_delta_processor.has_mvar?
    result[:font_metrics] =
      @metric_delta_processor.apply_font_metrics(region_scalars)
  end

  result
end

#apply_glyph(glyph_id, user_coords) ⇒ Hash

Apply deltas to a specific glyph

Parameters:

  • glyph_id (Integer) —

    Glyph ID

  • user_coords (Hash<String, Numeric>) —

    User coordinates

Returns:

  • (Hash) —

    Glyph delta result



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# File 'lib/fontisan/variable/delta_applicator.rb', line 98

def apply_glyph(glyph_id, user_coords)
  # Normalize and get region scalars
  normalized_coords = @axis_normalizer.normalize(user_coords)
  region_scalars = @region_matcher.match(normalized_coords)

  result = {
    glyph_id: glyph_id,
    normalized_coords: normalized_coords,
  }

  # Apply glyph outline deltas if gvar present
  if @glyph_delta_processor
    result[:outline_deltas] = @glyph_delta_processor.apply_deltas(
      glyph_id,
      region_scalars,
    )
  end

  # Apply metric deltas
  result[:metric_deltas] = @metric_delta_processor.apply_deltas(
    glyph_id,
    region_scalars,
  )

  result
end

#apply_glyphs(glyph_ids, user_coords) ⇒ Hash<Integer, Hash>

Apply deltas to multiple glyphs

Parameters:

  • glyph_ids (Array<Integer>) —

    Glyph IDs

  • user_coords (Hash<String, Numeric>) —

    User coordinates

Returns:

  • (Hash<Integer, Hash>) —

    Results by glyph ID



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# File 'lib/fontisan/variable/delta_applicator.rb', line 130

def apply_glyphs(glyph_ids, user_coords)
  # Normalize once for all glyphs
  normalized_coords = @axis_normalizer.normalize(user_coords)
  region_scalars = @region_matcher.match(normalized_coords)

  glyph_ids.to_h do |glyph_id|
    [glyph_id, {
      outline_deltas: @glyph_delta_processor&.apply_deltas(glyph_id,
                                                           region_scalars),
      metric_deltas: @metric_delta_processor.apply_deltas(glyph_id,
                                                          region_scalars),
    }]
  end
end

#axes ⇒ Hash

Get axis information

Returns:

  • (Hash) —

    Axis information from fvar



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# File 'lib/fontisan/variable/delta_applicator.rb', line 167

def axes
  return {} unless @fvar

  @fvar.axes.each_with_object({}) do |axis, hash|
    # Convert BinData::String to regular Ruby String
    tag = axis.axis_tag.to_s
    hash[tag] = {
      min: axis.min_value,
      default: axis.default_value,
      max: axis.max_value,
      name_id: axis.axis_name_id,
    }
  end
end

#axis_tags ⇒ Array<String>

Get available axis tags

Returns:

  • (Array<String>) —

    Axis tags



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# File 'lib/fontisan/variable/delta_applicator.rb', line 185

def axis_tags
  @axis_normalizer.axis_tags
end

#region_count ⇒ Integer

Get number of variation regions

Returns:

  • (Integer) —

    Region count



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# File 'lib/fontisan/variable/delta_applicator.rb', line 192

def region_count
  @region_matcher.region_count
end

#variable_font? ⇒ Boolean

Check if font is a variable font

Returns:

  • (Boolean) —

    True if variable font



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# File 'lib/fontisan/variable/delta_applicator.rb', line 160

def variable_font?
  !@fvar.nil?
end