Class: Marvi::Diagram::Grid

Inherits:
Object
  • Object
show all
Defined in:
lib/marvi/diagram.rb

Overview

A sparse character canvas that merges box-drawing line strokes so that crossing or joining connectors render as the correct junction glyph.

Constant Summary collapse

STROKE = 
{up: 1, down: 2, left: 4, right: 8}.freeze
MASK_TO_CHAR = 
{
  1 => "│", 2 => "│", 3 => "│",
  4 => "─", 8 => "─", 12 => "─",
  10 => "┌", 6 => "┐", 9 => "└", 5 => "┘",
  11 => "├", 7 => "┤", 14 => "┬", 13 => "┴", 15 => "┼"
}.freeze
CHAR_TO_MASK = 
MASK_TO_CHAR.each_with_object({}) do |(mask, char), h|
  # Keep the richest mask for each glyph so re-merging is lossless.
  h[char] = mask if !h.key?(char) || mask > h[char]
end.freeze

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Grid

Returns a new instance of Grid.



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# File 'lib/marvi/diagram.rb', line 64

def initialize
  @cells = {}
end

Instance Method Details

#line(row, col, strokes) ⇒ Object

Add line strokes at a cell, merging with any existing line glyph.



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# File 'lib/marvi/diagram.rb', line 75

def line(row, col, strokes)
  mask = strokes.sum { |s| STROKE.fetch(s) }
  existing = @cells[[row, col]]
  mask |= CHAR_TO_MASK[existing] if existing && CHAR_TO_MASK.key?(existing)
  @cells[[row, col]] = MASK_TO_CHAR.fetch(mask)
end

#set(row, col, char) ⇒ Object

Place an opaque glyph (box border, label text, arrowhead) that does not participate in stroke merging.



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# File 'lib/marvi/diagram.rb', line 70

def set(row, col, char)
  @cells[[row, col]] = char
end

#to_spans ⇒ Object 



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# File 'lib/marvi/diagram.rb', line 82

def to_spans
  return [] if @cells.empty?

  rows = @cells.keys.map(&:first)
  cols = @cells.keys.map(&:last)
  (rows.min..rows.max).map do |r|
    buffer = +""
    (cols.min..cols.max).each do |c|
      char = @cells[[r, c]]
      next if char == WIDE_FILLER
      buffer << (char || " ")
    end
    [Span.new(text: buffer.rstrip, color: COLOR)]
  end
end