Class: Clogs::Paragraph

Inherits:
Object
  • Object
show all
Defined in:
lib/clogs/paragraph.rb

Overview

Word-level text layout.

libui will happily wrap a whole attributed string for us, but it will not tell us where it put anything -- there is no hit-testing or caret API on uiDrawTextLayout. Shoes needs that geometry: links have to be clickable, para#hit has to map a pixel to a character, and the editor has to draw a caret.

So Clogs does its own line breaking. Each run is split into words, each word is measured once and cached, and lines are filled greedily. Drawing then batches adjacent words that share a style back into a single layout, so the common case still costs one libui text layout per line per style.

Defined Under Namespace

Classes: Placed, TextStyle

Constant Summary collapse

SIZES =

Shoes' named sizes, matching Scarpe's.

{
  inscription: 10, ins: 10, para: 12, caption: 14,
  tagline: 18, subtitle: 26, title: 34, banner: 48
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(runs, wrap_width, align: :left) ⇒ Paragraph

Returns a new instance of Paragraph.

Parameters:

  • runs (Array<Array(String, TextStyle)>) —

    text and its style

  • wrap_width (Numeric) —

    width to wrap at



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# File 'lib/clogs/paragraph.rb', line 84

def initialize(runs, wrap_width, align: :left)
  @runs = runs
  @wrap_width = wrap_width.to_f
  @align = align
  layout
end

Instance Attribute Details

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/clogs/paragraph.rb', line 27

def height
  @height
end

#lines ⇒ Object (readonly)

Returns the value of attribute lines.



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# File 'lib/clogs/paragraph.rb', line 27

def lines
  @lines
end

#placed ⇒ Object (readonly)

Returns the value of attribute placed.



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# File 'lib/clogs/paragraph.rb', line 27

def placed
  @placed
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/clogs/paragraph.rb', line 27

def width
  @width
end

Class Method Details

.line_height(style) ⇒ Object 



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# File 'lib/clogs/paragraph.rb', line 55

def line_height(style)
  key = [style.cache_key, :__line_height].freeze
  measure_cache[key] ||= begin
    w, h = measure("Hg", style)
    _ = w
    [0.0, h]
  end
  measure_cache[key][1]
end

.measure(text, style) ⇒ Object 



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# File 'lib/clogs/paragraph.rb', line 37

def measure(text, style)
  return [0.0, line_height(style)] if text.empty?

  key = [style.cache_key, text].freeze
  measure_cache[key] ||= begin
    block = TextBlock.new(
      [Run.new(text: text, size: style.size, family: style.family,
        bold: style.bold, italic: style.italic, color: style.color)],
      -1,
      default_family: style.family,
      default_size: style.size
    )
    dims = [block.width, block.height]
    block.free
    dims
  end
end

.measure_cache ⇒ Object

Cache of [style_key, text] => [width, height]. Text-heavy apps repeat the same words constantly, and each miss costs an attributed string, a text layout and two FFI calls.



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# File 'lib/clogs/paragraph.rb', line 33

def measure_cache
  @measure_cache ||= {}
end

.tokenize(text) ⇒ Object

Split into words while keeping the whitespace attached to the preceding word, so that trailing spaces do not start a new line on their own.



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# File 'lib/clogs/paragraph.rb', line 93

def self.tokenize(text)
  text.scan(/\n|[^\s]+[ \t]*|[ \t]+/)
end

Instance Method Details

#align_line(from, line_width, _line_height) ⇒ Object 



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# File 'lib/clogs/paragraph.rb', line 145

def align_line(from, line_width, _line_height)
  return if @align == :left || @wrap_width <= 0

  shift = case @align
  when :center then (@wrap_width - line_width) / 2.0
  when :right then @wrap_width - line_width
  else 0.0
  end
  return if shift <= 0

  (from...@placed.size).each { |i| @placed[i].x += shift }
end

#boxes_for(owner) ⇒ Object

Bounding boxes for everything contributed by owner, used to make links clickable. One box per line the owner appears on.



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# File 'lib/clogs/paragraph.rb', line 197

def boxes_for(owner)
  items = @placed.select { |i| i.owner.equal?(owner) }
  items.group_by(&:y).map do |y, line_items|
    x0 = line_items.map(&:x).min
    x1 = line_items.map { |i| i.x + i.width }.max
    h = line_items.map(&:height).max
    [x0, y, x1 - x0, h]
  end
end

#draw(painter, ox, oy) ⇒ Object

Draw, batching runs that share a line and a style.



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# File 'lib/clogs/paragraph.rb', line 159

def draw(painter, ox, oy)
  batch = []
  flush = lambda do
    next if batch.empty?

    first = batch.first
    text = batch.map(&:text).join
    style = first.style
    block = TextBlock.new(
      [Run.new(text: text, size: style.size, family: style.family, bold: style.bold,
        italic: style.italic, underline: style.underline, color: style.color)],
      -1,
      default_family: style.family,
      default_size: style.size
    )
    if style.bg
      h = batch.map(&:height).max
      w = batch.sum(&:width)
      painter.fill_rect(ox + first.x, oy + first.y, w, h, style.bg)
    end
    block.draw(painter, ox + first.x, oy + first.y)
    block.free
    batch = []
  end

  @placed.each do |item|
    prev = batch.last
    if prev && (prev.y != item.y || !prev.style.same_run_as?(item.style) ||
        prev.style.bg != item.style.bg)
      flush.call
    end
    batch << item
  end
  flush.call
end

#index_at(px, py) ⇒ Object

Character index nearest to a point, for text selection.



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# File 'lib/clogs/paragraph.rb', line 208

def index_at(px, py)
  line = @placed.select { |i| py >= i.y && py < i.y + i.height }
  line = @placed if line.empty?
  return 0 if line.empty?

  item = line.find { |i| px < i.x + i.width } || line.last
  frac = item.width.zero? ? 0 : (px - item.x) / item.width
  item.char_offset + (frac * item.text.length).round.clamp(0, item.text.length)
end

#layout ⇒ Object 



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# File 'lib/clogs/paragraph.rb', line 97

def layout
  @placed = []
  x = 0.0
  y = 0.0
  line_start = 0
  line_height = 0.0
  char_offset = 0
  max_x = 0.0

  flush_line = lambda do
    align_line(line_start, x, line_height)
    max_x = [max_x, x].max
    y += line_height.positive? ? line_height : 0
    x = 0.0
    line_height = 0.0
    line_start = @placed.size
  end

  @runs.each do |text, style|
    self.class.tokenize(text.to_s).each do |token|
      if token == "\n"
        line_height = self.class.line_height(style) if line_height.zero?
        char_offset += 1
        flush_line.call
        next
      end

      w, h = self.class.measure(token, style)
      # Trailing spaces should not force a wrap.
      stripped = token.rstrip
      effective_w = stripped == token ? w : self.class.measure(stripped, style)[0]

      if x.positive? && @wrap_width.positive? && x + effective_w > @wrap_width
        flush_line.call
      end

      @placed << Placed.new(token, style, x, y, w, h, style.owner, char_offset)
      char_offset += token.length
      x += w
      line_height = [line_height, h].max
    end
  end
  flush_line.call

  @width = max_x
  @height = y
end