custom helpers with block nesting?

[dfl]

I'm using some custom SVG helper methods that work well, but am having trouble getting a nested tspan. Here is a simplified test example:

require 'victor'

class SvgWrapper

  def initialize svg, cx, cy, chart=nil
    @svg, @cx, @cy, @chart = svg, cx, cy, chart
  end

  # forward to SVG object
  def method_missing method, *args, &block
    @svg.send method, *args, &block if @svg.respond_to? method
  end

  def text_at_angle str, angle, r, _opts={}
    opts = {fill: :black, text_anchor: :middle }.merge! _opts
    opts[:background] = :white if opts.delete(:foreground)
    dx,dy,da = opts.delete(:offset_x).to_f, opts.delete(:offset_y).to_f, opts.delete(:offset_a).to_f
    da *= -1 if angle.between?(45,225) # leading or lagging for readability
    x,y = polar_to_cartesian(angle+da, r)
    str = str.to_s
    # p extra = yield(@svg).last(3)     if block_given?
    text str, {x: x+dx, y: y+dy}.merge(opts) do |t|
      yield(t) if block_given?
    end
    return [x+dx, y+dy]
  end

  def deg_to_rad d
    Math::PI * (d % 360)/180.0
  end

  def polar_to_cartesian degree, radius, cx=nil, cy=nil, offset=0
    rad = deg_to_rad(degree+offset)
    x = radius * Math.cos(rad) + (cx || @cx)
    y = radius * Math.sin(rad) + (cy || @cy)
    return x, y
  end

end


dim = 500
svg = Victor::SVG.new( width: dim, height: dim )

draw = SvgWrapper.new( svg, dim/2, dim/2 )
draw.rect x: 0, y: 0, width: dim, height: dim, fill: 'white'
draw.text_at_angle "Hello, World!", 45.0, 100 do |t|
  t.tspan "cruel"
end

puts svg.to_s

output is missing the tspan. Can you please tell me what am I doing wrong?

<rect x="0" y="0" width="500" height="500" fill="white"/>
<text x="320.71067811865476" y="320.71067811865476" fill="black" text-anchor="middle">
Hello, World!
</text>

[DannyBen]

Well - here also, I would consider inverting the perspective and using inheritance/composition:

# Your code in a separate, testable module
module SVGUtils
  def text_at_angle str, angle, r, _opts={}
    # ...
  end

  def deg_to_rad d
    # ...
  end
end

# Your extended class
class SVG < Victor::SVG
  include SVGUtils
end

# Or, if you prefer to create a monkey patch extension:
class Victor::SVG
  include SVGUtils
end

In general, I would recommend avoiding redefining method_missing or messing with the transfer of blocks, since it is a low level Victor feature.

Also - you cannot use both a text argument and a block to text. One or the other only.

Here is a working example, achieving the basis of what you want.
I used blue_text as an alternative to your text method, to represent a method that adds a specially crafted SVG element.

require 'victor'

class SVG < Victor::SVG
  def blue_text(&block)
    text fill_color: :blue, &block
  end
end

svg = SVG.new

# Option 1: Using build
svg.build do
  blue_text do 
    _ "hello"
    tspan "cruel"
    _ "world"
  end
end

# Option 2: No build
svg.blue_text do 
  svg._ "hello"
  svg.tspan "cruel"
  svg._ "world"
end

puts svg.to_s

output:

<text fill-color="blue">
hello
<tspan>
cruel
</tspan>
world
</text>