Class: Dommy::CanvasRenderingContext2D

Inherits:
Object
  • Object
show all
Includes:
Bridge::Methods
Defined in:
lib/dommy/html_canvas_element.rb

Overview

The 2D drawing context — every drawing call is a no-op, state setters are remembered (so ctx.fillStyle round-trips), and read-backs return zeroed data of the right shape. Enough for asset loaders / fingerprint probes / chart feature-detection to run without throwing.

Constant Summary collapse

STATE_DEFAULTS =

Drawing-state attributes that round-trip a value (default per spec where it matters; a plain "" otherwise).

{
  "fillStyle" => "#000000", "strokeStyle" => "#000000",
  "globalAlpha" => 1.0, "globalCompositeOperation" => "source-over",
  "lineWidth" => 1.0, "lineCap" => "butt", "lineJoin" => "miter", "miterLimit" => 10.0,
  "lineDashOffset" => 0.0, "font" => "10px sans-serif", "textAlign" => "start",
  "textBaseline" => "alphabetic", "direction" => "inherit",
  "shadowBlur" => 0.0, "shadowColor" => "rgba(0, 0, 0, 0)",
  "shadowOffsetX" => 0.0, "shadowOffsetY" => 0.0,
  "imageSmoothingEnabled" => true, "imageSmoothingQuality" => "low", "filter" => "none"
}.freeze

Instance Method Summary collapse

Methods included from Bridge::Methods

included

Constructor Details

#initialize(canvas) ⇒ CanvasRenderingContext2D

Returns a new instance of CanvasRenderingContext2D.



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# File 'lib/dommy/html_canvas_element.rb', line 105

def initialize(canvas)
  @canvas = canvas
  @state = STATE_DEFAULTS.dup
end

Instance Method Details

#__js_call__(method, args) ⇒ Object 



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# File 'lib/dommy/html_canvas_element.rb', line 133

def __js_call__(method, args)
  case method
  # All drawing/state-machine operations: nothing is painted.
  when "save", "restore", "scale", "rotate", "translate", "transform", "setTransform",
       "resetTransform", "getTransform", "beginPath", "closePath", "moveTo", "lineTo",
       "bezierCurveTo", "quadraticCurveTo", "arc", "arcTo", "ellipse", "rect", "roundRect",
       "fill", "stroke", "clip", "fillRect", "strokeRect", "clearRect", "fillText", "strokeText",
       "drawImage", "putImageData", "setLineDash", "drawFocusIfNeeded", "scrollPathIntoView", "reset"
    nil
  when "getLineDash" then []
  when "measureText" then TextMetrics.new(args[0].to_s)
  when "createLinearGradient", "createRadialGradient", "createConicGradient", "createPattern"
    CanvasGradient.new
  when "getImageData" then ImageData.new(args[2].to_i.abs, args[3].to_i.abs)
  when "createImageData" then created_image_data(args)
  when "isPointInPath", "isPointInStroke" then false
  when "getContextAttributes" then {}
  end
end

#__js_get__(key) ⇒ Object 



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# File 'lib/dommy/html_canvas_element.rb', line 110

def __js_get__(key)
  return @canvas if key == "canvas"
  return @state[key] if @state.key?(key)

  Bridge::ABSENT
end

#__js_set__(key, value) ⇒ Object 



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# File 'lib/dommy/html_canvas_element.rb', line 117

def __js_set__(key, value)
  return Bridge::UNHANDLED unless @state.key?(key)

  @state[key] = value
  value
end