A bridge between Ruby and HTML5 canvas for Sinatra using Websocket.
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README.md

Fontaine

A bridge between Ruby and HTML5 canvas for Sinatra using Websocket. Basically, this allows you to make <canvas> based apps in Ruby.

Installation

Add this line to your application's Gemfile:

gem 'fontaine'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fontaine

Usage

Just put this in your pipe:

require 'sinatra/base'
require 'fontaine/canvas' #the meat of everything canvas-related
require 'fontaine/bootstrap' 
require 'sinatra-websocket'
require 'haml' #not strictly necessary, but recommended

class Sample < Sinatra::Base
  register Sinatra::Fontaine::Bootstrap::Assets
  set :server, 'thin'
  set :sockets, []
  
  get '/' do
    
    @canvas = Fontaine::Canvas.new("TEST_CANVAS", 500, 500, "Your browser does not support the canvas tag", 
      :style => "border:1px solid #000000;") do |canvas|
        
        canvas.on_click do |x, y, button| #when there's a click, do this:
          if button.eql? '0' #left click will give you a solid red rectangle
            canvas.fill_style("#FF0000")
            canvas.fill_rect(x.to_i-25, y.to_i-25, 50, 50)
          else #right click will give you the outline of a blue rectangle
            canvas.stroke_style("blue")
            canvas.stroke_rect(x.to_i-25, y.to_i-25, 50, 50)
          end
          
        end
    end
    
    if request.websocket?
      @canvas.listen(request, settings)
    else
      haml :index
     
    end
  end
  
end

views/index.haml

%script{:src => "/javascripts/jquery-1.9.1.js", :type => "text/javascript"}
= bootstrap_fontaine
= @canvas.display

sample_config.ru

require './sample'
run Sample

and smoke it! (After you've put jquery-1.9.1.js into /public/javascripts/)

rackup sample_config.ru

Ok, that's pretty complicated. Let me give you some further explanations. We'll start with
making a new Canvas:

Fontaine::Canvas.new("TEST_CANVAS", 500, 500, "Your browser does not support the canvas tag", 
  :style => "border:1px solid #000000;")

This is pretty simple. The first parameter is simply the id of the canvas you will be displaying. The second and third parameters are the width and height of the canvas. The fourth is the alt text if the user's browser doesn't support . Finally, the fifth parameter is a hash of any other html options you wish to add to the canvas. In this case, I'm giving it a border.

Next, while initializing, you can give it a block of code to execute when the user takes actions related to the canvas. (Note, you can do this at any point once the canvas is initialized by passing a block to any of the action methods). The block will be whatever code you want to run in response to those actions. In addition, each action is yielded a few parameters from the javascript event call. For more information on specific actions available and their parameters, see the Action Methods section.

That's only half the story, though. You've got to be able to draw on the canvas! You can use any of the methods from here and they will work pretty much how you'd expect, with a couple exceptions (see Exceptions and Issues). Most of the time, you simply can directly use a 'rubyfied' version of the same method. For example, instead of calling @canvas.fillRect(), you call @canvas.fill_rect. The other major exception is that rather than setting canvas attributes with '=', you'll simply use a method of the same name (canvas.fill_style("#FF0000"), not canvas.fill_style = "#FF0000")

Alright, so you've got your action methods set up and you know how to draw on the canvas, you just have to get it going. In the sinatra file this is pretty simple. When you get a request, listen! Pass in the request and the sinatra settings.

if request.websocket?
  @canvas.listen(request, settings)
end

The view is almost as easy:

%script{:src => "/javascripts/jquery-1.9.1.js", :type => "text/javascript"}
= bootstrap_fontaine
= @canvas.display

Bam! You need jquery. I've tested on 1.9.1, but not any other versions. bootstrap_fontaine gives you access to the fontaine javascript file. @canvas.display will display the canvas.

Action Methods

NOTE: All coordinates are in relation to the canvas, not to the document 0, 0 is the top-left corner of the canvas, for example.

on_open Yields nothing- runs when the document is created

on_click Yields x, y, and button

on_mousedown Yields x, y, and button

on_mouseup Yields x, y, and button

on_mouseover Yields x and y

on_mouseout Yields x and y

on_mousemove Yields x and y

on_keydown Yields key_code

(Note, key_code is not the ascii value of the key pressed. See javascript documentation on the difference between the keyCode and the value)

on_keyup Yields key_code

on_keypress Yields which (This is the ascii value of the key pressed)

Drawing methods

You can use any of the methods from here and they will work pretty much how you'd expect, with a couple exceptions (see Exceptions and Issues). Most of the time, you simply can directly use a 'rubyfied' version of the same method. For example, instead of calling @canvas.fillRect(), you call @canvas.fill_rect. The other major exception is that rather than setting canvas attributes with '=', you'll simply use a method of the same name (canvas.fill_style("#FF0000"), not canvas.fill_style = "#FF0000")

Exceptions and Issues

Currently, all drawing methods must be called within an Action Method block.

Any "Drawing" method that returns an attribute doesn't "really" give you the attribute. It returns the value of the attribute from the last time you changed it from the ruby Canvas object. In other words, if I call

@canvas.fill_style("blue")

on the ruby side, then later call

canvas.fillStyle = "#FF0000"

in the javascript, when I call

@canvas.fill_style

in ruby, it'll still return "blue".

Basically, this is because websocket is impatient. It doesn't have a protocol for waiting for the javascript to return information before executing the next line of code. So, I faked it and track everything on the fontaine canvas object.

If you stick to just using the fontaine canvas methods, this mostly doesn't have an impact, except that the get_image_data method, the measure_text method, and the "Pixel Manipulation" methods aren't working right now. Don't even try.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

##Future Features/Goals

Soon

  • Implement on_keystroke methods for each key. For example, on_keystroke_a or on_keystroke("a").
  • Allow calling of drawing methods outside of action blocks

Later

  • Figure a more elegant way to bootstrap the javascript, avoiding rackup and extending canvas
  • Add a scheduler or some other way to "wait" for get methods from the javascript

In the distant future, when apes rule the Earth

  • Implement this in Ruby on Rails
  • Implement audio and video tags