linjunpop / r2d

A Ruby 2D graphics interface.

R2D - A Ruby 2D Graphics Interface

Installing

To install the gem, use:

$ gem install r2d

Drawing

Shapes and images can be drawn procedurally using the methods below:

Available Parameters

x = an 'x' coordinate (number)
y = an 'y' coordinate (number)
s = the size   (number)
w = the width  (number)
h = the height (number)
c = the color  (string)
 or...
c = [r, g, b, a]
 where...
  r = red   (number) 0..255
  g = green (number) 0..255
  b = blue  (number) 0..255
  a = alpha (number) 0..255

Shapes

draw_line(x1, y1, x2, y2, c)
draw_triangle(x1, y1, x2, y2, x3, y3, c)
draw_square(x, y, s, c)
draw_rect(x, y, w, h, c)
draw_text(x, y, string, c)

Examples

draw_line(100, 150, 300, 350, "red")
draw_triangle(200, 50, 100, 300, 400, 300, "orange")
draw_square(10, 30, 50, [255, 255, 100, 150])
draw_rect(20, 20, 40, 40, [0, 255, 0, 255])
draw_text(50, 50, "Hello world!", "blue")

Images

draw_img(x, y, img_path)

Examples

draw_img(50, 100, "galaxy.jpg")

Shape and Image Classes

Each shape has an associated class. Shapes can be instantiated and added to the window using Window.add(shape) and removed with Window.remove(shape).

Lines

l = Line.new(x1, y1, x2, y2, c)

l.x1 = 10
l.y1 = 10
l.color = "yellow"

Window.add(l)
Window.remove(l)

Triangles

t = Triangle.new(x1, y1, x2, y2, x3, y3, c)

t.color = "green"
t.x3 = 75
t.y3 = 150

Squares

s = Square.new(x, y, s)
s = Square.new(x, y, s, c)

s.width = 25
s.height = 50
s.color = "red"

Window.add(s)

Rectangles

r = Rectangle.new(x, y, w, h)
r = Rectangle.new(x, y, w, h, c)

r.x = 10
r.y = 20
r.width = 200
r.height = 50
r.color = "blue"

Window.add(r)

Images

img = Image.new(x, y, img_path)

img.x = 10
img.y = 20

Audio

Songs

These are long audio clips. (More soon.)

s = Song.new("track.mp3")
s.play
s.playing?  # true
s.pause
s.paused?   # true
s.stop
s.loop

Sounds

Sounds are short audio clips. (More soon.)

s = Sound.new("snare.mp3")
s.play

The Window

Window Attributes

Attributes change the appearance and behavior of the window. These must be applied before displaying the window with Window.show.

Setting the window size:

Window.width = w
Window.height = h

Changing the background color, where color is a string or an array of [r, g, b, a] values.

Window.background = color

Showing the cursor over the window (default = true):

Window.cursor = false

Setting the title (default = "Learn Ruby"):

Window.title = "Hello world!"

Adding/Removing Objects

Objects can be added and removed from the window using:

r = Rectangle.new(50, 50, 100, 100)
Window.add(r)
Window.remove(r)

Additionally, all objects have an add and remove convenience method which will do the same:

r = Rectangle.new(50, 50, 100, 100)
r.add
r.remove

If an object is already in the window, add will return false. Similarly, if the object is not in the window, remove will return false.

r = Rectangle.new(50, 50, 100, 100)

r.add     # true
r.add     # false - already in window
r.remove  # true
r.remove  # false - not in window

All objects can be removed from the window using:

Window.clear

Capturing Input

To capture a single key press where <key_string> is any valid keyboard character a..z, A..Z, 0..9, and string representing arrows, alt, control, shift, etc:

Window.on_key <key_string> do
  #...
end

Examples

Window.on_key 'm' do
  puts "You pressed 'm'"
end

Window.on_key 'up' do
  puts "Up arrow pressed"
end

Window.on_key 'space' do
  puts "Spacebar pressed"
end

Mouse Buttons

Mouse input can also be captured using the 'mouse_left' and 'mouse_right' strings.

Window.on_key 'mouse_right' do
  puts "Mouse clicked in the window"
end

Keys Pressed Down

To detect whether a key is held down, use either...

Window.key_down <key_string> do
  #...
end

or Window.update:

Window.update do
  if key_down? <key_string>
    #...
  end
end

Examples

The two examples below are equivalent and both execute in the main update loop.

Window.key_down 'x' do
  puts "'x' pressed at #{Time.now}"
end

Window.update do
  if key_down? 'x'
    puts "'x' pressed at #{Time.now}"
  end
end

The Update Loop

The Window.update block represents the main update loop. Anything in this block will update 60 times per second (by default):

Window.update do
  #...
end

Mouse Positions

Mouse positions are relative to the top left corner of the window.

Window.mouse_x  # current 'x' position
Window.mouse_y  # current 'y' position

Showing the Window

Use Window.show to display the window. This should only be called once.

s = Square.new(100, 100, 50, "red")
s.add

Window.show

Helpers

The Window class has a number of helpers aliased to aid learning:

• update
• on_key
• key_down

update do
  #...
end

key_down 'x' do
  #...
end

Visual shapes and images also have knowledge of the Window class, so they can be added and removed from the window using their helper methods.

s = Square.new(x, y, s)

# Add and remove calling the `Window` class
Window.add(s)
Window.remove(s)

# Add and remove using the helper methods
s.add
s.remove

Helpful Snippets

Get Mouse Position When Changed

x = Window.mouse_x

Window.update do
  if Window.mouse_x != x
    puts x = Window.mouse_x
  end
end