The window

Learn how to create and configure a window

Creating a window

As you saw in the “get started” tutorial, the simplest thing you can do in Ruby 2D is require the gem and show the window:

require 'ruby2d'


If you’d like to follow along, save this code to a file named window.rb and run it using the standard Ruby interpreter on the command line, like so:

ruby window.rb

You should see a black, empty window with a size of 640-by-480 pixels and a title bar with the text “Ruby 2D”.

Setting attributes

When you don’t set any window attributes, the default values will be used. You can change these attributes by using the set method. Let’s try changing the window title before we show it:

require 'ruby2d'

set title: "Hello World!"


Notice the title bar of the window is now set to the new text we provided. The Ruby 2D domain-specific language (DSL) makes it easy to change things in a natural and intuitive way. Here, we’re calling a method called set and passing it a Hash with aSymbol called :title as the key, and a String with the text "Hello World! as the value. Alternatively, we could write it this way to make these details more explicit:

set( { :title => "Hello World!" } )

This is a bit verbose, especially for Ruby, so we’ll stick to the style in the original example.

Let’s play with some other attributes. The black background is a little boring, so let’s change it! We can set it to something more interesting, like the color blue:

set background: 'blue'

Try some other colors, like red, orange, lime, fuchsia, or roll the dice with random. When there are multiple attributes we want to set, we can chain them together for convenience:

set title: 'Howdy', background: 'navy'

Great! You’ve got the basics of setting attributes down. Here are all the attributes you can set:

Attribute Description
:title The title of the window. Default: "Ruby 2D"
:background The background color of the window. Any valid Ruby 2D Color is acceptable. Default: "black"
:width The width of the window in pixels. Default: 640
:height The height of the window in pixels. Default: 480
:viewport_width The width of the viewport in pixels, the visible part of the window. Default is the width of the window at the time show is called.
:viewport_height Same as :viewport_width above, but for setting the height.
:resizable Determines if the window can be resized, either true or false. Default: false
:borderless Determines if the window has a border, either true or false. Default: false
:fullscreen Determines if the window will be shown in fullscreen mode, either true or false. Default: false
:diagnostics Prints debugging information to the console, either true or false. This is mostly useful when working on Ruby 2D itself. Default: false

Getting attributes

Sometimes it’s also helpful to get the value of a window attribute, so there’s a method for that too called get:

get :width  # returns `640`, for example

For every attribute you can set, you can also get its value by providing the Symbol. Also, unlike set, you can only get one attribute at a time.

There are also a few extra attributes that you can get:

Attribute Description
:window The window object itself, just in case you want to inspect it.
:frames The number of frames that have been rendered since the start.
:fps The current frame rate expressed in frames per second (a Float).
:mouse_x The x-coordinate position of the mouse, relative to the window.
:mouse_y The y-coordinate position of the mouse, relative to the window.

The Window class

When you require 'ruby2d', a new window is instantiated for you by calling Sometimes it might be convenient to reference the Window class directly, for example when retrieving attributes:

Window.title   # returns "Ruby 2D"
Window.width   # returns 640
Window.height  # returns 480

The update loop

The window also manages the update loop, one of the few infinite loops in programming you’ll encounter that isn’t a mistake. Every window has a heartbeat, a loop that runs 60 times per second, or as close to it as the computer’s performance will allow. Using the update method, we can enter this loop and make the window come to life!

Say we’re bored with the static background we currently have. Let’s try changing it to a random color every second. Here’s a complete Ruby program to do just that:

require 'ruby2d'

tick = 0

update do
  if tick % 60 == 0
    set background: 'random'
  tick += 1


Ah, much better! How does this work? First, we set a variable called tick to 0. Then, we enter the update loop and do something interesting, like dividing tick by 60 and checking if its remainder equals 0. Each cycle of the loop, we increment tick by one. When the remainder does equal 0, we know a second has passed (assuming the window is running at about 60 frames per second), and we set the background color to 'random'. Pretty cool, huh?

Closing the window

When you’re done with a window, there’s nothing left to do but close it. In the examples above, you probably closed the window by clicking the “close” button on the title bar itself, or perhaps using a keyboard shortcut (like “Command-Q” on a Mac or “ALT+F4” on Windows), or using a menu bar, or right-clicking its icon, or whatever. The point is, you had to do it through the user interface in some way. But, what if instead you wanted to close the window with code? Well, there’s a method for that too!

Using close, you can programmatically close the window after calling show. This can be a bit tricky because once you show the window, you enter the window’s infinite loop and the code that follows won’t be reached until after the window is closed and the loop is exited. Don’t worry though, this isn’t some catch-22 — we just have to make sure to call close from within the loop. Here’s an example of a complete Ruby program where close is called after the window is shown and while the loop is running, taking advantage of the update method you learned about earlier.

require 'ruby2d'

t =

update do
  # Close the window after 5 seconds
  if - t > 5 then close end


Each turn of the window’s loop, it checks if the time we saved in variable t is greater than five seconds earlier than the current time. When it is, close is called and the window goes away.

That’s it!

You’ve learned all there is to know about the window in Ruby 2D. Continue to the next topic ▸

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