Covered In This Episode:
- Creating a Window
- Basic Event Handling
Hello Everybody and welcome to making games with Ruby episode 3, Basics. I’m Tyler and these videos are brought to you by manwithcode.com.
Today we’re just going to be talking about the very basics of game creation, just getting a window on the screen. The code for this episode is on manwithcode.com, if you’re not there already. http://manwithcode.com/322/making-games-with-ruby-ep-3-basics
Lets get started!
We’re going to start by requiring in the libraries we need, which for now is only rubygems and rubygame:
require 'rubygems' require 'rubygame'
Then we’re going to create the main Game class, and stub out all the methods in it:
class Game def initialize end def run! end def update end def draw end end
And after that we’re going to add the code to run the game:
g = Game.new g.run!
So far this is just some very basic structure, nothing really happens yet. I’m going to run the code just to double check we have no syntax errors…
The first thing we’re going to do is initialize everything we’ll need:
def initialize @screen = Rubygame::Screen.new [640, 480], 0, [Rubygame::HWSURFACE, Rubygame::DOUBLEBUF] @screen.title = "Pong" @queue = Rubygame::EventQueue.new @clock = Rubygame::Clock.new @clock.target_framerate = 60 end
Some of this is self explaitory, but let’s break it down. The first line of
initialize creates the window for our game, Rubygame calls this a Screen. The first argument
[640, 480] is the size of the screen, the second is the screen depth (you don’t need to worry about this), the last one is a list of flags we pass to rubygame. HWSURFACE means we want it to be accelerated on the graphics card if available, and DOUBLEBUF means we want the screen to be double buffered. Double buffering is a way of drawing to the screen. I won’t go into too much detail right now to explain double buffering, but I will in a later episode.
The second line has an obvious purpose, it sets the title at the top of the screen to Pong
The fifth line is setup so we can handle events, I’ll talk more about this later.
The last two lines are the setup so we can limit the framerate to 60 frames per second. The frame rate is how many times the screen is drawn every second (we’ll be doing our drawing in the
Game#draw method). If we let this go unchecked, our game will run as fast as possible which isn’t desireable since top speed will be different on different computers, and depending on what the game is doing at a particular moment in time. I think 60 is a good number, but we can easily change it later if we want.
Next we’re going to setup the main game loop:
def run! loop do update draw @clock.tick end end
This loops indefinately until we decide in a different part of the code to end the game.
@clock.tick is what allows us to limit our framerate. You can now run the game, it should just be a black screen. You can see the title at the top, like we set in the initialize function.
But if you try to close the window… Nothing happens!!! To close it try pressing CTRL+C in the command prompt window, or you may have to go to the task manager and kill it from there. To fix this problem, we need to talk about the event queue.
We’re going to start by defining the
def update @queue.each do |ev| case ev when Rubygame::QuitEvent Rubygame.quit exit end end end
Whenever the user gives us some input, presses a key, moves the mouse, etc. the Rubygame adds an event for this input onto the queue. We handle these events in our update method.
@queue.each loops over each event, and we have a case statement that handles the event depending on the type. For closing the window, the event type is
Rubygame::QuitEvent, which is generated whenever the user presses the close window button or ALT+F4.
Now if you run the game, the window should appear and you should be able to close it now! Yay!
This is the final source listing for this episode:
require 'rubygems' require 'rubygame' class Game def initialize @screen = Rubygame::Screen.new [640, 480], 0, [Rubygame::HWSURFACE, Rubygame::DOUBLEBUF] @screen.title = "Pong" @queue = Rubygame::EventQueue.new @clock = Rubygame::Clock.new @clock.target_framerate = 60 end def run! loop do update draw @clock.tick end end def update @queue.each do |ev| case ev when Rubygame::QuitEvent Rubygame.quit exit end end end def draw end end g = Game.new g.run!
This brings us to the end of the episode.
If you have any questions, comments, or suggestions, leave a comment on this page or email me at firstname.lastname@example.org.
Thank you very much for watching! Goodbye!