Displaying Text to the Player

00:00 In the previous lesson, you went all “Pew, pew!” and I went, “Whoa!” Your game now has sound! In this lesson, I’ll show you how to display text messages to the user informing them whether they won or lost.

00:13 Things happen in a game where you might want to show some text on the screen. Our project will be kept simple, only showing text for the win and loss conditions.

00:22 With the tools shown in this lesson, you could also add a score or number of lives or anything else you wanted to the screen. Text is often thought of as its own thing.

00:32 When you code, you don’t think about how the letters are displayed—just that they’re letters. This is a convenient abstraction, but at the heart of your computer’s display is still pixels, and something somewhere has to know what pixels to turn on and off to show that letter A.

00:47 This becomes a bit obvious in the case of a game, because you’re not dealing with those abstractions anymore, but drawing the pixels themselves. This means you have to load a font.

00:58 You’re going to use that font to generate a raster image of your text, then blit that text to the screen like any other sprite. Let’s see how that’s done.

01:09 This is back inside of utils.py. I’ve added a utility method for writing text to a surface. Let me scroll to the bottom here.

01:18 The print_text() function takes a surface to write to, a string to write, a font to use, and an optional color. The first step is to use the font object’s .render() method, which renders the text into a new surface.

01:33 The True parameter here turns anti-aliasing on. This smooths the edges of the text, making it look less ragged. With a text surface in hand, you now want to blit that to the target surface. As you’ve seen before, blitting something requires a bounding rectangle specifying the size of the item being blitted.

01:53 The .get_rect() method of the text_surface determines the text’s bounding box. Line 29 does something neat. It sets the position of the bounding rect by changing its .center attribute.

02:06 The new value for .center is set to the center of the target surface, which will be the screen. The result of this line is that the text message will be printed at the center of the screen. If you were building a more general utility method, you might want to put extra parameters in to control where the text goes.

02:24 For our simple purposes, the center of the screen will do. Finally, with the math done and the bounding box and blit positions known, the target surface’s blit method is called to actually display the text.

02:42 This is the game.py file. The first thing you need to do is import your newly written print_text() function from the utils file.

02:51 I’m going to add some code to detect win and loss conditions, then show a message. You’ll recall from the utils.py file, the print_text() method needs a font. Here, I load that font. By loading None, the default font will be used.

03:07 The 64 here is the size of the font. The .message attribute is where I store the message being displayed. As nothing is being displayed right now, it is the empty string. Let me scroll down a bit.

03:22 This is inside of the ._game_logic() method in the area that detects when the ship is destroyed. Here, I modify the .message attribute to inform the user that they lost. A little further down, and here I’m detecting the win condition.

03:38 It checks if all the rocks are gone and the ship still exists. If so, the player won. Once again, the .message attribute gets set, this time to the win condition.

03:50 With the win and loss detection code in place, all that is left to do is show the message. Let me go down to the ._draw() method. Here, I check if there is a message.

04:00 If there is, the print_text() utility function is called, writing that message to the screen. Let’s see this in action.

04:12 There’s the first case. Losing is the easy part. Let me try that again.

04:25 I’m the king of the rock breakers! There it is, I win! No cheating involved, honest. You’ve built an Asteroids clone, congratulations! In the last lesson, I’ll summarize, suggest some changes you can try out, and point you at a couple of places where you can get more information.