WEBVTT 00:00.090 --> 00:00.620 Hello again! 00:00.990 --> 00:06.660 In this video, we're going to look at making it a basic window in SFML. So let's start off by looking 00:06.660 --> 00:08.910 at the things we need to know about SFML. 00:09.630 --> 00:17.430 These classes are defined in the SFML slash "graphics" dot "hpp" header. They are inside the "sf" namespace. 00:18.570 --> 00:20.580 The "Window" is a base class. 00:21.030 --> 00:24.390 This represents a window on the screen which does nothing, really. 00:24.390 --> 00:25.620 So that is not very interesting. 00:26.490 --> 00:32.580 We are going to use the "RenderWindow", which is a subclass of "Window". And this is a window which supports 00:32.600 --> 00:33.090 rendering. 00:33.600 --> 00:37.620 So you can use this for doing two-dimensional drawing, inside a window on the screen. 00:38.730 --> 00:44.550 There is also the "Event", which is a union, not a class, and this will contain details about user interaction 00:44.550 --> 00:44.970 events. 00:45.690 --> 00:50.910 So if the user clicks on the window, or if they press a key, while the window has focus. 00:53.110 --> 00:55.090 There are three important member functions 00:55.090 --> 00:58.180 of the RenderWindow. clear() will, obviously, clear the window. 00:58.660 --> 01:00.820 draw() will do drawings in the window. 01:00.820 --> 01:05.440 But this will only affect a memory buffer which is maintained by the window. 01:05.980 --> 01:08.440 It will not change anything that the user sees on the screen. 01:09.370 --> 01:14.440 To do that, we call display(). And that will make the contents of the memory buffer appear on the 01:14.440 --> 01:14.920 display. 01:15.490 --> 01:22.870 So, when we write a game or a simulation, we have a loop in which we clear the window, update the frame, 01:22.870 --> 01:25.630 and then we display it, and make it visible to the user. 01:26.020 --> 01:28.630 So these are the member functions that we use for doing that. 01:31.740 --> 01:32.310 In the code, 01:32.310 --> 01:38.670 I have a "constants.h" file which has the parameters for the game. And for this program, it is just the height 01:38.670 --> 01:39.930 and width of the window. 01:42.110 --> 01:48.200 In the main program, we include the SFML graphics header. And also our constants header, of course. 01:49.550 --> 01:52.400 We start off by creating an object of this RenderWindow. 01:52.970 --> 01:59.600 The constructor takes a vector which contains the width and the height of the window. And you can also 01:59.600 --> 02:03.410 provide a C++ string, which will be the title of the window. 02:05.510 --> 02:11.420 Usually it is a good idea to limit the frame rate. So this controls how often the window will update 02:11.420 --> 02:12.230 the display. 02:13.100 --> 02:19.580 If you have this too high, then the game is going to use a lot of CPU power, just updating the window. 02:20.840 --> 02:23.780 If you have this too low, then the game will appear to be "jerky". 02:24.470 --> 02:31.430 So 60 is the normal value for games. And then we have our loop where we update the window. 02:32.090 --> 02:39.020 So while the window is open. We start off by clearing the window. And this argument will set the window 02:39.020 --> 02:40.370 to have a black background. 02:41.780 --> 02:44.180 And then we check for user interaction events. 02:45.080 --> 02:47.960 We call the pollEvent() member the function of the window. 02:48.350 --> 02:51.230 So the window will stop and wait for some user event. 02:51.980 --> 02:56.150 If it times out, this will return false and carry on with the rest of the programme. 02:56.600 --> 02:58.820 If there is an event, then we check the type. 02:59.540 --> 03:04.670 And because this event is a union, we always need to check the type before we do anything with it. 03:06.720 --> 03:12.020 "Event::Closed" means the user has done something which will close the window. So on Windows, 03:12.030 --> 03:16.820 this means clicking the 'X' in the corner, or doing all "Alt-F4". On a mMc, 03:16.830 --> 03:19.410 that would mean clicking the red button in the top left. 03:19.770 --> 03:21.640 Or, I think it is "Command F4". 03:23.220 --> 03:27.210 And in that case, we close the game window, which will terminate this loop. 03:29.880 --> 03:31.920 And we can also check for particular keys. 03:32.370 --> 03:35.670 So this is a static member function of the Keyboard class. 03:36.420 --> 03:38.330 And the argument will be the key to check for. 03:38.850 --> 03:44.280 So if the user presses the escape key, then we close the window again. And terminate the loop. 03:46.050 --> 03:51.480 In the actual game, we are going to do some calculations here, which will compute the next frame, but 03:51.480 --> 03:52.590 we are not doing anything here. 03:53.100 --> 03:57.560 And then finally we display the updated graphics. The next frame in the game. 04:00.410 --> 04:08.810 So I can click on the 'X', and that sends a "Close" event, and the game terminates. Or I can press the escape 04:08.810 --> 04:11.660 key, and that will also cause the game to terminate. 04:12.140 --> 04:13.490 Okay, so that is it for this video. 04:13.820 --> 04:14.600 I will see you next time. 04:14.810 --> 04:16.690 Until then, keep coding!