WEBVTT 00:00.180 --> 00:00.980 Hello again. 00:00.990 --> 00:04.170 In this video, we are going to look at the game manager. 00:05.070 --> 00:08.190 We have implemented the basic features of our game. 00:08.460 --> 00:10.620 Obviously, there is still a lot more that we could add. 00:10.620 --> 00:15.210 But before we go any further, we need to think about the organization of our code. 00:15.930 --> 00:17.610 Our main() function is too long. 00:17.760 --> 00:22.110 Ideally, a function should fit into a single screen, so you can see all the code without having to do 00:22.110 --> 00:23.070 any scrolling. 00:23.520 --> 00:26.940 And also, there is a lot of code which is duplicated across the program. 00:27.690 --> 00:33.870 So we are going to step aside for a minute and refactor the code. And we are going to start off, in this 00:33.870 --> 00:40.050 video, by moving the code from the main() function into a new class which will manage the game. 00:42.730 --> 00:48.280 This class will have the game window as a data member, and also all the entities from the game. 00:48.850 --> 00:55.450 It will have a constructor, to start things off, and a run() member function, which will perform the game 00:55.450 --> 00:56.080 loop. 00:56.590 --> 00:59.330 There is also going to be a new feature, reset(). 00:59.350 --> 01:04.390 So this will reinitialize the entities. So we can use that to allow the user to restart the game. 01:05.620 --> 01:08.570 And we are also going to allow the user to pause the game. 01:08.590 --> 01:11.270 So this means that the ball will appear to stop moving. 01:11.290 --> 01:14.170 The user cannot move the paddle across the screen, and so on. 01:15.040 --> 01:17.200 So the entities are not being updated. 01:17.320 --> 01:19.600 However, the entities are still redrawn. 01:19.630 --> 01:24.340 So if we cover up the game window and then uncover it, it will still look normal. 01:25.900 --> 01:29.500 We need to know what the game's current state is. 01:29.500 --> 01:35.200 So we are going to have a member for that. And we are going to use a class enum, which is another 01:35.200 --> 01:36.100 C++11 feature. 01:37.210 --> 01:42.940 In the class definition, we need to include the headers for all the entities, and also the constants. 01:43.690 --> 01:49.240 Then we have all the members, so we have the game window, the background and so on. And we are using 01:49.240 --> 01:50.920 in-place initialization. 01:51.460 --> 01:57.100 And we can do this because all these constants are constant expressions, they are constexpr. If they 01:57.100 --> 01:59.050 were just normal const, we could not do this. 02:00.040 --> 02:05.860 So this means that when we create an object of game, then by default, game window will have these dimensions 02:05.860 --> 02:10.210 and that title, the ball will have these dimensions and so on. 02:12.950 --> 02:20.120 You will notice that I had to change this to a C string literal and not a C++ string, because C++ strings 02:20.120 --> 02:23.570 cannot be constexpr. At least, not in this version of C++. 02:24.530 --> 02:30.350 And we also need to have the vector initialized separately, because vectors are not constexpr either. 02:30.560 --> 02:31.580 Or, not yet. 02:33.020 --> 02:38.060 Then we have our class enum with the game's states, and then we have the member. 02:38.150 --> 02:44.630 So initially, we assume that the game is going to be running. And then we have the declaration of the 02:44.630 --> 02:45.650 member functions. 02:48.870 --> 02:50.460 In the game constructor, 02:50.460 --> 02:56.910 we do not need to provide an initialization list, because the class already has sensible initial values. 02:57.390 --> 03:01.560 If we did put anything in here, it would just override the default values. 03:01.560 --> 03:03.450 But we do not need to do that. 03:03.960 --> 03:11.010 All we need to do, is to populate the vector of bricks, the same code as we had before, and to set the 03:11.010 --> 03:16.260 frame rate for the window. In the reset() member function, 03:16.440 --> 03:23.370 we want to restore all the bricks to their original position. So all the destroyed bricks will be drawn 03:23.370 --> 03:23.690 again. 03:23.700 --> 03:25.380 They will come back to life, if you like. 03:25.500 --> 03:28.500 And the easiest way to do that is just to draw everything again. 03:30.540 --> 03:33.690 And then we have the one member function with the game loop. 03:34.530 --> 03:39.450 I will come back to this in a minute. But the basic loop is the same. 03:39.450 --> 03:44.910 So we clear the screen, check for events. (Skip ahead a bit) 03:45.900 --> 03:48.030 Then we update all the entities. 03:48.300 --> 03:50.010 We handle collisions. 03:50.970 --> 03:53.280 We erase all the removed bricks. 03:53.760 --> 03:57.150 And then we draw the updated graphics. 03:57.270 --> 04:01.770 So that is all the same code that you have seen before, with just a couple of little extra features. 04:04.620 --> 04:08.430 The first one is that we only do the updates if the game state is not "paused". 04:09.400 --> 04:15.370 So we do not do any of this update, collision handling and erasing, but we do display the graphics. 04:17.340 --> 04:22.560 And then we have this code for the pause and reset. The reset is very simple: we just check for the 04:22.680 --> 04:26.610 user pressing the 'r' key, and then we call the reset() function. 04:28.000 --> 04:30.400 We check for the user pressing the 'p' key. 04:30.940 --> 04:36.040 If they press it when the game is running, it will pause it. And if they press the key again, then the game 04:36.130 --> 04:37.060 will resume. 04:37.630 --> 04:40.480 So we just invert the state of the game. 04:42.010 --> 04:47.080 There is a complication here, because if the user holds down the key, then it is going to send an event 04:47.080 --> 04:51.130 on every iteration, until the user releases the key. 04:51.580 --> 04:56.220 So we could have a situation where the user presses the key, and that pauses the game. 04:56.260 --> 04:57.490 Then they hold it down. 04:57.820 --> 05:03.430 The next iteration gets the key again, so it resumes the game. Then the next iteration pauses and 05:03.430 --> 05:03.960 so on. 05:03.970 --> 05:08.860 So we have this kind of "whipsaw" effect, and we want to avoid that. 05:09.250 --> 05:12.040 So we put in a check to see if the key has already been pressed. 05:12.550 --> 05:14.560 So that is the purpose of this variable. 05:15.100 --> 05:22.630 So initially, the key has not been pressed. And then, the first time, this variable will be false. 05:22.630 --> 05:29.230 So we go into this, and we invert the state of the game. And then we set the flag to true. 05:29.920 --> 05:34.650 And then the next time, if the user holds the key down, then this will be true. 05:34.660 --> 05:42.850 So we skip over this. And if the user releases the key, or presses some other key, then we go into here. 05:42.850 --> 05:44.680 And this will set the flag to false. 05:46.620 --> 05:49.230 And finally, in the main() function, this is now very simple. 05:49.290 --> 05:51.600 We just create an object of the game. 05:51.690 --> 05:52.610 The game manager. 05:52.620 --> 05:54.510 So this will initialize everything. 05:54.960 --> 05:59.010 And then we call the run() member function and that will start up the game loop. 05:59.310 --> 06:00.780 So that will keep on running. 06:00.840 --> 06:06.900 And when the game loop terminates, then this function call will return, and we exit the program. 06:14.490 --> 06:15.480 So, there we are. 06:17.340 --> 06:19.530 I am busy playing this game, rather badly! 06:20.580 --> 06:22.200 And then the phone rings. 06:23.250 --> 06:24.360 (Just put this over here) 06:25.650 --> 06:27.180 (I do not want anyone to know I'm playing this game!) 06:28.350 --> 06:28.910 (Okay) 06:30.040 --> 06:32.220 (The phone call is over) And you can see the window looks normal. 06:32.310 --> 06:37.290 We do not have any busy cursor, or black screen, or "window not responding" message. 06:38.610 --> 06:39.900 And then we can continue. 06:42.600 --> 06:43.290 And then... 06:47.040 --> 06:50.040 If I want to restart, then I just press the "r" key. 06:51.180 --> 06:52.650 And then all the bricks reappear. 06:53.040 --> 06:58.200 I suppose I should really make the ball go back to the initial position, and the paddle, but that would 06:58.200 --> 06:59.960 require some changes to the entity. 07:00.330 --> 07:04.830 But if you want to do that, if you want to make the ball and the paddle go back to the initial positions 07:04.830 --> 07:08.310 when the user resets the game, then that would be a useful exercise. 07:09.080 --> 07:10.440 Okay, so that is it for this video. 07:10.470 --> 07:11.340 I will see you next time. 07:11.340 --> 07:13.230 But until then, keep coding.