C++ & SFML // Simple Event Queue System with Timings

In a previous post (C++ & SFML // Simple Timer), I showed how you can create a simple timing system in SFML to display messages on the screen.

In this one I created a very simple "Messaging Dispatcher" that receives messages and displays them. I followed along with the Ring Buffer design by Robert Nystrom in "Game Programming Patterns" to create this little demonstration.

https://gameprogrammingpatterns.com/event-queue.html

Here, when E is released, it fires a message to the dispatcher. Each message has a random time to display between 1 and 4 seconds.

The code can be found here:

https://github.com/l-paz91/SFML/tree/main/Simple%20Message%20Dispatcher

There are a few caveats with this simple system:

• The queue is a fixed size so it will reject messages when full,
• The queue doesn't create an empty slot until the top message has finished displaying; if this was set to display for 5 minutes and all the other messages in the queue only want to display for 1 second, the queue will be held up waiting for the top message to finish.
• The dispatcher shouldn't really be handling the time.
• Everything is passed by value.

All these things are fixable with some brain power but getting the first implementation out of the way is key to figuring the fixes out. For the next step, it would make sense to create a class that handles the updating and displaying of the messages that it receives from the dispatcher. This way the dispatcher only has to worry about getting the messages to the right place each update.

As the class is static, you could have anything send messages to the dispatcher. it could also be modified to display sprites or play sounds (although I would define a set of events as enums instead of sending the sprite/sound itself).

The code may look a little odd in the dispatcher but the above link to the chapter in Robert's book explains what it's doing far better than I will be able to.

C++ & SFML // Simple Timer

So I'm currently working my way through making a clone of Space Invaders using SFML and I got to the point where I needed to do something after X amount of seconds. Usually I use FLTK and that would've been simple using it's callback system however SFML is event based and as such doesn't really supply a "timer system" out of the bag like fltk.

Therefore I googled and eventually found pieces of what I was looking for and managed to put this simple demonstration together for those who just want to figure out how to get seconds displayed on the screen. This is what the "tutorial" will give you:

The program does 2 things:

1) Display the number of seconds since the program started

2) Every second it chooses a random message (from 4) to display.

Very exciting. Let's begin.

Here is the full code:

https://github.com/l-paz91/SFML/tree/main/Simple%20Timer

Have a look, it's all in main for simplicity. 

There is a clock that is restarted at the beginning of the main loop and assigned to DeltaTime.

SFML have handily provided a way to get the DeltaTime as seconds. All you have to do then is += that to a variable defined outside the loop and you have your seconds since the program started.

For the text, I just made a variable that holds the max time we want to show the text for (maxDelay) and another variable to hold the elapsedTime. Getting the elapsed time is the same as getting the seconds above only when updating which message to display, there is a check to see if the elapsed time has gone above the max delay. If so, it changes the message and resets the elapsed time back to zero.

The concepts here can be used for many other things like displaying a sprite for a given amount of time as well creating more complicated things, like an event queue system that dispatches events based on the elapsed time (much more useful for larger projects than above).

Check out this post: C++ & SFML // Simple Event Queue System with Timings

for an example on how this can be put together.

LP's 12 Months of Games // Thomas Was Late [C++ & SFML]

Completed Via Tutorial

The 4th game taught in "Beginning C++ Games Programming" by John Horton and there are some more things I found strange:

• The engine class had 4 functions but only the constructor and 1 other function were defined in the cpp; the others were given their own cpp file....I have honestly never seen this. I can understand wanting to keep the code "manageable" but just collapse the function? There are class definitions in Unreal Engine thousands of lines long. If you're having trouble use Alt+G to directly go to the function or just Shift+F and search.
• The private const member variables in classes. If they're private, they can only be used within the class anyway so move them out of the class and into a private namespace in the cpp. Those variables are padding out the size of the class; all those bytes add up; especially if you are creating many instances of the class (as games often do). The const variables in the namespace will still be static but at least they're only being created once instead however many times you have created instances of the class they were in.
• There are also other implications on your classes to do with move/copy constuctors caused by const members.
• I've also seen some "Variable const x", especially in function argument parameters. Yes the compiler will accept it but it's good practice when declaring a const variable to have the const before the type. You may see const after a function declaration but that is promising that function doesn't modify any member variables inside the function. The const before the function return type specifies that return value cannot be modified.
• The given code doesn't actually work or compile. 
• Pointer pointers were introduced....in a book aimed at those who have never programmed before....I have no words. I know you can't create a 2d array without using values defined at compile time but that's because it's an array; just use a vector. This is not Beginning C Games Programming.
• The LevelManager should be holding an instance of the level vector array, this eliminates the need to new anything up. In the original code the pointer is returned to a different class. If it has to be a pointer at least ensure that whatever is holding the pointer frees it properly in the destructor (or better yet, use smart pointers).
• He includes headers in cpp's that have already been included in the matching header file.

I will admit, I did find this funny though:

Finished Result:

The tutorial spanned from chapters 14 - 18 and I stopped halfway through 17 because the game is severely broken:

I don't have time to get this working nor do I really care. There was something going on with the drawing and ordering of the sprites vs the background. Left and right were only for the green shape, A and D were for the red. It knew this when input was received yet for some reason it decided to apply the updates to some other sprite.

There's only space invaders left now which should be more fun; this one was a bit dry.

Code:

No code drop for this one. The authors repository for the book is here though:

https://github.com/PacktPublishing/Beginning-Cpp-Game-Programming-Second-Edition

LP's 12 Months of Games // Zombie Arena [C++ & SFML]

Completed Via Tutorial

Another tutorial finished from "Beginning C++ Games Programming" by John Horton. 

Please do not use this book to learn C++. Some things boggled the mind when following this tutorial like:

• variable + 0 (???)
• Creating a header, only for it to contain functions that are neither marked as extern or static or within a namespace. One function returns a raw pointer which is deleted somewhere else...
• #pragma once #ifndef #define combo (pick one. I like ifndef define because it's slightly more portable).
• Constant float to int/int to float with no casting or safety in place. For example, he'll choose to make an int variable but only use it with a float???
• Singleton classes. Don't get me wrong, I like singletons but this is not the best way to do it. The constructor should be private with copy and assignment deleted. There should instead be a static public function that declares and returns a reference to a static instance of the class to ensure it is destroyed properly.
• Member functions that don't modify are not marked as const nor is anything returned by const reference if it can be.
• Initialises class members in the constructor body instead of via initialiser list; this causes the member variable to be default initialised and then assigned again.
• Const member variables are initialised in the class body definition??? static const integral types yes, but otherwise for linking sake, it's best to initialise const members in the constructor.

One thing that really bugged me was all the event handling for input was done in main. I am a firm believer that objects should handle input events themselves. That said, the author promised at the end of this game that there will be better code handling in the next two projects so I'll hold further judgement until I finish the book.

Finished Result:

I was having fun with this one by the end. I quite like "Demakes" and I think this style would make a good Left 4 Dead demake. The hitboxes on the zombies are a bit janky and I'd like some background music but other than that I'm actually pretty happy with this one. 

It taught some solid SFML concepts that I can take away to personal projects. I'm itching now to start Tetris or my own version of pong to apply what I've learnt but I'm going to finish the book first as he mentioned using more advanced sound features, particle effects an split-screen in the upcoming chapters.

Code:

https://github.com/l-paz91/ZombieArena

There's a code drop for this one as I feel I changed it enough. Assets haven't been included for copyright reasons but here is the authors repository:
https://github.com/PacktPublishing/Beginning-Cpp-Game-Programming-Second-Edition

Chapter 22 // Exercise 7, 8, 9, 10, 11, 12, 13, 14 - Principles & Practice Using C++

The following exercises are once again all word-y ones. Some of this stuff is interesting to learn but I'm not writing any essays; I've done my time.

Chapter 22 // Exercise 7

We have "missed" many important languages. In particular, we essentially had to cut all developments after C++. Make a list of five modern languages that you think ought to be covered and write a page and a half (lol) - along the lines of the language sections in this chapter - on three of those.

So I guess the 4 "major" ones not covered would be; Python, Java, Javascript (and all it's fecking friends) and C#. I couldn't decide on the 5th but I guess Objective-C is pretty popular with those iOS programmers *shudder*.

Chapter 22 // Exercise 8, 9, 10

8) What is C++ used for and why? Write a 10- to 20-page report.

9) What is C used for and why? Write a 10- to 20-page report.

10) Pick a language (not C or C++) and write a 10- to 20-page description of its aims, origins and facilities.

In all seriousness; C++ is used by people who like programming and C is used by people who like torturing themselves; just use C++ (unless you're in embedded systems or something).

Java - Used by people for reasons unknown.

Chapter 22 // Exercise 11

Who currently holds the Lucasian Chair in Cambridge?

According to this source:

https://www.cam.ac.uk/news/michael-cates-elected-19th-lucasian-professor

It's Professor Michael Cates. I had no idea what the Lucasian Chair was before this; it was founded in 1663 and is one of the most prestigious academic postings in the world? Apparently, in Star Trek: TNG, Data is the current holder.

Chapter 22 // Exercise 12, 13, 14

12) Of the language designers mentioned in this chapter, who has a degree in mathematics, who does not?

13) Of the language designers mentioned in this chapter, who has a Ph.D? In which field? Who does not have a Ph.D?

14) Of the language designers mentioned in this chapter, who has received the Turing Award?

David Wheeler: Awarded the worlds first PhD in Computer Science in 1951 (very cool). 

Maurice Wilkes: PhD in Physics. Turing Award in 1967.

Stanley Gill: Mathematic degree (I think). Has PhD, not sure what in.

John Backus: Doesn't have a PhD, but has a bachelors and masters in mathematics. Turing Award in 1977.

Grace Murray Hopper: PhD and BSc in mathematics.

John McCarthy: PhD and BSc in mathematics. Turing Award in 1971.

Peter Naur: PhD in Philosophy. Turing Award in 2005.

Edsger Dijkstra: Has a PhD, doesn't say what in. I'm guessing Computer Science. Turing Award in 1972.

Niklaus Wirth: PhD in Electrical Engineering and Computer Science. Turing Award in 1984.

Anders Hejlsberg: Has no PhD but is the current lead dev for C# at Microsoft, found him on Teams. I always find it amusing that I can just send fellow Microsoft employees a DM. There is a part of me that just wants to send Satya Nadella "yo whattup??". But I like my job and don't want to lose it.

Kristen Nygaard: Msc in Mathematics. No PhD. Turing Award in 2001.

Ole-Johan Dahl: Unsure what education he has. Turing Award in 2001.

Dennis Ritchie: BSc in Physics and Applied Mathematics. PhD never officially received. Turing Award in 1983.

Ken Thompson: BSc in eletrical engineering and computer science. No PhD. Turing Award in 1983.

Doug McIlroy: BSc in Engineering Physics. PhD in Applied Mathematics. 

Brian Kernighan: BSc in Enegineering Physics. PhD in Electrical Engineering.

Martin Richards: BSc in Mathematics. PhD in Programming Language Design and Implementation.

Christopher Strachey: BSc in Natural Sciences Tripos.

Bjarne Stroustrup: MSc in Mathematics and Computer Science. PhD in Computer Science.

Alex Stepanov: Not a lot of info on this man.

LP's 12 Months of Games // Basic Pong [C++ & SFML]

Completed Via Tutorial 

This is the second project taught in "Beginning C++ Games Programming" by John Horton. The two chapters mainly focused on teaching classes and multiple files so the actual pong game was lacking.

Finished Result:

The "bat" is far to quick and moves off the sides. The ball scrapes along the bat or becomes stuck resulting in ridiculous scores and there's no states like a menu or game over. The basics are there though but I'll be improving this over the next week to add better collision, sounds and "english" (where the ball bounces off the bat with a certain velocity) as well as multiplayer.

I did finally learn how to use Github with Visual Studio though in this exercise. It's quite painless once you get used to it. I still prefer Perforce but for project sharing/collaboration, Github is the clear winner. That won't stop me from using Perforce though.

Code:

I modified the code in the book however it's mainly from the tutorial so I won't be posting. The next Pong game I will though.

LP's 12 Months of Games // Timber!! [C++ & SFML]

Completed via Tutorial

I started a book called "Beginning C++ Games Programming" by John Horton. It's aimed at those who've never used C++ before and teaches you how to make 5 games using SFML. I thought this would be the perfect introduction to SFML as I could ignore the bits about C++ and focus on the library. I was right.

I've just completed the first game; Timber!! I've used sfml once, many years ago to try and make pong. At the time I had been learning cpp for about 6 months and found it utterly confusing. This time, thanks to experience with FLTK and DirectX it was more "ah so this is how I get a sprite, this is how I draw it, this is how you poll events" etc.

I'd say this project would take a while for a complete C++ beginner but it was perfect to showcase on how to get to grips with sfml. I'm looking forward to the other 4 games and learning other sfml features.

As for the tutorial itself; I don't like the amount of hardcoded numbers and the fullscreen game (I prefer windowed when debugging). All the textures rely on the screen being a certain size as well but I can remedy that in my own projects. Also, the author is extremely bias to arrays and OOP with the code being very java-ry. I wouldn't recommend the book for first time C++ programmers as I feel it would teach some bad habits; make sure you use Principles & Practice for cpp.

Finished Result:

The assets were all provided by the book and I made a few adjustments to the code but other than that it's pretty much what the book gives.

I will say I'm extremely surprised by just how easy SFML actually is to use. I'm already formulating how to get a tetris game working or match 3 from just doing this simple game. So I guess it was a good tutorial overall.

Code:

A code drop will not be provided for this one as it's mainly from the book.

Challenge // LP's 12 Months of Games

So I'm an engine programmer...I like optimisation and tool creation. I'm at my happiest when making/doing things that makes gameplay programmers lives easier. That's mainly because I find the more gameplay aspects of games, well, tedious. 

The problem with this mindset though is that ultimately it makes me a terrible engine programmer. I can't make the best game engines if I don't know how games work. Like I know how a game works in the logical sense of how a computer understands it but I don't understand the nuances of level design, timing, AI, suspense, re-playability, state, message dispatching, entity systems, stat balancing...the list is endless. Hats off to gameplay programmers; you are wizards to me.

That's why, I'm designating the next 12 months as the year of games (it was originally supposed to be a new years resolution but I always fail at those so I'm starting early to try and trick myself). I'm going to attempt to make a game every month; no matter how shitty or simple; I want to make a game that has a start, a middle and an end. I've already got some ideas like:

• Slenderman clone in UE4 (I already half started this in 2020 and then got bored when I had to actually make the game)
• Tetris
• Solitaire
• Pong
• Space Invaders
• Doom
• Five Nights At Freddy's clone
• Super Mario World clone (not the entire game...jesus like 1 or 2 levels)
• Game Jam entry (probably Ludem Dare or Haunted PS1)
• Bejewelled clone
• Minecraft??

I want a good mix between styles, like shoot-em-up, platform, 3D, strategy, etc. Also I need them to be well documented so I don't get caught up in deciding what game mechanics to put in. I've noticed that if there is too much choice, I get overwhelmed and abandon the project. I think that's why I'm such a terrible gameplay programmer; the ability to do anything is too much and I just want very specific projects like; implement rotating images. Add animated gif support.

For the more classic games I'd like to just use C++ and DirectX or FLTK/SFML and then Unreal for the 3D games...I might even make slenderman in UE5 as I've not even opened that thing yet.

I'm saying 12 games because I feel that's more realistic, however if I feel like making something new every weekend I'm not going to stop myself. I'll update this post with games as I finish (or not finish them) and I'm excited to see how I've done by November 6th 2022.......

EDIT:

- Timber!! [C++ & SFML] (Nov 2021)

- Basic Pong [C++ & SFML] (Nov 2021)

- Zombie Arena [C++ & SFML] (Nov 2021)

- Thomas Was Late [C++ & SFML] (Nov 2021)

- Alien Invaders Basic [C++ & SFML] (Dec 2021)

- Alien Invaders Part 2 [C++ & SFML] (Jan 2022)

Chapter 22 // Exercise 6 - Principles & Practice Using C++

In this exercise I am using Visual Studio 2019 and a modified version of the std_lib_facilities header found here.

Chapter 22 // Exercise 6

For each language mentioned in this chapter, look at a popular textbook and see what is used as the first complete program. Write that program in all of the other languages. Warning: This could easily be a 100-program project.

Github: 

Due to the warning I decided to do something different as I don't have that much time (and I get bored easily). So instead, I went back to Chapter 3 (had a nostalgia trip) and decided to implement Exercise 2:

"Write a program in C++ that converts from miles to kilometres". 

This needs input, output and some mild arithmetic; perfect.

As for the languages; I spent a couple days doing the previous exercise and that was just Hello World programs so I chose 9 of the 20 languages I got running. 5 of them are languages I'm most likely to use (and most have VS support). The other 4 are "legacy" languages and completely outside my comfort zone.

1) C++

To start off here is the nice C++ console version:

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/cpp.cpp

2) C

This was trickier than I expected. Reading in from the console is not as nice as cin >>. Also I forgot that bool isn't a native type in C but was added in C99 via stdbool.h. I also spent a bit too much time faffing about with VS Code so I could build and run C code in that. Honestly doesn't feel worth it; will continue to use VS.

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/C.c

3) Visual Basic

This was a task. First I had to google how to make functions in VB, then how to make variables, then how to write if else and compare.....This language is strange. It uses = for equality AND assignment disgusting. I also hate how everything is english yet cobol....

Dim number As Integer = 0

is way more tedious than

int number = 0;

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/Visual%20Basic.vb

4) Python

So I learnt that Python doesn't support const values and I found this answer from Stackoverflow amusing:

"No there is not. You cannot declare a variable or value as constant in Python. Just don't change it"

Just don't change it. If only it were that simple. It's also weird not having a main and everything is out in the open with no brackets. I hate loosely typed languages and languages that insist on not instead of !. I think I'm just set in my ways at this point.

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/Python.py

5) Java

The only good thing about Java is that it uses semi-colons; praise be to semi-colons and brackets. The importing of everything and creating NEW of everything annoys me constantly though. When I'm making apps it just feels like every other line is 

SomeType = new SomeType(Stupid.Long.Type.Name);

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/Java.java

6) C#

This one took me about 5 minutes; I was surprised. It was like a Java version of Visual Basic....I guess that sums up C# in a nutshell.

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/C%23.cs

7) Pascal

This was truly the strangest so far...the function definition is so unnecessarily complicated. Also when multiplying a float (or real in Pascal) with another float, the point was always in the wrong place. I couldn't figure this out and frankly I don't care enough.

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/Pascal.pas

8) Fortran

This one took me a good 40 minutes and I initially almost gave up as I could not for the life of me figure out how to get functions to work. I now see where Visual Basic comes from. It wasn't completely awful once I'd figured out the function definition and logical operators/loops. I can understand why no one wants to learn it anymore though...

https://github.com/l-paz91/principles-practice/blob/master/Chapter%2022/Exercise%206/Fortran95.f95

9) Cobol

I'd honestly rather program in straight up assembly than this monstrosity. It's ironic that the syntax was chosen for "readability" but ultimately it makes it more confusing. Also, calling a variable a 'picture' because you give the computer a 'picture of the value' is stupid.

This one I had to skip because it was just too different. I think Cobol has user defined functions but I couldn't figure out how to make one. Variables need to be declared up front in a "data bank" of some sorts which is almost identical to ASM.

I feel sorry for anyone who was forced to use this language professionally.

10) Simula87

And I also gave up on this one because I just couldn't anymore. The further I stray from C++, the more I want to jump off a cliff.

// Conclusion

This exercise was amazing and I highly recommend that you choose an exercise from Chapter 3 and implement it in other languages. It made me realise that Visual Studio is God, semi-colons must always end an expression and loosely typed languages should have a word with themselves (pun intended).

Attempting the exercise in Pascal, Fortran, Cobol and Simula was the most "enlightening" though. Bjarne said he made C++ for a "more enjoyable" programming experience; he wasn't lying. Programming in C++ is pure joy, not just in comparison to "legacy" languages but new ones as well. I can safely say that there is no other language I would rather program in and it's not because C++ was my first language but I genuinely believe it's the easiest and most straight forward language of them all.

Learn C++ first.

A huge shout out to TutorialsPoint though for their excellent overview of all the ancient languages.