Plywood: A New Cross-Platform Open Source C++ Framework

https://preshing.com/20200526/a-new-cross-platform-open-source-cpp-framework/

by petercooper • 6 years ago

196 71 6 years ago

preshing.com

anarchyrucks• 6 years ago

Title needs an edit to clarify what kind of framework this is.

choeger• 6 years ago

from the examples, I would say, the type that includes the kitchen sink.

alharith• 6 years ago

But my kitchen sink just has dishes in it.

chrisseaton2• 6 years ago

Framework... for what? Turns out it's a framework for writing games, graphics, sound, that kind of thing.

MaxBarraclough• 6 years ago

Apparently it includes a partial C++ parser too.

Zolomon• 6 years ago

From the article: "Please note that Plywood, by itself, is not a game engine! It’s a framework for building all kinds of software using C++."

chrisseaton2• 6 years ago

It seems pretty clearly focused on writing games and similar doesn’t it? Given those are all the examples.

eismcc• 6 years ago

Library from authors Arc80 game engine. Author appears to significant game engine experience:

I’ve worked in the game industry for 14 years. Until 2015, I worked as a Technical Architect at Ubisoft Montreal, on franchises such as Rainbow Six, Child of Light and Assassin’s Creed. Before that, I spent a few years developing desktop graphics software at Corel.

petey283• 6 years ago

Most open source C++ projects are libraries that are meant to be integrated into other applications. Plywood is the opposite of that: It gives you a workspace into which source code and libraries can be integrated. A single Plywood workspace can contain several applications – a webserver, a game engine, a command-line tool. Plywood simplifies the task of building and sharing code between them.

I think this works as a good overview.

badsectoracula3• 6 years ago

Well, that is implied by the title: "Plywood: A New [...] Framework". Frameworks are by definition about providing the core elements to build your stuff on top of them[0].

[0] https://en.wikipedia.org/wiki/Software_framework

craftinator• 6 years ago

It has been my experience that most software posted on HN has little description of what it does, and no description of why it exists. The parent comment was highlighting the excellently concise mission statement written on the first page. I wish every project would do as well.

wtracy3• 6 years ago

The word "framework" by itself provides no indication of how specialized the tool is, or what problem(s) it aims to solve.

The above description indicates that it is a very general-purpose framework (handling things as disparate as game engines and web servers) and that it aims to enable code reuse, not just eliminate boilerplate code.

ngold• 6 years ago

So unreal engine, blender and visual studio? All talking to each other?

e12e• 6 years ago

Actually, you could probably argue that Blender already is these four things (a framework, blender, unreal engine and visual studio (the latter two as part of the game engine(defunct) and editor for example)).

m0zg• 6 years ago

So basically sort of like a monorepo.

BruceEel3• 6 years ago

Runtime reflection is, in my opinion, the biggest missing feature in standard C++.

Opinions?

jfkebwjsbx3• 6 years ago

What is definitely missing is compile time reflection. I don’t think many devs care about the runtime one.

pjmlp5• 6 years ago

We can anyway generate the runtime one at compile time, that is how many Java and .NET compiler plugins and annotation processors work.

preshing5• 6 years ago

Perhaps, but it's easily overlooked because every project that needs runtime reflection badly enough has already rolled their own. (Some game engines have multiple reflection systems, eg. shader parameters vs. serialization.) This framework takes a particular approach and makes it an (almost) standalone component.

jcranmer3• 6 years ago

For a statically-compiled language, runtime reflection is probably a violation of the zero-cost overhead principle. There is a limited amount of reflection that can be done cheaply that has some value: getting the address of the vtable of an object [assuming it has one] for uniqueness, or getting function pointer identities for generic invokable objects.

Given compile-time reflection, providing standard library functionality for certain runtime reflection tasks (such as providing a list of field information for a struct/class/union, or listing function arguments) could be useful. On the other hand, it could end up being a locale-like scenario where it's either overkill or too weak for your use case, never in the middle.

jcelerier• 6 years ago

Yes (with large preference for compile-time reflection / metaclasses - runtime reflection can easily be derived from that) : http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p070...

pjmlp5• 6 years ago

It is a big pain when you need to implement stuff like serialization or data type mappers for stuff like RPC or database access.

However with template metaprogramming and constexpr if there is already quite something when can do into supporting it, today, specially with C++20.

Post C++20, there are ongoing plans to have support for static reflection at compile time, and metaclasses.

Microsoft demoed the current state of their VC++ prototype at Virtual C++2020 days.

"Dynamic Polymorphism with Metaclasses and Code Injection"

https://www.youtube.com/watch?v=drt3yXI-fqk

badsectoracula3• 6 years ago

Strictly speaking, you can do it without that stuff, here are some snippets of a test i was doing in Borland C++ Builder 1 (from 1996, that is pre-C++98) a few years ago [0] (not using any of BCB's C++ extensions) which end up with this [1] (it is a bunch of controls thrown in a form mainly to test stuff, but the interesting bit is the property editor at the right).

If you do not mind relying a bit too hard on the preprocessor you can also do it in plain C [2] (i mean, the C++ approach still relies on it a lot, but the C one goes all the way :-P).

A game engine (for a big published game, not my own stuff) i worked on at the past used this approach (the C++ one) heavily and i think it is also quite common in some frameworks.

Though personally outside of experimentation i just use Free Pascal which provides the functionality as a core feature of the language (and next version will allow attaching arbitrary attributes to properties, which addresses my "i'd like to have a description for this property for the editor without writing a GetPropertyDescription method" wish :-P).

[0] https://pastebin.com/eCYs1tv8

[1] https://i.imgur.com/Ry5114y.png

[2] https://pastebin.com/8udWrNcv

flumpcakes• 6 years ago

Sorry for the noob question: can you explain how it helps with serialization or database access?

I've read simliar statements before but I don't think I understand how it helps.

jcranmer3• 6 years ago

I've recently been toying with #[derive] macros in Rust.

I have to say that framing reflection in terms of deriving an implementation of an interface is pretty powerful. But C++ makes it harder to do this than Rust, because you need to mutate the class definition to insert these methods in C++, but the Rust definition happens outside of the class (as vtable pointers are not contained within the class but passed around separately).

kccqzy• 6 years ago

Not necessarily so. Consider std::hash, which is a template heavily specialized by many types. Then containers like std::unordered_set use these specializations. You can totally turn a Rust trait into a C++ templated struct, and then turn Rust impls into template specializations of that struct.

I have to say that framing reflection in terms of deriving an implementation of an interface is pretty powerful.

Just wait till you see Haskell's Generic. (Not to be confused with generics in other languages.) It turns out for most applications you don't even need to derive an implementation of an interface.

gpderetta3• 6 years ago

you do not need the vtable to be inside the object itself. For example c++ std::function act similarly to an rust impl trait. But the lack of static reflection (or equivalent builtin functionality [1]) means you have to build a dedicated class for each C++ concept (the equivalent of rust trait), although libraries can help.

[1] the currently non existing equivalent in C++ has been sometimes refererred as virtual concept. Once upon a time, in the 2.x era, g++ had an extension known as 'signature' which would do exactly that.

pierrebai• 6 years ago

And somewhat unfortunately, C++ has plan for a kind of reflection in the future [1]. But it's not here today. I'm wary of relying on a parser though: it could prove a real drag as C++ evolve and you need to keep the parser up to date.

[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p059...

billfruit• 6 years ago

Does it include UI components? Or is it designed to be used with third-party UI components like QT?

wtracy3• 6 years ago

No.

It looks to be focused on projects that do not use any UI toolkit at all. CLI applications and games, basically.

FlyingSnake• 6 years ago

Will it replace the now defunct Djinni framework from Dropbox?

wtracy3• 6 years ago

Plywood is C++ only, so no.

rambojazz• 6 years ago

I’m releasing part of that game engine as an open source framework

I'm curious what this means exactly. Does it mean that requires the non-open source part to function? Or is it a standalone part of the non-open source engine that can be used by other projects (like a library)?

preshing5• 6 years ago

It's the latter: A standalone framework that can be used by other projects. It's like a library (or suite of libraries) with separate modules for platform abstraction, containers, JSON, etc. A bit more "batteries included" than vanilla C++, and you only link with what you use. These modules are organized into a workspace that helps set up new build pipelines, to compensate for the lack of a standard build system in C++.

flohofwoe• 6 years ago

My guess would be it's the parts of the game that are generally useful and polished enough to be used as the base for other games (or non-game applications).

Games often have parts that don't quite belong to the engine layer, but also not strictly to this specific game. It might be small adhoc helper modules, glue code to other 3rd party libraries or similar random stuff.

hobo_mark3• 6 years ago

I see often, including in this case, that GitHub contains only a squashed version of the development history. Assuming that the developer keeps working on top of the original branch with full history, is there a way to keep a squashed and a not-squashed branch in sync automatically?

bluejekyll• 6 years ago

When you say “squashed” vs “not-squashed”, are you referring to the “squash” merge feature in Github?

If so, that turns a PR branch into a single commit onto the target branch (master). Unless the old branches are kept around, the unsquashed commits won’t be available.

hobo_mark3• 6 years ago

I'm referring to the squash feature of git rebase. The developer collapsed years of commits into one before pushing to GitHub, I am wondering if there is a way to keep working on top of the original history privately, and pushing to the "clean" history on GitHub, without having to cherry-pick all new commits for GitHub by hand.

Rexxar• 6 years ago

In this particular case it seems justified as the framework was part of a bigger project. So probably the majority of the commit history would not be relevant to the project in its current state.

morio• 6 years ago

Browsing over the code I'd say it's solid and seems to have been used in production. Just about the right amount of abstraction for practical use.

Some parts could be replaced by standard C++ library functionality by now. My biggest issue so far: Use of bare pointers, especially in parser code. This should not appear in new code written in 2020. I'm kind of baffled by that as he seems to use stuff like std::move.

This is no replacement for either Unreal or Unity for sure, it's pretty basic in functionality.

phaedrus• 6 years ago

I think "no bare pointers, ever" is overly dogmatic. Raw pointers still have a place, especially in game programming. The standard smart pointer types cover many common situations, but do not cover all situations (nor do I think were intended to).

h0l0cube2• 6 years ago

The standard smart pointer types cover many common situations, but do not cover all situations (nor do I think were intended to).

They also add a level of indirection, which can manifest as cache misses. If you're iterating through large numbers of objects, memory locality can be a huge gain.

jonnypotty3• 6 years ago

Yeah but I read a thing somewhere that it's bad so I'm gonna tell everyone not to do it cos I'm clever.

ebj73• 6 years ago

I think it's interesting to look at his code. I have not worked on games myself, but I've understood that most big game studios write their own versions of STL containers, in order to have close control over each and every CPU cycle spent, and in order not to get burnt by changes in the STL, or by slight, or not so slight, variations in performance between different implementations of the STL.

I see that he does the same, keeping his own lightweight string class implementation, for instance, and also his own lightweight smart pointer implementations (Owned and Borrowed). I suspect that he also uses bare pointers and new for similar reasons.

It would be interesting to know if he thinks it is necessary, or if he could have used std::string, std::unique_ptr and std::make_unique instead in this framework.

jonnypotty3• 6 years ago

How do you tell that code has been used in production by browsing it? Game programmers aren't scared of pointers really are they?

Also as stated its not a game engine so why would it be a replacement for unreal or unity?

andi9992• 6 years ago

It is not just open source, it is under MIT license... so now I am interested

andi9992• 6 years ago

Ok, I am curious about the downvotes What is wrong with my comment. Open source can mean a lot (e.g. gpl) some of which cannot be used for production (in my and some other ppls environment). This one can, which is great. Reading on mobile it took 2 minutes to find out. So I thought i spare other ppl the hassle to find out themselves. And yes I believe licensing matter, and open source is too general a term.

jonnypotty3• 6 years ago

You seemed to be suggesting the open source might have some not good things about it. You can't do that ;)

nightowl_games• 6 years ago

I usually wouldn't care about yet another c++ game framework, but this author's prototypes are so impressive and artistic that it makes me believe he's doing something more than just playing around with technology.

huxingyi• 6 years ago

This framework has the potential to become another Qt if UI is been added. The coding style and document[0] are solid and similar with Qt[1]. Giving the Qt is heading in an unpopular way[2], I am looking forward to this framework.

[0] https://plywood.arc80.com/docs/modules/runtime/api/string/St... [1] https://doc.qt.io/qt-5/qstring.html [2] https://www.qt.io/blog/qt-offering-changes-2020

Plywood: A New Cross-Platform Open Source C++ Framework

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