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I hate: Programming Wayland applications (https://www.p4m.dev)

158 points by dwdz about 8 hours ago | 145 comments | View on ycombinator

diath about 7 hours ago |

Wayland was designed from the point of view of theoretical purists. It's basically "how would a display server work in an ideal world", unfortunately, that design turns out to also be impractical and straight up developer/user hostile.

m132 about 7 hours ago |

I agree that the lack of standardization around the "insecure" things is a bad idea. Insecure operations don't have to be available by default, or even universally supported, but a central registry of interfaces for e.g. retrieving all windows on a desktop would certainly help preventing fragmentation.

At the same time, most of this post really is just a rant essentially saying that a low-level library is so flexible that using it directly results in code so verbose it can hardly be read. Yes, that's how good low-level designs always are.

You can turn a generic portable asynchronous ANSI C interface into a simple, blocking and platform-specific one with an abstraction layer. You can integrate it with all sorts of existing event loops and programming frameworks. You can customize it all you like but using it directly in an application will cost you a lot of patience. At the same time, you can't go in the opposite direction; from a "simple" blocking black-box interface to something that can reasonably host a complex GUI toolkit. If you're after simplicity, go higher-level.

zabzonk about 7 hours ago |

Seems like complaining about how difficult to use Win32 and COM are. And they are if you use them directly! You don't do that - you use libraries that others have sweated over, as you did with raylib.

mizmar about 4 hours ago |

>and I still don't know what's the difference between them (wl_display_roundtrip() & wl_display_dispatch()) and in what order to call them on

I've been struggling with this initially as well, it's pretty poorly explained in docs. Short explanation:

Wayland-client library implements a queues over the socket. So to get it, you have to think about when is the socket read from and written to, and when are the queues pulled from or pushed to. There is always a default queue, but for example EGL+OpenGL creates it's own queue, which further makes it more confusing.

- `wl_display_dispatch_pending()` only pulls messages from default queue to callbacks

- `wl_display_dispatch()` also tries to do blocking read on the socket if no messages are in queue

- quite recently `wl_display_dispatch_queue_timeout()` was finally added, so you can do non-blocking read from the socket. earlier you had to hack the function yourself

- `wl_display_flush()` writes enqueued messages in queue to socket

- `wl_display_roundtrip()` sends a ping message and does blocking wait for response. the purpose is that you also send all enqueued requests and receive and process all responses. for example during init you call it to create registry and enumerate the objects, and you call it for second time to enumerate further protocol objects that got registered in registry callback, such as seat

- `eglSwapBuffers()` operates on its own queue, but reading from socket also enqueues to default queue, so you should always call `wl_display_dispatch_pending()` (on default queue) afterwards

There is also a way to get around being stuck in `eglSwapBuffers()` during window inhibition: disable the blocking with `eglSwapInterval(0)` and use `wl_surface_frame()` callback, and you get notified in callback when you can redraw and swap again. But you can't do blocking reads with `wl_display_dispatch()` anymore, have to use the timeout variant. After using it this way, you can also easily manage multiple vsynced windows independently on the same thread, and even use wayland socket in epoll event loop. None of this is documented of course.

The clipboard interface is definitely compromised a bit by being shared with drag-and-drop events, but it's not that complicated. Also there is a pitfall when you copy-paste to your own application and don't use any async event loop, you can get deadlocked by being expected to write and read on the same file descriptor at the same time.

firtoz about 7 hours ago |

The separate process for clipboard: yep... I'm having to do this to be able to get the cursor position myself in Wayland... (This is for a screen recorder app)

fonheponho about 6 hours ago |

I have no love lost for Wayland, but this:

> Make easy things easy. Make hard things doable.

is generally unachievable. Instead, pick one:

- easy things easy, hard things impossible

- easy things tedious, hard things possible

(Unless you want to maintain two sets of interfaces in parallel.)

javier2 about 7 hours ago |

I have used quite a bit of Gtk and QT, and have had to touch X11 or Wayland very little directly, EXCEPT for one case where I wanted to provide a global hotkey...

65a about 7 hours ago |

As a user, I like wayland. X11 was a security disaster. Wayland is much better about tearing.

What scares me though are all the responsibilities passed to compositors, because what ends up happening is that each compositor may reimplement what should be common functionality in annoying ways. This is especially true for input things, like key remapping. This ultimately fragments linux desktop experiences even harder than it was before.

motorpixel about 6 hours ago |

Writing 1300 lines of non-cross-platform windowing code sounds like masochism. GLFW is right there.

Avicebron about 7 hours ago |

I sidestep by using neovim as my environment for pretty much everything and you can bridge the SPICE virtio clipboard channel to Wayland. You can get clipboard sharing to work natively on wlroots compositors.

chromadon about 2 hours ago |

This has been my experience also.

The API feels like a hardcore OOP/C++ developer's first C interface.

vatsachak about 7 hours ago |

Callbacks are bad?

breve about 6 hours ago |

Probably best off using a UI library like Avalonia: https://avaloniaui.net/

It satisfies the requirement to "make easy things easy, make hard things doable" and it also gets you cross platform support.

bleudeballe about 6 hours ago |

Sure puts the Wayland in Weyland-Yutani

izacus about 7 hours ago |

The constant loud bile spewing over Wayland and systemd just won't stop here, will it?

It's getting a bit boring, especially since none really does more than complain.

DonHopkins about 7 hours ago |

The Decompositing Compositors, there's nothing much anyone can do.

https://www.youtube.com/watch?v=HMKaM3FdsgY

toinewx about 7 hours ago |

unreadable font

James_K about 6 hours ago |

Reminds me somewhat of Vulkan. I think the trend of making the actual specification of something lower level and less convenient is rather logical. Why burden implements with a load of convenience functions when that could be left up to libraries?

jmclnx about 7 hours ago |

I can say I hate all GUI programming! Luckily, all my professional programming deals with back-end processing, so I was able to avoid GUIs :)

So I feel your pain. I did hear programming for Wayland is harder than X11, but I never did either so I have no idea if that is true.

bbor about 6 hours ago |

Poor soul — they missed `wlroots` in their googling! You’re not supposed to be solving these issues yourself.