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选题: 20191203 Solutions to the tiny window manager challenge
sources/tech/20191203 Solutions to the tiny window manager challenge.md
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[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Solutions to the tiny window manager challenge)
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[#]: via: (https://jvns.ca/blog/2019/12/03/solutions-to-the-tiny-window-manager-challenge/)
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[#]: author: (Julia Evans https://jvns.ca/)
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Solutions to the tiny window manager challenge
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======
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Hello! Last week I posted a small [programming challenge to write a tiny window manager that bounces windows around the screen][1].
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![][2]
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I’ll write a bit about my experience of solving the challenge, or you can just skip to the end to see the solutions.
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### what’s a window manager?
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An X window manager is a program that sends messages to the X server (which is in charge of drawing your windows) to tell it which windows to display and where.
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I found out that you can trace those events with `xtrace`. Here’s some example output from xtrace (for the toy window manager which is just moving windows about)
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```
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000:<:02d8: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=560 y=8}
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000:<:02da: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=554 y=12}
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000:<:02dc: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=548 y=16}
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000:<:02de: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=542 y=20}
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000:<:02e0: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=536 y=24}
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000:<:02e2: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=530 y=28}
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000:<:02e4: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=524 y=32}
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```
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### you can run programs without a window manager
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You technically don’t _need_ a window manager to run graphical programs – if you want to start an xterm in a window-manager-less X session you can just run
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```
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xterm -display :1
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```
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and it’ll start the xterm. Here’s a screenshot of an X session with no window manager open. I even have 2 windows open! (chrome and an xterm). It has some major usability problems, for example I don’t think you can resize or move or switch between windows. Which is where the window manager comes in!
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<https://jvns.ca/images/no-wm.png>
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### move a window with XMoveWindow
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The challenge was to make the window bounce around the screen.
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In the [tinywm source][3] they use `XMoveResizeWindow` to move and resize windows, but I found in the [docs][4] that there’s also a function called `XMoveWindow`. Perfect!
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Here’s what it looks like. What could be simpler, right? And it works just the way I’d expect!
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```
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XMoveWindow(display, windowID, x, y)
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```
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Except…
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### problem: multiple `XMoveWindow`s don’t work
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I ran into a problem (which I got stuck on for a couple of hours) where when I ran XMoveWindow twice, it would only apply the last move.
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```
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XMoveWindow(display, windowID, 100, 200)
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usleep(2000 * 1000); # sleep for 2 seconds
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XMoveWindow(display, windowID, 300, 400)
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```
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I’d expect this to move the window once, wait 2 seconds, and them move it again. But that was not what happened! Instead, it would pause for 2 seconds and then move the window once (to the second location).
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### use xtrace to trace window manager events
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I used xtrace to trace the events and found out that my `ConfigureWindow` events that `XMoveWindow` was sending were all being sent at the same time. So it seemed like X was batching the events. But why?
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### XSync forces X to process events
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I didn’t know why this was happening, but I emailed Julian about it and he pointed me in the direction of [XSync][5], which forces X to process all the events you’ve sent it. Sure enough, I used XSync and everything worked beautifully.
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### solutions
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I asked people to email me if they completed the challenge, and 4 people did! Here are their solutions. All the solutions I got implemented more features than I did, so I’d encourage you to look at all the solutions if you’re interested in how to solve this problem!
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* [Kacper Słomiński’s solution][6] (which uses `XQueryTree` to find the windows to bounce, which is nice)
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* [@whichxyj’s solution][7]
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* [Alexsey Lagoshin’s stressfulwm][8], which allows bouncing multiple windows:
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* [Aldrin Martoq Ahumada’s bouncywm-ruby][9], which is the only solution in a language other than C I got! It uses an Xlib Ruby library that looks pretty straightforward to use.
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* one really nice one with fancier bouncing effects which I’ll post here later if the person sends me the source
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* [my solution][10]
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Here’s a gif of Alexsey’s solution. Apparently `XQuartz` on a Mac performs better than Xephyr!
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![][11]
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And Aldrin’s solution, with a great use of `xeyes`:
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![][12]
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### thanks!
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Thanks to everyone who emailed me a solution, and if you write your own implementation I’d love to post it here too, especially if you write one that isn’t in C or Ruby! I’m [[email protected]][13]
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--------------------------------------------------------------------------------
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via: https://jvns.ca/blog/2019/12/03/solutions-to-the-tiny-window-manager-challenge/
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作者：[Julia Evans][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://jvns.ca/
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[b]: https://github.com/lujun9972
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[1]: https://jvns.ca/blog/2019/11/25/challenge--make-a-bouncy-window-manager/
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[2]: https://jvns.ca/images/bouncewm.gif
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[3]: http://incise.org/tinywm.html
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[4]: https://tronche.com/gui/x/xlib/window/XMoveWindow.html
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[5]: https://tronche.com/gui/x/xlib/event-handling/XSync.html
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[6]: https://gist.github.com/jvns/d5a0a4daf300f3dd7fa76d13b5aa2d53
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[7]: https://github.com/whichxjy/bounce-wm/blob/master/bounce-wm.c
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[8]: https://github.com/ayzenquwe/stressfulwm
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[9]: https://github.com/aldrinmartoq/bouncywm-ruby
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[10]: https://gist.github.com/jvns/c7a297fc4e17e797fd7b76b68860e55c
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[11]: https://raw.githubusercontent.com/ayzenquwe/stressfulwm/d06531d286a5f00424bf12f7c77b18e11437ff20/gif/example.gif
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[12]: https://raw.githubusercontent.com/aldrinmartoq/bouncywm-ruby/f6d424b6107c1349c8ee338b6a46c7116c6d1ea7/demo/demo.gif
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[13]: https://jvns.ca/cdn-cgi/l/email-protection
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