[#]: collector: (lujun9972) [#]: translator: ( ) [#]: reviewer: ( ) [#]: publisher: ( ) [#]: url: ( ) [#]: subject: (Solutions to the tiny window manager challenge) [#]: via: (https://jvns.ca/blog/2019/12/03/solutions-to-the-tiny-window-manager-challenge/) [#]: author: (Julia Evans https://jvns.ca/) Solutions to the tiny window manager challenge ====== Hello! Last week I posted a small [programming challenge to write a tiny window manager that bounces windows around the screen][1]. ![][2] I’ll write a bit about my experience of solving the challenge, or you can just skip to the end to see the solutions. ### what’s a window manager? 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. 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) ``` 000:<:02d8: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=560 y=8} 000:<:02da: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=554 y=12} 000:<:02dc: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=548 y=16} 000:<:02de: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=542 y=20} 000:<:02e0: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=536 y=24} 000:<:02e2: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=530 y=28} 000:<:02e4: 20: Request(12): ConfigureWindow window=0x004158e5 values={x=524 y=32} ``` ### you can run programs without a window manager 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 ``` xterm -display :1 ``` 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! ### move a window with XMoveWindow The challenge was to make the window bounce around the screen. 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! Here’s what it looks like. What could be simpler, right? And it works just the way I’d expect! ``` XMoveWindow(display, windowID, x, y) ``` Except… ### problem: multiple `XMoveWindow`s don’t work 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. ``` XMoveWindow(display, windowID, 100, 200) usleep(2000 * 1000); # sleep for 2 seconds XMoveWindow(display, windowID, 300, 400) ``` 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). ### use xtrace to trace window manager events 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? ### XSync forces X to process events 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. ### solutions 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! * [Kacper Słomiński’s solution][6] (which uses `XQueryTree` to find the windows to bounce, which is nice) * [@whichxyj’s solution][7] * [Alexsey Lagoshin’s stressfulwm][8], which allows bouncing multiple windows: * [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. * one really nice one with fancier bouncing effects which I’ll post here later if the person sends me the source * [my solution][10] Here’s a gif of Alexsey’s solution. Apparently `XQuartz` on a Mac performs better than Xephyr! ![][11] And Aldrin’s solution, with a great use of `xeyes`: ![][12] ### thanks! 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] -------------------------------------------------------------------------------- via: https://jvns.ca/blog/2019/12/03/solutions-to-the-tiny-window-manager-challenge/ 作者：[Julia Evans][a] 选题：[lujun9972][b] 译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID) 本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 [a]: https://jvns.ca/ [b]: https://github.com/lujun9972 [1]: https://jvns.ca/blog/2019/11/25/challenge--make-a-bouncy-window-manager/ [2]: https://jvns.ca/images/bouncewm.gif [3]: http://incise.org/tinywm.html [4]: https://tronche.com/gui/x/xlib/window/XMoveWindow.html [5]: https://tronche.com/gui/x/xlib/event-handling/XSync.html [6]: https://gist.github.com/jvns/d5a0a4daf300f3dd7fa76d13b5aa2d53 [7]: https://github.com/whichxjy/bounce-wm/blob/master/bounce-wm.c [8]: https://github.com/ayzenquwe/stressfulwm [9]: https://github.com/aldrinmartoq/bouncywm-ruby [10]: https://gist.github.com/jvns/c7a297fc4e17e797fd7b76b68860e55c [11]: https://raw.githubusercontent.com/ayzenquwe/stressfulwm/d06531d286a5f00424bf12f7c77b18e11437ff20/gif/example.gif [12]: https://raw.githubusercontent.com/aldrinmartoq/bouncywm-ruby/f6d424b6107c1349c8ee338b6a46c7116c6d1ea7/demo/demo.gif [13]: https://jvns.ca/cdn-cgi/l/email-protection