杂记 | Misc Notes

1. fontregister: Windows 下没有管理员权限时安装字体的小工具
2. 在Windows下Putty用Linux字体时可能需要选上Cleartype选项
3. x11vnc: 可以在终端开一个vnc server连接到一个已有的X会话上去
4. pomodoro: 工作25分钟，休息5分钟。一个有趣的工作模式
5. network-manager的共享网络模式(shared to other computers)似乎变的好用了（以前我这完全不能用)
6. Firefox添加书签时没有“在边栏显示”的选项，但是去书签管理看属性还是有的。

1. fontregister: a tool that allows you to register new fonts in Windows without admin privilege.
2. In putty on Windows, you may need to choose the "Cleartype" option when using Linux fonts
3. x11vnc: to create a vnc server that connects to a existing X session
4. pomodoro: work for 25 minutes, then rest for 5 minutes. A good way of time managing.
5. The "shared to other computers" mode in network-manager works well now.
6. In recent Firefox, there's no "load this bookmark in the sidebar" option when you add a new bookmark. However you can still find it, by checking the properties of an existing bookmark in the bookmark manager.

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Determine Perspective Lines With Off-page Vanishing Point

In perspective drawing, a vanishing point represents a group of parallel lines, in other words, a direction. For any point on the paper, if we want a line towards the same direction (in the 3d space), we simply draw a line through it and the vanishing point. But sometimes the vanishing point is too far away, such that it is outside the paper/canvas. In this example, we have a point P and two perspective lines L1 and L2. The vanishing point VP is naturally the intersection of L1 and L2. The task is to draw a line through P and VP, without having VP on the paper. I am aware of a few traditional solutions: 1. Use extra pieces of paper such that we can extend L1 and L2 until we see VP. 2. Draw everything in a smaller scale, such that we can see both P and VP on the paper. Draw the line and scale everything back. 3. Draw a perspective grid using the Brewer Method. #1 and #2 might be quite practical. #3 may not guarantee a solution, unless we can measure distances/p...

Chasing an IO Phantom

My home server has been weird since months ago, it just becomes unresponsive occassionally. It is annoying but it happens only rarely, so normally I'd just wait or reboot it. But weeks ago I decided to get to the bottom of it. What's Wrong My system set up is: Root: SSD, LUKS + LVM + Ext4 Data: HDD, LUKS + ZFS 16GB RAM + 1GB swap Rootless dockerd The system may become unresponsive, when the IO on HDD is persistantly high for a while. Also: Often kswapd0 has high CPU High IO on root fs (SSD) From dockerd and some containers RAM usage is high, swap usage is low It is very strange that IO on HDD can affect SSD. Note that when this happens, even stopping the IO on HDD does not always help. Usually restarting dockerd does not help, but rebooting helps. Investigation: Swap An obvious potential root cause is the swap. High CPU on kswapd0 usually means the free memory is low and the kernel is busy exchanging data between disk and swap. However, I tried the following steps, none of the...

Moving Items Along Bezier Curves with CSS Animation (Part 2: Time Warp)

This is a follow-up of my earlier article. I realized that there is another way of achieving the same effect. This article has lots of nice examples and explanations, the basic idea is to make very simple @keyframe rules, usually just a linear movement, then use timing function to distort the time, such that the motion path becomes the desired curve. I'd like to call it the "time warp" hack. Demo See the Pen Interactive cubic Bezier curve + CSS animation by Lu Wang ( @coolwanglu ) on CodePen . How does it work? Recall that a cubic Bezier curve is defined by this formula :

B (t) = (1 - t)^{3} P_{0} + 3 (1 - t)^{2} t P_{1} + 3 (1 - t) t^{2} P_{2} + t^{3} P_{3}, 0 \leq t \leq 1.

In the 2D case,

B (t)

has two coordinates,

x (t)

and

y (t)

. Define

x_{i}

to the be x coordinate of

P_{i}

, then we have:

x (t) = (1 - t)^{3} x_{0} + 3 (1 - t)^{2} t x_{1} + 3 (1 - t) t^{2} x_{2} + t^{3} x_{3}, 0 \leq t \leq 1.

So, for our animated element, we want to make sure that the x coordiante (i.e. the "left" CSS property) is \(...

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