# 2022

## A Guide to Running GUI Applications in a Docker Container

Containers are not usually associated with GUI applications, but there may be times when one might still want to run such a program inside a container, for example to isolate the application’s dependencies. Installing a GUI application in a container means that not only the application, but also all its specific dependencies are encapsulated inside the container (respectively, the container image), and can therefore reliably be removed from the system in a single step.

The primary challenge is to let a container communicate with the host’s display system, so that it can create GUI windows on the host. A GUI application will likely also need to share files with the host system, which in turn requires the appropriate user permissions.

## In Praise of Pic (and pikchr)

In praise of what? Pic? Pic? Pic, the old diagram generation “little language” and half brother of roff (or troff or groff), from the days when Unix was young? Yes, indeed, that pic.

## Running a GUI Application in a Docker Container: Users, Permissions, Dockerfile

In a previous post, I explored the possibilities of running a GUI application inside a Docker container. In the current post, I will continue where we left off before, adding some details to make the process more convenient.

## A Fix for Pysolfc on Linux Mint 21 Vanessa

There are problems playing the pysolfc solitaire game on the latest release of Linux Mint 21 (Vanessa).

The game requires the formatter module from the Python Standard Library, which had been deprecated since Python 3.4, and has been removed in Python 3.10.

An easy, but ad-hoc workaround goes as follows:

## Running a GUI Application in a Docker Container

Containers are not usually associated with GUI applications, but there may be times when one might still want to run such a program inside a container, for example to isolate the application’s dependencies. Installing a GUI application in a container means that not only the application, but also all its specific dependencies are encapsulated inside the container (respectively, the container image), and can therefore reliably be removed from the system in a single step.

## Using Xsession to Set an Environment Variable Without a Shell

The freedesktop project, arguably the most important Linux organization you’ve never heard of, has (among many other noble deeds) done an admirable job clearing up the mess of local cache and config files in one’s home directory. But how does one override their defaults, if this requires setting environment variables globally, for all processes, and outside an explicit shell environment?

## A Look at the HDF5 Format

I occasionally see references to the HDF5 file format, but I have never encountered it in the wild. But a recent project generated multiple data sets simultaneously, in addition to metadata. Was there a better way than maintaining a collection of flat files? This prompted me to look at HDF5.

## The Heilmeier Catechism

George H. Heilmeier, director of DARPA (the advanced-technology research agency of the US Defense Department) from 1975 to 1977, formulated a set of questions to help evaluate research proposals.

## A Strictly Geometrical Proof of the Altitude Theorem

The Altitude Theorem or Geometric Mean Theorem is a result from high-school geometry. In a right triangle, the altitude $h$ on the hypotenuse divides the hypotenuse into two segments, $p$ and $q$. The theorem now states that $h^2 = pq$ or, equivalently, $h = \sqrt{pq}$: the altitude equals the geometric mean of the segments of the hypotenuse.

The content of this theorem is a bit surprising, because the altitude and the hypotenuse segments seem geometrically somewhat “unrelated”: it’s not clear how one could (geometrically) be transformed into the other. And although the theorem can be proven in many different ways, many of the proofs are at least partially algebraic, and therefore do not provide an intuitive, geometric sense why it is true. But it turns out that a very elegant, strictly geometric proof of this proposition can be constructed.

## Two Further Hugo Gotchas

I just wasted one hour and five minutes, dealing with two of these opaque, unexpected, and almost undiagnosable showstopper roadblocks that Hugo will throw your way - much too often, in my opinion.