Text.Measure

Measuring the visible bounds of text is incredibly hard
and tons of material have been written about this.

In this module, we take a pragmatic approach that produces
reasonable results without having to load and parse font files.
The drawback of this: The steps described below have to be repeated
for every new font we'd like to support.

A detailed introduction to typography and how fonts are specified
can be found [here](https://learn.microsoft.com/en-us/typography/opentype/spec/otff).

In general, we need to know the height and width of a piece of printed text
to properly align it with the rest of the drawing.

Text height:
  there are different types of "height" when it comes to text, and I won't go
  into the details here. Suffice to say that we are interested in vertically aligning
  atom labels, charges, implicit hydrogen count and mass numbers in a
  way that feels natural. For this, wir are mostly interested in "capHeight" of
  a font: The height of capital letters (without descenders). This, together
  with the Em-square size can be read from font files.

Text width:
  While computing the height of a piece of text is non-trivial, computing its
  width is insane. Every glyph has its own specific width, sometimes depending
  on its neighbouring glyphs (see ligatures and kerning). Fortunately, there
  is a quite simple method to get good approximations without being overly
  complicated. It is described on [stackoverflow](https://stackoverflow.com/questions/16007743/roughly-approximate-the-width-of-a-string-of-text-in-python)
  We use Python (because it has support for almost everything) to parse
  the true type font file we are interested in and generate a dictionary
  of the glyphs and their widths we are interested in. Using this to compute
  the width of a piece of text at a given font size is efficient and simple
  but not perfectly exact because it ignores kerning. It also requires large
  dictionaries if we want to support lots of unicode characters.

Note: The Python script used to extract the glyph widths can be found in the
      `resources` directory.