It's Not Just Unicode, It's Hemi-Semi-Demicode!

Demicode is a Python command line tool to explore the current, broken state of fixed-width rendering for Unicode in terminals and code editors. However, because terminals support styling a program's output with ANSI escape sequences, they also are more amenable to helpful visualization than code editors.

• Fixed-Width Character Blots
• Features
• Installation
• Versions
• Etc

Fixed-Width Character Blots

Demicode's core functionality is the fixed-width character blot, which visualizes a single grapheme cluster's fixed-width rendering. Since the current state-of-the-art uses two fixed-width columns at most, each blot is one more column, that is, three columns wide. That extra padding makes glaringly obvious when theoretical and actual width diverge. For terminals, said padding comes in two forms, with the first using U+0020 space in a different color to highlight any overlap and the second using █ U+2588 full block to obstruct those same bits.

The following screenshot shows an example for demicode's output --with-curation when running in Terminal.app on macOS. Out of the nine terminals I have been testing—Alacritty, Hyper, iTerm2, Kitty, Rio, Terminal.app, Visual Studio Code's terminal, Warp, and wezTerm—I find Terminal.app's and iTerm2's handling of overly wide glyphs the least bad. However, even with demicode using ANSI escape codes to line up columns, Terminal.app still manages to distort the column grid, as the lines for the technologist, person: red hair, and rainbow flag emoji in the screenshot below illustrate. I haven't found an effective work-around, despite trying several alternatives such as rendering character information first and blots second.

Features

Demicode supports the following features:

• Display fixed-width character blots together with helpful metadata one grapheme per line.
• Or, display --in-grid/-g to fit many more graphemes into the same window, albeit without metadata.
• For code points that combine with variation selectors, automatically show the code point without and with applicable variation selectors.
• Optionally display blots --in-more-color/-c and --in-dark-mode/-d. The first option may be given twice for even more color. The second option usually is superfluous because demicode automatically detects dark mode. See screenshot below.
• Run --with-curation and --with-… other carefully selected groups of graphemes. Or provide your own graphemes as regular command line arguments. Both literal strings and Unicode's U+… notation are acceptable. Quote several U+… forms to group them into a grapheme.
• Automatically download necessary files from the Unicode Character Database (UCD) and Common Locale Data Repository (CLDR) and then cache them locally.
• Automatically detect the most recent version of the UCD and the CLDR. Since CLDR data serves one, non-normative purpose only, emoji sequence names, demicode always utilizes the latest version. But --ucd-version lets you pick older UCD versions at will.
• In interactive mode, page the output. Let user control whether to go backward or forward while also automatically adjusting to terminal window size.
• On Linux and macOS, page backward and forward with the left and right arrow keys. On other operating systems, use b or p followed by ‹return› to page backward; just ‹return› or alternatively f or n followed by ‹return› to page forward; and just ‹control-c› or alternatively q or x followed by ‹return› to terminate demicode. All of these, no ‹return› required, work on Linux and macOS, too. Plus ‹delete› or ‹shift-tab› to page backward; ‹space› or ‹tab› to page forward; and ‹escape› to terminate. So which triple is yours?
• In batch mode, i.e., with standard in or out redirected, emit all character blots at once and consecutively.

Installation

Demicode is written in Python and distributed through PyPI, the Python Packaging Index. Since it utilizes recent language and library features, it requires Python 3.11 or later. The best option for installing demicode is using pipx. If you haven't installed pipx yet, brew makes that easy on Linux or macOS:

% brew install pipx
==> Fetching pipx
==> Downloading https://ghcr.io/v2/homebrew/core/pipx/manifests/1.2.0
...
🍺  /usr/local/Cellar/pipx/1.2.0: 885 files, 11.2MB
==> Running `brew cleanup pipx`...
Disable this behavior by setting HOMEBREW_NO_INSTALL_CLEANUP.
Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
%

Once you have pipx installed, installing demicode is trivial:

% python --version
Python 3.11.1
% pipx install demicode
  installed package demicode 0.5.0, installed using Python 3.11.5
  These apps are now globally available
    - demicode
done! ✨ 🌟 ✨
% demicode --with-curation
...

The output of the last command should look something like the first screenshot.

Versions

• v1.4.0 (2024/08/23): Prepare for the release of Unicode 16.0
  • Demicode now works with "future" versions that already have UCD files on the web. Hence demicode --ucd-version 16.0.0 works today even though Unicode 15.1.0 still is the current version and demicode's default.
  • Demicode's code generation is now distangled from UCD parsing and its Unicode property definitions reflect the current pre-release data for 16.0.0.
  • Grapheme cluster breaking now supports the 15.0.0, 15.1.0, and pre-release 16.0.0 versions of the algorithm. It passes all official tests. The only change necessary was getting code generation to work for 16.0.0. The resulting tests passed without changes to implementation.
• v1.3.0 (2024/01/07):
  • Automate running demicode in popular terminals on macOS and collecting either performance data or screenshots.
  • Fix crash when mirror directory has not yet been created. Thanks to yohann84L for reporting this bug.
• v1.2.0 (2023/10/30):
  • Mirroring of UCD files has been refactored and now uses an explicit manifest for tracking locally available versions. --ucd-mirror-all causes demicode to eagerly download all files for all versions, enabling fully disconnected operation. --ucd-list-versions lists all versions contained in mirror directory.
  • With --inspect-latency/-T, demicode now measures page rendering latency. Initial results suggest that the nine measured terminals are reasonable fast rendering styled text, taking between 4–9 ms on a four-year-old macOS laptop. But when demicode also queries the terminal for the current column, the spread of average latencies explodes to 10–946 ms.
  • To better track provenance of experimental results, demicode gains the ability to determine terminal name and version—based on environment variables, ANSI escape codes, and, on macOS, bundle identifiers.
  • Demicode now uses GitHub actions for CI.
• v1.1.0 (2023/10/17):
  • Improve terminal intput/output, notably by --incrementally/-i displaying character blots, which is significantly slower but allows for measuring the size of blots.
  • Fix crashing bug in path handling for mirrored CLDR files.
  • Make internal handling of UCD data more uniform, with an eye towards evolving demicode's UCD abstractions into a more generally useful library.
  • Switch from mypy to pyright, address pyright's improved diagnostics, integrate type checking into runtest.py, and improve test script output.
• v1.0.0 (2023/09/19):
  • Support grapheme cluster segmentation according to Unicode 15.1 and 15.0.
  • Tabulate bit size of Unicode properties, alternative groups of required properties for --stats.
  • Update internal interface for UCD data to favor generic access to properties.
• v1.0.0b1 (2023/09/12):
  • In interactive mode, render every page from scratch, taking terminal size into account. This enables paging forward and backward. On Linux and macOS, use left and right arrow keys to control paging.
  • In batch mode, i.e., when standard input or output are redirected, emit all character blots without paging.
  • Test file loading and property look up for every supported UCD version to squash any remaining crashing bugs. Nonetheless, advise in tool help that default, i.e., latest version produces best results.
  • In preparation of Unicode 15.1, add support for the Canonical_Combining_Class, Indic_Syllabic_Category, and Script properties. Remove support for unused Dash, Noncharacter_Code_Point, Variation_Selector, and White_Space properties again.
  • Clean up UCD file loading. Eliminate most boilerplate and private helper functions in demicode.ucd.
  • Eliminate global instance of UnicodeCharacterDatabase. Leverage independent instance for collecting statistics, eliminating need for two tool runs to collect all data.
• v0.7.0 (2023/09/06) Clearly distinguish between user errors and unexpected exceptions; print traceback only for the latter. Modularize test script using unittest. In preparation of Unicode 15.1, specify which versions to use for code generation.
• v0.6.0 (2023/09/05) Fix handling of emoji data for early versions of Unicode. Suppress blot for unassigned code points or sequences that are more than one grapheme cluster; add explanatory note.
• v0.5.0 (2023/09/04) Optimize range-based Unicode data for space and bisection speed. Improve built-in selections of graphemes; notably, the Unicode version oracle now displays exactly one emoji per detectable Unicode version.
• v0.4.0 (2023/09/01) Fix bug in URL creation for UCD files and move local cache to the OS-specific application cache directory. Restructure and simplify code to compute width(), renamed from wcwidth() due to changes.
• v0.3.0 (2023/09/01) Add support for grapheme clusters in addition to individual code points; account for emoji when calculating width; expose binary emoji properties; log server accesses; add tests; and improve property count statistics.
• v0.2.0–0.2.3 (2023/08/13) First advertised release, with more robust UCD mirroring, more elaborate output, and support for dark mode. Alas, screenshot links and README still needed some TLC.
• v0.1.0 (2023/08/06) First, downlow release

Etc

The project name is a play on the name Unicode: Fixed-width rendering of Unicode can't get by with a single uni-column—from the Latin unus for one—but requires at the very least a demi-view—from the Latin dimidius for half via the French demi also for half. As so happens, hemi and semi mean half as well, tracing back to Greek and Latin origin, respectively.

Alas, the real question is whether hemisemidemi-anything is cumulative, i.e., ¹⁄₈, or just reinforcing, i.e., still ¹⁄₂.

I am working on a technical blog post to provide more on motivation, technical background, and first findings after blotting far too many Unicode code points. One unexpected outcome is a test that should identify the Unicode version supported by a terminal just by displaying a bunch of emoji. 😳

I 💖 Unicode!

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Demicode is © 2023–2024 Robert Grimm and has been released under the Apache 2.0 license.