RetroTxt - Limitations and known issues
These are known unfixable problems due to restrictions with the browser or operating system.
- BBS era ANSI
- Microsoft Windows line artefacts
- MIME sniffing
- Unsupported text formats
- Missing or invalid characters
- Fonts and styling accuracy
BBS era ANSI
A lot of Bulletin Board System era ANSI art that relied on an 80x25 fixed terminal with cursor positioning to create motion and animations do not convert using RetroTxt.
Fixing this would require a considerable amount of programming work for little reward as it would be a massive hit to browser performance and most larger and complicated ANSI would probably never render as the browser would flag the tab as unresponsive.
Microsoft Windows line artefacts
Microsoft Windows applies font hinting that causes line artefacts
████ with sequences of block and other elements.
Browser MIME sniffing will often override RetroTxt, forcing text files to download rather than display in a tab.
- Firefox will usually produce incorrect MIME sniffing results with the
- Chromium-based browsers can produce incorrect MIME sniffing results with the
Unsupported text formats
Due to limitations with the current Unicode specification Atari ATASCII and Commodore PETSCII texts are not supported.
Binary formats such as .xbin and .bin are not supported as browsers refuse to render unknown file data in a browser page.
Missing or invalid characters
The following five characters, when used by text encoded in CP-437 will not display correctly in a web browser.
ü ì Å É ¥
One of the many issues with legacy 8-bit character encodings is that not all code pages use every available character. So while the original IBM CP-437 used by many ANSI art pieces has a full set of 256 characters, the legacy Windows CP-1252 used by all modern browsers has five undefined characters that they will ignore.
For example, fünf German for five, is a legitimate word in CP-437/OEM-US but breaks in Windows CP-1252.
Fonts and styling accuracy
The extension uses TrueType fonts which are affected by the operating system font hinting; ClearType on Windows, Quartz in macOS and FreeType on Linux. Oliver Schmidhauser has a useful summary of the issue.
Some fonts are for 40 columns (characters per line of text), but the extension doesn't enforce that limitation.
The browser and the operating system can make modifications the font width, height, and space for either accessibility or due to user applied themes.