Fixed font size in epub

[winstonma]

Environment

• Operating System: Ubuntu 24.04
• node --version: v20.17.0
• npm --version: 10.8.2
• yarn --version, if using Yarn:
• percollate --version: 4.2.3

Description

I first ran the following command to generate the epub file:

percollate epub https://stratechery.com/2024/enterprise-philosophy-and-the-first-wave-of-ai/ -o "Enterprise Philosophy and The First Wave of AI.epub"

Then open the generated epub in Foliate and KOReader. But when I tried to adjust the font size in both app didn't change the font size.

Upload the epub file for checking (I just convert the image in the epub file, other things untouched). Please rename the file into .epub extension and open with your favorite EPUB reader.

[winstonma]

Also wonder if it is possible that if the command didn't specify the output filename, percollate would use the title as the output filename?

[danburzo]

Thanks for reporting. This is the default CSS that ships with the EPUB, I don’t notice anything in there that could prevent the text from scaling in EPUB readers. In any case, you can either add to it with the --css option or replace it with the --style option. I would suggest trying to produce the EPUB without any styles by using:

touch empty-style.css && percollate epub --style empty-style.css https://stratechery.com/2024/enterprise-philosophy-and-the-first-wave-of-ai/ 

It would give us an idea if the issue is with the CSS or the XHTML markup.

Also wonder if it is possible that if the command didn't specify the output filename, percollate would use the title as the output filename?

It should use the simplified title (spaces replaced with dashes, etc.) as the output filename when using the percollate command on a single item.

[winstonma]

touch empty-style.css && percollate epub --style empty-style.css https://stratechery.com/2024/enterprise-philosophy-and-the-first-wave-of-ai/

Using the command provided I can adjust the font size. I guess it is caused by the CSS.

Then I tried to edit style.css in the epub, using Sigil. After the following line is removed then I can resize the font of the article in both epub reading app.

percollate/templates/default.css

Line 17 in e9992a7

font-size: 12pt;

It should use the simplified title (spaces replaced with dashes, etc.) as the output filename when using the percollate command on a single item.

Thanks

[danburzo]

Thanks for investigated! If that’s the case, this command should help producing EPUBs until the issue is resolved:

percollate epub --css "html { font-size: initial }" https://article

It remains to be investigated whether having a font-size on the html element in the default CSS is an EPUB antipattern on our side, or whether it makes sense to open issues with the reader apps mentioned.

[winstonma]

Thanks

I also checked the EPUB Spec. Here is my finding:

• Based on the font-size property, the px value is Absolute Lengths. I guess this is the reason why the font size is fixed. em value is Font-relative Lengths.
• Also any reason to avoid px measurements in epub? someone also pointed out the reader app would could not adjust the font with px value

Not sure if that help narrow down

[winstonma]

percollate/templates/default.css

Line 17 in e9992a7

font-size: 12pt;

@danburzo Just wonder if it is a good idea to replace px with em?