Bug 2096153

Cloning to focus on the Droid specific issue here. please ignore URW related description.

+++ This bug was initially created as a clone of Bug #2062386 +++

Description of problem:
Sometimes, when using a native font stack in CSS on a web page, fonts that are not in the font stack at all are substituted for the desired fonts.

This only seems to affect web pages viewed using:

- Fedora (not Ubuntu, Debian 11, or Manjaro)
- Firefox (not Chrome or Chromium)
- When using the RPM version or Mozilla's official build from their website (not the Flatpak)

Happens in the stable version of Firefox, Firefox Beta, and Firefox nightly.

Two substitutions I've identified so far:

- Droid Sans is substituted for Open Sans
- P052 is substituted for 'URW Palladio L' or Palatino

Substituting for Palatino may be less objectionable, since that's a generic choice, but URW Palladio L is rather specific and it's surprising to see the substitution. This also wouldn't be as objectionable if the font substitutions were better. Droid Sans doesn't look much like Open Sans at all, and P052 looks really ugly (it has unevenly sized letters). In Firefox Flatpak, it instead substitutes the better-looking 'TeX Gyre Pagella', and only does that for Palatino, not for 'URW Palladio L' (which was higher priority in my font stack). This is more desirable behavior.

The source of the problem seems to be that if you run the following command:

fc-match :family="Open Sans"

It returns Droid Sans.

Possibly related bugs:
https://bugzilla.redhat.com/show_bug.cgi?id=1820166
https://bugzilla.mozilla.org/show_bug.cgi?id=1406790

How reproducible:
Consistently

Steps to Reproduce:
1. Open a clean Fedora 35 install, and verify that Open Sans is not installed.
2. Create the following web page and view it in a browser:

```
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
  <style>
    h1,h2,h3,h4 {
      font-family: Open Sans, Fira Sans;
    }
  </style>
</head>
<body>
  <h1>Hello World</h1>
  <p>Lorem ipsum dolor sit amet.</p>
</body>
</html>
```

Alternately, view a real live (but more complex) website at https://www.maximumethics.dev/

Actual results:
Notice that the text on the webpage is displayed in Droid Sans, not Open Sans.

Expected results:
The webpage displays the next available font in the font stack, Fira Sans in this case, or the browser's default font if you don't have Fira Sans.

--- Additional comment from Akira TAGOH on 2022-03-30 09:26:08 UTC ---

Well, maybe good to file a separate bug to object each substitutions.

For Open Sans, google-droid-sans-fonts has the following config:
  <alias binding="same">
    <family>Open Sans</family>
    <accept>
      <family>Droid Sans</family>
    </accept>
  </alias>

This is the reason why you see that behavior.

For URW Palladio L, urw-base35-fonts-common has the following config:
  <alias binding="same">
    <family>URW Palladio L</family>
    <accept>
      <family>P052</family>
    </accept>
  </alias>

And finally for Palatino, it is in urw-base35-p052-fonts:
 <alias binding="same">
    <family>Palatino</family>
    <accept>
      <family>P052</family>
    </accept>
  </alias>

Although those urw config are coming from upstream. so if you have any objections for them, it would be good to talk with URW upstream.