[master] add NOTICE for browser.display.use_document_fonts

[nodiscc]

Aside from the minor inconvenience of having all pages display with default Serif/Sans Serif fonts (you get used to it), browser.display.use_document_fonts = false breaks functionality on websites using icon fonts (such as font awesome) to display UI elements/buttons/symbols/...

This is one of the main complaints I've heard from user.js users IRL/online. I have disabled this myself. A a lot of websites make heavy use of icon fonts, sometimes there's an alt text or other indication that this or that is the button you are looking for, but most often not. As it's only used to prevent fingerprinting I suggest that it can be disabled in https://github.com/pyllyukko/user.js/tree/relaxed. Should I send another patch?

[Thorin-Oakenpants]

breaks functionality on websites using icon fonts

AFAIK, this does not block icon fonts / glyphs : which is gfx.downloadable_fonts.enabled. I have document_fonts set to 0 - thus limiting myself to the basic 3 sets. And yet I can still get awesome font. I actually block all these as well (via uBo using no-remote-fonts: * true and then I can whitelist the few sites where it's needed (most sites for me I can easily guess the function of the missing button/icon/font).

But as for a relaxed branch, for sure (up to you guys). I just don't agree with your argument as to why.

[nodiscc]

Strange, with gfx.downloadable_fonts.enabled = true but browser.display.use_document_fonts = 0 I still get broken icons on many sites (eg https://imgur.com/)

[Thorin-Oakenpants]

You must be blocking it via some other mechanism - maybe something in NS?

http://terrillthompson.com/tests/icomoon/ - this is a simple test page

I have

• fonts:browser.display.use_document_fonts = 0
• glyphs: gfx.downloadable_fonts.enabled = true
• uBo blocks all remote fonts: no-remote-fonts: * true

I see broken icons for the player controls. But if I add an exception to uBo: no-remote-fonts: terrillthompson.com false - and refresh, I can see the play, forward and stop buttons.

[nodiscc]

It is unclear what's going on:

• I can see the glyphs on the test page http://terrillthompson.com/tests/icomoon/ even with browser.display.use_document_fonts + gfx.downloadable_fonts.enabled = false, and uBlock font blocking ON.
• With browser.display.use_document_fonts = 0 some icons from the uBlock popup menu are not displayed correctly (lock and refresh icons, a dot character is displayed instead), and glyphs are broken on many sites (for example the ? icon top-right of this page). Setting browser.display.use_document_fonts = 1 fixes these problems.
• I can never see the top button glyphs on https://imgur.com/ regardless of my settings.

Do you have the same results?

[pyllyukko]

http://terrillthompson.com/tests/icomoon/ - this is a simple test page

I have:

• browser.display.use_document_fonts = 0
• gfx.downloadable_fonts.enabled = true
• uBlock "Block remote fonts" -> false

I get:

Imgur:

Imgur (with browser.display.use_document_fonts = 1:

[nodiscc]

@pyllyukko your results are the same as mine, so it's safe to assume that browser.display.use_document_fonts = 0 introduces some problems. Ok to merge? _{You can also thest against the top right icon on https://dxr.mozilla.org/mozilla-central/source/}

PS. do you also have this problem? (broken ublock icons)

[Thorin-Oakenpants]

@nodiscc What are your default fonts in Options>Content>Fonts&Colors>Advanced ? Do you have DejaVu Sans?

The reason I ask is that your icons are not "invalid". That is the padlock and power icons are showing, they are just using the wrong font. If they were invalid you would see those rectangular hex symbols.

I went to a lot of trouble to day to read up on all this. It took them over 2 years to work out how to apply the patch, so excuse my ignorant less technical answer.

If your user-defined set of fonts returns an invalid character, THEN it will allow the font (local or downloaded) - this has mostly to do with PUA.

give priority to the user's preferred fonts when the use_document_fonts option is off (0), but for characters not supported in the user's choice of font, use the page's specified fonts (whether local or downloaded or both) as usual, rather than going directly to system fallback fonts. This allows things like Github icons to continue working, as the PUA codepoints used should not be found in the user's pref fonts (normally), and so they'll fall back to the appropriate icon font from the page.

https://bugzilla.mozilla.org/show_bug.cgi?id=789788#c66

The default Sans font on most Linux systems (DejaVu Sans) has glyphs for many of the PUA code points. I noticed this on github which uses this heavily all over the site. By pure dumb luck pvponline.com works because it happens to pick a dead region in DejaVu Sans.

That's the uBo issue - the icon code points in your default user defined fonts ARE valid (for the padlock and power button) for your user-defined font (the same issue as above re DejaVu Sans using PUA codepoints itself with its own glyphs). The issue with hex icons being displayed is different - that's when the font is blocked, and you fall back to the invalid chars.

EDIT: The other issue with broken glyphs is that a lot of icon fonts don't map to PUAs, so the solution is not perfect

sites and fonts exist that misusing character codes as defined by Unicode, and the result is a lack of interoperability/compatibility

I hope this helps. You could try changing your default fonts in a test profile - I don't know what comes in debian, sorry. Do you have Arial - that's what windows uses for the sans.

[nodiscc]

What are your default fonts in Options>Content>Fonts&Colors>Advanced ? Do you have DejaVu Sans?

@Thorin-Oakenpants It was set to serif (default value)

changing it to Droid Sans, DejaVu Sans, DejaVu Serif... or the generic sans-serif font... fixed the uBlock incorrect icon problem as well as incorrect icons on https://dxr.mozilla.org/ http://fontawesome.io/. Thanks!! (Setting it to Arial however caused the problem to reappear).

I can never display icons properly on http://imgur.com/ regardless of my configuration. So at least this particular website problem is not linked to browser.display.use_document_fonts.

So my particular problem was caused by having browser.display.use_document_fonts = 0 and having a configured fallback font (serif) that used the same Private Use Area unicode range as the fonts used by these pages/uBlock menu to display icons.

As the problems seems to be very specific to Debian (maybe derivatives?) there is no good reason to change the setting for everyone (it will be very hard to find a common font working on all systems). I have set browser.display.use_document_fonts = 0 and font.name.serif.x-western = sans-serif in my own user.js to work around this. Closing :)

If the problem arises again we can point other users here.

[Thorin-Oakenpants]

Your welcome, thanks for listening. I guess a super easy explanation is (and I am not an expert)

1. Your User-Defined-Fonts [Serif?] has valid chars for a range of codepoints, hopefully not PUA ones
2. If a character is not defined in your user-defined-fonts, then it is considered invalid and treated as a glyph, hopefully these are PUA
3. Invalid chars trigger a "go get the font" response - if the font is not available (blocked) then it falls back to the invalid hex char symbol
4. It does not matter if a font is local, downloaded, or bundled with an extension
5. The pref isn't really "glyphs" but "invalid chars", it was just the simplest easiest approach to glyphs

In a perfect world, system/browser default fonts would not use PUA, and all glyphs would use PUA - but we know this is not the case, hence weird things happen