Ubuntu – Disable system style for Firefox form input elements

firefoxgtkthemes

I use a dark theme in Lubuntu called Dorian. I'm quite happy with it. However, Firefox seems to inherit certain system colors for its form input elements, making them very difficult to see.

For example:

Checkboxes example
Buttons example

If I change the foreground color, I should also change the background color of textboxes, which is fine now, but is light-on-dark.
Textbox example

I can imagine solving this in several ways:

  1. Add a custom style sheet for Firefox to reverse the changes. (I use
    Stylish, so it's trivial to implement. However, CSS with form
    elements seems tricky.)
  2. Modifications to Dorian (I think you
    can customize a GTK theme for particular programs.)
  3. Disable the Ubuntu-Firefox-modifications Firefox addon.
  4. Find a setting in Firefox to prevent loading of system colors for
    input elements.
  5. Install Dorian Theme for Firefox. (I'm reluctant to this, since
    Dorian isn't actively updated, and Firefox is constantly.)

Of course, I also welcome other solutions I haven't thought of.

Best Answer

The CSS-based solutions are tricky to get right, in my experience. The one in Michael's answer worked on some sites but not all.

In Firefox 60, there's an easier solution. Go to about:config and set the following string value: widget.content.gtk-theme-override = Adwaita:light

(You have to right-click and select New -> String. Searching for gtk-theme-override won't find anything because the setting isn't there by default.)

Credit to Martin Stránský: https://bugzilla.mozilla.org/show_bug.cgi?id=1283086#c7

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