Firefox – How to make the Firefox’s message “… is now fullscreen” less obtrusive

firefoxfullscreenSecurityuser interface

Illustration of the problem

When a web page in Firefox switches to full-screen then even though the website is allowed to switch to full-screen automatically (Tools > Page Info > Permissions > Enter Fullscreen) Firefox show this annoying message for whole three seconds:
enter image description here

I know that I can disable the messages using this option full-screen-api.approval-required: false. Unfortunately this option disables the message also for unapproved websites and the approval confirmation "Remember this decision for …" does not ever show up:
enter image description here

The question

I do not want to undergo the security risk and disable the messages completely but the message from the first screenshot is too obtrusive for me. Is there any solution? For me ideal would be to show the message for a considerably shorter time like half a second. I also can accept not showing it at all but only for allowed websites.

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Best Answer

While this won't change the duration of the message, you can customize the message size, colors, border of the box and transparency with the UserChrome.css file. This will make the fonts smaller, for example:

#full-screen-warning-container {
    background-color:transparent !important;
    opacity: 0.4 !important;
}

#full-screen-warning-container[fade-warning-out] {
    transition-property: opacity !important;
    transition-duration: 1ms !important;
    opacity: 0.0 !important;
}

#full-screen-warning-message {
    padding: 15px !important;
}

.full-screen-description {
    font-size: 100% !important;
}

#full-screen-domain-text {
    font-size: 100% !important;font-weight:bold !important;
}

.full-screen-approval-button,#full-screen-remember-decision {
    font-size: 100% !important;
}

You can modify this code to position the box at an edge of the screen and make it appear only when you move your mouse over it.

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