Source/WebCore/Modules/modern-media-controls/controls/compact-activity-indicator.css

/*
 * Copyright (C) 2018 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

button.compact-activity-indicator > picture {
    --width: 27px;

    /* There are 23 frames in the sprite. */
    --number-of-frames: 23;

    width: var(--width) !important;
    height: 29.5px !important;
    
    -webkit-mask-size: calc(var(--number-of-frames) * 100%) 100%;

    /* We apply two animations in sequence, first the intro which goes for 8 frames (0 - 7) and whichs
       runs once, then the loop which starts after the intro (using a delay) and runs infinitely. */
    --spins: compact-activity-indicator-intro frames(8) calc(8s / 15), compact-activity-indicator-loop frames(15) 1s calc(8s / 15) infinite;

    /* When we fade out. */
    --fades-out: compact-activity-indicator-fades-out 500ms;
}

button.compact-activity-indicator.spins > picture {
    animation: var(--spins);
}

button.compact-activity-indicator.spins.fades-out > picture {
    animation: var(--spins), var(--fades-out);
}

/* This is the intro animation that runs once only and goes through the first 8 frames of the sprite. */
@keyframes compact-activity-indicator-intro {
    from { -webkit-mask-position-x: 0 }
    to   { -webkit-mask-position-x: calc(-7 * var(--width)) }
}

/* This is the main animation that runs infinitely once the intro has completed and goes through the frames 9 through 23 of the sprite. */
@keyframes compact-activity-indicator-loop {
    from { -webkit-mask-position-x: calc(-8 * var(--width)) }
    to   { -webkit-mask-position-x: calc(-22 * var(--width)) }
}

@keyframes compact-activity-indicator-fades-out {
    from { opacity: 1 }
    to   { opacity: 0 }
}