upstream-zulip/web/styles/banners.css

.banner-wrapper {
    container: banner / inline-size;
}

.banner {
    box-sizing: border-box;
    display: grid;
    grid-template: var(--banner-grid-template-rows) / var(
            --banner-grid-template-columns
        );
    grid-template-areas: var(--banner-grid-template-areas);
    place-items: start;
    border: 1px solid;
    border-radius: 6px;
}

.banner-link {
    color: var(--color-text-link);
    text-decoration: none;
    text-decoration-color: var(--color-text-link-decoration);

    &:hover {
        color: var(--color-text-link-hover);
        text-decoration-color: var(--color-text-link-decoration-hover);
    }

    &:active {
        color: var(--color-text-link-active);
        text-decoration-color: currentcolor;
    }
}

.banner-content {
    grid-area: banner-content;
    display: flex;
    align-items: flex-start;
    flex-wrap: wrap;
    width: 100%;
    gap: 0 0.625em; /* 10px at 16px/1em */
}

.banner-label {
    /* We allow the banner label to grow and shrink, and set
       the flex basis to 60% of the query container's width.
       When the width of the banner label goes below this
       flex basis value, the banner action buttons are wrapped
       on to the next line.  */
    flex: 1 1 60cqw;
    /* The padding and line-height values for the banner label
       are identical to those of the action buttons', to match
       the height of both of these elements. This is required to
       align the banner children elements vertically, since we
       cannot use flexbox center alignment as we also need to
       account for the UI when the banner has a muli-line label.
    */
    padding: 0.25em 0; /* 4px at 16px/1em */
    line-height: 1.25; /* 20px at 16px/1em */
    text-align: start;
}

.banner-action-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5em; /* 8px at 16px/1em */
}

.banner-action-buttons:empty {
    display: none;
}

.banner-close-button {
    display: flex;
    grid-area: banner-close-button;
    padding: 0.6875em; /* 11px at 16px/1em */
    margin-left: 0.3125em; /* 5px at 16px/1em */

    &:focus-visible {
        outline-offset: -2px;
    }
}

.navbar-alert-banner {
    border: unset;
    border-bottom: 1px solid;
    border-radius: 0;
    place-items: start center;

    .banner-content {
        justify-content: center;
        flex-wrap: nowrap;
    }

    .banner-label {
        /* Reset to initial value */
        flex: 0 1 auto;
    }

    .banner-action-buttons {
        flex-wrap: nowrap;
    }
}

/* This utility class defines the structure of the medium-type
   navbar banners where the banner action buttons are placed
   below the banner label. This utility class is required since
   unlike the normal banners, the navbar counterparts have
   horizontally centered elements, wherein the flex-basis logic
   won't apply and we need to manually apply these properties
   based on the container size queries below. */
.navbar-alert-medium-banner {
    .banner-content {
        flex-direction: column;
        align-items: center;
    }

    .banner-label {
        text-align: center;
    }

    .banner-action-buttons {
        flex-wrap: wrap;
        justify-content: center;
    }
}

@container banner (width >= 44em) and (width < 63em) {
    .navbar-alert-banner[data-process="desktop-notifications"] {
        @extend .navbar-alert-medium-banner;
    }
}

@container banner (width < 44em) {
    .navbar-alert-banner {
        @extend .navbar-alert-medium-banner;
    }
}

@container banner (width < 25em) {
    .banner-content {
        flex-direction: column;
    }

    .banner-label {
        /* Reset to initial value */
        flex: 0 1 auto;
    }

    .banner-action-buttons {
        flex-direction: column;
        width: 100%;
    }
}

.banner-neutral {
    background-color: var(--color-background-neutral-banner);
    color: var(--color-text-neutral-banner);
    border-color: var(--color-border-neutral-banner);
}

.banner-brand {
    background-color: var(--color-background-brand-banner);
    color: var(--color-text-brand-banner);
    border-color: var(--color-border-brand-banner);
}

.banner-info {
    background-color: var(--color-background-info-banner);
    color: var(--color-text-info-banner);
    border-color: var(--color-border-info-banner);
}

.banner-success {
    background-color: var(--color-background-success-banner);
    color: var(--color-text-success-banner);
    border-color: var(--color-border-success-banner);
}

.banner-warning {
    background-color: var(--color-background-warning-banner);
    color: var(--color-text-warning-banner);
    border-color: var(--color-border-warning-banner);
}

.banner-danger {
    background-color: var(--color-background-danger-banner);
    color: var(--color-text-danger-banner);
    border-color: var(--color-border-danger-banner);
}

@keyframes popup-banner-fadeIn {
    0% {
        opacity: 0;
        transform: translateY(
            calc(-1 * var(--popup-banner-translate-y-distance))
        );
    }

    100% {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes popup-banner-fadeOut {
    0% {
        opacity: 1;
        transform: translateY(0);
    }

    100% {
        opacity: 0;
        transform: translateY(
            calc(-1 * var(--popup-banner-translate-y-distance))
        );
    }
}

.popup-banner-animations {
    animation-name: popup-banner-fadeIn;
    animation-duration: 0.3s;
    animation-fill-mode: forwards;

    &.fade-out {
        animation-name: popup-banner-fadeOut;
    }
}

.popup-banner {
    @extend .popup-banner-animations;

    width: 100%;
}