zulip/web/styles/message_header.css

.message_header {
    vertical-align: middle;
    text-align: left;
    /* We can overflow-y if the font size gets big */
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    font-weight: 600;
    font-size: calc(15em / 14);
    line-height: 120%;
    position: relative;
    z-index: 0;
    background-color: var(--color-background);

    .message-header-contents {
        display: flex;
        align-items: center;
        justify-content: space-between;
        height: 28px;
        border: 1px solid var(--color-message-header-contents-border);
        border-bottom-color: var(--color-message-header-contents-border-bottom);
        border-radius: 7px 7px 0 0;
    }

    &.message_header_stream {
        /* Add box shadow to hide message border (first one) and message
           selected box shadow (second one) that are visible
           due to top borders of sticky recipient bar being curved. */
        box-shadow:
            -1px -5px 0 5px var(--color-background),
            1px -5px 0 0 var(--color-background);

        & a.message_label_clickable {
            color: var(--color-text-message-header);

            &:hover {
                color: var(--color-text-message-header) !important;
                text-decoration: none;
            }
        }

        .stream_topic_separator {
            line-height: 0;
            color: var(--color-message-header-icon-non-interactive);
            position: relative;
            top: 0.5px;
        }

        .stream_topic {
            display: inline-block;
            padding: 5px 6px 5px 2px;
            height: 17px;
            line-height: 17px;
            overflow: hidden;
            text-overflow: ellipsis;

            .message_label_clickable.narrows_by_topic {
                position: relative;
                top: 0.5px;
                overflow: hidden;
                text-overflow: ellipsis;
            }
        }

        .stream-privacy i {
            font-size: 15px;

            &.zulip-icon-globe,
            &.zulip-icon-hashtag {
                position: relative;
                top: -0.5px;
            }
        }
    }
}

.message_header_private_message {
    /* This is required for box-shadow appear above the message content. */
    z-index: 1;
    box-shadow:
        -1px -5px 0 5px var(--color-background),
        1px -5px 0 0 var(--color-background);
    background-color: var(--color-background);

    .message-header-contents {
        border-color: var(--color-private-message-header-border);
        border-bottom-color: var(--color-private-message-header-border-bottom);
        background-color: var(--color-background-private-message-header);
    }

    .message_label_clickable {
        display: flex;
        padding: 5px 0 5px 10px;
        font-weight: 600;
        height: 17px;
        line-height: 17px;
        color: var(--color-text-message-header);

        &:hover {
            color: var(--color-text-message-header) !important;
            text-decoration: none;
        }

        .private_message_header_icon {
            font-size: 15px;
            position: relative;
            top: 1px;
            width: 16px;
            height: 16px;
        }

        .private_message_header_name {
            overflow: hidden;
            text-overflow: ellipsis;
        }
    }
}

.message-feed {
    .recipient_row {
        /* Browser overlaps extra top padding of message header and
           the bottom border message if this margin is not present. */
        margin-bottom: 1px;
        border-radius: 5px;

        .message_row:last-of-type {
            border-radius: 0 0 7px 7px;
            border-bottom: 1px solid var(--color-message-list-border);

            .unread-marker-fill {
                border-radius: 0 0 0 7px;
                height: calc(100% - 2px);
            }

            .messagebox {
                border-radius: 0 0 7px 7px;
                padding-bottom: 4px;
            }
        }

        .message_header + .message_row {
            .messagebox {
                padding-top: 5px;
            }
        }
    }

    .message_header {
        position: sticky;
        top: var(--navbar-fixed-height);
        /* Needs to be higher than the z-index of date_row. */
        z-index: 4;
        box-shadow: 0 -1px 0 0 var(--color-background);

        .message-header-contents {
            margin-top: var(--header-padding-bottom);
        }

        &.sticky_header {
            box-shadow: var(--unread-marker-left) 0 0 0 var(--color-background);

            .recipient_row_date {
                display: block;
            }
        }
    }
}

.stream_label {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 5px 2px 5px 10px;
    height: 17px;
    line-height: 17px;
    position: relative;
    top: 0.5px;
    text-decoration: none;
    font-weight: 600;
    overflow: hidden;

    .recipient-row-stream-icon {
        font-size: 12px;
        line-height: 12px;
    }

    .zulip-icon.zulip-icon-globe {
        position: relative;
        top: 1px;
    }

    &:hover {
        text-decoration: none;
    }

    .stream-privacy {
        min-width: unset;
        width: 16px;
        height: 16px;

        .hashtag {
            padding-right: 0;

            &::after {
                font-size: 16px;
            }
        }
    }
}

.recipient_bar_controls {
    display: flex;
    flex-grow: 1;
    align-items: center;

    .external-topic-link {
        /* Vertically center the external link
           icon inside its containing anchor. */
        display: flex;
        align-items: center;
    }

    .change_visibility_policy {
        cursor: pointer;

        i {
            display: block;
        }
    }
}

.always_visible_topic_edit,
.on_hover_topic_read,
.stream_unmuted.on_hover_topic_unmute,
.stream_muted.on_hover_topic_mute {
    opacity: 0.7;

    &:hover {
        cursor: pointer;
        opacity: 1;
    }
}

.on_hover_topic_edit,
.on_hover_topic_unresolve,
.on_hover_topic_resolve,
.stream_unmuted.on_hover_topic_mute,
.stream_muted.on_hover_topic_unmute {
    opacity: 0.2;

    &:hover {
        cursor: pointer;
        opacity: 0.7;
    }
}

.recipient_row_date {
    color: var(--color-date);
    font-size: calc(12em / 14);
    padding: 0 10px;
    text-align: right;
    display: flex;
    align-items: center;
    font-style: normal;
    font-weight: 600;
    line-height: 17px; /* identical to box height, or 131% */
    letter-spacing: 0.04em;
    text-transform: uppercase;
    padding-top: 1px;

    /* Display the date when unchanged only for sticky headers. */
    &.recipient_row_date_unchanged {
        display: none;

        .sticky_header & {
            display: block;
        }
    }

    &.hide-date-separator-header {
        display: none;
    }
}

.recipient_bar_icon {
    color: var(--color-message-header-icon-interactive);
    opacity: 0.2;
    padding-left: 6px;
    padding-right: 6px;

    &:hover {
        opacity: 0.4 !important;
        cursor: pointer;
    }
}