amis/scss/components/_button-group.scss

.#{$ns}ButtonGroup {
    position: relative;
    display: inline-flex;
    vertical-align: middle;

    > .#{$ns}Button {
        position: relative;
        flex: 0 1 auto;
    }

    @if $Button-borderWidth>0 {
        > .#{$ns}Button {
            @include hover {
                z-index: 1;
            }

            &:focus,
            &:active,
            &.active {
                z-index: 1;
            }
        }

        .#{$ns}Button + .#{$ns}Button,
        .#{$ns}Button + .#{$ns}ButtonGroup,
        .#{$ns}ButtonGroup + .#{$ns}Button,
        .#{$ns}ButtonGroup + .#{$ns}ButtonGroup {
            margin-left: -$Button-borderWidth;
        }
    } @else if
        (
            variable-exists("ButtonGroup-divider-width") and
                variable-exists("ButtonGroup-divider-color")
        )
    {
        background-color: $ButtonGroup-divider-color;

        > .#{$ns}Button + .#{$ns}Button {
            margin-left: $ButtonGroup-divider-width;
        }
    }
}

.#{$ns}ButtonToolbar {
    display: inline-flex;
    flex-wrap: wrap;
    justify-content: flex-start;
    align-items: center;

    .#{$ns}ButtonGroup {
        width: auto;
    }
}

.#{$ns}ButtonGroup {
    > .#{$ns}Button:first-child {
        margin-left: 0;
    }

    @if $Button-borderWidth>0 {
        > .#{$ns}Button:not(:last-child),
        > .#{$ns}ButtonGroup:not(:last-child) > .#{$ns}Button {
            border-top-right-radius: 0;
            border-bottom-right-radius: 0;
        }

        > .#{$ns}Button:not(:first-child),
        > .#{$ns}ButtonGroup:not(:first-child) > .#{$ns}Button {
            border-top-left-radius: 0;
            border-bottom-left-radius: 0;
        }
    }
}

.#{$ns}ButtonGroup--vertical {
    flex-direction: column;
    align-items: flex-start;
    justify-content: center;

    .#{$ns}Button,
    .#{$ns}ButtonGroup {
        width: 100%;
    }

    > .#{$ns}Button + .#{$ns}Button,
    > .#{$ns}Button + .#{$ns}ButtonGroup,
    > .#{$ns}ButtonGroup + .#{$ns}Button,
    > .#{$ns}ButtonGroup + .#{$ns}ButtonGroup {
        margin-top: -$Button-borderWidth;
        margin-left: 0;
    }

    > .#{$ns}Button:not(:last-child),
    > .#{$ns}ButtonGroup:not(:last-child) > .#{$ns}Button {
        border-bottom-left-radius: 0;
        border-bottom-right-radius: 0;
    }

    > .#{$ns}Button:not(:first-child),
    > .#{$ns}ButtonGroup:not(:first-child) > .btn {
        border-top-left-radius: 0;
        border-top-right-radius: 0;
    }
}

.#{$ns}ButtonGroupControl {
    display: inline-block;

    > .#{$ns}ButtonGroup--sm {
        margin-top: ($Form-input-height - $Button--sm-height) / 2;
    }

    > .#{$ns}ButtonGroup--xs {
        margin-top: ($Form-input-height - $Button--xs-height) / 2;
    }
}