themes/docsy/assets/scss/support/_mixins.scss

// Some simple mixins.

@mixin bg-gradient-variant($parent, $color) {
    #{$parent} {
        background: $color linear-gradient(180deg, mix($body-bg, $color, 15%), $color) repeat-x !important;
    }
}

@mixin link-variant($parent, $color, $hover-color, $underline: false) {
    #{$parent} {
        color: $color;

        @if $underline {
            text-decoration: underline;
        }
    }
}

@mixin optional-at-root($sel) {
    @at-root #{if(not &, $sel, selector-append(&, $sel))} {
        @content;
    }
}

// placeholder allows styling of the placeholder used in search input etc.
@mixin placeholder {
    @include optional-at-root("::-webkit-input-placeholder") {
        @content;
    }


    @include optional-at-root(":-moz-placeholder") {
        @content;
    }


    @include optional-at-root("::-moz-placeholder") {
        @content;
    }


    @include optional-at-root(":-ms-input-placeholder") {
        @content;
    }
}