Bootstrap v4 media queries mixins converted to Less via less-plugin-sass2less

_breakpoints.less

// Breakpoint viewport sizes and media queries.
//
// Breakpoints are defined as a map of (name: minimum width), order from small to large:
//
//    (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px)
//
// The map defined in the `@grid-breakpoints` global variable is used as the `@breakpoints` argument by default.

// Name of the next breakpoint, or null for the last breakpoint.
//
//    >> breakpoint-next(sm)
//    md
//    >> breakpoint-next(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    md
//    >> breakpoint-next(sm, @breakpoint-names: (xs sm md lg xl))
//    md
.function-breakpoint-next(@name, @breakpoints: @grid-breakpoints, @breakpoint-names: map-keys(@breakpoints)) {
  @n: index(@breakpoint-names, @name);
  return: if(@n < length(@breakpoint-names), extract(@breakpoint-names, @n + 1), null);
}

// Minimum breakpoint width. Null for the smallest (first) breakpoint.
//
//    >> breakpoint-min(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    576px
.function-breakpoint-min(@name, @breakpoints: @grid-breakpoints) {
  @min: map-get(@breakpoints, @name);
  return: if(@min != 0, @min, null);
}

// Maximum breakpoint width. Null for the largest (last) breakpoint.
// The maximum value is calculated as the minimum of the next one less 0.1.
//
//    >> breakpoint-max(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    767px
.function-breakpoint-max(@name, @breakpoints: @grid-breakpoints) {
  @next: breakpoint-next(@name, @breakpoints);
  return: if(@next, breakpoint-min(@next, @breakpoints) - 1px, null);
}

// Returns a blank string if smallest breakpoint, otherwise returns the name with a dash infront.
// Useful for making responsive utilities.
//
//    >> breakpoint-infix(xs, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    ""  (Returns a blank string)
//    >> breakpoint-infix(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    "-sm"
.function-breakpoint-infix(@name, @breakpoints: @grid-breakpoints) {
  return: if(breakpoint-min(@name, @breakpoints) == null, "", "-@{name}");
}

// Media of at least the minimum breakpoint width. No query for the smallest breakpoint.
// Makes the @content apply to the given breakpoint and wider.
.media-breakpoint-up(@name, @breakpoints: @grid-breakpoints) {
  @min: breakpoint-min(@name, @breakpoints);
  & when (@min) {
    @media (min-width: @min) {
      @content;
    }
  }
& when not (@min) {
    @content;
  }
}

// Media of at most the maximum breakpoint width. No query for the largest breakpoint.
// Makes the @content apply to the given breakpoint and narrower.
.media-breakpoint-down(@name, @breakpoints: @grid-breakpoints) {
  @max: breakpoint-max(@name, @breakpoints);
  & when (@max) {
    @media (max-width: @max) {
      @content;
    }
  }
& when not (@max) {
    @content;
  }
}

// Media that spans multiple breakpoint widths.
// Makes the @content apply between the min and max breakpoints
.media-breakpoint-between(@lower, @upper, @breakpoints: @grid-breakpoints) {
  @min: breakpoint-max(@lower, @breakpoints);
  @max: breakpoint-max(@upper, @breakpoints);

  @media (min-width: @min) and (max-width: @max) {
    @content;
  }
}

// Media between the breakpoint's minimum and maximum widths.
// No minimum for the smallest breakpoint, and no maximum for the largest one.
// Makes the @content apply only to the given breakpoint, not viewports any wider or narrower.
.media-breakpoint-only(@name, @breakpoints: @grid-breakpoints) {
  @min: breakpoint-min(@name, @breakpoints);
  @max: breakpoint-max(@name, @breakpoints);

  & when (@min != null and @max != null) {
    @media (min-width: @min) and (max-width: @max) {
      @content;
    }
  }
& when not (@min != null and @max != null) if @max == null {
    .media-breakpoint-up(@name)
  } @else if @min == null {
    .media-breakpoint-down(@name)
  }
}