OverlayScrollbars/packages/overlayscrollbars/src/styles/sizeobserver.scss

@use 'sass:math';

$inflate-margin: 133px;
$shrink-scale: 0.1;

.os-size-observer,
.os-size-observer-listener {
  direction: inherit;
  pointer-events: none;
  overflow: hidden;
  visibility: hidden;
  box-sizing: border-box;
}

.os-size-observer,
.os-size-observer-listener,
.os-size-observer-listener-item,
.os-size-observer-listener-item-final {
  writing-mode: horizontal-tb;
  position: absolute;
  left: 0;
  top: 0;
}

.os-size-observer {
  z-index: -1;
  contain: strict;
  display: flex;
  flex-direction: row;
  flex-wrap: nowrap;
  padding: inherit;
  border: inherit;
  box-sizing: inherit;
  margin: -$inflate-margin;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  transform: scale($shrink-scale);

  &::before {
    content: '';
    flex: none;
    box-sizing: inherit;
    padding: 10px;
    width: 10px;
    height: 10px;
  }
}

.os-size-observer-appear {
  // "forwards" is important for older browsers
  animation: os-size-observer-appear-animation 1ms forwards;
}

.os-size-observer-listener {
  box-sizing: border-box;
  position: relative;
  flex: auto;
  padding: inherit;
  border: inherit;
  margin: -$inflate-margin;
  transform: scale(
    math.div(1, $shrink-scale)
  ); // scale(calc(1 / #{$shrink-scale})) not supported in ie11

  &.ltr {
    margin-right: -$inflate-margin * 2;
    margin-left: 0;
  }
  &.rtl {
    margin-left: -$inflate-margin * 2;
    margin-right: 0;
  }

  &:empty::before {
    content: '';
    width: 100%;
    height: 100%;
  }

  &:empty::before,
  & > .os-size-observer-listener-item {
    display: block;
    position: relative;
    padding: inherit;
    border: inherit;
    box-sizing: content-box;
    flex: auto;
  }
}

.os-size-observer-listener-scroll {
  box-sizing: border-box;
  display: flex;
}

.os-size-observer-listener-item {
  right: 0;
  bottom: 0;
  overflow: hidden;
  direction: ltr;
  flex: none;
}

.os-size-observer-listener-item-final {
  transition: none;
}

// choose the most lightweight animatable css prop: https://csstriggers.com/
@keyframes os-size-observer-appear-animation {
  from {
    cursor: auto;
  }
  to {
    cursor: none;
  }
}