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

.os-environment {
  --os-custom-prop: -1;
  position: fixed;
  opacity: 0;
  visibility: hidden;
  overflow: scroll;
  height: 200px;
  width: 200px;
  z-index: var(--os-custom-prop);

  div {
    width: 200%;
    height: 200%;
    margin: 10px 0;
  }

  &.os-environment-flexbox-glue {
    display: flex;
    flex-direction: row;
    flex-wrap: nowrap;
    height: auto;
    width: auto;
    min-height: 200px;
    min-width: 200px;

    div {
      flex: auto;
      width: auto;
      height: auto;
      max-height: 100%;
      max-width: 100%;
      margin: 0;
    }
  }

  &.os-environment-flexbox-glue-max {
    max-height: 200px;

    div {
      overflow: visible;

      &::before {
        content: '';
        display: block;
        height: 999px;
        width: 999px;
      }
    }
  }
}

.os-environment,
.os-viewport {
  -ms-overflow-style: scrollbar !important;
}
[data-overlayscrollbars=''],
[data-overlayscrollbars~='scrollbarHidden'],
html.os-viewport-scrollbar-hidden,
.os-viewport-scrollbar-hidden.os-environment,
.os-viewport-scrollbar-hidden.os-viewport {
  scrollbar-width: none !important;
}
[data-overlayscrollbars='']::-webkit-scrollbar,
[data-overlayscrollbars='']::-webkit-scrollbar-corner,
[data-overlayscrollbars~='scrollbarHidden']::-webkit-scrollbar,
[data-overlayscrollbars~='scrollbarHidden']::-webkit-scrollbar-corner,
html.os-viewport-scrollbar-hidden::-webkit-scrollbar,
html.os-viewport-scrollbar-hidden::-webkit-scrollbar-corner,
.os-viewport-scrollbar-hidden.os-environment::-webkit-scrollbar,
.os-viewport-scrollbar-hidden.os-environment::-webkit-scrollbar-corner,
.os-viewport-scrollbar-hidden.os-viewport::-webkit-scrollbar,
.os-viewport-scrollbar-hidden.os-viewport::-webkit-scrollbar-corner {
  display: none !important;
  width: 0px !important;
  height: 0px !important;
  visibility: hidden !important;
  background: transparent !important;
}

html.os-viewport-scrollbar-hidden,
html.os-viewport-scrollbar-hidden > body[data-overlayscrollbars] {
  box-sizing: border-box;
  margin: 0;
  width: 100%;
  height: 100%;
}

[data-overlayscrollbars~='host'],
.os-padding {
  position: relative;
}

[data-overlayscrollbars~='host'],
.os-padding {
  display: flex;
  flex-direction: row !important;
  flex-wrap: nowrap !important;
}

[data-overlayscrollbars~='grid'],
[data-overlayscrollbars~='grid'] .os-padding {
  display: grid;
  grid-template: 1fr / 1fr;
}

[data-overlayscrollbars~='grid'] > .os-padding,
[data-overlayscrollbars~='grid'] > .os-viewport,
[data-overlayscrollbars~='grid'] > .os-padding > .os-viewport {
  height: auto !important;
  width: auto !important;
}

.os-padding,
.os-viewport {
  box-sizing: inherit;
  position: relative;
  flex: auto !important;
  height: auto;
  width: 100%;
  padding: 0;
  margin: 0;
  border: none;
  z-index: 0;
}

.os-viewport {
  --os-vaw: 0;
  --os-vah: 0;

  &.os-viewport-arrange::before {
    content: '';
    position: absolute;
    pointer-events: none;
    z-index: -1;
    min-width: 1px;
    min-height: 1px;
    width: var(--os-vaw);
    height: var(--os-vah);
  }
}

[data-overlayscrollbars~='host'],
[data-overlayscrollbars~='viewport'] {
  overflow: hidden !important;
}
[data-overlayscrollbars~='overflowVisible'] {
  overflow: visible !important;
}
[data-overlayscrollbars-overflow-x='hidden'] {
  overflow-x: hidden !important;
}
[data-overlayscrollbars-overflow-x='scroll'] {
  overflow-x: scroll !important;
}
[data-overlayscrollbars-overflow-x='hidden'] {
  overflow-y: hidden !important;
}
[data-overlayscrollbars-overflow-y='scroll'] {
  overflow-y: scroll !important;
}

.os-padding,
.os-viewport {
  overflow: hidden;
}

.os-overflow-visible {
  overflow: visible;
}

.os-content {
  box-sizing: inherit;
}