Mailspring/app/static/components/disclosure-triangle.less

@import "ui-variables";
@import "ui-mixins";

.disclosure-triangle {
  flex-shrink: 0;
  padding: 7px;
  padding-top: 10px;
  width: 20px;
  visibility: hidden;

  div {
    transform:rotate(90deg);
    transition: transform 90ms linear;
    border-top: 4px solid transparent;
    border-bottom: 4px solid transparent;
    border-left: 7px solid @text-color-very-subtle;
  }

  &.visible {
    visibility: visible;
  }
  &.collapsed {
    div {
      transform:rotate(0deg);
    }
  }
}