discourse/app/assets/stylesheets/common/components/buttons.scss

// --------------------------------------------------
// Buttons
// --------------------------------------------------

// Base
// --------------------------------------------------

.btn {
  display: inline-block;
  margin: 0;
  padding: 6px 12px;
  font-weight: 500;
  font-size: $font-0;
  line-height: $line-height-small;
  text-align: center;
  cursor: pointer;
  transition: all 0.25s;
  box-sizing: border-box;
  min-height: 30px;

  &:active,
  &.btn-active {
    text-shadow: none;
  }
  &[disabled],
  &.disabled {
    cursor: default;
    opacity: 0.4;
  }
  .fa {
    margin-right: 7px;
  }
  &.no-text {
    .fa {
      margin-right: 0;
    }
  }
}

.btn.hidden {
  display: none;
}

// Default button
// --------------------------------------------------

.btn {
  border: none;
  color: $primary;
  font-weight: normal;
  background: $primary-low;

  &[href] {
    color: $primary;
    min-height: unset; // ovverides button defaults
  }
  .discourse-no-touch & {
    // only allow hover on no-touch devices
    &:hover,
    &.btn-hover {
      background: $primary-medium;
      color: $secondary;
    }
  }
  &[disabled],
  &.disabled {
    background: $primary-low;
    &:hover {
      color: dark-light-choose($primary-low-mid, $secondary-high);
    }
    cursor: not-allowed;
  }

  .d-icon {
    opacity: 0.7;
    line-height: $line-height-medium; // Match button text line-height
  }
  &.btn-primary .d-icon {
    opacity: 1;
  }
}

// Primary button
// --------------------------------------------------

.btn-primary {
  border: none;
  font-weight: normal;
  color: $secondary;
  background: $tertiary;

  &[href] {
    color: $secondary;
  }
  .discourse-no-touch & {
    // only allow hover on no-touch devices
    &:hover,
    &.btn-hover {
      background: dark-light-choose(
        scale-color($tertiary, $lightness: -20%),
        scale-color($tertiary, $lightness: 20%)
      );
    }
  }
  &:active,
  &.btn-active {
    @include linear-gradient(
      scale-color($tertiary, $lightness: -20%),
      $tertiary
    );
  }
  &[disabled],
  &.disabled {
    background: $tertiary;
  }
}

// Danger button
// --------------------------------------------------

.btn-danger {
  color: $secondary;
  font-weight: normal;
  background: $danger;
  &[href] {
    color: $secondary;
  }
  .discourse-no-touch & {
    // only allow hover on no-touch devices
    &:hover,
    &.btn-hover {
      background: dark-light-choose(
        scale-color($danger, $lightness: -20%),
        scale-color($danger, $lightness: 20%)
      );
    }
  }
  &:active,
  &.btn-active {
    @include linear-gradient(scale-color($danger, $lightness: -20%), $danger);
  }
  &[disabled],
  &.disabled {
    background: $danger;
  }
}

// Social buttons
// --------------------------------------------------

.btn-social {
  color: #fff;
  &:hover {
    color: #fff;
  }
  &[href] {
    color: $secondary;
  }
  &:before {
    margin-right: 9px;
    font-family: FontAwesome;
    font-size: $font-0;
  }
  &.google,
  &.google_oauth2 {
    background: $google;
    color: #333;
    border: 1px solid $primary-low;
    display: flex;
    align-items: center;
    justify-content: center;
    &:before {
      content: "";
      display: inline-block;
      width: 15px;
      height: 15px;
      // Background image url needs to be encoded for IE11
      background-image: url("data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Axlink%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink%22%20viewBox%3D%220%200%2048%2048%22%3E%3Cdefs%3E%3Cpath%20id%3D%22a%22%20d%3D%22M44.5%2020H24v8.5h11.8C34.7%2033.9%2030.1%2037%2024%2037c-7.2%200-13-5.8-13-13s5.8-13%2013-13c3.1%200%205.9%201.1%208.1%202.9l6.4-6.4C34.6%204.1%2029.6%202%2024%202%2011.8%202%202%2011.8%202%2024s9.8%2022%2022%2022c11%200%2021-8%2021-22%200-1.3-.2-2.7-.5-4z%22%2F%3E%3C%2Fdefs%3E%3CclipPath%20id%3D%22b%22%3E%3Cuse%20xlink%3Ahref%3D%22%23a%22%20overflow%3D%22visible%22%2F%3E%3C%2FclipPath%3E%3Cpath%20clip-path%3D%22url(%23b)%22%20fill%3D%22%23FBBC05%22%20d%3D%22M0%2037V11l17%2013z%22%2F%3E%3Cpath%20clip-path%3D%22url(%23b)%22%20fill%3D%22%23EA4335%22%20d%3D%22M0%2011l17%2013%207-6.1L48%2014V0H0z%22%2F%3E%3Cpath%20clip-path%3D%22url(%23b)%22%20fill%3D%22%2334A853%22%20d%3D%22M0%2037l30-23%207.9%201L48%200v48H0z%22%2F%3E%3Cpath%20clip-path%3D%22url(%23b)%22%20fill%3D%22%234285F4%22%20d%3D%22M48%2048L17%2024l-4-3%2035-10z%22%2F%3E%3C%2Fsvg%3E");
      background-repeat: no-repeat;
      background-size: cover;
    }
  }
  .mobile-view & {
    // Special case because we're using SVG here
    &.google,
    &.google_oauth2 {
      &:before {
        width: 17px;
        height: 17px;
      }
    }
  }
  &.instagram {
    background: $instagram;
    &:before {
      content: $fa-var-instagram;
    }
  }
  &.facebook {
    background: $facebook;
    &:before {
      content: $fa-var-facebook;
    }
  }
  &.cas {
    background: $cas;
  }
  &.twitter {
    background: $twitter;
    &:before {
      content: $fa-var-twitter;
    }
  }
  &.yahoo {
    background: $yahoo;
    &:before {
      content: $fa-var-yahoo;
    }
  }
  &.github {
    background: $github;
    &:before {
      content: $fa-var-github;
    }
  }
}

// Button Sizes
// --------------------------------------------------

// Small

.btn-small {
  padding: 3px 6px;
  font-size: $font-down-1;
}

// Large

.btn-large {
  padding: 9px 18px;
  font-size: $font-up-1;
  line-height: $line-height-small;
}

.btn-flat {
  background: transparent;
  border: 0;
  outline: 0;
  line-height: $line-height-small;
  .d-icon {
    opacity: 0.7;
  }
}