firefox/toolkit/content/widgets/moz-button/moz-button.css

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

:host {
  display: inline-block;
  height: fit-content;
  width: fit-content;
}

button {
  appearance: none;
  background: transparent;
  border: none;
  /* HTML button gets `font: -moz-button` from UA styles,
   * but we want it to match the root font styling. */
  font: inherit;
  /* Overridden on button-background, but still need to unset to not get the
   * UA styles */
  color: inherit;
  width: 100%;

  &:focus-visible {
    outline: none;
  }

  padding-inline-start: var(--button-outer-padding-inline-start, var(--button-outer-padding-inline));
  padding-inline-end: var(--button-outer-padding-inline-end, var(--button-outer-padding-inline));
  padding-block-start: var(--button-outer-padding-block-start, var(--button-outer-padding-block));
  padding-block-end: var(--button-outer-padding-block-end, var(--button-outer-padding-block));
}

@media not ((prefers-contrast) or (forced-colors)) {
  button.badged::after {
    background-color: var(--button-attention-dot-color, var(--attention-dot-color));
  }
}

.button-background {
  box-sizing: border-box;
  min-height: var(--button-min-height);
  border: var(--button-border);
  border-radius: var(--button-border-radius);
  background-color: var(--button-background-color);
  color: var(--button-text-color);
  padding: var(--button-padding);
  font-weight: var(--button-font-weight);
  /* Ensure font-size isn't overridden by widget styling (e.g. in forms.css) */
  font-size: var(--button-font-size);
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;

  &[size=small] {
    min-height: var(--button-min-height-small);
    font-size: var(--button-font-size-small);
  }

  &.badged::after {
    content: "";
    position: absolute;
    height: 6px;
    width: 6px;
    inset-block-start: var(--space-xxsmall);
    inset-inline-end: var(--space-xxsmall);
    background-color: var(--attention-dot-color);
    border-radius: var(--border-radius-circle);
  }

  button:hover > & {
    background-color: var(--button-background-color-hover);
    border-color: var(--button-border-color-hover);
    color: var(--button-text-color-hover);
  }

  button:hover:active:not(:disabled) > & {
    background-color: var(--button-background-color-active);
    border-color: var(--button-border-color-active);
    color: var(--button-text-color-active);
  }

  button:disabled > & {
    background-color: var(--button-background-color-disabled);
    border-color: var(--button-border-color-disabled);
    color: var(--button-text-color-disabled);
    opacity: var(--button-opacity-disabled);
  }

  button:focus-visible > & {
    outline: var(--focus-outline);
    outline-offset: var(--focus-outline-offset);
  }

  &[type="primary"] {
    background-color: var(--button-background-color-primary);
    border-color: var(--button-border-color-primary);
    color: var(--button-text-color-primary);

    button:hover > & {
      background-color: var(--button-background-color-primary-hover);
      border-color: var(--button-border-color-primary-hover);
      color: var(--button-text-color-primary-hover);
    }

    button:hover:active:not(:disabled) > & {
      background-color: var(--button-background-color-primary-active);
      border-color: var(--button-border-color-primary-active);
      color: var(--button-text-color-primary-active);
    }

    button:disabled > & {
      background-color: var(--button-background-color-primary-disabled);
      border-color: var(--button-border-color-primary-disabled);
      color: var(--button-text-color-primary-disabled);
    }
  }

  &[type="destructive"] {
    background-color: var(--button-background-color-destructive);
    border-color: var(--button-border-color-destructive);
    color: var(--button-text-color-destructive);

    button:hover > & {
      background-color: var(--button-background-color-destructive-hover);
      border-color: var(--button-border-color-destructive-hover);
      color: var(--button-text-color-destructive-hover);
    }

    button:hover:active:not(:disabled) > & {
      background-color: var(--button-background-color-destructive-active);
      border-color: var(--button-border-color-destructive-active);
      color: var(--button-text-color-destructive-active);
    }

    button:disabled > & {
      background-color: var(--button-background-color-destructive-disabled);
      border-color: var(--button-border-color-destructive-disabled);
      color: var(--button-text-color-destructive-disabled);
    }
  }

  &[type~=ghost] {
    background-color: var(--button-background-color-ghost);
    border-color: var(--button-border-color-ghost);
    color: var(--button-text-color-ghost);

    button:hover > & {
      background-color: var(--button-background-color-ghost-hover);
      border-color: var(--button-border-color-ghost-hover);
      color: var(--button-text-color-ghost-hover);
    }

    button:hover:active:not(:disabled) > & {
      background-color: var(--button-background-color-ghost-active);
      border-color: var(--button-border-color-ghost-active);
      color: var(--button-text-color-ghost-active);
    }

    button:disabled > & {
      background-color: var(--button-background-color-ghost-disabled);
      border-color: var(--button-border-color-ghost-disabled);
      color: var(--button-text-color-ghost-disabled);
    }
  }

  &.labelled {
    gap: var(--space-small)
  }

  &[type~=icon]:not(.labelled) {
    background-size: var(--icon-size-default);
    background-position: center;
    background-repeat: no-repeat;
  }

  &[type~=icon]:not(.labelled),
  &:not(.labelled):has(img) {
    width: var(--button-size-icon);
    height: var(--button-size-icon);
    padding: var(--button-padding-icon);

    &[size=small] {
      width: var(--button-size-icon-small);
      height: var(--button-size-icon-small);
    }
  }

  img,
  &[type~=icon]:not(.labelled) {
    -moz-context-properties: fill, fill-opacity, stroke;
    fill: var(--button-icon-fill);
    stroke: var(--button-icon-stroke);
  }

  img {
    width: var(--icon-size-default);
    height: var(--icon-size-default);
    pointer-events: none;
  }
}