dots/usr/share/themes/Dracula/gtk-3.20/widgets/_buttons.scss

/***********
 * Buttons *
 ***********/
// stuff for .needs-attention
$_dot_color: if($variant=='light', $selected_bg_color,
                                   lighten($selected_bg_color,15%));
@keyframes needs_attention {
  from {
    background-image: -gtk-gradient(radial,
                                    center center, 0,
                                    center center, 0.01,
                                    to($_dot_color),
                                    to(transparent));
  }

  to {
    background-image: -gtk-gradient(radial,
                                    center center, 0,
                                    center center, 0.5,
                                    to($selected_bg_color),
                                    to(transparent));
  }
}

%button,
button {
  @at-root %button_basic, & {

    min-height: 24px;
    min-width: 16px;
    padding: 4px 8px;
    border: none;
    border-radius: 3px;
    transition: $button_transition;

    @include button(normal);

    &.flat {
      @include button(undecorated);
      // to avoid adiacent buttons borders clashing when transitioning, the transition on the normal state is set
      // to none, while it's added back in the hover state, so the button decoration will fade in on hover, but
      // it won't fade out when the pointer leave the button allocation area. To make the transition more evident
      // in this case the duration is increased.
      transition: none;

      &:hover {
        transition: $button_transition;
        transition-duration: 500ms;

        &:active { transition: $button_transition; }
      }
    }

    &:hover {
      @include button(hover,$selected_bg_color,$selected_fg_color);
      -gtk-icon-effect: highlight;
    }

    &:active,
    &:checked {
      @include button(active,darken($selected_bg_color,5%),$selected_fg_color);

      transition-duration: 50ms;
    }

    &:backdrop {
      &.flat, & {
        @include button(backdrop);

        transition: $backdrop_transition;
        -gtk-icon-effect: none;

        &:active,
        &:checked { @include button(backdrop-active); }

        &:disabled {
          @include button(backdrop-insensitive);

          &:active,
          &:checked { @include button(backdrop-insensitive-active); }
        }
      }
    }

    &.flat { &:backdrop, &:disabled, &:backdrop:disabled { @include button(undecorated); }}

    &:disabled {
      @include button(insensitive);

      &:active,
      &:checked { @include button(insensitive-active); }
    }

    &.image-button {
      min-width: 24px;
      padding-left: 4px;
      padding-right: 4px;
    }

    &.text-button {
      padding-left: 16px;
      padding-right: 16px;
    }

    &.text-button.image-button {
      padding-left: 8px;
      padding-right: 8px;

      label {
        padding-left: 8px;
        padding-right: 8px;
      }
    }

    &:drop(active) {
      color: $drop_target_color;
      border-color: $drop_target_color;
      box-shadow: inset 0 0 0 1px $drop_target_color;
    }
  }

  @at-root %button_selected, & {
    row:selected & {
      @if $variant == 'light' { border-color: $selected_borders_color; }

      &.flat:not(:active):not(:checked):not(:hover):not(disabled) {
        color: $selected_fg_color;
        border-color: transparent;

        &:backdrop { color: if($variant=='light', $backdrop_base_color, $backdrop_fg_color); }
      }
    }
  }


  // big standalone buttons like in Documents pager
  &.osd {
    min-width: 24px;
    min-height: 32px;

    &.image-button { min-width: 32px; }

    color: $osd_fg_color;
    border-radius: 5px;
    outline-color: transparentize($osd_fg_color, 0.7);  //FIXME: define a color var?

    @include button(osd);

    border: none;
    box-shadow: none;

    &:hover {
      @include button(osd-hover);

      border: none;
      box-shadow: none;
    }

    &:active,
    &:checked {
      @include button(osd-active);

      border: none;
      box-shadow: none;
    }

    &:disabled {
      &:backdrop, & {
        @include button(osd-insensitive);

        border: none;
      }
    }

    &:backdrop {
      @include button(osd-backdrop);

      border: none;
    }
  }

  //overlay / OSD style
  @at-root %osd_button,
  .osd & {
    @include button(osd);

    &:hover { @include button(osd-hover); }

    &:active,
    &:checked { &:backdrop, & { @include button(osd-active); }}

    &:disabled { &:backdrop, & { @include button(osd-insensitive); }}

    &:backdrop { @include button(osd-backdrop); }

    &.flat {
      @include button(undecorated);

      box-shadow: none; //FIXME respect no edge on the button mixin
      text-shadow: 0 1px black;
      -gtk-icon-shadow: 0 1px black;

      &:hover { @include button(osd-hover); }

      &:disabled {
        @include button(osd-insensitive);
        background-image: none;
        border-color: transparent;
        box-shadow: none;
      }

      &:backdrop { @include button(undecorated); }

      &:active,
      &:checked { @include button(osd-active); }
    }
  }

  // Suggested and Destructive Action buttons
  @each $b_type, $b_color in (suggested-action, $purple),
                             (destructive-action, $destructive_color) {
    &.#{$b_type} {
      @include button(normal, $b_color, white);

      &.flat {
        @include button(undecorated);

        color: $b_color; //FIXME: does it work on the dark variant?
      }

      &:hover { @include button(hover, $b_color, white); }

      &:active,
      &:checked { @include button(active, $b_color, white); }

      &:backdrop,
      &.flat:backdrop {
        @include button(backdrop, $b_color, white);
        label { color: transparentize(white, 0.5);}
        &:active,
        &:checked { @include button(backdrop-active, $b_color, white); }

        &:disabled {
          @include button(backdrop-insensitive, $b_color, white);
          label { color: transparentize(white, 0.5);}

          &:active,
          &:checked { @include button(backdrop-insensitive-active, $b_color, white); }
        }
      }

      &.flat {
        &:backdrop, &:disabled, &:backdrop:disabled {
          @include button(undecorated);

          color: transparentize($b_color, 0.2);
        }
      }

      &:disabled {
        @include button(insensitive, $b_color, white);
        label { color: transparentize($selected_fg_color, 0.2); }
        &:active,
        &:checked { @include button(insensitive-active, $b_color, white); }
      }

      .osd & {
        @include button(osd, $b_color);

        &:hover { @include button(osd-hover, $b_color); }

        &:active,
        &:checked { &:backdrop, & { @include button(osd-active, $b_color); }}

        &:disabled { &:backdrop, & { @include button(osd-insensitive, $b_color); }}

        &:backdrop { @include button(osd-backdrop, $b_color); }
      }
    }
  }

  .stack-switcher > & {
    // to position the needs attention dot, padding is added to the button
    // child, a label needs just lateral padding while an icon needs vertical
    // padding added too.

    outline-offset: -3px; // needs to be set or it gets overriden by GtkRadioButton outline-offset

    > label {
      padding-left: 6px;  // label padding
      padding-right: 6px; //
    }

    > image {
      padding-left: 6px;   // image padding
      padding-right: 6px;  //
      padding-top: 3px;    //
      padding-bottom: 3px; //
    }

    &.text-button {
      // compensate text-button paddings
      padding-left: 10px;
      padding-right: 10px;
    }

    &.image-button {
      // we want image buttons to have a 1:1 aspect ratio, so compensation
      // of the padding added to the GtkImage is needed
      padding-left: 2px;
      padding-right: 2px;
    }

    &.needs-attention {
      > label,
      > image { @extend %needs_attention; }

      &:active,
      &:checked {
        > label,
        > image {
          animation: none;
          background-image: none;
        }
      }
    }
  }

  //inline-toolbar buttons
  .inline-toolbar &, .inline-toolbar &:backdrop {
    border-radius: 2px;
    border-width: 1px;
    @extend %linked;
  }

  .primary-toolbar & { -gtk-icon-shadow: none; } // tango icons don't need shadows

  .linked > &,
  .linked > &:hover,
  .linked > &:active,
  .linked > &:checked,
  .linked > &:backdrop { @extend %linked; }

  .linked.vertical > &,
  .linked.vertical > &:hover,
  .linked.vertical > &:active,
  .linked.vertical > &:checked,
  .linked.vertical > &:backdrop { @extend %linked_vertical; }
}

%needs_attention {
  animation: needs_attention 150ms ease-in;
  $_dot_shadow: _text_shadow_color();
  $_dot_shadow_r: if($variant=='light',0.5,0.45);
  background-image: -gtk-gradient(radial,
                                  center center, 0,
                                  center center, 0.5,
                                  to($_dot_color),
                                  to(transparent)),
                    -gtk-gradient(radial,
                                  center center, 0,
                                  center center, $_dot_shadow_r,
                                  to($_dot_shadow),
                                  to(transparent));
  background-size: 6px 6px, 6px 6px;
  background-repeat: no-repeat;

  @if $variant == 'light' { background-position: right 3px, right 4px; }

  @else { background-position: right 3px, right 2px; }

  &:backdrop { background-size: 6px 6px, 0 0;}

  &:dir(rtl) {
    @if $variant == 'light' { background-position: left 3px, left 4px; }

    @else { background-position: left 3px, left 2px; }
  }
}

toolbar {
  button {
    &:hover { @include button(normal,darken($bg_color,7%));}
    &:active { @include button(normal,darken($bg_color,12%));}
  }
}
// all the following is for the +|- buttons on inline toolbars, that way
// should really be deprecated...
.inline-toolbar toolbutton > button { // redefining the button look is
                                      // needed since those are flat...
  @include button(undecorated);

  &:hover { color: $selected_bg_color; }

  &:active,
  &:checked{ color: darken($selected_bg_color, 5%); }

  &:disabled {
    color: $backdrop_text_color;

    &:active,
    &:checked { color: transparentize(darken($selected_bg_color, 5%),0.7); }
  }

  &:backdrop {
    color: $backdrop_text_color;

    &:active,
    &:checked { color: darken($selected_bg_color, 5%); }

    &:disabled {
      color: $backdrop_text_color;

      &:active,
      &:checked { color: transparentize(darken($selected_bg_color, 5%),0.7); }
    }
  }
}

// More inline toolbar buttons
toolbar.inline-toolbar toolbutton,
toolbar.inline-toolbar toolbutton:backdrop {
  > button.flat {
    &:backdrop {
      border-color: transparent;
      box-shadow: none;
    }
  }
}

%linked_middle {
  border: 1px solid $borders_color;
  border-radius: 0;
  border-right-style: none;
  box-shadow: inset 0px 1px 0px 0px $top_highlight;
}

%linked {
  @extend %linked_middle;

  &:first-child {
    border-top-left-radius: 3px;
    border-bottom-left-radius: 3px;
  }

  &:last-child {
    border-top-right-radius: 3px;
    border-bottom-right-radius: 3px;
    border-right-style: solid;
  }

  &:only-child {
    border-radius: 3px;
    border-style: solid;
  }
}

%linked_vertical_middle {
  border-style: solid solid none solid;
  border-radius: 0;
}

%linked_vertical{
  @extend %linked_vertical_middle;

  &:first-child {
    border-top-left-radius: 3px;
    border-top-right-radius: 3px;
  }

  &:last-child {
    border-bottom-left-radius: 3px;
    border-bottom-right-radius: 3px;
    border-style: solid;
  }

  &:only-child {
    border-radius: 3px;
    border-style: solid;
  }
}

%undecorated_button {
  background-color: transparent;
  background-image: none;
  border-color: transparent;
  box-shadow: inset 0 1px transparentize(white,1),
              0 1px transparentize(white, 1);
  text-shadow: none;
  -gtk-icon-shadow: none;
}

/* menu buttons */
modelbutton.flat,
.menuitem.button.flat {
  min-height: 26px;
  padding-left: 5px;
  padding-right: 5px;
  border-radius: 3px;
  outline-offset: -2px;

  @extend %undecorated_button;

  &:hover { background-color: $popover_hover_color; }

  &:selected { @extend %selected_items; }

  &:backdrop,
  &:backdrop:hover { @extend %undecorated_button; }

  // FIXME: remove the following when the checks/radios rewrite lands
  check:last-child,
  radio:last-child { margin-left: 8px; }

  check:first-child,
  radio:first-child { margin-right: 8px; }
}

modelbutton.flat arrow {
  background: none;

  &:hover { background: none; }

  &.left { -gtk-icon-source: -gtk-icontheme("pan-start-symbolic"); }

  &.right { -gtk-icon-source: -gtk-icontheme("pan-end-symbolic"); }
}

button.color {
  padding: 4px;

  colorswatch:only-child {
    &, overlay { border-radius: 0; }

    @if $variant == 'light' {
      box-shadow: 0 1px _text_shadow_color();

      &:disabled,
      &:backdrop { box-shadow: none; }
    }
  }
}

notebook, list, .view, popover {
  button {
    box-shadow: inset 0px 0px 0px 1px $borders_color;
    &:backdrop {
      box-shadow: inset 0px 0px 0px 1px $borders_color;
    }
  }
  .linked > button {
    box-shadow: none;
  }
}