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

/************
 * GtkScale *
 ************/
 $scale_slider_bg: if($variant == 'light', $base_color, lighten($base_color, 10%));
 $scale_trough_bg: if($variant == 'light', transparentize(black,0.86), lighten(transparentize($bg_color,0.86), 47%));
%scale_trough {
  background-color: $scale_trough_bg;
  border: none;
  border-radius: 3px;
  margin: 0;

  &:disabled { background-color: transparentize(black,0.86); }

  &:backdrop {
    background-color: transparentize(black,0.86);
    transition: $backdrop_transition;

    &:disabled { background-color: transparentize(black,0.86); }
  }
}

%scale_highlight {
  border: none;
  background-color: $selected_bg_color;
  border-radius: 3px;
  margin: 0;

  &:disabled {
    border: none;
    background-color: transparentize(black, 0.86);
  }

  &:backdrop,
  &:active:backdrop {
    border-color: lighten($selected_bg_color, 5%);
    background-color: lighten($selected_bg_color, 5%);
    &:disabled {
      background-color: transparentize(black, 0.9);
    }
  }
}

scale {
  // sizing
  $_marks_lenght: 6px;
  $_marks_distance: 6px;

  min-height: 16px;
  min-width: 16px;
  padding: 8px;

  &.horizontal {
    trough,
    progress { min-height: 6px; }
  }

  &.vertical {
    trough,
    progress { min-width: 6px; }
  }

  // the slider is inside the trough, so to have make it bigger there's a negative margin

  slider {
    min-height: 16px;
    min-width: 16px;
    margin: -7px;

    background-color: $scale_slider_bg;
    box-shadow: inset 0 1px $top_highlight,
                0px 0px 1px 1px rgba(0,0,0,0.1);
    border-radius: 12px;

    transition: $button_transition;
    transition-property: background, border, box-shadow;

    &:active {
      background-color: $purple;

      &:disabled {
        background-color: $insensitive_bg_color;
        box-shadow: inset 0 1px $top_highlight,
                    0px 0px 1px 1px rgba(0,0,0,0.05);
      }
    }
  }

  // click-and-hold the slider to activate
  &.fine-tune {
    &.horizontal {
      padding-top: 9px;
      padding-bottom: 9px;
      min-height: 16px;
    }

    &.vertical {
      padding-left: 9px;
      padding-right: 9px;
      min-width: 16px;
    }

    // to make the trough grow in fine-tune mode
    slider { margin: -6px; }

    fill,
    highlight,
    trough {
      border-radius: 5px;
      -gtk-outline-radius: 7px;
    }
  }

  // the backing bit
  trough {
    @extend %scale_trough;

    outline-offset: 2px;
    -gtk-outline-radius: 5px;
    outline-color: transparent;
  }

  // the colored part of the backing bit
  highlight { @extend %scale_highlight; }

  // this is another differently styled part of the backing bit, the most relevant use case is for example
  // in media player to indicate how much video stream as been cached
  fill {
    @extend %scale_trough;

    &:backdrop, & { background-color: $borders_color; }

    &:disabled {
      &:backdrop, & {
        border-color: transparent;
        background-color: transparent;
      }
    }

    // OSD
    .osd & {
      background-color: mix($osd_fg_color, $osd_borders_color, 25%);

      &:disabled {
        &:backdrop, & {
          border-color: transparent;
          background-color: transparent;
        }
      }
    }
  }

  slider {
    border-color: $base_color;
    border: none;
    border-radius: 12px;

    background-color: $scale_slider_bg;
    box-shadow: inset 0 1px $top_highlight,
                0px 0px 1px 1px rgba(0,0,0,0.1);

    &:hover { @include button(hover-alt, $edge: $shadow_color); }

    &:active { border-color: $selected_borders_color; }

    &:disabled {
      background-color: $insensitive_bg_color;
      box-shadow: inset 0 1px $top_highlight,
                  0px 0px 1px 1px rgba(0,0,0,0.1);
      }

    &:backdrop,
    &:backdrop:disabled {
      transition: $backdrop_transition;

      background-color: $insensitive_bg_color;
      box-shadow: inset 0 1px $top_highlight,
                  0px 0px 1px 1px rgba(0,0,0,0.1);
    }

    // ...on selected list rows
    row:selected & { &:disabled, & { border-color: $selected_borders_color; } }

    // OSD
    .osd & {
      @include button(osd);
      border-color: darken($osd_borders_color, 3%);
      background-color: opacify($osd_bg_color, 1); // solid background needed here

      &:hover {
        @include button(osd-hover);
        background-color: opacify($osd_bg_color, 1); // solid background needed here
      }

      &:active {
        @include button(osd-active);
        background-color: opacify($osd_bg_color, 1); // solid background needed here
      }

      &:disabled {
        @include button(osd-insensitive);
        background-color: opacify($osd_bg_color, 1); // solid background needed here
      }

      &:backdrop {
        @include button(osd-backdrop);
        background-color: opacify($osd_bg_color, 1); // solid background needed here

        &:disabled {
          @include button(osd-backdrop-insensitive);
          background-color: opacify($osd_bg_color, 1); // solid background needed here
        }
      }
    }
  }

  value { color: gtkalpha(currentColor, 0.4); }

  marks {
    color: gtkalpha(currentColor, 0.4);

    @each $marks_class, $marks_pos, $marks_margin in (top, top, bottom),
                                                     (bottom, bottom, top),
                                                     (top, left, right),
                                                     (bottom, right, left) {
      &.#{$marks_class} {
        margin-#{$marks_margin}: $_marks_distance;
        margin-#{$marks_pos}: -($_marks_distance + $_marks_lenght);
      }
    }
  }

  &.fine-tune marks {
    @each $marks_class, $marks_pos, $marks_margin in (top, top, bottom),
                                                     (bottom, bottom, top),
                                                     (top, left, right),
                                                     (bottom, right, left) {
      &.#{$marks_class} {
        margin-#{$marks_margin}: $_marks_distance;
        margin-#{$marks_pos}: -($_marks_distance + $_marks_lenght - 3px);
      }
    }
  }

  &.horizontal {
    indicator {
      min-height: $_marks_lenght;
      min-width: 1px;
    }

    &.fine-tune indicator { min-height: ($_marks_lenght - 3px); }
  }

  &.vertical {
    indicator {
      min-height: 1px;
      min-width: $_marks_lenght;
    }

    &.fine-tune indicator { min-width: ($_marks_lenght - 3px); }
  }

  // *WARNING* scale with marks madness following

  // FIXME: OSD and selected list rows missing, I don't feel like adding the other 144 assets needed for those...
  $suffix: if($variant == 'light', '', '-dark');

  @each $dir_class, $dir_infix in ('horizontal', 'horz'),
                                  ('vertical', 'vert') {
    @each $marks_infix, $marks_class in ('scale-has-marks-above', 'marks-before:not(.marks-after)'),
                                        ('scale-has-marks-below', 'marks-after:not(.marks-before)') {
      @each $state, $state_infix in ('', ''),
                                    (':hover', '-hover'),
                                    (':active', '-active'),
                                    (':disabled', '-insensitive'),
                                    (':backdrop', '-backdrop'),
                                    (':backdrop:disabled', '-backdrop-insensitive') {
        &.#{$dir_class}.#{$marks_class} {

          slider {
            &#{$state} {
              // an asymmetric slider asset is used here, so the margins are uneven, the smaller
              // margin is set on the point side.
              min-height: 16px;
              min-width: 16px;
              margin: -7px;
              border: none;
              border-radius: 50%;

              background-color: $scale_slider_bg;
              box-shadow: inset 0 1px $top_highlight,
                          0px 0px 1px 1px rgba(0,0,0,0.1);
              }
          }

          &.fine-tune slider {
            // bigger negative margins to make the trough grow here as well
            margin: -7px;
          }
        }
      }
    }
  }

  &.color {
    min-height: 0;
    min-width: 0;

    trough {
      background-image: image($borders_color);
      background-repeat: no-repeat;
    }

    &.horizontal {
      padding: 0 0 15px 0;

      trough {
        padding-bottom: 4px;
        background-position: 0 -3px;
        border-top-left-radius: 0;
        border-top-right-radius: 0;
      }

      slider {
        &:dir(ltr), &:dir(rtl) { // specificity bumb
          &:hover, &:backdrop, &:disabled, &:backdrop:disabled, & {
            margin-bottom: -15px;
            margin-top: 6px;
          }
        }
      }
    }

    &.vertical {
      &:dir(ltr) {
        padding: 0 0 0 15px;

        trough {
          padding-left: 4px;
          background-position: 3px 0;
          border-bottom-right-radius: 0;
          border-top-right-radius: 0;
        }

        slider {
          &:hover, &:backdrop, &:disabled, &:backdrop:disabled, & {
            margin-left: -15px;
            margin-right: 6px;
          }
        }
      }

      &:dir(rtl) {
        padding: 0 15px 0 0;

        trough {
          padding-right: 4px;
          background-position: -3px 0;
          border-bottom-left-radius: 0;
          border-top-left-radius: 0;
        }

        slider {
          &:hover, &:backdrop, &:disabled, &:backdrop:disabled, & {
            margin-right: -15px;
            margin-left: 6px;
          }
        }
      }
    }

    &.fine-tune {
      &.horizontal {
        &:dir(ltr), &:dir(rtl) { // specificity bump
          padding: 0 0 12px 0;

          trough {
            padding-bottom: 7px;
            background-position: 0 -6px;
          }

          slider {
            margin-bottom: -15px;
            margin-top: 6px;
          }
        }
      }

      &.vertical {
        &:dir(ltr) {
          padding: 0 0 0 12px;

          trough {
            padding-left: 7px;
            background-position: 6px 0;
          }

          slider {
            margin-left: -15px;
            margin-right: 6px;
          }
        }

        &:dir(rtl) {
          padding: 0 12px 0 0;

          trough {
            padding-right: 7px;
            background-position: -6px 0;
          }

          slider {
            margin-right: -15px;
            margin-left: 6px;
          }
        }
      }
    }
  }
}