gnome-shell/data/theme/gnome-shell-sass/widgets/_check-box.scss

/* Check Boxes */

// these are equal to the size of the SVG assets
$check_height: 22px;
$check_width: 24px;


.check-box {
  StBoxLayout { spacing: .8em; }
  StBin {
    width: $check_width;
    height: $check_height;
    background-image: url("resource:///org/gnome/shell/theme/checkbox-off.svg");
  }
  &:focus StBin { background-image: url("resource:///org/gnome/shell/theme/checkbox-off-focused.svg"); }
  &:checked StBin { background-image: url("resource:///org/gnome/shell/theme/checkbox.svg"); }
  &:focus:checked StBin { background-image: url("resource:///org/gnome/shell/theme/checkbox-focused.svg"); }
}