gnome-shell/data/theme/gnome-shell-sass/widgets/_ibus-popup.scss

// IBus Candidate Popup

.candidate-popup-boxpointer {
  @extend .popup-menu-boxpointer;
}

.candidate-popup-content {
  padding: $base_padding;
  spacing: $base_padding;
  @extend .popup-menu-content;
}

.candidate-index {
  padding: 0;
  padding-right: $base_padding;
  color: $insensitive_fg_color;
}

.candidate-box {
  padding: $base_padding $base_padding*2 $base_padding $base_padding*2;
  border-radius: $base_border_radius;
  &:selected { background-color: $selected_bg_color; color: $selected_fg_color; }
  &:hover { background-color: $hover_bg_color; color: $hover_fg_color; }
}

.candidate-page-button-box {
  height: 2em;
  .vertical & { padding-top: $base_padding*2; }
  .horizontal & { padding-left: $base_padding*2; }
}

.candidate-page-button { padding: $base_padding;}

.candidate-page-button-previous { border-radius: $base_border_radius 0px 0px $base_border_radius; border-right-width: 0;box-shadow: none;}
.candidate-page-button-next { border-radius: 0px $base_border_radius $base_border_radius 0px;box-shadow: none;}
.candidate-page-button-icon { icon-size: $base_icon_size; }