superset-frontend/packages/superset-frontend/src/dashboard/stylesheets/resizable.less

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
.resizable-container {
  background-color: transparent;
  position: relative;

  /* re-resizable sets an empty div to 100% width and height, which doesn't
  play well with many 100% height containers we need
 */
  & ~ div {
    width: auto !important;
    height: auto !important;
  }
}

.resizable-container--resizing {
  /* after ensures border visibility on top of any children */
  &:after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    box-shadow: inset 0 0 0 2px @indicator-color;
  }

  & > span .resize-handle {
    border-color: @indicator-color;
  }
}

.resize-handle {
  opacity: 0;
  z-index: @z-index-above-dashboard-charts;

  &--bottom-right {
    position: absolute;
    border: solid;
    border-width: 0 1.5px 1.5px 0;
    border-right-color: @gray;
    border-bottom-color: @gray;
    right: 16px;
    bottom: 16px;
    width: 8px;
    height: 8px;
  }

  &--right {
    width: 2px;
    height: 20px;
    right: 4px;
    top: 50%;
    transform: translate(0, -50%);
    position: absolute;
    border-left: 1px solid @gray;
    border-right: 1px solid @gray;
  }

  &--bottom {
    height: 2px;
    width: 20px;
    bottom: 4px;
    left: 50%;
    transform: translate(-50%);
    position: absolute;
    border-top: 1px solid @gray;
    border-bottom: 1px solid @gray;
  }
}

.resizable-container:hover .resize-handle,
.resizable-container--resizing .resize-handle {
  opacity: 1;
}

.dragdroppable-column .resizable-container-handle--right {
  /* override the default because the inner column's handle's mouse target is very small */
  right: -10px !important;
}

.dragdroppable-column .dragdroppable-column .resizable-container-handle--right {
  /* override the default because the inner column's handle's mouse target is very small */
  right: 0px !important;
}

.resizable-container-handle--bottom {
  bottom: 0 !important;
}