Styling Splitters

Styling splitters is fully customizable using CSS (or SCSS), the `theme` property is used to select the proper styling class and apply it to the Splitpanes component.
The default style is called `default-theme`, its SCSS definition can be found below ( warning : This is for reference only! If you decide to copy this CSS code, you must rename the ".default-theme" specifier to something else, so it wouldn't conflict the library theme CSS definition):

.splitpanes.default-theme {
  .splitpanes__pane {
    background-color: #f2f2f2;
  }
  .splitpanes__splitter {
    background-color: #fff;
    box-sizing: border-box;
    position: relative;
    flex-shrink: 0;
    &:before,
    &:after {
      content: '';
      position: absolute;
      top: 50%;
      left: 50%;
      background-color: rgba(0, 0, 0, 0.15);
      transition: background-color 0.3s;
    }
    &:hover:before,
    &:hover:after {
      background-color: rgba(0, 0, 0, 0.25);
    }
    &:first-child {
      cursor: auto;
    }
  }
}
.default-theme {
  &.splitpanes .splitpanes .splitpanes__splitter {
    z-index: 1;
  }
  &.splitpanes--vertical > .splitpanes__splitter,
  .splitpanes--vertical > .splitpanes__splitter {
    width: 7px;
    border-left: 1px solid #eee;
    cursor: col-resize;
    &:before,
    &:after {
      transform: translateY(-50%);
      width: 1px;
      height: 30px;
    }
    &:before {
      margin-left: -2px;
    }
    &:after {
      margin-left: 1px;
    }
  }
  &.splitpanes--horizontal > .splitpanes__splitter,
  .splitpanes--horizontal > .splitpanes__splitter {
    height: 7px;
    border-top: 1px solid #eee;
    cursor: row-resize;
    &:before,
    &:after {
      transform: translateX(-50%);
      width: 30px;
      height: 1px;
    }
    &:before {
      margin-top: -2px;
    }
    &:after {
      margin-top: 1px;
    }
  }
}

Alternatively, here is the default theme compiled to CSS:

.splitpanes.default-theme .splitpanes__pane {
  background-color: #f2f2f2;
}
.splitpanes.default-theme .splitpanes__splitter {
  background-color: #fff;
  box-sizing: border-box;
  position: relative;
  flex-shrink: 0;
}
.splitpanes.default-theme .splitpanes__splitter:before, .splitpanes.default-theme .splitpanes__splitter:after {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  background-color: rgba(0, 0, 0, 0.15);
  transition: background-color 0.3s;
}
.splitpanes.default-theme .splitpanes__splitter:hover:before, .splitpanes.default-theme .splitpanes__splitter:hover:after {
  background-color: rgba(0, 0, 0, 0.25);
}
.splitpanes.default-theme .splitpanes__splitter:first-child {
  cursor: auto;
}

.default-theme.splitpanes .splitpanes .splitpanes__splitter {
  z-index: 1;
}
.default-theme.splitpanes--vertical > .splitpanes__splitter,
.default-theme .splitpanes--vertical > .splitpanes__splitter {
  width: 7px;
  border-left: 1px solid #eee;
  cursor: col-resize;
}
.default-theme.splitpanes--vertical > .splitpanes__splitter:before, .default-theme.splitpanes--vertical > .splitpanes__splitter:after,
.default-theme .splitpanes--vertical > .splitpanes__splitter:before,
.default-theme .splitpanes--vertical > .splitpanes__splitter:after {
  transform: translateY(-50%);
  width: 1px;
  height: 30px;
}
.default-theme.splitpanes--vertical > .splitpanes__splitter:before,
.default-theme .splitpanes--vertical > .splitpanes__splitter:before {
  margin-left: -2px;
}
.default-theme.splitpanes--vertical > .splitpanes__splitter:after,
.default-theme .splitpanes--vertical > .splitpanes__splitter:after {
  margin-left: 1px;
}
.default-theme.splitpanes--horizontal > .splitpanes__splitter,
.default-theme .splitpanes--horizontal > .splitpanes__splitter {
  height: 7px;
  border-top: 1px solid #eee;
  cursor: row-resize;
}
.default-theme.splitpanes--horizontal > .splitpanes__splitter:before, .default-theme.splitpanes--horizontal > .splitpanes__splitter:after,
.default-theme .splitpanes--horizontal > .splitpanes__splitter:before,
.default-theme .splitpanes--horizontal > .splitpanes__splitter:after {
  transform: translateX(-50%);
  width: 30px;
  height: 1px;
}
.default-theme.splitpanes--horizontal > .splitpanes__splitter:before,
.default-theme .splitpanes--horizontal > .splitpanes__splitter:before {
  margin-top: -2px;
}
.default-theme.splitpanes--horizontal > .splitpanes__splitter:after,
.default-theme .splitpanes--horizontal > .splitpanes__splitter:after {
  margin-top: 1px;
}

By altering the above styles, it is possible to achieve neat visual adjustments. Please note how each Splitpanes references our new `theme="my-theme"`

<script>
  import { Pane, Splitpanes } from 'svelte-splitpanes';
</script>

<Splitpanes theme="my-theme" horizontal style="height: 400px">
  <Pane>
    <Splitpanes theme="my-theme">
      <Pane>
        <span>1</span>
      </Pane>
      <Pane>
        <span>2</span>
      </Pane>
      <Pane>
        <span>3</span>
      </Pane>
    </Splitpanes>
  </Pane>
  <Pane>
    <em class="specs">
      <p>
        In this example the splitters are thin lines but the reactive touch zone is spread to 30
        pixels all around!
      </p>
    </em>
  </Pane>
</Splitpanes>

<style global lang="scss">
  .splitpanes.my-theme {
    .splitpanes__pane {
      background-color: #f8f8f8;
    }
    .splitpanes__splitter {
      background-color: #ccc;
      position: relative;
      &:before {
        content: '';
        position: absolute;
        left: 0;
        top: 0;
        transition: opacity 0.4s;
        background-color: rgba(255, 0, 0, 0.3);
        opacity: 0;
        z-index: 1;
      }
      &:hover:before {
        opacity: 1;
      }
      &.splitpanes__splitter__active {
        z-index: 2; /* Fix an issue of overlap fighting with a near hovered splitter */
      }
    }
  }
  .my-theme {
    &.splitpanes--vertical > .splitpanes__splitter:before {
      left: -30px;
      right: -30px;
      height: 100%;
      cursor: col-resize;
    }
    &.splitpanes--horizontal > .splitpanes__splitter:before {
      top: -30px;
      bottom: -30px;
      width: 100%;
      cursor: row-resize;
    }
  }
</style>