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>