wp-calypso/packages/components/src/tabs/style.module.scss

@use '@wordpress/base-styles/colors';
@use '@wordpress/base-styles/mixins';
@use '@wordpress/base-styles/variables';
@use '../utils/_theme-variables' as theme;

.tablist {
	display: flex;
	align-items: stretch;
	overflow-x: auto;

	&:where( [aria-orientation='horizontal'] ) {
		width: fit-content;
	}

	--direction-factor: 1;
	--direction-start: left;
	--direction-end: right;
	--selected-start: var( --selected-left, 0 );
	&:dir( rtl ) {
		--direction-factor: -1;
		--direction-start: right;
		--direction-end: left;
		--selected-start: var( --selected-right, 0 );
	}

	@media not ( prefers-reduced-motion ) {
		&[data-indicator-animated]::before {
			transition-property: transform, border-radius, border-block;
			transition-duration: 0.2s;
			transition-timing-function: ease-out;
		}
	}
	position: relative;
	&::before {
		content: '';
		position: absolute;
		pointer-events: none;
		transform-origin: var( --direction-start ) top;

		// Windows high contrast mode.
		outline: 2px solid transparent;
		outline-offset: -1px;
	}

	/* Using a large value to avoid antialiasing rounding issues
			when scaling in the transform, see: https://stackoverflow.com/a/52159123 */
	--antialiasing-factor: 100;
	&[aria-orientation='horizontal'] {
		--fade-width: 4rem;
		--fade-gradient-base: transparent 0%, #{colors.$black} var( --fade-width );
		--fade-gradient-composed: var( --fade-gradient-base ), #{colors.$black} 60%, transparent 50%;
		&.is-overflowing-first {
			mask-image: linear-gradient( to var( --direction-end ), var( --fade-gradient-base ) );
		}
		&.is-overflowing-last {
			mask-image: linear-gradient( to var( --direction-start ), var( --fade-gradient-base ) );
		}
		&.is-overflowing-first.is-overflowing-last {
			mask-image: linear-gradient( to right, var( --fade-gradient-composed ) ),
				linear-gradient( to left, var( --fade-gradient-composed ) );
		}

		&.has-compact-density {
			gap: 1rem;
		}

		&::before {
			bottom: 0;
			height: 0;
			width: calc( var( --antialiasing-factor ) * 1px );
			transform: translateX( calc( var( --selected-start ) * var( --direction-factor ) * 1px ) )
				scaleX( calc( var( --selected-width, 0 ) / var( --antialiasing-factor ) ) );
			border-bottom: var( --wp-admin-border-width-focus ) solid theme.$components-color-accent;
		}
	}

	&[aria-orientation='vertical'] {
		flex-direction: column;

		&::before {
			/* Adjusting the border radius to match the scaling in the y axis. */
			border-radius: variables.$radius-small /
				calc(
					variables.$radius-small / ( var( --selected-height, 0 ) / var( --antialiasing-factor ) )
				);
			top: 0;
			left: 0;
			width: 100%;
			height: calc( var( --antialiasing-factor ) * 1px );
			transform: translateY( calc( var( --selected-top, 0 ) * 1px ) )
				scaleY( calc( var( --selected-height, 0 ) / var( --antialiasing-factor ) ) );
			background-color: color-mix( in srgb, theme.$components-color-accent, transparent 96% );
		}
		&[data-select-on-move='true']:has( :is( :focus-visible, [data-focus-visible] ) )::before {
			box-sizing: border-box;
			border: var( --wp-admin-border-width-focus ) solid theme.$components-color-accent;
			/* Adjusting the border width to match the scaling in the y axis. */
			border-block-width: calc(
				var( --wp-admin-border-width-focus, 1px ) /
					( var( --selected-height, 0 ) / var( --antialiasing-factor ) )
			);
		}
	}
}

.tab {

	/* Resets */
	border-radius: 0;
	background: transparent;
	border: none;
	box-shadow: none;

	flex: 1 0 auto;
	white-space: nowrap;
	display: flex;
	align-items: center;
	cursor: pointer;
	line-height: 1.2; // Characters in some languages (e.g. Japanese) may have a native higher line-height.
	font-weight: 400;
	color: theme.$components-color-foreground;

	&[aria-disabled='true'] {
		cursor: default;
		color: theme.$components-color-gray-600;
	}

	&:not( [aria-disabled='true'] ):is( :hover, [data-focus-visible] ) {
		color: theme.$components-color-accent;
	}

	&:focus:not( :disabled ) {
		box-shadow: none;
		outline: none;
	}

	// Focus indicator.
	position: relative;
	&::after {
		position: absolute;
		pointer-events: none;

		// Draw the indicator.
		// Outline works for Windows high contrast mode as well.
		outline: var( --wp-admin-border-width-focus ) solid theme.$components-color-accent;
		border-radius: variables.$radius-small;

		// Animation
		opacity: 0;

		@media not ( prefers-reduced-motion ) {
			transition: opacity 0.1s linear;
		}
	}

	&[data-focus-visible]::after {
		opacity: 1;
	}

	[aria-orientation='horizontal'] & {
		padding-inline: variables.$grid-unit-05 * 4;
		height: variables.$grid-unit-05 * 12;
		scroll-margin: 24px;

		&::after {
			content: '';
			inset: variables.$grid-unit-05 * 3;
		}
	}

	.has-compact-density[aria-orientation='horizontal'] & {
		padding-inline: 0;

		&::after {
			// Add enough inset to prevent the focus ring (which is 1.5px thick)
			// from being visually clipped by the tablist.
			inset-inline: 2px;
		}
	}

	[aria-orientation='vertical'] & {
		padding: variables.$grid-unit-05 * 2 variables.$grid-unit-05 * 3;
		min-height: variables.$grid-unit-05 * 10;

		&[aria-selected='true'] {
			color: theme.$components-color-accent;
			fill: currentColor;
		}
	}
	[aria-orientation='vertical'][data-select-on-move='false'] &::after {
		content: '';
		inset: var( --wp-admin-border-width-focus );
	}
}

.tab__children {
	flex-grow: 1;

	display: flex;
	align-items: center;

	[aria-orientation='horizontal'] & {
		justify-content: center;
	}
	[aria-orientation='vertical'] & {
		justify-content: start;
	}
}

.tab__chevron {
	flex-shrink: 0;
	margin-inline-end: variables.$grid-unit-05 * -1;
	[aria-orientation='horizontal'] & {
		display: none;
	}
	opacity: 0;
	[role='tab']:is( [aria-selected='true'], [data-focus-visible], :hover ) & {
		opacity: 1;
	}
	// The chevron is transitioned into existence when selectOnMove is enabled,
	// because otherwise it looks jarring, as it shows up outside of the focus
	// indicator that's being animated at the same time.
	@media not ( prefers-reduced-motion ) {
		[data-select-on-move='true'] [role='tab']:is( [aria-selected='true']  ) & {
			transition: opacity 0.15s 0.15s linear;
		}
	}
	&:dir( rtl ) {
		rotate: 180deg;
	}
}

.tabpanel {
	&:focus {
		box-shadow: none;
		outline: none;
	}

	&[data-focus-visible] {
		box-shadow: 0 0 0 var( --wp-admin-border-width-focus ) theme.$components-color-accent;
		// Windows high contrast mode.
		outline: 2px solid transparent;
		outline-offset: 0;
	}
}