_screen-reader.scss
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			// Only display content to screen readers
			//
			// See: https://a11yproject.com/posts/how-to-hide-content/
			// See: https://hugogiraudel.com/2016/10/13/css-hide-and-seek/

			@mixin sr-only {
			position: absolute;
			width: 1px;
			height: 1px;
			padding: 0;
			overflow: hidden;
			clip: rect(0, 0, 0, 0);
			white-space: nowrap;
			border: 0;
			}

			// Use in conjunction with .sr-only to only display content when it's focused.
			//
			// Useful for "Skip to main content" links; see https://www.w3.org/TR/2013/NOTE-WCAG20-TECHS-20130905/G1
			//
			// Credit: HTML5 Boilerplate

			@mixin sr-only-focusable {
			&:active,
			&:focus {
			position: static;
			width: auto;
			height: auto;
			overflow: visible;
			clip: auto;
			white-space: normal;
			}
			}

costcalc/bootstrap-4.3.1/scss/mixins/_screen-reader.scss19657233d360gh-pages