src/vs/base/browser/ui/inputbox/inputBox.ts/InputBox/width
class InputBox:	public set width(width: number) {
		if (this.options.flexibleHeight && this.options.flexibleWidth) {
			// textarea with horizontal scrolling
			let horizontalPadding = 0;
			if (this.mirror) {
				const paddingLeft = parseFloat(this.mirror.style.paddingLeft || '') || 0;
				const paddingRight = parseFloat(this.mirror.style.paddingRight || '') || 0;
				horizontalPadding = paddingLeft + paddingRight;
			}
			this.input.style.width = (width - horizontalPadding) + 'px';
		} else {
			this.input.style.width = width + 'px';
		}

		if (this.mirror) {
			this.mirror.style.width = width + 'px';
		}
	}