in js/reveal.js [3791:3817]
function navigatePrev() {
// Prioritize revealing fragments
if( previousFragment() === false ) {
if( availableRoutes().up ) {
navigateUp();
}
else {
// Fetch the previous horizontal slide, if there is one
var previousSlide;
if( config.rtl ) {
previousSlide = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.future' ) ).pop();
}
else {
previousSlide = toArray( dom.wrapper.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR + '.past' ) ).pop();
}
if( previousSlide ) {
var v = ( previousSlide.querySelectorAll( 'section' ).length - 1 ) || undefined;
var h = indexh - 1;
slide( h, v );
}
}
}
}