in js/reveal.js [1682:1710]
function getComputedSlideSize( presentationWidth, presentationHeight ) {
var size = {
// Slide size
width: config.width,
height: config.height,
// Presentation size
presentationWidth: presentationWidth || dom.wrapper.offsetWidth,
presentationHeight: presentationHeight || dom.wrapper.offsetHeight
};
// Reduce available space by margin
size.presentationWidth -= ( size.presentationWidth * config.margin );
size.presentationHeight -= ( size.presentationHeight * config.margin );
// Slide width may be a percentage of available width
if( typeof size.width === 'string' && /%$/.test( size.width ) ) {
size.width = parseInt( size.width, 10 ) / 100 * size.presentationWidth;
}
// Slide height may be a percentage of available height
if( typeof size.height === 'string' && /%$/.test( size.height ) ) {
size.height = parseInt( size.height, 10 ) / 100 * size.presentationHeight;
}
return size;
}