in site/semantic/src/definitions/modules/sticky.js [465:572]
stick: function(scroll) {
var
cachedPosition = scroll || $scroll.scrollTop(),
cache = module.cache,
fits = cache.fits,
element = cache.element,
scrollContext = cache.scrollContext,
context = cache.context,
offset = (module.is.bottom() && settings.pushing)
? settings.bottomOffset
: settings.offset,
scroll = {
top : cachedPosition + offset,
bottom : cachedPosition + offset + scrollContext.height
},
direction = module.get.direction(scroll.top),
elementScroll = (fits)
? 0
: module.get.elementScroll(scroll.top),
// shorthand
doesntFit = !fits,
elementVisible = (element.height !== 0)
;
if(elementVisible) {
if( module.is.initialPosition() ) {
if(scroll.top >= context.bottom) {
module.debug('Initial element position is bottom of container');
module.bindBottom();
}
else if(scroll.top > element.top) {
if( (element.height + scroll.top - elementScroll) >= context.bottom ) {
module.debug('Initial element position is bottom of container');
module.bindBottom();
}
else {
module.debug('Initial element position is fixed');
module.fixTop();
}
}
}
else if( module.is.fixed() ) {
// currently fixed top
if( module.is.top() ) {
if( scroll.top <= element.top ) {
module.debug('Fixed element reached top of container');
module.setInitialPosition();
}
else if( (element.height + scroll.top - elementScroll) >= context.bottom ) {
module.debug('Fixed element reached bottom of container');
module.bindBottom();
}
// scroll element if larger than screen
else if(doesntFit) {
module.set.scroll(elementScroll);
module.save.lastScroll(scroll.top);
module.save.elementScroll(elementScroll);
}
}
// currently fixed bottom
else if(module.is.bottom() ) {
// top edge
if( (scroll.bottom - element.height) <= element.top) {
module.debug('Bottom fixed rail has reached top of container');
module.setInitialPosition();
}
// bottom edge
else if(scroll.bottom >= context.bottom) {
module.debug('Bottom fixed rail has reached bottom of container');
module.bindBottom();
}
// scroll element if larger than screen
else if(doesntFit) {
module.set.scroll(elementScroll);
module.save.lastScroll(scroll.top);
module.save.elementScroll(elementScroll);
}
}
}
else if( module.is.bottom() ) {
if( scroll.top <= element.top ) {
module.debug('Jumped from bottom fixed to top fixed, most likely used home/end button');
module.setInitialPosition();
}
else {
if(settings.pushing) {
if(module.is.bound() && scroll.bottom <= context.bottom ) {
module.debug('Fixing bottom attached element to bottom of browser.');
module.fixBottom();
}
}
else {
if(module.is.bound() && (scroll.top <= context.bottom - element.height) ) {
module.debug('Fixing bottom attached element to top of browser.');
module.fixTop();
}
}
}
}
}
},