Current File : //proc/985914/root/data/old/home/stash/atlassian-stash/static/util/region-scroll-forwarder.js
define('util/region-scroll-forwarder', [
'bacon',
'jquery',
'underscore',
'util/bacon',
'util/function'
],
/**
* Forward scroll events from a source to one or many targets
*
* @exports util/region-scroll-forwarder
*/
function(
Bacon,
$,
_,
baconUtil,
fn
) {
"use strict";
/**
* Given a scroll property to listen to, determines the region that we're in and forwards scroll events.
* When leaving a region, that region will be scrolled to the 'near' edge.
* Allows for 'grouped' regions and will only scroll the 'nearest' region in each group to the edge.
* This is useful when disjoint regions are actually forwarding to the same underlying object. E.g.
*
* ------------------- top
* |
* | region A - scroll the window while we're in this region
* |
* |-----
* |
* | region B - scroll an internal div while we're in this region
* |
* |-----
* |
* | region C - scroll the window while we're in this region
* |
* ------------------- bottom
*
* When a scroll event jumps from region A to C (e.g. user pressed PgDn), there is no need to scroll
* A to the edge, because C will be affecting the window more accurately. But region B affects a different
* element, so must be scrolled to the edge.
*
* @param {Bacon.Property} scrollProperty - Bacon Property that emits { top : number }
* @param {Array<{setScrollTop : function(number), getHeight : function() : number, groupId : * }>} regions
*/
function RegionScrollForwarder(scrollProperty, regions) {
var destroyed = new Bacon.Bus();
regions = _.map(regions, function(region) {
var cachedHeight = null;
return $.extend({}, region, {
getCachedHeight : function() {
if (cachedHeight == null) {
cachedHeight = region.getHeight();
}
return cachedHeight;
},
invalidateCache : function() {
cachedHeight = null;
}
});
});
var latestForwardingInfo;
// Subscribe to the scrollProperty so we can set the initial scrollTop for regions
scrollProperty.subscribe(function(e) {
// Only operate on the initial event.
if (!e.isInitial()) {
return;
}
var initialScroll = e.value().top;
var offset = 0;
var currentRegion;
// set the scrollTop for all regions
_.forEach(regions, function(region) {
var height = region.getCachedHeight();
var isBelow = offset + height >= initialScroll;
if (!currentRegion && isBelow) {
currentRegion = region;
region.setScrollTop(initialScroll - offset);
} else {
region.setScrollTop(isBelow ? 0 : height);
}
offset += height;
});
})(); // invoke to unsub straight away
var forwardingInfo = scrollProperty
.takeUntil(destroyed)
.slidingWindow(2,2)
.map(fn.spread(function(previousScrollInfo, scrollInfo) {
var offset = 0;
var prevRegion;
var diff = scrollInfo.top - previousScrollInfo.top;
var region;
var offsetSoFar = 0;
_.some(regions, function(currentRegion) {
var height = currentRegion.getCachedHeight();
if (!region && offsetSoFar + height >= scrollInfo.top) {
region = currentRegion;
offset = offsetSoFar;
}
if (!prevRegion && offsetSoFar + height >= previousScrollInfo.top) {
prevRegion = currentRegion;
}
offsetSoFar += height;
return region && prevRegion;
});
if (!region) {
throw new Error("No forwardee handles " + scrollInfo.top);
}
var info = {
scrollInfo : scrollInfo,
localTop : scrollInfo.top - offset,
diff : diff,
forwardTo : region,
previousRegion: prevRegion
};
return info;
}));
function scrollRegionsToEdge(regions, getEdge) {
_.chain(regions)
.filter(function(region, i, regions) { // unique by groupId, ensuring first region is chosen
return !_.some(regions.slice(0, i), function(otherInfo) {
return region.groupId && region.groupId === otherInfo.groupId;
});
})
.forEach(function(region) {
region.setScrollTop(getEdge(region) === 'bottom' ? region.getCachedHeight() : 0);
});
}
var stopForwarding = forwardingInfo
.onValue(function(forwardingInfo) {
latestForwardingInfo = forwardingInfo;
var forwardToRegion = forwardingInfo.previousRegion;
// scroll all the regions between now and last time to their closest edge
if (forwardToRegion !== forwardingInfo.forwardTo) {
var betweens = baconUtil.toArray(baconUtil.takeBetween(Bacon.fromArray(regions), {
start : forwardToRegion,
end : forwardingInfo.forwardTo,
startInclusive : true,
endInclusive : false
}));
var scrollingDown = forwardingInfo.diff > 0;
scrollRegionsToEdge(
scrollingDown ? betweens.reverse() : betweens,
fn.constant(scrollingDown ? 'bottom' : 'top'));
}
forwardingInfo.forwardTo.setScrollTop(forwardingInfo.localTop);
});
// Force all regions back to the right place - should have no affect unless offsets have changed.
// Regions above the currently focused one are scrolled to the bottom.
// Regions below the currently focused one are scrolled to the top.
function resetPositions() {
_.invoke(regions, 'invalidateCache');
if (latestForwardingInfo) {
var regionIndex = _.indexOf(regions, latestForwardingInfo.forwardTo);
scrollRegionsToEdge(_.reject(regions, function(region) {
return region === latestForwardingInfo.forwardTo ||
(region.groupId && region.groupId === latestForwardingInfo.forwardTo.groupId);
}), function(region) {
return _.indexOf(regions, region) < regionIndex ? 'bottom' : 'top';
});
latestForwardingInfo.forwardTo.setScrollTop(Math.min(latestForwardingInfo.localTop, latestForwardingInfo.forwardTo.getCachedHeight()));
}
}
return {
regionChanges : forwardingInfo.map('.forwardTo').skipDuplicates(),
forwardingInfo : forwardingInfo,
heightsChanged : resetPositions,
destroy : function() {
stopForwarding();
destroyed.push(true);
destroyed.end();
}
};
}
return RegionScrollForwarder;
});
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