New <trackName>_hideKids=1 directive to URL parsing to turn off super track or composite children and &ignoreCookie=1 settings

[Brian Lee]

For Track Hubs that want to build links to their Hubs with specific subtracks turned on or off via one URL string there is a new URL parameter <trackName>_hideKids=1 on that can allow one to configure the display more easily.  Along with setting is ignoreCookie=1 to prevent cart clashes. 

Here is an example of using this with a native track group on the UCSC Genome Browser: 

https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&hideTracks=1&ncbiRefSeqCurated=full&refSeqComposite=full&ncbiRefSeqCurated_sel=1&refSeqComposite_hideKids=1&ignoreCookie=1

For the hg38 database, this hides all tracks (&hideTracks=1) then turns on the RefSeq composite (refSeqComposite=full), but hides all the subtracks (refSeqComposite_hideKids=1) and then turns on one specific subtrack (&ncbiRefSeqCurated=full) and to checkmark a box to display that track (&ncbiRefSeqCurated_sel=1). Lastly there is an added "&ignoreCookie=1" setting that prevents conflicts form occurring on loading these links that might intersect with pre-existing settings in a user's browser.

This can be useful for a Track Hub as well. In the below example &hubUrl=http://hgdownload.soe.ucsc.edu/hubs/gtex/hub.txt loads the GTEx signal hub. By default this hub has about 26 signal tracks displayed of over a 1000 signal tracks from Female Donors aged (20-49 years), inside a super track that has even more signal tracks from multiple age groups.

This below URL will now load just one subtrack from that group, turning off the default 26 subtracks, and then turning one female Artery - Tibial (GTEX-11EM3-2226-SM-5H11Y) track:

https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg19&hubUrl=http://hgdownload.soe.ucsc.edu/hubs/gtex/hub.txt&hideTracks=1&gtexRnaSignalFemaleYoung_hideKids=1&gtexRnaSignalFemaleYoung=full&gtexRnaSignalSRR1311348=full&ignoreCookie=1

Here is a similar link that loads a specific male Heart - Left Ventricle (GTEX-11LCK-0926-SM-5A5KA) track that is likewise instead a super track in a composite group that has over 1400 subtracks:

https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg19&hubUrl=http://hgdownload.soe.ucsc.edu/hubs/gtex/hub.txt&hideTracks=1&gtexRnaSignalMaleYoung_hideKids=1&gtexRnaSignalMaleYoung=full&gtexRnaSignalSRR1311243=full&ignoreCookie=1