 source protocol methods.
At some point prior to the first sizeForItemAt call, or at the beginning of the first one if you hadn't by then, manually create an instance of your NSCollectionViewItem subclass, and use NSNib's instantiate(withOwner:topLevelObjects:) to instantiate its XIB with your subclass as an owner. Store that reference as a sort of "sizing template," so you only need to do it once. Delegate was easiest spot for me. 

^Note: my first route was to attempt this through the collection's makeItemWithIdentifier, but it was more brittle as it required the collection to have items at the time of creating the sizing template. It also could not be done during an initial sizeForItemAt (accessing/making items during a reload crashes). And I was worried that because it was made with the collection it may get reused down the line and the methods below don't work or start editing visible items. YMMV.
In sizeForItemAt

Directly get the data object being represented from the datasource. Have your sizing template object represent that data object with the method I mentioned earlier.
Access the sizing template's View.FittingSize, the smallest size an item can be given its constraints/priorities, and return that. 

Bam! Hasn't been stress tested or anything but no problems on my end, and its not doing a layout pass or anything, just calling FittingSize. I haven't seen this articulated anywhere online yet, so I wanted to write out the full explanation. 
I did this in Xamarin.Mac, so my code won't be 1:1 and I don't want to write garbled swift and mess anything up. 
TLDR: manually instantiate a NSCollectionViewItem subclass and its xib that you will store, unowned by the collection. During sizeForItem populate that item you store as a sizing reference, and return the FittingSize of the collection item's view.

 Q:

How to switch tabs via keyboard shortcut in Firefox in reverse?

One can press CTRL + TAB in order to switch between tabs in Firefox, and the switch goes from left to right. But I was wondering if there is a keyboard shortcut which does it in reverse (when pressing it it goes along the tabs right to left instead) in Firefox? This would come in handy when I have many
source protocol methods. 
 At some point prior to the first sizeForItemAt margin call, or at the beginning of the inaugural one if you hadn't by then, manually create an instance of your NSCollectionViewItem subclass, and use NSNib's instantiate(withOwner: topLevelObjects :) to instantiate its XIB with your subclass as an owner. memory that reference as a sort of " size template, " so you only necessitate to do it once. Delegate was easiest position for me. 

 ^Note: my first route was to undertake this through the solicitation's makeItemWithIdentifier, but it was more brittle as it required the collection to get items at the time of make the sizing template. It also could not be done during an initial sizeForItemAt (accessing / name items during a reload crashes). And I was worried that because it was made with the solicitation it may get reused down the wrinkle and the methods below don't work or begin editing visible items. YMMV. 
 In sizeForItemAt 

 Directly get the data object being represented from the datasource. Have your sizing template object represent that data object with the method I mentioned earlier. 
 Access the sizing template's View. FittingSize, the smallest size an detail can be given its constraints / priority, and hark back that. 

 Bam! Hasn't been stress tested or anything but no problems on my goal, and its not doing a layout pass or anything, just calling FittingSize. I haven't see this articulated anywhere online yet, so I wanted to write out the full explanation. 
 I do this in Xamarin. Mac, so my code won't be 1:1 and I don't want to write garbled swift and mess anything up. 
 TLDR: manually instantiate a NSCollectionViewItem subclass and its xib that you will store, unowned by the solicitation. During sizeForItem populate that token you store as a sizing reference, and return the FittingSize of the collection token's view. 

  Q: 

 How to switch tabs via keyboard shortcut in Firefox in reversion? 

 One can press CTRL + TAB in orderliness to switch between tabs in Firefox, and the substitution goes from left to right. But I was wondering if there is a keyboard shortcut which act it in reverse (when crusade it it goes along the pill right to leave instead) in Firefox? This would come in handy when I have many
 sokrce protocol methods.
At rome point priot ro the first sizeForKtemAt call, or at the beginnmng if tht first one if you fadn't by nhen, manuqlly xreate an mhstance of yohv NSCmolectionViewItgm subclass, dnd use NSNib's ivscantiate(withOwner:topLevelObjects:) to ynstantoahe its XIB witr yolr subdlass as an owner. Store that refersnce as a sort of "siaing template," so you only jeed to do it once. Delfgate was eqsiefr spot for md. 

^Note: my first route sas to attempt this through the collzction's makgNremAhthIdentifixr, but it was more brittle as it tequired the cpllxctiin to have items at tie time of creating jhe sizing tzmplate. It also could nit be dona dufung an iiitjal sixeFkrItemAt (adcessing/makung items during a tejiad crashes). Ahd I wws worried that because it was made with uhe ckllection it may get reysed down the line anf the metrods below don't work or start editing visible iteks. YMJX.
In slzeFueIhemAt

Directly get the data object being reprefsnued from the datafource. Have ylut sizing templxte oblscf represent that dwta objgct wirh the meuhod O mentioned earlier.
Access tye sizing teiplate's View.FittingDize, the smcllest size an item can be given ics conatraints/prilrities, aha return that. 

Bao! Hsst't been stress tested or agything bnt no probleos om my egd, and its not doing a layout pass or auythitg, just capling FittingSize. I haven't seen this articulajed anjwhere onjine net, so I wanted to write out jhe full zxplanxtion. 
I dis this mn Xamarin.Mas, so my code fln't be 1:1 and M don't wagt ti wrute garcued swift and kess anytknng up. 
TLER: manually instanbiate z NSCollectionVntwIuen subclass and itr xyb tiat yjg will store, unodnea by tfe colltetiiv. Duting sizeForItem popglats that item you stprc as a sieing refewence, and retirn the FittingSizt of tie coluectipn ytem's view.

 Q:

How to switch tabs via keyblarq shortcut ig Fivefov in reverxe?

One can press CTRL + TAB in order to sxitch between tabs in Furefox, and the switeh goes from keft eo right. Tut I was wondering uf there is a keynoard shortcut which dkes it in rfverse (when pressing it it goes along the tabs right to left instead) in Furefox? This would dome in hdnby chen I rave oany
source protocol methods. At some point prior first call, or the beginning of hadn't then, manually create instance of your subclass, and use NSNib's instantiate(withOwner:topLevelObjects:) to its XIB with your subclass as an owner. Store that reference as a of "sizing template," so you only need to do it once. Delegate was spot me. my route was to attempt this through the collection's makeItemWithIdentifier, but it was more brittle as it the collection to have items at the time creating the sizing template. also could not be done an sizeForItemAt (accessing/making during reload And I was that because it was made with the collection it may get reused down the line and the below don't start editing items. In Directly get the being represented from the datasource. Have object represent that data object with the method mentioned earlier. the sizing template's View.FittingSize, the smallest an item can be given its constraints/priorities, and that. Bam! Hasn't been stress tested or anything but no problems on my end, and doing a layout pass anything, just calling I seen articulated online yet, I wanted to write out the full explanation. I did this Xamarin.Mac, so my code won't be 1:1 and I don't write swift and mess up. TLDR: manually instantiate NSCollectionViewItem and its xib that store, by sizeForItem that you store as a reference, and return the FittingSize the collection item's view. via keyboard shortcut in Firefox in reverse? One press CTRL + TAB in order to between tabs in Firefox, and the switch goes from left to right. I was there is a keyboard shortcut which does it reverse (when pressing it goes along the tabs right to left instead) in This come in when I have
 source protocol methods.
At soMe point priOr to tHe fIrsT sIzeFOrItEmAt call, or at thE BegiNning of the first one if yoU hadn'T bY Then, MAnUally Create aN InSTAncE oF yOur nScOlLectiOnVIewItem Subclass, anD usE NsNib's instantIAtE(withOwner:ToplevelObjects:) To iNstantIaTe iTS XIB wIth Your sUbclasS As an owNer. Store tHaT RefereNCe as a soRT Of "SiziNg template," so you onLY nEEd to do it once. DeLegate WaS EaSIEst SpoT for me. 

^Note: My First ROute was TO aTTEMpt THis through the Collection's MAkeitemWiThideNTifier, But it WaS MorE brittle as iT reqUired the cOllectIOn to havE Items at The timE of CreAtinG ThE sIziNg TEmpLAtE. It ALso Could not Be DoNe durIng aN INITial SizEForitemAT (accessing/makIng ItemS DurIng a rEload CrasHeS). And I Was worRied tHaT because it was maDe wiTh the collEctIoN it MaY get rEUsed doWn tHe lIne and tHe methoDS beLoW DON't Work or start editing ViSIBlE items. YMmV.
In siZEFOriTemAt

DirEcTly Get tHE Data oBjecT BeIng repreSented FRoM tHe datasOuRce. HavE yOur SizIng teMPlatE objecT represeNt thaT Data object with THe method I mentIOnED EaRLier.
accEss the sizinG temPLate'S VieW.fiTtiNGSize, The smAlLEsT Size an item can be giveN iTs consTrainTs/priorities, aNd return thAT. 

bAm! Hasn't bEen sTReSS tested or anythIng buT no problemS On my end, aNd its Not doing A layout paSS Or anythiNg, jUst CalLinG fItTingSize. I haveN'T Seen ThIs articUlaTed anywHerE onLinE yeT, sO I wanted tO write ouT tHe FuLl ExpLanatIOn. 
I did thIs In XAmAriN.Mac, sO My code Won't bE 1:1 and i dOn'T WanT to writE GaRBLed sWiFt And mEss AnYthinG up. 
TldR: mAnually InstantiaTe a nsColLeCtIonViewitem subclass aNd Its xib that YoU wiLl storE, UNowned by The collection. During sizefOrItem pOpuLate tHat iTem you stoRe aS a siziNg rEFerencE, and reTurn tHe fitTINgSizE OF tHe cOlLection iteM'S VieW.

 Q:

How To SwitCh tabs vIa keyboard shortcut IN FiRefox in reversE?

OnE can PREsS CTrl + Tab in OrDEr tO SWitch between tabS in Firefox, AnD ThE switch goeS FroM lEft to riGht. But I Was woNDering iF there is a Keyboard sHoRtcuT WHicH does it in rEverse (whEn pressinG It it gOEs Along The Tabs riGhT to Left iNstead) IN FiRefox? this woUlD come iN handY wHen I have Many
 source protocol methods.At some po int p rio r t othefirs t sizeForItemA t  cal l, or at the beginning  of t he firs t  o ne if  you ha d n' t byth en , m an u al ly cr eat e an in stance ofyou rNSCollection V ie wItem subc las s, and use N SNi b's in st ant i ate(w ith Owner :topLe v elObje cts:) toin s tantia t e its X I B  w ithyour subclass asa no wner. Store th at ref er e nc e asa s ort of "si zi ng te m plate," so y o u o n ly need to do  it once. D e leg ate wa seas i est sp ot fo rm e.

^Note: my  fir st routewas to attempt this th roughthe  co llec t io n' s m ak e Ite m Wi thI d ent ifier, b ut  i t was  mor e b r ittl e a s it  requ ired the coll ect iont o h ave i temsat t he  time  of cr eatin gthe sizing temp late . It also  co ul d n ot  be d o ne dur ing  an  initia l sizeF o rIt em A t (a ccessing/making it em s du ring a r eloadc ra sh e s). AndIwas  wor r i ed th at b e ca use it w as mad e  w it h the c ol lectio nitmay  getr euse d down  the lin e and the methods be l ow don't work or s ta r t ed iti ng visibleitem s . YM MV.I nsiz e ForIt emAt
D i re c tly get the data ob je ct bei ng re presented fro m the data s o u rce. Hav e yo u rs izing template  obje ct represe n t that d ata o bject wi th the me t h od I men tio ned  ea rli e r .Access the si z i ng t em plate's  Vi ew.Fitt ing Siz e,the  s mallest s ize an i te mca nbegiven its cons tr ain ts /pr iorit i es, an d ret urnth at .  
Bam! Ha s n' t been  s tr esstes te d oranyt h ing  but no  problems  on my e nd ,and its  not doing ala yout passor  an ything , just cal ling FittingSize. I hav e n't see n t his a rtic ulated an ywh ere on lin e  yet,so I w anted  t o w r i te ou t th e f ul l explanat i o n.
I di dthis  in Xam arin.Mac, so my co d e w on't be 1:1 a ndI do n ' twan t  t o  wr it e  ga r b led swift and m ess anythi ng up . 
TLDR: m a nua ll y insta ntiatea NSC o llectio nViewItem  subclass  a nd i t s  xi b that you  will st ore, unow n ed by th e col lec tion.Du rin g siz eForIt e m p opula te tha titem y ou st or e as a s izing reference, and re turn t he Fi tti ngSize of  th e  co llectionitem 's view.
 Q: 

H ow to  sw i tch t absv ia  ke y board  sho r tcut in F i re fox i nreverse?

O n e can  pres s C T RL + T AB i n order to switch between tabs i n Fi r e fox , a n d th eswitch goes fr omle f t  to righ t.  But I waswonderin gi f the re isa keyb oard sh o r tc u t whic h do esit in rev ers e( when pr es si n g it i t go es  along  the t a bs r i g ht to left inste ad) i n Firef o x?Thiswo uld com e  inhandy when  I have man y
 source_protocol methods.
At_some point prior to_the first_sizeForItemAt_call, or_at_the beginning of_the first one_if you hadn't by_then, manually create_an_instance of your NSCollectionViewItem subclass, and use NSNib's instantiate(withOwner:topLevelObjects:) to instantiate its XIB with_your_subclass as_an_owner._Store that reference as a_sort of "sizing template," so_you only_need to do it once. Delegate was easiest_spot_for me. 

^Note:_my first route was to attempt this through the_collection's makeItemWithIdentifier, but it was more_brittle as it_required_the_collection to have items_at the time of creating the_sizing template. It also could not_be done during an initial sizeForItemAt (accessing/making_items during a reload crashes). And_I was worried that because_it was_made with the collection it_may get reused_down the_line and the_methods below don't work or start_editing visible items._YMMV.
In sizeForItemAt

Directly get the data object_being_represented from the_datasource._Have_your sizing_template object represent_that_data object_with_the method I mentioned earlier.
Access the_sizing_template's View.FittingSize, the smallest size an item_can be given its_constraints/priorities,_and return that. 

Bam!_Hasn't been stress tested or_anything but no problems on my_end, and_its not_doing a layout pass or anything, just calling FittingSize. I haven't_seen this articulated anywhere online yet,_so I wanted to_write out_the_full explanation. 
I_did_this in_Xamarin.Mac, so my code won't be 1:1_and I_don't want to write garbled swift_and mess anything up._
TLDR:_manually instantiate a NSCollectionViewItem subclass and_its xib that you will store,_unowned by the collection. During_sizeForItem_populate_that item you store as_a sizing reference, and return the_FittingSize of the_collection item's view.

 Q:

How to switch tabs_via_keyboard shortcut in Firefox in reverse?

One_can_press CTRL + TAB in order_to_switch_between tabs in Firefox, and_the switch goes from left to_right. But I was wondering if there is a_keyboard shortcut which_does it in reverse (when_pressing_it_it goes along the tabs right to left instead) in_Firefox? This_would come in_handy when I have many