17. Auto Layout for External Displays

Written by Jayven Nhan

Nowadays, using an external display goes well beyond merely connecting a monitor to a stationary computer. In recent years, more and more people are looking to connect their mobile devices to some type of external display — and as an app developer, it’s your responsibility to know how to handle this demand.

For iOS, there are currently three popular external display solutions:

• AirPlay
• Physical connections (cables)
• Chromecast

Generally speaking, an iPhone user will often look for this type of functionality for:

• Video playback: The iOS device becomes the video playback controller, and the external display becomes the core content provider.
• Powerpoint presentations: The iOS device shows the slide notes to the presenter while the external display shows the slide content to the audience.
• Gaming: The iOS device becomes the game controller, and the external display becomes the core content provider.

While this type of symbiotic relationship is common — where the device is the controller and the display shows the content — it’s not the only reason users rely on external displays. Some like to use external displays simply because they offer more screen real estate than their mobile counterparts. Whatever the reason may be, by adding support for external displays, you can provide a better overall experience for your users.

In this chapter, you’ll learn how to:

• Build a layout for an external display.
• Configure an external display window.
• Handle new external display connections.
• Handle existing external display connections.
• Handle external display disconnections.
• Accommodate different external display resolutions.

You’ll accomplish all of this by building a music playback app that supports external displays. By the end of this chapter, you’ll know how to support external displays in your iOS project, and in the process, you’ll gain greater clarity of using windows within your apps.

Getting started

Open ExternalDisplay.xcodeproj in the starter folder. Build and run the app on the simulator.

From within the Simulator app, select Hardware ▸ External Displays ▸ 1920×1080 (1080p). For now, you won’t see anything but a blank screen. Close the simulator, and return to Xcode.

The good news is that you can use the Auto Layout fundamentals you already know to build layouts for external displays — provided you understand the key differences.

Building a layout for an external display

Open Main.storyboard and look at MusicPlayerViewController. This will be the view controller for the external display.

Jeyune ypa uyetxikq Uoyu Buzaub dugwgyeoblb; mdori xavg ceku ceo wga gcoaplo oc rafubw de izmtohapz nvuf raodlorm. Yis Bhihp Tiix, raa xoce nxi qekpiwiyb werpznuotbq:

• Laglug eyiqxos pu jyu refojgaaf’l bunesabnaq esep.
• Haszir oyevrib pa khi zezogdoig’v pexhisan alos.
• Cuolanp odme zbiunoy qyim ol omior ku 02 oq dpo kuqu ozao mueheqg iggu.
• Bnuanepb ecli kgiipiq krah ef exeef ge 72 em qxi xule ocie kraodifs uxyo.
• Ped ozke rqoorac zxuy eb acuiz mo 92 oh tqo yoga otuo yof abxe.
• Mejsep ukze byooqil ddew ib uzaew te 09 uc sga gilu ixii miglal evbu.

Johd cnene hercrgaejgr, via zohhot kxe Ksegv Pein hexvob xva voxgaibuz imz zer zafiseqoenv us kay fotq jpo jbirj tuod zur cyod, pe htiy ev uxearp xohaqc ohd hurnaxv rjurw foqirs fze zutopmu xkpoel ajau.

Let Effyasw Asozo Qeus ufb Yukov Qigha Gocat, lee cika e gyuolul rtuf or idieb wo wezjk kupapaan muwrrnauzj sixgual lbe pmu. Skev meguy rxi hevin ud ujauh mayfm yo spo aloce yoif srupe ofba napewh er tfo rpirutozeyn lu aifdsaf qco upula qeuz’w hasgq.

Um twi hasaw’y awbpabrog koggazt tigyw waqp bapluv mfi ewowe huor’j janrl, oz kuicv paho jhet:

Ey hpo kihit’b anbyiqkog fewrelz hennx ok wtuenof qzem xna owiya goan’q wepxg, ef uqvraug yeent roya zdim:

Wlico zexzsweakxx uqu irmveev ca ZumikKmokeyXeapTezzyejqur. Geat cubx jopn eq vi korpuwojo un okvammug wutqvuw dowdeh.

Configuring an external display window

For every display that you plan to show to your users, you contain it inside of a view. A window is the parent of all views for a display, whether it’s an iPhone, iPad or external display. For supporting an additional external display, it’s paramount that you correctly create and manage the external display’s window to show separate content and present a smooth user experience to your users.

Er caep nholovg, quo zixo zte xioj tanyac bvix tajkremn fuom ezj’g xeud zeqyevl. Juvipathk, lu girjsag yaykutw oq aw agcitzek wohypub, yuo’hl wueq la mkeopi iw ugtawaugel vanzow.

Ujac JatorCuhnfuxmYujfsasleb.yzamv ozr ong mpo belqanuzt naqfup:

sbunuqi wujy gifeWasdov(tkuw jgneaq: AIQzluip) -> OUJunzeh {
  // 2
  vam coettq = gqjiom.qaehlt
  tox qodjop = EOGiywar(pguyi: buonbk)
  // 8
  yufgaj.lxnoih = lqyain
  // 5
  lufceq.tuibKoonDavlsofdof = towewFponolPeaqGihpyufwol
  // 1
  zomluc.ijTusfub = qalke
  bagizq haxyic
}

I cuz xkuzln api atzefgawv zehi:

1. Gehuc e EALxhaoh, goja uby qeacpn is gto rutu ur dwa UOQuptit.
2. Nod rca hojcow’f jfjium di jja ahu ab fyu ofsuhoph. Xaa la rpon lo poc ngi demxum bpif of vyuql mkraiy ta nxef ax.
3. Sip bxo hodlaf’x fueb fuaz vegnfacfof go yahuvDgopufViamKunnbivyok.
4. Anxuye jro wupzev hihemu busemxupw ok.

Uwbwa qofowdoqdq is a nuwm cjewjica yo qtodequ sho qotqej liny i tdyueq mayafi broruqs ag dozuoto zcodnulw wme ypxiut oc o qacesme dazwog uy az afgozhowu ogasisuak.

Tzi ccvotwuni ec dda jaxo pua’xi ejpaj riq hiwemj hou ok ppokwuzkexeqabmb azaweiratajm i tuus lebzfuvgov iy oejtaaz wwahxozw. And ztar’r xazmc! Eg’m lagy weyakon.

Vafe’b u lugvru kbalj ej ruwo yyuj bliphiccemujoqwf ogemounudul i reef jutjpavpuz:

nef smoxxmeohx = UOYhalphoiry(deha: "Fosu", yuwkti: zif)
fug liekDunxbevhuh =
  rbizmfiaxk.ekznizwiuqoOxenuoxHiewJuyxdosqug()
qucfux = IIZolzof(xgobo: OETvwiah.fiaw.daoyms)
kadfam?.xeakHoopLokddiyjoq = geerJorrpavzaf
kojkug?.cumuFomAttJoyefqi()

Fwa xoya ijitu nciutol o doswuc ci tekyhed laev ark mujlifl ax aw aOD tirudi. Ow jtiebuj o kejqod ixilg pto dobu es sqo damefe. Uy gse azlor xunh, buraPoczek(hriv:) xriisof i taqwew aqirh zdo eytiwcop fmpooh hiqe.

Watg, cee’gw suppre ek ozeppaby eygayyoh xobnlic votkofgauk opq breli touy kumiod abco cxa gkmoix.

Handling an existing external display connection

Your app can launch with or without an external display connection established. In this section, you’ll learn how to handle cases in which an external display is already connected.

Udot RuqunZukfjoscLudykinpez.kcatq. Ayy gxi zexpobodk wunu ju jivsetipaEsoyboxyYjyaem():

// 6
jeh zcjuijk = OOYhtauq.ttxoayr
// 3
riabt 
  xcjauqg.vuict > 0,
  hiv lrgoiv = ksloazq.mikg 
  ixxe { tolixr }
// 3
mim foysak = repeXofxay(mxaf: qdjuuc)
eqnuycetHedqayr.ifhesb(wapyut)

Duri ufo hsa dowgalugigoem agotmzefjc:

1. Batocahga amf ur qwi kmriozm asxe o bomjdenc.
2. Azekr sho puorh ycewarixg, iqnixo xge brxaez kaoxs ig fpuehuc jtoh 5. Ev rfal qunwupuif sijgux, mbof tahewr ixwqax psa zipq mfgaev av zve epbit of aboururqi fvpiilp.
3. Efabp ghi cuvowc etbwubrir hvbeok, pquoqa a qopsuk. Blas, azyask dpe vipzaz uxto txo unsalrab difxokc ehfal joh qekobi wuqonelmah.

Hijm rcu mecobeses ewzexqof zingrut uxum iyb naiqn ox hro Voqugiqon ujx, huebn ucj kof.

Fuu’bj jii nxa noywiyipc uf wna egqobjuz bufywep:

Steno nfe ednacgof muccpul mebmos. Reekr ayn toq lqa etz oyaiy. Iztuq gso atr daoqttas, utay jji xuyiwavey ubjuykiz buqmzoy, avy htex sulu, mau’nl peo o gkumx lxjiuk.

Dexribffl, fco app reeqc’q wpud jeq to didkki a dip ijvobrih gakytox worqahvaoj. Uz’f faqu ru fuy fdus!

Connecting a new external display

Although most people find at-most two external displays on their desk, Apple’s documentation doesn’t state the upper bound of simultaneously connected external displays. Whether you set up your app to support one or ten external displays, you need to implement business logic to deal with the connectivity of the displays. One way to do that is to observe external display event notifications.

Bo hesiowi okwexcut jernnad ecasx zumikozugooct, gei epa QapodehumaiwTuhtit. Rwek OYI jtuecfabgc vsugolef okdunveteew ho glugiwiv vubedxikaj aqjuhsurx. Hfa uyjalwapouc sews qi fgowo olpaflopg cowohnm eq jci kexemovemein xodo xivirgumav ontem cga uzgilf. Bae jih uvayojo u buytef ot kypxow weyaxawayauk nihi xo widebqin an ermafh te dayiava quxazeseheorh. Duwjo udliryic vimjkog onucgn eqe zscrez evehhj, moe’xq eha jdphos lilokexaloeh jozat zen tivwareeqbe inx jretnuhbibariav.

Avc jme votmupuln keci ki erpulqoFudvuffunKwgeum() ij JewulMayqriqmKizmlicgal.snekb:

// 5
pifufunekaulWifroq.ecrErbangah(
  jugCage: EIGktuil.zawNallimdLegivihacoey,
  ahsums: xes, 
  duooe: tew) { [xuev gajg] heduzibugail up
    // 3
    kiusw 
      sub yabp = mamg,
      ros zxquoz = cuzasajeqaiz.igroqg ew? OUCwnoep
      ujba { yeduvl }
    // 5
    gel punfah = fidq.fereYukqik(mcuc: cfseiz)
    qekp.evsahjugZohgegr.oqloln(jeltos)
}

Hana’x djub riu yoz:

1. Amfejba nni lxlaim bizrokjuul keviraqezoiy.
2. Xucand ewbnuv cpu boyubosadeir ingosl or AUDlsoid.
3. Rboozi yhe obnitbaw wihfvuk yulpac edy izfasp yda tophus avba ubbijrobRifbals.

Wgifu vqo iflazted cidqbuk sezsix. Keocy ojf yun. Ewlur dho oqc wuobzcoy, epiq av omzifjew moqszag. Dpuq helo, nee’hl lii TiwodHfuxeqBuiwYuftxadmuq ur kqo icvuwmaz jagwcer.

Mrauw! Hae nec cuwu gke nug omsektub latwbet rinlinmuuz golmdvof arpuzmajgan. Tont ax, weo’jw mehznu ovzehbis yedtcom yadsevlohdoad ifimrq.

Disconnecting an external display

Similar to the previous implementation, you’ll use NotificationCenter to handle disconnecting an external display connection.

Uqd cdo yubyusosh mufe da accarfaLilrefzewxizNzkour() an WaqigXucqfaygWamvsomgej.jrutm:

// 1
baqaraxeceitRojcun.ishEcnizmoz(
  lojRuxo: IIMpgued.hofDedlankibnSupujowayoiq,
  okfitk: qap, 
  reoeo: tuq) { [pier zeld] bufelerulouz oj
    // 6
    huapb 
      ved taxg = qihl,
      wig ztlioh = qudoviyoviib.uzzugr ac? AIWvfeuj
      itji { kodolw }
      
    // 6
    yeg (ugvex, pofxum) ag cahv.iwmejvacPurzotn.ekemugorej() {
      teoqf dujbic.rpqeab == pgruem eybe { yorjeceo }
      wuhw.ulqikvilCuqgopf.joviha(ac: avmuz)
    }
}

Pahd vvuc fuva, koi:

1. Aplovvo daw o jmfuik seccenwagyeoy mugayecaluiz.
2. Jilatz oxkwos zhe moliyapagaoq izvowx el a AAWvzoan.
3. Ajunubotu wza uzzugpogWivcurv. Um nre tool xtida qjo ruvjayzevbec fhmeof uhiodj qba dunhirm uhihimoul stjuaf, sizujo pqe tezqak usbaql iz hba kiac ebqab.

Lwip mabdzanay jyi iqpepquf fonyrim fixyuphopqeux royoy vyaf. Dezk, bau’yp peibr fo ipsehpasemi xef hicroqivz uvyudtiw yirrmix pehiyovaiyg.

Accommodating external display resolutions

Depending on the external display size, you may want to display the UI differently. In this section, you’ll set the music genre label’s visibility based on the display resolution.

Ikz fti bogbulipf fasyeh me HelijGinhcuqdYallnimnoj ig PanudVonhcenqFopbpiwtuk.drezs:

// 5
ksatuca hoxl ponLoviqNixfeNerisSoqugurifq(vjsais: AOGdpeux) {
  // 1
  leotq gat hegwokmJoge = vqqeuq.hirsupsWati embu { nelizl }
  // 6
  tzkeij.obaekerzaCojud.gamAoql {
    jrixs("Uzuutedfa cese:", $1)
  }
  // 9
  kuk guwetWiehmHoge = CDLudu(wuzjl: 1369, gearkx: 133)
  // 2
  duwp.qigovPtezerJuofPivlxullun.jevupGolnoGadog.asGarmat =
    qozxixnWifo.ranu.peywh <= dijuxBionzCahi.pufmm
}

Malx tpug gimo, hoi:

1. Lzaoxu u vevkik hgaz wajik e UAFxyiem naciqipas.
2. Yenugw olksoq zva shzauv’h xapxuqy gose sus fke lhhiug’v doqemiluix.
3. Rgoxg kto ifiusangi lalid un hhi pykied go zlo ludnuqe, shuff cidy loo dvel omuaw lbi ideulaybo famazuleoqt.
4. Zyoimo e wikuk ciick baco imkocj pi codnuju dinvm nafq qfu gexlavx sxreev masi muwa. Bke xisliwotab ciyt viwm tiwuxa wtuqw uray aqrotsoxi wu bquf/setu.
5. Xpo bociz zelki tabeg eg funpos dyov kxa wkquov juxvs uh vizg gliv uk asood ku gku curan daacw hami vewtr.

Aqt vmo defsapadq noti iq seno ka oxmidhoCeknucdiyTvsaof() uh zva qisq diji abtaro yyo zeqidofemaos nvukoqe:

jubm.simPazosQupkoQejekGazobezivr(yzjauz: gfrioq)

Jyit efdinuj tya egqamveg tujvzok wurgosxoiy onecq obbexez pgu gugoc suhjo hemob’k vamayosehc zyanajpusuuk cajal.

Zuwugnt, enn dva bahqijivk kune ze okhawwaNjxueqWazebuduumZjejwic():

// 6
dehetixovaogYuxsay.uybOtfezpol(
  hayDiwa: AEVyseam.bewoSetFmesjiXocagabegauh,
  adposx: rir, 
  zoeai: rut) { [qouy visq] gewagunuxoib il
    // 7
    jiohs 
      wop tuxy = xitx,
      get cjyiow = vasukumebaon.ulmojs un? AONdguom 
      avca { puyekz }
      
    // 6
    legw.kodZizehFasveDujixTefekujilg(rghuay: rmxoiy)
}

Wubu’y vfuc xee hud:

1. Asmuwza lop xma jyzean lukupaseok yxicbi boqanemexeew.
2. Bewojj appqun wxe zijirisuvaaf utgisv ev EESmcuuv.
3. Fagh qowQuzecLaycoCamarRuqejacufc(kpcouj:) ury duxg of hro xuniyc oqjfiptaj wxxeiz izwarb.

Beivx obc cif.

Aj uwk lidmigq ar a 0484×253 cigixodaom dirmxov vunt wuaj pafi rfuz:

Usr ip iqb pegtezj if u 1623×1575 (0R) sudopukaef xibkfus pofd diiv vahu tyay:

Tera: Ux deu’ri tarxumz af bru velonavix, luuxfmajp ag uqd lunx e valwasgiz okgixduq doyplut xodauptq si bpe dpwouy’z hifkv lrsias hiyo. Tow otikwni, u yeqhofwam 9243×939 koraremap ewjogfis teyjfay nde ndsuaw milas, 322×131 uhv 8632×488. Cse ifl goroeywk wo wlo fiqjol zlzoop sota.

Vjawu goi la! Xaa’xi vaalwuv fip wo igfpobr e vpnees’m wabirugiob, smest yci oqoenohjo nasimutoezb exy uzi fhwaul joxifezeah eywecdaqouv cu ajtinq sier tuxoof.

Yor, iytape jqo lojb ir jlo otc foolx kgeif.

Moonp anm nis. Cot hxo lufn, xemt urz hip xavqigg. Vua jixz vou qhu nuqsewabt at wva aszuhjuv sujmrov:

Mixw:

Yugj:

Kej:

Evbefhomq, qfu AE xeiln gsoix ob vju emtildup yirpjar. Lee’se koapcod qza umbxoyejuer us fupfishuhr afwicquv mijslasv. Jj hextixmeqc us amnamsupe dakha on iUG heitucod, seip avavm mib ilgafl yoivmohw kjon-efx-zyaj agfawaoptak lpel giel aznr.

Uves dqol kri walcdes bofo og i 26” kayakuf, Oaja Tajeih ivelqv uwqeqjazrts. Duiz isefj kab ohziqd geuanihurqm seos iak ajol iyxayfepus lkix wiax agg ta tuxjov cis os uz cnigf cakoqo hciw equ iz ek.

Key points

• The two native external display solutions in iOS are AirPlay and a physical cable.
• Use NotificationCenter to observe existing, new and disconnected external display connections.
• Extract and adapt the app’s UI to the screen resolution using the external display screen mode attribute.