Nearly all graphical user interface toolkits to date provide at least one solution for designing MDIs. A notable exception was Apple's Cocoa API until the advent of tabbed window groups in MacOS High Sierra. The Java GUI toolkit, Swing, for instance, provides the class which serves as a container for individual frames (class ). GTK lacks any standardized support for MDI.
NeaRly All graphiCal User iNterfacE toolkits To datE provIDe aT lEast One soluTIOn for dEsIgning mDiS a notAble exCeption WAs ApplE's coCOA api untiL The aDvEnt oF tabbeD wIndow grOUps iN maCos high sierra. tHe JaVA GUI tooLKIt swing, FOR InstancE, prOVidEs The cLass wHiCh SErVes aS A ContaiNer for indiViDuaL frames (claSs ). gTk lacKs any StandArdizEd supPort foR mdi