I'd call it "user interface code". If you refer to the stack dump below, you see that the TextEditor pretty much directly invokes the Compiler, triggered by a keystroke event that is handled by the hierarchy of morphs and generated by the Morphic main loop (with a slight diversion via the ToolSet layer).
UndefinedObject>>DoIt
Compiler>>evaluateCue:ifFail:
Compiler>>evaluateCue:ifFail:logged:
Compiler>>evaluate:in:to:notifying:ifFail:logged:
[] in SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
BlockClosure>>on:do:
SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
SmalltalkEditor(TextEditor)>>printIt
SmalltalkEditor(TextEditor)>>printIt:
SmalltalkEditor(TextEditor)>>dispatchOnKeyboardEvent:
SmalltalkEditor(TextEditor)>>keyStroke:
[] in [] in TextMorphForEditView(TextMorph)>>keyStroke:
TextMorphForEditView(TextMorph)>>handleInteraction:fromEvent:
TextMorphForEditView>>handleInteraction:fromEvent:
[] in TextMorphForEditView(TextMorph)>>keyStroke:
StandardToolSet class>>codeCompletionAround:textMorph:keyStroke:
ToolSet class>>codeCompletionAround:textMorph:keyStroke:
TextMorphForEditView(TextMorph)>>keyStroke:
TextMorphForEditView>>keyStroke:
TextMorphForEditView(TextMorph)>>handleKeystroke:
KeyboardEvent>>sentTo:
TextMorphForEditView(Morph)>>handleEvent:
TextMorphForEditView(Morph)>>handleFocusEvent:
[] in HandMorph>>sendFocusEvent:to:clear:
BlockClosure>>on:do:
PasteUpMorph>>becomeActiveDuring:
HandMorph>>sendFocusEvent:to:clear:
HandMorph>>sendEvent:focus:clear:
HandMorph>>sendKeyboardEvent:
HandMorph>>handleEvent:
HandMorph>>processEvents
[] in WorldState>>doOneCycleNowFor:
Array(SequenceableCollection)>>do:
WorldState>>handsDo:
WorldState>>doOneCycleNowFor:
WorldState>>doOneCycleFor:
PasteUpMorph>>doOneCycle
[] in MorphicProject>>spawnNewProcess
[] in BlockClosure>>newProcess