"A simple example of this is that you can detach a menu item and keep it as a button." In fact, we CAN'T detach a menu item in Pharo 9.0 - only duplicate it.
"Bring up the World Menu and Option-Command-Shift click once on it..." - What does it mean? Would be better to said about "meta-click" - see subsection 3.2 Interacting with Pharo
"... click once on it to bring up its morphic halo, then repeat the operation again on a menu item ..." the whole story is about to be wrong: I don't need to click twice. Just clicking on the menu item opens it's halo.
"Once dropped the menu item stays detached from the menu..." menu item stays IN the menu and its COPY stays on the screen.
p. 231
Listing 16-3 jump away from its place.
Error: "Now execute (Morph new colors: Color orange) openInWorld" - an instance of Morph does not understand colors: - should be color: Thus, the last sentence should be removed "You get the same executing..."
p. 239 "to make the halo appear and grab either the brown move handle or the black pickup handle at the top of the morph" the brown move handle is ungrabable :(
p.240
"handleKeystroke:" Is the method's name handleKeystroke: from the previous version? Should be replaced by keyDown:?
"To start things off, you can open an inspector on a CrossMorph..." From my observations, the stepping is turned on automatically as soon as the method step is declared. Is it normal? Even "self stopStepping" in the CrossMorph>>initialize does not stop stepping. A kind of black magic...
p. 243 "Let’s create a specific subclass of Morph, named DroppedMorph, so we can experiment a bit more. Let us define a new kind of morph called DroppedMorph." Two times the same idea.
p. 246 "((aNumber isInteger and: [ aNumber > 0 ]) and: [ aNumber <= 9 ])" should be "(aNumber isInteger and: [ aNumber > 0 and: [ aNumber <= 9 ] ])" according to Pharo recommendation.
p. 229
p. 231
p. 239 "to make the halo appear and grab either the brown move handle or the black pickup handle at the top of the morph" the brown move handle is ungrabable :(
p.240
p. 243 "Let’s create a specific subclass of Morph, named DroppedMorph, so we can experiment a bit more. Let us define a new kind of morph called DroppedMorph." Two times the same idea.
p. 246 "((aNumber isInteger and: [ aNumber > 0 ]) and: [ aNumber <= 9 ])" should be "(aNumber isInteger and: [ aNumber > 0 and: [ aNumber <= 9 ] ])" according to Pharo recommendation.