The Xerox star did not have overlapping windows at the time the mac group got to see it. I believe it had popup menus but no concept of a common menubar with pulldown menus the way mac had (and still has). Some of the features it lacked then were added later - overlapping windows was among them.
"There is a significant difference between using the Mac and Smalltalk. [Xerox PARC Alto Workstation] Smalltalk has no Finder, and no need for one, really. Drag-and- drop file manipulation came from the Mac group, along with many other unique concepts: resources and dual-fork files for storing layout and international information apart from code; definition procedures; drag-and-drop system extension and configuration; types and creators for files; direct manipulation editing of document, disk, and application names; redundant typed data for the clipboard; multiple views of the file system; desk accessories; and control panels, among others.
The [Apple] Lisa group invented some fundamental concepts as well: pull down menus, the imaging and windowing models based on QuickDraw, the clipboard, and cleanly internationalizable software. The Mac and Lisa designers had to invent their own architectures."
One account of the differences is here: http://www.folklore.org/StoryView.py?story=On_Xerox,_Apple_a...
According to Bruce Horn:
"There is a significant difference between using the Mac and Smalltalk. [Xerox PARC Alto Workstation] Smalltalk has no Finder, and no need for one, really. Drag-and- drop file manipulation came from the Mac group, along with many other unique concepts: resources and dual-fork files for storing layout and international information apart from code; definition procedures; drag-and-drop system extension and configuration; types and creators for files; direct manipulation editing of document, disk, and application names; redundant typed data for the clipboard; multiple views of the file system; desk accessories; and control panels, among others.
The [Apple] Lisa group invented some fundamental concepts as well: pull down menus, the imaging and windowing models based on QuickDraw, the clipboard, and cleanly internationalizable software. The Mac and Lisa designers had to invent their own architectures."