EA's reverse engineering will only create the static class structure and optionally class diagrams for each package. It does not create a single diagram for an entire application. In any real world example this will be too large to benefit anyone.
Instead I would recommend making use of your knowledge of the product, and some of EA's features to make more useful diagrams.
For example:
The hierarchy view shows you multiple levels of relationships for the currently selected class. The relationships window shows more information about each of the direct relationships to the current class, and also allows you to drop the objects onto the diagram. Finally, the Insert Related command (in the context menu of an object on a diagram) allows you to insert many related objects all at once.
So, with appropriate use of known significant objects you should be able to achieve some more useful diagrams.
However, if you still want to pursue that path we have a scripting example that adds all elements under the selected package to the selected diagram. A warning though, this could take quite some time, especially the layout at the end.
dim left
dim top
dim width
dim height
dim padding
dim layoutLeft
dim layoutWidth
layoutLeft = 10
left = layoutLeft
top = 10
width = 100
height = 100
padding = 30
layoutWidth = 2000
sub AddElementToDiagram ( theDiagram, theElement )
' Cast theDiagram to EA.Diagram so we get intellisense
dim currentDiagram as EA.Diagram
set currentDiagram = theDiagram
' Cast theElement to EA.Element so we get intellisense
dim currentElement as EA.Element
set currentElement = theElement
' Add the element to the diagram
dim diagramObjects as EA.Collection
set diagramObjects = currentDiagram.DiagramObjects
if left + width > layoutWidth then
left = layoutLeft
top = top + height + padding
end if
dim testDiagramObject as EA.DiagramObject
set testDiagramObject = diagramObjects.AddNew( "l=" & left & ";r=" & left + width & ";t=" & top & ";b=" & top + height & ";", "" )
testDiagramObject.ElementID( currentElement.ElementID )
testDiagramObject.Update()
left = left + width + padding
end sub
sub AddElementsToDiagram ( theDiagram, thePackage )
' Cast thePackage to EA.Package so we get intellisense
dim currentPackage as EA.Package
set currentPackage = thePackage
' Iterate through all elements and add them to the diagram
dim currentElement as EA.Element
for each currentElement in currentPackage.Elements
AddElementToDiagram theDiagram, currentElement
next
' Recursively process any child packages
dim childPackage as EA.Package
for each childPackage in currentPackage.Packages
AddElementsToDiagram theDiagram, childPackage
next
end sub
dim rootPackage as EA.Package
set rootPackage = GetTreeSelectedPackage()
dim currentDiagram as EA.Diagram
set currentDiagram = GetCurrentDiagram()
AddElementsToDiagram currentDiagram, rootPackage
ReloadDiagram currentDiagram.DiagramID
GetProjectInterface().LayoutDiagram currentDiagram.DiagramGUID, 0