My understanding of Announcements is not so good yet, but here is another opportunity. While I was trying to trace some code execution to troubleshoot a ticket that I logged for Mondrian, I bumped into some behaviour that seems strange, which I would like to understand. At the end I propose a fix. For the short example, execute [MOEasel open] then <Generate View> on the following: ----8<---- view shape rectangle size: 20. view interaction registerForEvent: MOMouseDown forNode: #yourself updateNode: [ :v | "self halt." view forNode: v do: [ view nodes: (1 to: 2) ] ] updateLayout: true. view nodes: (1 to: 4). ----8<---- Click on a node and observe that node successfully has two nodes within it. Now uncomment the "self halt" and <Generate View>, then click on a node. When the pre-debugger for 'halt' appears, click <Proceed>. Surprisingly a MNU now occurs in MOAnnouncement>>registerForEvent:forNode:updateNode:updateLayout due to 'ann viewRenderer' now returning nil. Observe this occurs immediately after the execution of 'updateBlock' which contained the 'self halt' The extended example modifies MOAnnouncement>>registerForEvent:forNode:updateNode:updateLayout as follows... | domainNode btcRenderer1 btcRenderer1test btcRenderer2 btcRenderer2test btcRenderer1test2 | self on: eventClass do: [:ann | "----8<---- begin debug code " btcRenderer1 := ann viewRenderer. btcRenderer1test := (self viewRenderer == ann viewRenderer ). "self halt." btcRenderer2 := ann viewRenderer. btcRenderer2test := (self viewRenderer == ann viewRenderer ). { self viewRenderer. btcRenderer1. btcRenderer2. btcRenderer1test. btcRenderer2test. } inspect. "----8<---- end debug code " ann element removeAllEdges; removeAllNodes. <Generate View> on the same code as the short example with the 'self halt' commented out, then click on a node. An inspector pops up showing array { aMOViewRenderer. aMOViewRenderer. aMOViewRenderer. true. true. } Then uncomment the 'self halt' in the extended example, <Generate View> and click on a node. <Proceed> at the pre-debugger. An inspector pops up now showing array { aMOViewRenderer. aMOViewRenderer. nil. true. false. } 'ann viewRenderer ' has lost its value following the 'self halt.' Proposed fix: It can be seen from the second inspector that 'self viewRenderer' is identical to 'ann viewRenderer' and retains its value across the 'self halt', and so might be used in its place. thanks for you attention, your thoughts would be appreciated. cheers, -ben