VBox immediately after HBox in pattern of Measure(s),HBox,VBox,Measure(s) does not split system
If start with any number of measures, followed by a single HBox, followed by any number of measures, e.g.:
After inserting a VBox before that measure after the HBox, the resulting layout incorrectly shows no visual change:
However, the debugger clearly shows that the VBox has been inserted, even though the visual layout does not reflect that fact:
Turns out system layout was not adding an implicit line break when enountered VBox right after HBox in this situation.