Rosetta bridge plugins have an initial size of 0x0 pixel. Ardour's AU window size is set relative to the previous size. So the window grows by the actual real initial size of the AU View. However the window is already allocated and has a non-zero width given by the plugin's toolbar.
This lead to oversize windows.
df21698ea7 Fix relative AU window sizing
gtk2_ardour/au_pluginui.h | 2 ++
gtk2_ardour/au_pluginui.mm | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)