This likely broke in 3.x when Ardour migrated to context dependent
shortcuts (rather than GTK managed menu shortcuts).
While there is Gtkmm2ext::Application::hide, there is currently no
bindable action and hence no way to add a dedicated
shortcut. Furthermore, since this is a special NSApplication menu,
updating the menu-item when the action is bound is not trivial.
gtk_application_hide() is only implemented for macOS and
there is likely a better use for "H" shortcut anyway.
[Details] g_idle_add () which was used for this purpose used G_PRIORITY_DEFAULT_IDLE>=200 which was too low for correct main menu requests processing, like showing Mixer or Big Clock Window.
The priority was increased to G_PRIORITY_HIGH_IDLE = 100.
According to GTK manual (https://developer.gnome.org/glib/stable/glib-The-Main-Event-Loop.html#G-PRIORITY-HIGH-IDLE:CAPS)
GTK+ uses G_PRIORITY_HIGH_IDLE + 10 = 110 for resizing operations, and G_PRIORITY_HIGH_IDLE + 20 = 120 for redrawing operations.
I assume that during record or playback on tracks there are too many redraw request which didn't give any chance for main menu request to be processed in time with old priority value.
This change must be considered as a hot fix so far.
The issue might be deeper. Will be investigated with Paul.
[Feature reviewed] AMishyn
[Reviewed by] PDavis, GZharun
