wxWidgets dark mode on macOS - c++

Question

According to the release notes for 3.1.3 (https://raw.githubusercontent.com/wxWidgets/wxWidgets/v3.1.3/docs/changes.txt) dark mode support has been added to wxWidgets for Mojave+.
For the documentation for wxSysColourChanged, it still states that this is for Windows only but I thought the dark mode support for macOS should include this too? Dark mode is only a recent addition to Windows UWP apps and not Win32 (see dark mode on Windows 10 for a discussion of that on the forum).
In any case I cannot get the event to fire, although switching to dark mode does indeed correctly update the GUI elements eg. wxlistctrl and wxbutton without me having to manually enforce colour changes.
I am trying to capture the system colour change event so that I can manually redraw my own "owner-drawn" custom GUI elements correctly dark/light.
I hook up the Bind in the constructor to my event but nothing works:
Bind(wxEVT_SYS_COLOUR_CHANGED, &myFrame::OnSystemColourChanged, this);
void myFrame::OnSystemColourChanged(wxSysColourChangedEvent &event)
{
wxSystemAppearance s = wxSystemSettings::GetAppearance();
wxString dark = s.IsDark() ? "it's dark" : "it's light";
wxString m("System colour changed - ");
m += dark;
::wxMessageBox(m);
event.Skip();
}
I have got this open as a query on the forum (here) and they recommended the mailing list but I notice that wxWidgets questions are quickly addressed on here, particularly by VZ so here's hoping!
Am I missing some method of detecting colour changes?

Answer 1

OK, I managed to get the code to hit. I debugged it by adding a wxApp-level HandleEvent override function to see what events were being handled by the application (yes all events go through here):
void myApp::HandleEvent(wxEvtHandler *handler, wxEventFunction func, wxEvent& event) const
{
wxApp::HandleEvent(handler, func, event);
}
wxSysColourChanged events are indeed passing through this.
I managed to get my main frame's handler to hit by hooking up differently. Instead of
Bind(wxEVT_SYS_COLOUR_CHANGED, &myFrame::OnSystemColourChanged, this);
I used this instead:
Bind(wxEVT_SYS_COLOUR_CHANGED, wxSysColourChangedEventHandler(myFrame::OnSystemColourChanged), this);
I have no idea why &myFrame::OnSystemColourChanged wouldn't be recognised.
Also, I could not get any message boxes to show up in my event handler. ::wxMessageBox and wxMessageDialog did not show. cout output did show up but no popup GUI dialogs.
I am not going to be showing message boxes in this handler anyway so it isn't a problem but was trying to show a message for debugging/testing purposes.