Ignore gesture events when zoom gesture isn't active

[filip-hejsek]

On wxGTK+Wayland, right-clicking sends the last GestureEnd event again, which was not caught by the existing workaround.

Instead of trying to pattern-match the false events, let's ignore all events unless we received a GestureStart event first.

(This has a merge conflict with #542. If you merge #542 first, you can use 5548e10. If you merge this first, I will rebase #542.)

[filip-hejsek]

I also got a minimal example that reproduces the bug:

#include <wx/wx.h>

class MyApp : public wxApp {
public:
	virtual bool OnInit() {
		auto frame = new wxFrame(NULL, wxID_ANY, "Zoom Gesture Test", wxDefaultPosition, wxSize(300, 200));

		auto myControl = new wxControl(frame, wxID_ANY);
		myControl->EnableTouchEvents(wxTOUCH_ZOOM_GESTURE);

		myControl->Bind(wxEVT_GESTURE_ZOOM, [](auto &event) {
			wxLogDebug("Zoom Gesture%s at (%d, %d) zoom factor %f",
			           event.IsGestureStart() ? " Start" : event.IsGestureEnd() ? " End" : "",
			           event.GetPosition().x, event.GetPosition().y, event.GetZoomFactor());
		});

		myControl->Bind(wxEVT_CONTEXT_MENU, [myControl](auto &) {
			wxMenu menu;
			menu.Append(wxID_ANY, "Menu Item");
			myControl->PopupMenu(&menu);
		});

		frame->Show();

		return true;
	}
};

wxIMPLEMENT_APP(MyApp);

[filip-hejsek]

And I found the culprit:

        g_signal_connect (m_zoom_gesture, "begin",
                          G_CALLBACK(zoom_gesture_begin_callback), win);
        g_signal_connect (m_zoom_gesture, "scale-changed",
                          G_CALLBACK(zoom_gesture_callback), win);
        g_signal_connect (m_zoom_gesture, "end",
                          G_CALLBACK(zoom_gesture_end_callback), win);
        g_signal_connect (m_zoom_gesture, "cancel",
                          G_CALLBACK(zoom_gesture_end_callback), win);

wxWidgets treats cancel events the same as end events, and always generates a GestureEnd event for them. But GTK can send cancel events even when a gesture isn't active (and can also send both a cancel and an end event for a gesture).

[arch1t3cht]

Thanks for debugging this. In that case I'd like to report this upstream first so that the relevant github issue can be linked in a code comment (so future developer can more easily tell whether the issue is still present or has since been fixed).

I'll do that soon unless you want to do it yourself.

[filip-hejsek]

wxWidgets/wxWidgets#26211

[filip-hejsek]

Rebased and added the link to the comment.

[arch1t3cht]

Thanks!