Finding mouse location in Python + GTK + OpenCV.

Expanding on the tutorial:

https://nofurtherquestions.wordpress.com/2017/03/03/python-3-5-gtk-3-glade-and-opencv/

it originally had shown the following structure:

- window1 (GtkWindow)
    - box1 (GtkBox)
        - grayscaleButton (GtkToggleButton)
        - image (GtkImage)

According to https://stackoverflow.com/a/24388310/189995 GtkImage does not generate events, so if you want to find the mouse location, put your GtkImage inside a GtkEventBox:

- window1 (GtkWindow)
    - box1 (GtkBox)
        - grayscaleButton (GtkToggleButton)
        - eventbox (GtkEventBox)
            - image (GtkImage)

and in eventbox set the Common -> Events -> Pointer Motion so you can add a handler to the motion-notify-event event.

Now you can write your handler:

class Handler:
    …
    …
    …
    def onMotionNotifyEvent(*args):
        global current_mouse_location

        event = args[1]

        current_mouse_location = event.x, event.y