Moveable Goocanvas::Widgets

[Robert Gründler <doobre gmail com>]

Hi,

i'm trying to put native Gtk Widgets like Gtk::Button on a canvas. The 
canvas should have 2 modes, a locked and an unlocked mode. in the 
unlocked mode, the widgets should be moveable with the mouse, in the 
locked mode they should act as they usually do, ie. a Gtk::Button 
dispatches its signal_clicked() event etc.

I was unable to detect the button_press, -release or motion_notify 
events on the Goocanvas::Widget objects itself, even when passing false 
to the 'after' parameter of the connect method. So i'm simply listening 
to the signals of the native Gtk::Widget objects, which for some reason 
only works for the button_press and button_release signals. The 
signal_motion_notify_event is never dispatched from those widgets on the 
canvas.

This resulted in the next workaround, listening to the motion notify 
event on the canvas itself, handling the dragging logic in there, which 
brought me to a point where i'm really stuck now. The 
motion_notify_event from the Goocanvas::Canvas itself is dispatched 
correctly, even if the mouse is over a child Widget. However, i'm not 
receiving the signal anymore as soon as the left mouse button is clicked 
on a widget on the canvas...

_canvas->signal_motion_notify_event().connect(sigc::mem_fun(*this, 
&MyWindow::on_canvas_motion_notify_event, false);

bool MyWindow::on_canvas_motion_notify_event(GdkEventMotion* event) { // 
<-- not called when the mouse button has been pressed on a widget on the 
canvas
 std::cout << "motion detected" << std::endl; 
}


Does anyone know why this is happening ?
Any hints greatly appreciated, thanks !


-robert