spurious motion event when creating child in custom widget in GTK4
Version: the latest git GTK4
There is a custom widget which will create a child widget (a GtkComboBox) at the position and grab focus when you click the mouse on it. But when the child widget show up, the custom widget will receive a motion event if you register a GtkEventControllerMotion to it. When you set the motion event controller to GTK_PHASE_TARGET, you will receive the motion event signal exactly once and hover over the child widget do not trigger the motion signal.
The click and motion combined so that they will trigger a GestureDrag gesture. And that breaks the logic designed to custom widget to handle the drag gesture.
There is a simple custom widget in Rust to illustrate the issue: https://discourse.gnome.org/t/spurious-motion-signal-in-gtk4/7326/5