Comment 14 for bug 1795135

On gnome-shell, if I run xinput test-xi2, side-maximize it on the left by dragging the window to the left edge, the window will end up aligned to the left screen edge. However, moving the pointer towards that edge will sometimes issue events like:

EVENT type 6 (Motion)
    device: 2 (16)
    detail: 0
    flags:
    root: -0.86/139.21
    event: -0.86/75.21
    buttons:
    modifiers: locked 0 latched 0 base 0 effective: 0
    group: locked 0 latched 0 base 0 effective: 0
    valuators:
        0: -0.86
    windows: root 0xd6 event 0x4600001 child 0x0

As can be seen in https://bugzilla.gnome.org/show_bug.cgi?id=756463 , this negative coordinate fools GTK+ into thinking it should synthesize crossing events as those happen.