libwnck should use StaticGravity when positioning windows on viewport change

Submitted by Sam Spilsbury @smspillaz

Link to original bug (#638483)

Description

Created attachment 177340 Use StaticGravity on MOVERESIZE request for viewport change.

Currently libwnck uses ForgetGravity (eg gravity=0) when sending a _NET_MOVERESIZE_WINDOW request to the window manager when positioning a window to change its viewport. This causes the window manager to use the gravity specified in the window size hints, which could end up being a gravity with an actual value (eg NorthWest or SouthEast gravity) causing the window to be displaced by the decoration extents it is repositioned on to another viewport.

According to the EWMH [1], libwnck should be using StaticGravity, since it positions the windows without knowledge of the decoration size. The window manager can then handle this request appropriately.

[1] http://standards.freedesktop.org/wm-spec/wm-spec-1.3.html#id2506756

Attached is a patch to do this

Patch 177340, "Use StaticGravity on MOVERESIZE request for viewport change.":
0001-Use-StaticGravity-when-sending-_NET_MOVERESIZE_WINDO.patch