The option can currently be activated from Virtual Desktops Settings -> Advanced. A better home and preview would be better for these settings.
In more detail, this option can make a wallpaper, larger than the geometry of the zone, scroll appropriately with each desk change. Consider a nice panorama picture, which is as wide as the total desks' width. Then, at most, E will scroll the background by 1 / (number of desks) for each desk change. The direction of the scrolling is dependent on the desk change itself. Also, the user can specify a coefficient of maximum scrolling for each axis. If the coefficient is 0, the wallpaper will not move.
More advanced animations can be constructed with edje. The data item "directional_freedom" "(1|0) (1|0)" can toggle the actual wallpaper scrolling done by E for each axis. A message with the current x/y position, panning w|h, and zone w|h is sent to the background edje with each desk change animation tick. An example embryo script that handles the message, and changes a hypothetical "a1" part in the "e/desktop/background" group is shown below:
public message(Msg_Type:type, id, ...) {
if (type == MSG_INT_SET) {
new x = getarg(2);
new y = getarg(3);
// new max_x = getarg(4);
// new max_y = getarg(5);
// new w = getarg(6);
// new h = getarg(7);
custom_state(PART:"a1", "default", 0.0);
set_state_val(PART:"a1", STATE_FILL_POS, 0.0, 0.0, -x / 4, -y / 4);
set_state(PART:"a1", "custom", 0.0);
}
}
SVN revision: 40543
648d75caab