Shared Ally Vision Problem

[elexis]

Today a problem has occured with a game on r16838. Player 4 (yellow) researched a the tech at the market at minute 10. Then at minute 11 his ally (Player 3, green) scouted the enemy base (Player 2, red). Player 4 could see the units in the field of view of the scouting cavalry, however the buildings and resources were invisible.

Furthermore the units were still visible after the scout left for about 30 seconds (the units become invisible one by one).

Reproduce by replaying the attached file with r16838, 10x speed to fast forward and change the perspective to player 4 with the developers overlay.

Refs #2055.

There was a similar bug, fixed in r16359 (thanks to trompetin17 for finding the revision), so maybe it is only missing an update somewhere.

[mimo]

Maybe not connected, but I was wondering how are mirages treated when the loss is shared: if a player has a mirage entity, is it copied to the allied player ? or if both have the same mirage entity, is there a logic to keep the most recent one for both ? and all these potential problems which did not happen when the loss was shared at the start of the game.

[Itms]

In 16842:

Correctly compute the masks for shared visibility updates. The old code was working only because of luck when shared vision was always reciprocal.

Refs #2055, fixes #3327