[PATCH] Allow proper technology queueing

[Deiz]

Currently, a technology that supersedes another can only be researched if its predecessor has been completed.

It seems fairly common for players to leave the mining techs alone until the town phase (at which point there are two pairs available). I do similarly with the infantry techs, quickly researching both pairs before sending off an army.

In light of this, and the way that a tech's successor(s) will immediately appear after you begin researching it, I think queuing is desirable.

My patch adds the ability to queue a technology if a technology that it supersedes is being researched at the same building. The inverse of this is also implemented, for removing a tech from the queue.

As an example: If you're in the city phase, you can queue a tech from each of the three mining tech pairs. If you remove the tech from the second pair, the techs from pairs two and three will be dequeued, but the tech from pair one will be left to complete.

I also fixed a bug that occurred when a building was destroyed while researching (would attempt to get the technology manager for an invalid player).

[Kieran P]

Conversation on IRC:

quantumstate: what do you guys think about ​http://trac.wildfiregames.com/ticket/1521 ? My main concern is that only the building where the previous technology is being researched has the next tech available to research which isn't what I would expect (sorry if it has been discussed before, I am not up to date with the logs). #1521 makes it so that you can queue up the techs in a series, but only in one building. implementation becomes significantly trickier without that limitation since you need to introduce locks

k776: Right. So if I research something, it disappears from available into the production queue and shows the next available tech in the same building? And you can't do it in another building because it can't start until the first research is done? And then you have to make sure you cancel the second research if you cancel the first? so lots of problems with queuing. I suggest we hold this off till Alpha 12.

[Deiz]

In 12396:

Avoid an edge case when buildings are destroyed while researching, leaving techs stuck. Refs #1521.

[Kieran P]

Backlogged until a decision is reached.

[michael]

The idea is that a tech becomes available after you've researched its precursor because the knowledge gained is linear.

[michael]

But I guess my comment above was tinted by my experience with "Age of Empires" types of games where the player "moves through the ages" in an historical linear fashion. In our game, this is not the case. Instead of "learning new things" you are really just purchasing new equipment and whatnot, not really "researching new knowledge." So, in this context, queuing techs is okay.