Fix: prevent useless pathfinder run for blocked vehicles #8568
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SamuXarick
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Jan 14, 2021
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| uint32 r = VehicleEnterTile(v, v->tile, x, y); | ||
| if (HasBit(r, VETS_CANNOT_ENTER)) { |
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I wondered if the pathfinder prevention checks should be also added to VETS_CANNOT_ENTER, but I wasn't able find a situation where HasBit(r, VETS_CANNOT_ENTER) is true for testing that.
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Fix #7670 and supersede #7822.
Motivation / Problem
As found in #7670, a road vehicle blocked by another vehicle may enter in an "loop" of intensive pathfinder calls.
This happens because starting tile for path search is not cached and as the vehicle did not move since previous call, the cached path is discarded and a new one has to be determined.
Description
This solution is similar to the one in #7822, but a lot less invasive and does not require a savegame bump.
When a road vehicle is blocked by another one, just push its current location and the direction to follow found by pathfinder on top of the existing cache.
That way on next run it will just retrieve the heading instead of recalculating it.
While in the area I noticed the speed of the blocked vehicle was not updated, so I fixed it.
Limitations
I only tested using the save from #7670 (comment) but I don't see how it could cause issues.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.