A bridge (span or tower) must be splashed when it gets damaged below
SCT_MINEFF. Likewise when its last supporting sector (bridge head or
tower) gets damaged below SCT_MINEFF, unless EASY_BRIDGES is enabled.
We need to check this whenever a bridge head, span or tower gets
damaged. This is done in three places, and all of them screw up:
* checksect() ignores damage to bridge heads. It also leaves writing
back the sector it checks to the caller, which never happens when
it's called from sct_postread().
Note that checksect() drowns all planes on bridges it splashes.
Functions that need to exempt flying planes from such a fate have to
splash bridges themselves.
* sect_damage() ignores damage to bridge towers, and damage to bridge
spans unless EASY_BRIDGES is enabled. It then runs checksect(),
which compensates for these omissions, but happily drowns the planes
sect_damage() attempts to protect.
* eff_bomb() ignores damage to bridge heads. Collateral damage makes
sect_damage() run, which compensates for the omission.
This causes the following bugs:
* Efficiency damage going through sect_damage() can drown planes it
shouldn't. This affects pinpoint bombing when collateral damage
splashes a bridge, and strategic bombing. The drowned planes then
crash and burn when they attempt to land at their (just splashed)
base.
* Efficiency damage to bridge heads not going through sect_damage()
fails to collapse unsupported bridges. This affects pin-bombing
efficiency without collateral damage, and ground combat. Also deity
commands edit, setsector and add, but that could be regarded as a
feature.
* If the sector file somehow ends up with an inefficient bridge span,
it collapses on every read again and again, until it collapses on a
write. Related problems exist with other actions of checksect(),
and they're not addressed here.
* If the sector file somehow ends up with adjacent inefficient bridge
towers, checksect() on any of them recurses infinitely:
- checksect() inefficient tower T1
- knockdown() T1, but don't write that back to the sector file
- bridgefall() T1; this reads all adjacent sectors, including
inefficient towert T2
- checksect() T2
- knockdown() T2, but don't write that back to the sector file
- bridgefall() T1; this reads adjacent sectors including T1
- checksect() T1
...
This commit creates a new function bridge_damaged() to splash any
bridges that became inefficient or unsupported after damage to a
sector. To avoid the inifinite recursion, we call it in
sct_prewrite() instead of checksect().
No uses knockdown() outside bridgefall.c remain, so give it internal
linkage.
Markus Armbruster
40eb78eb74