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Bugfix for errors in FindNearestHangar function in aircraft_cmd.c #235

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DorpsGek opened this issue Jul 4, 2006 · 5 comments
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Bugfix for errors in FindNearestHangar function in aircraft_cmd.c #235

DorpsGek opened this issue Jul 4, 2006 · 5 comments
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flyspray This issue is imported from FlySpray (https://bugs.openttd.org/) patch from FlySpray This issue is in fact a Patch, but imported from FlySrpay

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@DorpsGek
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DorpsGek commented Jul 4, 2006

mart3p opened the ticket and wrote:

If the “send to depot” button is pressed for an aircraft in flight, it will go to the hangar at the next airport in its orders. If the next airport has no hanger (i.e. a heliport) the function FindNearestHangar is called which should send the aircraft to the nearest airport with a hangar.

There are a couple of bugs in this function. Most serious is use of v->tile to determine the aircraft’s position when checking the distance to airports. While an aircraft is in flight v->tile is set to zero. This causes the function to always find the most northerly airport (airport_tile nearest zero) and the aircraft is sent there!

There are also some problems in the test that large aircraft shouldn't be sent to a small airport (with high risk of crash). The test for a large aircraft is incorrect. Also only the Small airport type is checked, it should also check for Commuter airports. The code here should be the same as that used for the same test in MaybeCrashAirplane.

In fact, it is only under unusual circumstances that FindNearestHangar will be called for aeroplanes (it is mainly used for helicopters). It can occur if there is a heliport in the plane’s orders. If the “send to depot” button is pressed while the plane is circulating the heliport (unable to land), then the FindNearestHangar function is called and the plane will go to the most northerly airport.

This patch corrects these problems.

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Reported version: 0.4.7
Operating system: All

This issue was imported from FlySpray: https://bugs.openttd.org/task/235
@DorpsGek
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Darkvater wrote:

Why this change:

- if (HASBIT(v->subtype, 1) && st->airport_type == AT_SMALL &&
+ if ((AircraftVehInfo(v->engine_type)->subtype & AIR_FAST) &&

Why not v->subtype & AIR_FAST?

This comment was imported from FlySpray: https://bugs.openttd.org/task/235#comment387

@DorpsGek
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mart3p wrote:

v->subtype for aircraft uses the following values:
0 - Helicopter
2 - Aeroplane (small or large)
4 - Shadow
6 - Helicopter rotor

To determine weather a plane can land at a small airport it is necessary to use AircraftVelInfo->subtype which uses the values:
0 - Helicopter
1 - AIR_CTOL (conventional take-off and landing)
2 - AIR_FAST (fast/large aircraft - can only use large airport)

This test needs to be the same as the test in the function MaybeCrashAirplane, I have used the same code as used there.

This comment was imported from FlySpray: https://bugs.openttd.org/task/235#comment388

@DorpsGek
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Darkvater wrote:

The question was is there any reason to use AircraftVehInfo(engine)->subtype instead of v->subtype. Are there any circumstances where these two might differ, as logically they should be the same.

Eg, when you build an aircraft, its subtype is set:
v->subtype = (avi->subtype & AIR_CTOL ? 2 : 0);

This comment was imported from FlySpray: https://bugs.openttd.org/task/235#comment389

@DorpsGek
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mart3p wrote:

Maybe logically they should be the same but in fact their use differs, as shown by the values that are used in each case (in comment above). As you see from the code used when an aircraft is built:
v->subtype = (avi->subtype & AIR_CTOL ? 2 : 0);
the vehicle subtype is set to either 2 or 0, regardless of whether avi->subtype has the AIR_FAST bit set.

This comment was imported from FlySpray: https://bugs.openttd.org/task/235#comment390

@DorpsGek
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Darkvater closed the ticket.

Reason for closing: Fixed

Point taken, subtype only registers if the plane is a plane or a chopper, nothing about its speed or other flying capabilites, which you would want to know to decide if a plane should land there or not. Patch applied, bug closed.

This comment was imported from FlySpray: https://bugs.openttd.org/task/235

@DorpsGek DorpsGek added flyspray This issue is imported from FlySpray (https://bugs.openttd.org/) Vehicles patch from FlySpray This issue is in fact a Patch, but imported from FlySrpay labels Apr 6, 2018
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