Patch: Close airports

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

Hello,

This is my first attempt at a patch for OpenTTD. I have implemented a feature that I spotted in the suggestions forum, which is to allow airports to be 'closed'. When closed, aircraft already in the airport will proceed as normal, but those flying to the airport will be denied landing, that is, after the final approximation they will detour as though the landing runway were already in use. This way, the airport will eventually get empty, and this can be useful, for instance, if you try to upgrade a busy airport (you do not have to change the orders of all aircraft with that airport on their schedule).

I am hesitant about the best GUI for this feature, and did not want to spend too long coding an interface for now, so this is the first approach: To close an airport, you have to open the station window and ctrl+click on the airport button; an indicator will appear at the top right corner of the 'waiting' area to show that the airport is now closed. It acts as a toggle, so ctrl+clicking again will reopen the airport. If the airport is destroyed while closed and later rebuilt, it will also be reopened.

The patch itself is quite small. It applies against r10737. Any suggestions or comments will be welcome, particularly about the GUI.

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EDIT: Current status:
Patches against: 0.6.0 | 0.6.1 | 0.7.x - disable | 0.7.x - hide | 1.0.0 - disable | 1.0.0 - hide | 1.0.1 - disable | 1.0.1 - hide | r19740 - disable | r19740 - hide

rav · **Posted:** Wed Aug 01, 2007 5:04 pm

wow, thanks!

I did the suggestion, and I tried to create a patch for it, but couldn't pull it off, great job!

flake · **Posted:** Wed Aug 01, 2007 5:42 pm

Personally i like hotkeys in games, so i have nothing against strg + something to do even important stuff (like switching signals).
I would like to strg + klick on "accepts" to close an airport.
But maybe in this case a button would be better....

MeusH · **Posted:** Wed Aug 01, 2007 6:28 pm

It would be nice to make this patch cover all station types (railway, road and water).
A text button or a graphical button would be better than CTRL+click:
I'm almost sure many people won't know about this feature - I don't CTRL+click everything even if I'm bored

But I have currently no idea how would graphical button look like. Stop sign would be good, but the graphic must be black & white (actually black & transparent) and have a really small size

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

flake wrote:

Personally i like hotkeys in games, so i have nothing against strg + something to do even important stuff (like switching signals).
I would like to strg + klick on "accepts" to close an airport.
But maybe in this case a button would be better....

MeusH wrote:

A text button or a graphical button would be better than CTRL+click:
I'm almost sure many people won't know about this feature - I don't CTRL+click everything even if I'm bored

This is precisely what I meant about the GUI... I'm just not sure what the best option is. And I didn't want to put effort into that before I received some feedback on the feature itself. Now that I did, we can discuss about the GUI.

MeusH wrote:

It would be nice to make this patch cover all station types (railway, road and water).

Yes, it would be nice, but I have no clue as to how to implement it. For planes it was easy, because I knew that, at some point, a check must be made to allow a plane to land or not, so you just add a flag and make the landing also depend on that flag. I guess something similar could be done for road vehicles, so that they would just queue up in front of the stop, and ships should be easier---just arriving at the dock and waiting there without loading/unloading. But I'm sure trains would be a totally different thing.

MeusH · **Posted:** Wed Aug 01, 2007 7:11 pm

cirdan wrote:

But I'm sure trains would be a totally different thing.

Maybye bouncing off station just like if there were clear tiles (no railway)?
However, this would require change in code not related to stations I think

richk67 · **Posted:** Wed Aug 01, 2007 10:52 pm

cirdan wrote:

For planes it was easy, because I knew that, at some point, a check must be made to allow a plane to land or not, so you just add a flag and make the landing also depend on that flag.

There may be a problem with this. When you leave aircraft circling in the holding stack, they are still in the state machine of the airport. When you place the replacement airport, the states will almost certainly not match. (Obviously like-for-like replacements will work.)

So if an aircraft is at position 22 of a commuter airport you are replacing with a city airport, then next position is 23. On the commuter, this is in the holding stack, in the city airport, it is the helilanding position.

What would probably work safer, is to ensure that when you place an airport, any aircraft already at the airport (which can only be flying aircraft), get sent to the airport intercept point using AircraftNextAirportPos_and_Order(v);

Could be quite useful. I intended doing a similar function in my NewGRF_ports branch, but having a fully separate holding stack linked to the station record. Thus, you could happily delete the airport, and there would be no problem as the aircraft would not be in the state machine anyway, but in the holding stack.

MHTransport · **Joined:** Thu Mar 25, 2004 12:32 am **Posts:** 97

Great; very useful.

Please add it to all stations.

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

richk67 wrote:

cirdan wrote:

For planes it was easy, because I knew that, at some point, a check must be made to allow a plane to land or not, so you just add a flag and make the landing also depend on that flag.

There may be a problem with this. When you leave aircraft circling in the holding stack, they are still in the state machine of the airport. When you place the replacement airport, the states will almost certainly not match. (Obviously like-for-like replacements will work.)

So if an aircraft is at position 22 of a commuter airport you are replacing with a city airport, then next position is 23. On the commuter, this is in the holding stack, in the city airport, it is the helilanding position.

What would probably work safer, is to ensure that when you place an airport, any aircraft already at the airport (which can only be flying aircraft), get sent to the airport intercept point using AircraftNextAirportPos_and_Order(v);

You make quite a point here. I've tested what you say and you are partly right: There's a bug, but it's not my patch's fault.

To demonstrate this, take the attached savegame. It was prepared with vanilla r10737 (that is, without my patch, although with a lot of cheating to speed things up). The game should load paused, and there's an aircraft flying above a commuter airport, in position 22 (I think). The cheat to build while paused is enabled, so bulldoze the commuter airport and replace it with a city airport. You will see that, indeed, the plane moves erratically for a while, then gets it straight.

So my opinion is that we have found a bug already present in the code. It seems that removing or readding an airport does not update the state of the planes in its holding stack.

richk67 · **Posted:** Thu Aug 02, 2007 9:08 am

Yeah, probably a current bug. But your patch is an ideal point at which to correct it!

Incidentally, the example I gave is lucky that it picks a position in the air. You could possibly find one where the next position is say landed and taxiing, or at a helipad etc. The helipad one is worst, as helipads rarely contain aircraft movement orders, and so it would die horribly.

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

richk67 wrote:

Yeah, probably a current bug. But your patch is an ideal point at which to correct it!

I've been looking closer and maybe it isn't a bug after all. The 'erratic behaviour' that I observed is caused by the multiple entry points that airports now have (something I didn't know about). When an airport is replaced, the code is careful enough to update all aircraft heading for the station (via UpdateAirplanesOnNewStation).

The only case that is missed is when removing an airport. Planes will automatically switch to using the dummy airport finite state machine, but their position isn't updated. The attached one-line patch would fix this.

richk67 · **Posted:** Thu Aug 02, 2007 11:19 am

Juicy! One line patches may yet make trunk

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

Ok, this is the second version of the patch. As there didn't seem to be objections to the feature itself, I've focused on the interface. After studying the code and improving my GUI skills a little (well, they couldn't get any worse), I've added a new button at the bottom of the station window, which nicely reads 'Close airport' and works as expected, so there's no more need to press ctrl, or even to guess that ctrl should be used.

The patch applies against r10765.

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

Please disregard my previous patches. It appears that OpenTTD has this nice feature called 'Multiplayer' that allows several clients to play the same game and that requires, ahem, that those clients remain in sync, so you can't have code that freely modifies the game state without alerting the other clients.

The good news is that I've fixed it. The attached version of the patch is multiplayer-friendly. Clients won't desync if you close an airport, and you won't be able to close a competitor's airport.

rav · **Posted:** Sun Aug 05, 2007 3:17 pm

cirdan wrote:

Please disregard my previous patches. It appears that OpenTTD has this nice feature called 'Multiplayer' that allows several clients to play the same game and that requires, ahem, that those clients remain in sync, so you can't have code that freely modifies the game state without alerting the other clients.

The good news is that I've fixed it. The attached version of the patch is multiplayer-friendly. Clients won't desync if you close an airport, and you won't be able to close a competitor's airport.

you might want to update the first post in this topic

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

rav wrote:

you might want to update the first post in this topic

Done, thanks.

mikeel · **Joined:** Mon Jun 03, 2002 9:55 am **Posts:** 66

hi, i tried to compile using build ottd but it say "Unknown patch format"...
why? I'm the only with this problem?

cirdan · **Joined:** Sat Apr 07, 2007 6:08 pm **Posts:** 177

mikeel wrote:

hi, i tried to compile using build ottd but it say "Unknown patch format"...
why? I'm the only with this problem?

I don't know if I can be of much help with that... I run linux, so I have little use for BuildOTTD. What I can tell you is that the patch is in standard unified format, and applies cleanly (patch -p1) against revision r10765 (and possibly others).

I've searched for the source code of BuildOTTD in SourceForge, but apparently there are only two binaries for download. Browsing through the SourceForge SVN web gateway, however, I've come to the conclusion that BuildOTTD expects patches in some specific format (which I don't know about). I can try to adapt the patch if someone tells me which format it is.

mikeel · **Joined:** Mon Jun 03, 2002 9:55 am **Posts:** 66

hi
looking to other patches, i changed your code making it buildOTTD-friendly.
It's a simple change, when you declare the file you want patch you must code in this way:

Code:

Index: src/aircraft_cmd.cpp
===================================================================
--- src/aircraft_cmd.cpp   (revision 10765)
+++ src/aircraft_cmd.cpp   (working copy)

I've changed the lines and now i've compiled it.

I found this patch very intresting, but i think i found a bug: when there are a lot of aircraft in queue, it's quite impossible to bulldoze the airport, becouse it says "aircraft in the way" also if the airpot is empty. maybe becouse everytime there's an aircraft trying to land?

glx · **Posted:** Fri Aug 10, 2007 5:17 pm

Why not use svn diff to make the patch ?

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Patch: Close airports

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