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[[File:Fgaddonslogo202x89.png|right]]  
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To make it easier to create '''addons''' there is since FlightGear 2017.3 a new way to create addons. In essence FlightGear will load an overlay XML into the property tree and start a well known Nasal function.<ref>{{cite web
{{forum|10000|FlightGear Addons}}
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314620#p314620
== Background ==
   |title  =  <nowiki> Re: New Feature: Addon - "API" </nowiki>  
{{See also|Howto:Creating a simple modding framework}}
   |author =  <nowiki> Torsten </nowiki>  
 
   |date  =  Jul 19th, 2017
ATC chatter was removed in 2015, see fgdata commit: [https://sourceforge.net/p/flightgear/fgdata/ci/81607f734e13add9be02816ddaec305d05bc4e47/ 81607f734e13add9be02816ddaec305d05bc4e47]
   |added  =  Jul 19th, 2017
 
and the devel list messages referenced in the commit log.
the other relevant commit is this: b60736ba7add2a7cd39af3d8a974d5be3ea46e8b
It would not be very difficult to restore this functionality, or even generalize/improve it significantly (which was the scope of the original discussion on the devel list)<ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=288388#p288388
   |title  =  <nowiki> Re: Whatever happened to radom radio  </nowiki>  
   |author =  <nowiki> Hooray </nowiki>  
   |date  =  Jun 11th, 2016
   |added  =  Jun 11th, 2016
   |script_version = 0.40  
   |script_version = 0.40  
   }}</ref>
   }}</ref>


The restored functionality could be distributed as a tarball that is extracted into $FG_ROOT - alternatively, into $FG_HOME, because Nasal files there are treated as overlays, which basically means that you can install user-specific extensions there without having to tamper with $FG_ROOT, it would only take  very minor changes to turn the chatter feature into a corresponding "addon" - not unlike fgcamera ...<ref>{{cite web
We now have a simple way to add addons to FlightGear without the need to mess around with <code>FGData/Nasal</code> or <code>FGHome/Nasal</code> directories.<ref name="Forum_announcement">{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=288392#p288392
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314563#p314563
   |title  =  <nowiki> Re: Whatever happened to radom radio  </nowiki>  
   |title  =  <nowiki> New Feature: Addon - "API" </nowiki>  
   |author =  <nowiki> Hooray </nowiki>  
   |author =  <nowiki> Torsten </nowiki>  
   |date  =  Jun 11th, 2016
   |date  =  Jul 18th, 2017
  |added  =  Jun 11th, 2016
  |script_version = 0.40
   }}</ref>
   }}</ref>


we should absolutely stop telling anyone to edit preferences.xml in FG_ROOT; any documentation or advice which says to should be changes ASAP. <ref>{{cite web
{{TOC limit|3}}
  |url    = https://forum.flightgear.org/viewtopic.php?p=192632#p192632
 
  |title  =  <nowiki> Re: NavCache:init failed:Sqlite error:Sqlite API abuse </nowiki>  
== Installing and using an addon ==
  |author = <nowiki> zakalawe </nowiki>  
Download and copy the addon to a directory on your computer.
  |date  = Oct 26th, 2013
 
  |added  =  Oct 26th, 2013
If you use the launcher, select the Add-ons page from the icon bar on the left, then find the section Add-on Module folders and click the Add(+) button. Select the folder where you put the addon. Once the addon is shown in the list, make sure its check box is selected.
  |script_version = 0.40
 
  }}</ref>
Use the command line switch <code>--addon=/path/to/some/addon</code>.<ref name="Forum_announcement"/>
 
== Creating an addon ==
There is a very simple Skeleton addon available in FGAddon to be used as a template.<ref name="Forum_announcement"/> See {{fgaddon source|path=Addons/Skeleton}}.
 
A leading slash (<code>/</code>) in this section indicates the base directory of the directory structure of the addon.


As of 12/2017, the addon API is in the process of being significantly updated <ref>https://sourceforge.net/p/flightgear/mailman/message/36146017/</ref> <ref>https://sourceforge.net/p/flightgear/mailman/message/36150159/</ref> <ref>https://sourceforge.net/p/flightgear/mailman/message/36150444/</ref>
=== Minimum configuration ===
An addon may be installed in a directory anywhere on your hard disk and need at least two files:


== Good to know ==
* <code>/addon-config.xml</code> - A standard [[PropertyList XML files|PropertyList XML file]] to be used to populate or modify the [[property tree]]. (Same as to be used in <code>--config=foo.xml</code>)
this API does nothing more than loading a overlay XML into the property tree and starts a well known Nasal function<ref>{{cite web
* <code>/addon-main.nas</code> - The Nasal hook for the logic. This file needs a function called <code>main()</code> which will be called from the global addon initializer (<code>addons.nas</code>)
  |url    = https://forum.flightgear.org/viewtopic.php?p=314620#p314620
  |title  =  <nowiki> Re: New Feature: Addon - "API" </nowiki>  
  |author =  <nowiki> Torsten </nowiki>  
  |date  =  Jul 19th, 2017
  |added  =  Jul 19th, 2017
  |script_version = 0.40
  }}</ref>


=== Additional common files ===
* <code>/addon-metadata.xml</code> - A PropertyList XML file with metadata about the addon it.
* <code>/addon-menubar-items.xml</code> - A PropertyList XML file describing menus to be added to the FlightGear menu bar.
* <code>/gui/dialogs/&lt;my-foobar-dialog&gt;.xml</code> - PropertyList XML files to create custom dialogs.


The new addon "API" lets you add a config.xml to override the settings in defaults.xml.
=== Good to know ===
The new addon mechanism lets you add a <code>addon-config.xml</code> to override the settings in <code>defaults.xml</code> and other files.


That easily allows to
That will allow an addon to
*  Override key bindings (as in the spoken atc addon)
*  Override key bindings (as in the spoken ATC addon)
*  Add or override autopilots and property rules
*  Add or override autopilots and property rules
*  And of course introduce XML-statemachines
*  Introduce XML state machines


Unless your really want to add/change/remove those at runtime, this should cater for most use cases.<ref>{{cite web
Unless your really want to add/change/remove those at runtime, this should cater for most use cases.<ref>{{cite web
Line 74: Line 67:
   }}</ref>
   }}</ref>


=== Sound Support ===
Sound support is available using fgcommand's.


* [[Property tree]]
See [[Nasal FAQ]] "play-audio-sample"
* [[PropertyList XML File]]
* [[FlightGear configuration via XML]]
* [[Properties persistent between sessions]]
* [[FlightGear_configuration_via_XML#preferences.xml]]
* [[Nasal]]


== Overlays ==
https://sourceforge.net/p/flightgear/flightgear/ci/5acf2e26d085b7553b2387b9753e9253e8b4bff4


Torsten ended up using a fairly clever method to come up with this idea for implementing addon support via PropertyList-XML overlays loaded via the --config argument - however, that also brings with it all the power for conflicting with stuff you are loading using the same mechanism, and/or any defaults you have customied. So just be aware of how this works - and again, kudos to Torsten for coming up with such a fancy approach to make this work, despite people arguing for the better part of a decade that FlightGear would not have "proper addon/modding" support" ... ;-)
[[Hackathon Proposal:Addon specific Sound Queues]]
With that being said, it would probably be a good idea to formalize the whole method and stop using tons of embedded Nasal, and instead document/favor the use of io.load_nasal() and/or io.include() to load Nasal code from the addon directory.
Equally, such code should ideally wrap setlistener and settimer/maketimer to honor the /sim/signal "events" - but apart from that, it's a really clever idea<ref>{{cite web
  |url    =  https://forum.flightgear.org/viewtopic.php?p=295617#p295617
  |title  =  <nowiki> Re: Whatever happened to radom radio chatter?? </nowiki>
  |author =  <nowiki> Hooray </nowiki>
  |date  =  Sep 27th, 2016
  |added  =  Sep 27th, 2016
  |script_version = 0.40
  }}</ref>


== API ==
== Addon initialization ==
On initialization fgfs takes care of:
* Through {{flightgear source|path=src/Main/options.cxx|text=<code>options.cxx</code>}}:<ref name="Forum_announcement"/>
** Creating a property under <code>/addons/addon[n]/path=/path/to/some/addon</code>
** Loading <code>/path/to/some/addon/addon-config.xml</code> into the property tree (same as <code>--config=/path/to/some/addon/addon-config.xml</code>)
** Adding <code>/path/to/some/addon</code> to the list of allowed directories (same as <code>--fg-aircraft=/path/to/some/addon</code>)
* Through {{fgdata source|path=Nasal/addons.nas|text=<code>addons.nas</code>}}:
** Loading <code>/foo/bar/baz/addon-main.nas</code> into namespace <code>__addon[ADDON_ID]__</code>
** Calling <code>main(addonGhost)</code> from <code>/foo/bar/baz/addon-main.nas</code>.


We now have a simple API to add addons to FlightGear without the need to mess around with FGData/Nasal or FGHome/Nasal directories. FlightGear now accepts the command line switch --addon=/path/to/some/addon (note: command line switch is just that: a command line switch - not an option to be entered into the launcher). fgfs (through options.cxx) takes care of
== Aircraft specific config (addon-hints) ==
* creating a property under /addons/addon[n]/path=/path/to/some/addon
Some addons need per-aircraft configuration. While addons should strive to be self-contained (ie. the addon should contain means to
* adding /path/to/some/addon/config.xml as a config file (same as --config=/path/to/some/addon/config.xml)  
detect different aircraft and apply config from whithin the addon) there is also the possibility for the addon to read so called "addon-hints".
* adding /path/to/some/addon to the list of allowed directories (same as --fg-aircraft=/path/to/some/addon)


The addon may be installed anywhere on your hard disk and it needs at least two files:
For this, a special property tree exists: <code>/sim/addon-hints/<addon>/...</code>
* config.xml - a standard PropertyList to be used to populate or modify the property tree. (Same as to be used in --config=foo.xml)
The tree is expected to be populated from the aircraft.xml file. The addon can then read the properties from a common place regardless of loaded aircraft.
* main.nas - the Nasal hook for the logic. This file needs a function called main() which will be called from the global addon initialier (FGData/addons.nas)


It is pretty simple but does it's job nicely with our two addons we currently have in FGAddon (ATCChatter and SpokenATC). There is a /very/ simple Skeleton addon available to be used as a boilerplate here: https://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Addons/Skeleton/ As always: feedback is much appreciated. <ref>{{cite web
<syntaxhighlight lang="xml">
  |url    =  https://sourceforge.net/p/flightgear/mailman/message/35951307/
<sim>
  |title  =  <nowiki> [Flightgear-devel] Simple API for creating FlightGear addons/plugins </nowiki>  
   <addon-hints>
   |author =  <nowiki> Torsten Dreyer </nowiki>
    <my-addon>
  |date  =  Jul 18th, 2017
        ...
  |added  =  Jul 18th, 2017
    </my-addon>
  |script_version = 0.40
   </addon-hints>
  }}</ref> <ref> {{cite web
</sim>
  |url    =  https://forum.flightgear.org/viewtopic.php?p=314563#p314563
</syntaxhighlight>
  |title  =  <nowiki> New Feature: Addon - "API" </nowiki>  
   |author =  <nowiki> Torsten </nowiki>  
  |date  =  Jul 18th, 2017
  |added  =  Jul 18th, 2017
  |script_version = 0.40
  }}</ref>


Triggered by this addon, Torsten has overhauled the addon "API" to make it a little easier to use.  
== APIs ==
{{hatnote|For more details about these APIs, see the readme file, {{readme file|add-ons}}.}}
=== C++ API ===
There is a C++ API on FlightGear's side that handle some on the addon related tasks manly through the <code>AddonManager()</code>, <code>Addon()</code> and <code>AddonVersion()</code> classes.


Along with this, he added the spoken ATC feature as an addon to fgaddon: https://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Addons/SpokenATC/
=== Nasal API ===
It is now very easy to use (given you have FlightGear compiled from git HEAD or use FlightGear 2017.3.x or later.
The Nasal add-on API lives in the 'addons' namespace and can for example do queries to <code>AddonManager()</code> and read data from <code>addons.Addon</code> objects. It can for example compare addon versions if there is dependencies.


you need at least these commits:  
== Background ==
{{See also|Howto:Creating a simple modding framework}}


FlightGear: https://sourceforge.net/p/flightgear/flightgear/ci/f6698a0b1f9e8c0791314aa09cbe1625927ef3ff/
ATC chatter was removed in 2015, see fgdata commit: [https://sourceforge.net/p/flightgear/fgdata/ci/81607f734e13add9be02816ddaec305d05bc4e47/ 81607f734e13add9be02816ddaec305d05bc4e47]


FGData: https://sourceforge.net/p/flightgear/fgdata/ci/5c1f4a69f131a55521050f4631b8fda42f050dd2/
And the devel list messages referenced in the commit log.
* Get the addon from https://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Addons/SpokenATC/
the other relevant commit is this: b60736ba7add2a7cd39af3d8a974d5be3ea46e8b
* start flightgear with --addon=/your/full/path/to/SpokenATC
It would not be very difficult to restore this functionality, or even generalize/improve it significantly (which was the scope of the original discussion on the devel list)<ref>{{cite web
  |url    =  https://forum.flightgear.org/viewtopic.php?p=288388#p288388
  |title  =  <nowiki> Re: Whatever happened to radom radio  </nowiki>
  |author =  <nowiki> Hooray </nowiki>
  |date  =  Jun 11th, 2016
  |added  =  Jun 11th, 2016
  |script_version = 0.40
  }}</ref>


done.<ref>{{cite web
The restored functionality could be distributed as a tarball that is extracted into $FG_ROOT - alternatively, into $FG_HOME, because Nasal files there are treated as overlays, which basically means that you can install user-specific extensions there without having to tamper with $FG_ROOT, it would only take  very minor changes to turn the chatter feature into a corresponding "addon" - not unlike fgcamera ...<ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314562#p314562
   |url    =  https://forum.flightgear.org/viewtopic.php?p=288392#p288392
   |title  =  <nowiki> Re: Spoken ATC </nowiki>  
   |title  =  <nowiki> Re: Whatever happened to radom radio  </nowiki>  
   |author =  <nowiki> Torsten </nowiki>  
   |author =  <nowiki> Hooray </nowiki>  
   |date  =  Jul 18th, 2017
   |date  =  Jun 11th, 2016
   |added  =  Jul 18th, 2017
   |added  =  Jun 11th, 2016
   |script_version = 0.40  
   |script_version = 0.40  
   }}</ref>
   }}</ref>


We should absolutely stop telling anyone to edit preferences.xml in FG_ROOT; any documentation or advice which says to should be changes ASAP. <ref>{{cite web
  |url    =  https://forum.flightgear.org/viewtopic.php?p=192632#p192632
  |title  =  <nowiki> Re: NavCache:init failed:Sqlite error:Sqlite API abuse </nowiki>
  |author =  <nowiki> zakalawe </nowiki>
  |date  =  Oct 26th, 2013
  |added  =  Oct 26th, 2013
  |script_version = 0.40
  }}</ref>


== Implementation ==
As of 12/2017, the addon API is in the process of being significantly updated <ref>https://sourceforge.net/p/flightgear/mailman/message/36146017/</ref> <ref>https://sourceforge.net/p/flightgear/mailman/message/36150159/</ref> <ref>https://sourceforge.net/p/flightgear/mailman/message/36150444/</ref>
For the time being, the addon.nas module will:
* initialize addons configured with --addon=foobar command line switch
*  loop over /addons/addon[n] nodes
*  get root path in /addons/addon[n]/path property (set by options.cxx from --addon=/foo/bar)
*  load main.nas therein into namespace __addon[n]__
*  call function main() from that main.nas with addon-path as arg


== List of Addons ==
You can find the official repository at {{fgaddon source|path=Addons}}


It depend on a change to options.cxx to accept an optional --addon argument <ref>https://sourceforge.net/p/flightgear/flightgear/ci/f6698a0b1f9e8c0791314aa09cbe1625927ef3ff/</ref>
* [https://github.com/slawekmikula/flightgear-addon-hudheli Additional Heli HUD's] - ([https://github.com/slawekmikula/flightgear-addon-hudheli/blob/master/doc/manual.md manual]) - encapsulation of HeliHUD package as an addon
 
* [https://github.com/PlayeRom/flightgear-addon-aerotow-everywhere Aerotow Everywhere] AI towing aircraft for gliders at every airport.<ref>{{cite web
== List of Addons ==
  |url    =  https://forum.flightgear.org/viewtopic.php?t=40742
* [[Landing Rate addon]] [https://forum.flightgear.org/viewtopic.php?f=6&t=33101&p=327787#p327787]
  |title  = <nowiki> Re: Aerotow Everywhere </nowiki>
* [[YASim Development Tools]] (by jsb)
  |author =  <nowiki> Roman Ludwicki (PlayeRom) </nowiki>
* [[Model Cockpit View]]
  |date  =  Aug 14th, 2022
* [[FGPlot]]
  |added  =  Aug 14th, 2022
  |script_version = 0.40
  }}</ref>
* [https://github.com/SP-NTX/AnotherGUI AnotherGUI] - An add-on that adds a new GUI style.
* ATC Chatter (ported by Torsten) {{progressbar|100}}
* ATC Chatter (ported by Torsten) {{progressbar|100}}
* [[Spoken ATC]] (ported by Torsten <ref>{{cite web
* [[Cargo Towing Addon]] <ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314095#p314095
  |url    =  https://forum.flightgear.org/viewtopic.php?t=36824
  |title  =  <nowiki> Re: Cargo Towing Addon </nowiki>
  |author =  <nowiki> Wayne Bragg (wlbragg) </nowiki>
  |date  = 
  |added  = 
  |script_version = 0.40
  }}</ref>
* cockpit-view (work in progress by wkitty42)<ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=316498#p316498
   |title  =  <nowiki> Re:  </nowiki>  
   |title  =  <nowiki> Re:  </nowiki>  
   |author =  <nowiki> Torsten </nowiki>  
   |author =  <nowiki> wkitty42 </nowiki>  
   |date  =  Jul 10th, 2017  
   |date  =  Aug 13th, 2017  
   |added  =  Jul 10th, 2017  
   |added  =  Aug 13th, 2017  
   |script_version = 0.40  
   |script_version = 0.40  
   }}</ref>)
   }}</ref>
* [[Oscilloscope_addon]]  
* [[Earthview#Customization]] - High resolution customization
* [[PAR_instrument]] (Precision Approach Radar and Ground Controlled Approach)
* [[FaceTrackNoIR]] (ported by HHS)<ref>{{cite web
* [[FGCamera]] (work in progress by Torsten <ref>{{cite web
   |url    =  https://sourceforge.net/p/flightgear/mailman/message/36454826/
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314650#p314650
   |title  =  <nowiki> Re: </nowiki>  
   |title  =  <nowiki> Re: Alternative camera control </nowiki>  
   |author =  <nowiki> Unknown, HHS</nowiki>
   |author =  <nowiki> Torsten </nowiki>  
   |date  =  Nov 1th, 2018
   |date  =  Jul 19th, 2017
   }}</ref> - An addon to interface this [[Head tracking|head tracker]] with FlightGear
  |added  =  Jul 19th, 2017
* [https://forum.flightgear.org/viewtopic.php?f=5&t=24792 Fencemaker] (Eases creating Fence-like scenery objects. Originally by VaLeo, converted to an addon by sfr) - ([https://www.mediafire.com/file/cf0la63v9g352md/fencemaker_addon.zip/file download])<ref>{{cite web
  |script_version = 0.40
   |url    = https://forum.flightgear.org/viewtopic.php?f=5&t=24792&start=45#p390066
   }}</ref> <ref>{{cite web
   |title  = <nowiki> Re: </nowiki>
   |url    = https://forum.flightgear.org/viewtopic.php?p=319804#p319804
   |author = <nowiki> Stefan Frank </nowiki>
   |title  = <nowiki> Re: New Feature: Addon - "API" </nowiki>  
   |maintainer = <nowiki> Stefan Frank </nowiki>
   |author = <nowiki> slawekmikula </nowiki>  
   |date  = Aug 8th, 2021
   |date  = Oct 2nd, 2017
   }}</ref>
   |added  = Oct 2nd, 2017
* [https://github.com/PlayeRom/flightgear-addon-fgcamera FGCamera] - ([https://github.com/PlayeRom/flightgear-addon-fgcamera/blob/master/Docs/manual.md manual]) - [[FGCamera | Wiki Page]]
  |script_version = 0.40
* [[FGPlot]]
   }}</ref>)  
* [[Ground Services]] (ported by ThomasS)<ref>{{cite web
* [[Ground Services]] (ported by ThomasS<ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=316400#p316400  
   |url    =  https://forum.flightgear.org/viewtopic.php?p=316400#p316400  
   |title  =  <nowiki> Re:  </nowiki>  
   |title  =  <nowiki> Re:  </nowiki>  
Line 194: Line 200:
   |added  =  Aug 12th, 2017  
   |added  =  Aug 12th, 2017  
   |script_version = 0.40  
   |script_version = 0.40  
   }}</ref>)
   }}</ref>
* cockpit-view (work in progress by wkitty42 <ref>{{cite web
* {{fgaddon source|path=Addons/Headtracker/|text=Headtracker addon}} Helps integrate FaceTrackNoIR and opentrack with FlightGear.
   |url    =  https://forum.flightgear.org/viewtopic.php?p=316498#p316498
* [[HighAirTrader]] An in-sim mini game in which you transport goods to different airports.
* [https://github.com/tdammers/fg-hoppie-acars Hoppie ACARS client] - connect to [http://www.hoppie.nl/acars Hoppie's ACARS], used on VATSIM and other networks.
* [https://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Addons/Illuminator/ Illuminator] - configure lights attached to 3D models (e.g. taxi light, landing light or a light attached to a scenery model like a light pole) at runtime.
* [https://github.com/slawekmikula/flightgear-addon-protocolkml KML Exporter (Google Earth)] - ([https://github.com/slawekmikula/flightgear-addon-protocolkml/blob/master/doc/manual.md manual])
* [[Landing Rate addon]] [https://forum.flightgear.org/viewtopic.php?f=6&t=33101&p=327787#p327787]
* [https://github.com/slawekmikula/flightgear-addon-linuxtrack LinuxTrack Head Tracker integration] - ([https://github.com/slawekmikula/flightgear-addon-linuxtrack/blob/master/doc/manual.md manual])
* [https://github.com/slawekmikula/flightgear-addon-littlenavmap LittleNavMap integration] - ([https://github.com/slawekmikula/flightgear-addon-littlenavmap/blob/master/doc/manual.md manual])
* [https://github.com/PlayeRom/flightgear-addon-logbook Logbook] all your flights to CSV file.<ref>{{cite web
  |url    =  https://forum.flightgear.org/viewtopic.php?t=41070
  |title  =  <nowiki> Re: Logbook Add-on </nowiki>
  |author =  <nowiki> Roman Ludwicki (PlayeRom) </nowiki>
  |date  =  Dec 11th, 2022
  |added  =  Dec 11th, 2022
  |script_version = 0.40
  }}</ref>
* [https://gitlab.com/mdanil/flightgear-hax mdanilov hax!]: landing evaluation and aircraft development tools, TerraSync toggler
* [[Model Cockpit View]]
* [https://github.com/SP-NTX/MPChatImprovments MPChatImprovments] Multi-key commands for Multiplayer, new features for chat,...
* [[Oscilloscope addon]] - Allows displaying a property of Nasal function over time
* [[PAR instrument]] - Precision Approach Radar and Ground Controlled Approach
* [[Red Griffin ATC]] - Speaking Air Traffic Controller<ref>{{cite web
  |url    =  https://forum.flightgear.org/viewtopic.php?f=6&t=36755
  |title  =  <nowiki> Re:  </nowiki>
  |author =  <nowiki> RedGriffin </nowiki>
  |date  =  Jan 6th, 2020
  |added  =  Jan 6th, 2020
  |script_version = 1.0.0 RC2
  }}</ref>
* [https://github.com/tdammers/fg-simbrief-addon SimBrief import] - Import flightplans, weights, fuel, and winds alof, from SimBrief.
* [[Spoken ATC]] (ported by Torsten)<ref>{{cite web
   |url    =  https://forum.flightgear.org/viewtopic.php?p=314095#p314095
   |title  =  <nowiki> Re:  </nowiki>  
   |title  =  <nowiki> Re:  </nowiki>  
   |author =  <nowiki> wkitty42 </nowiki>  
   |author =  <nowiki> Torsten </nowiki>  
   |date  =  Aug 13th, 2017  
   |date  =  Jul 10th, 2017  
   |added  =  Aug 13th, 2017  
   |added  =  Jul 10th, 2017  
   |script_version = 0.40  
   |script_version = 0.40  
   }}</ref>)
   }}</ref>
* [[A Failure Management Framework for FlightGear]]
* [[Spoken GCA]] - An offline ground controlled approach (GCA) addon
* [https://gitlab.com/mdanil/flightgear-hax mdanilov hax!]: landing evaluation and aircraft development tools, TerraSync toggler
* [https://gitlab.com/mdanil/flightgear-mickey Tiny HUD for mouse flying in FlightGear] - Visual feedback for mouse flying, to make up for mouse's lack of self-centering
* [https://github.com/slawekmikula/flightgear-addon-vfrflight VFRFlight integration] - ([https://github.com/slawekmikula/flightgear-addon-vfrflight/blob/master/doc/manual.md manual])
* [https://github.com/slawekmikula/flightgear-addon-vfrnavigator VFR Flying Helper] - ([https://github.com/slawekmikula/flightgear-addon-vfrnavigator/blob/master/doc/usage.md manual])
* [[YASim Development Tools]] (by jsb)
* [https://github.com/hbeni/fgfs-noGroundDamage noGroundDamage] - Addon to temporarily disable damage after landing and for ground operations for the c172/c182
 
== Experimental Addons ==
 
Addons which are in the development stage/unfinished but can be used as a quick view of addon functionality
* [https://github.com/slawekmikula/flightgear-addon-missions FlightGear Missions addon] - Add-on for missions/adventures code


== Ideas ==
== Ideas ==
 
=== Hooking into features using legacy OpenGL code ===
== Hooking into features using legacy OpenGL code ==
{{See also|Unifying the 2D rendering backend via canvas}}
{{See also|Unifying the 2D rendering backend via canvas}}
In 09/2018, James suggested that legacy features using raw OpenGL calls (e.g. HUD/2D panels) could be easily replaced via scripted Canvas/Nasal solutions at the mere cost of providing a mechanism to hook into the legacy code implementing these features (namely, the HUD/instrumentation subsystems) <ref>https://sourceforge.net/p/flightgear/mailman/message/36399261/</ref>
In 09/2018, James suggested that legacy features using raw OpenGL calls (e.g. HUD/2D panels) could be easily replaced via scripted Canvas/Nasal solutions at the mere cost of providing a mechanism to hook into the legacy code implementing these features (namely, the HUD/instrumentation subsystems) <ref>https://sourceforge.net/p/flightgear/mailman/message/36399261/</ref> <ref>https://sourceforge.net/p/flightgear/mailman/message/36399261/</ref>


=== Catalog & Package Manager support ===
=== Catalog & Package Manager support ===
if this works with more complex, pre-existing addons such as [[Bombable]], where the file layout is a replica of the old FGData layout, these types of mature addons might be better as SourceForge FlightGear sub-projects rather than being copied into FGAddon. Maybe the config file and nasal script could be used to automate the installation process ?<ref>{{cite web
if this works with more complex, pre-existing addons such as [[Bombable]], where the file layout is a replica of the old FGData layout, these types of mature addons might be better as SourceForge FlightGear sub-projects rather than being copied into FGAddon. Maybe the config file and nasal script could be used to automate the installation process ?<ref>{{cite web
   |url    =  https://sourceforge.net/p/flightgear/mailman/message/35953179/  
   |url    =  https://sourceforge.net/p/flightgear/mailman/message/35953179/  
Line 235: Line 278:
== References ==
== References ==
{{Appendix}}
{{Appendix}}
== Related content ==
=== Wiki articles ===
* [[FG Add-on FAQ]]
* [[FlightGear configuration via XML]]
* [[FlightGear configuration via XML#preferences.xml]]
* [[Nasal]]
* [[Property tree]]
* [[Properties persistent between sessions]]
* [[PropertyList XML File]]
=== Forum topics ===
* {{forum link|t=32561|title=New Feature: Addon - "API"}}
=== Readme files ===
* {{readme file|add-ons}}
* {{readme file|gui}} - Details on how to add menus and custom dialogs.
=== Source code ===
==== FGAddon ====
* {{fgaddon source|path=Addons/Skeleton}} - Skeleton addon to be used as a template.
==== FGData ====
* {{fgdata source|path=Nasal/addons.nas}}
==== FlightGear ====
* {{flightgear source|path=src/Main/options.cxx}}
* {{flightgear source|path=src/Add-ons/}}
[[Category:FlightGear addons| ]]

Latest revision as of 10:06, 15 February 2024

Fgaddonslogo202x89.png

To make it easier to create addons there is since FlightGear 2017.3 a new way to create addons. In essence FlightGear will load an overlay XML into the property tree and start a well known Nasal function.[1]

We now have a simple way to add addons to FlightGear without the need to mess around with FGData/Nasal or FGHome/Nasal directories.[2]

Installing and using an addon

Download and copy the addon to a directory on your computer.

If you use the launcher, select the Add-ons page from the icon bar on the left, then find the section Add-on Module folders and click the Add(+) button. Select the folder where you put the addon. Once the addon is shown in the list, make sure its check box is selected.

Use the command line switch --addon=/path/to/some/addon.[2]

Creating an addon

There is a very simple Skeleton addon available in FGAddon to be used as a template.[2] See flightgear/fgaddon/trunk/Addons/Skeleton.

A leading slash (/) in this section indicates the base directory of the directory structure of the addon.

Minimum configuration

An addon may be installed in a directory anywhere on your hard disk and need at least two files:

  • /addon-config.xml - A standard PropertyList XML file to be used to populate or modify the property tree. (Same as to be used in --config=foo.xml)
  • /addon-main.nas - The Nasal hook for the logic. This file needs a function called main() which will be called from the global addon initializer (addons.nas)

Additional common files

  • /addon-metadata.xml - A PropertyList XML file with metadata about the addon it.
  • /addon-menubar-items.xml - A PropertyList XML file describing menus to be added to the FlightGear menu bar.
  • /gui/dialogs/<my-foobar-dialog>.xml - PropertyList XML files to create custom dialogs.

Good to know

The new addon mechanism lets you add a addon-config.xml to override the settings in defaults.xml and other files.

That will allow an addon to

  • Override key bindings (as in the spoken ATC addon)
  • Add or override autopilots and property rules
  • Introduce XML state machines

Unless your really want to add/change/remove those at runtime, this should cater for most use cases.[3]

We have some instructions how to use SVN in our wiki. It covers mostly aircraft development but the workflow is pretty much the same for addons.[4]

Sound Support

Sound support is available using fgcommand's.

See Nasal FAQ "play-audio-sample"

https://sourceforge.net/p/flightgear/flightgear/ci/5acf2e26d085b7553b2387b9753e9253e8b4bff4

Hackathon Proposal:Addon specific Sound Queues

Addon initialization

On initialization fgfs takes care of:

  • Through options.cxx:[2]
    • Creating a property under /addons/addon[n]/path=/path/to/some/addon
    • Loading /path/to/some/addon/addon-config.xml into the property tree (same as --config=/path/to/some/addon/addon-config.xml)
    • Adding /path/to/some/addon to the list of allowed directories (same as --fg-aircraft=/path/to/some/addon)
  • Through addons.nas:
    • Loading /foo/bar/baz/addon-main.nas into namespace __addon[ADDON_ID]__
    • Calling main(addonGhost) from /foo/bar/baz/addon-main.nas.

Aircraft specific config (addon-hints)

Some addons need per-aircraft configuration. While addons should strive to be self-contained (ie. the addon should contain means to detect different aircraft and apply config from whithin the addon) there is also the possibility for the addon to read so called "addon-hints".

For this, a special property tree exists: /sim/addon-hints/<addon>/... The tree is expected to be populated from the aircraft.xml file. The addon can then read the properties from a common place regardless of loaded aircraft. 

<sim>
  <addon-hints>
    <my-addon>
        ...
    </my-addon>
  </addon-hints>
</sim>

APIs

For more details about these APIs, see the readme file, $FG_ROOT/Docs/README.add-ons.

C++ API

There is a C++ API on FlightGear's side that handle some on the addon related tasks manly through the AddonManager(), Addon() and AddonVersion() classes.

Nasal API

The Nasal add-on API lives in the 'addons' namespace and can for example do queries to AddonManager() and read data from addons.Addon objects. It can for example compare addon versions if there is dependencies.

Background

See also Howto:Creating a simple modding framework.

ATC chatter was removed in 2015, see fgdata commit: 81607f734e13add9be02816ddaec305d05bc4e47

And the devel list messages referenced in the commit log. the other relevant commit is this: b60736ba7add2a7cd39af3d8a974d5be3ea46e8b It would not be very difficult to restore this functionality, or even generalize/improve it significantly (which was the scope of the original discussion on the devel list)[5]

The restored functionality could be distributed as a tarball that is extracted into $FG_ROOT - alternatively, into $FG_HOME, because Nasal files there are treated as overlays, which basically means that you can install user-specific extensions there without having to tamper with $FG_ROOT, it would only take very minor changes to turn the chatter feature into a corresponding "addon" - not unlike fgcamera ...[6]

We should absolutely stop telling anyone to edit preferences.xml in FG_ROOT; any documentation or advice which says to should be changes ASAP. [7]

As of 12/2017, the addon API is in the process of being significantly updated [8] [9] [10]

List of Addons

You can find the official repository at flightgear/fgaddon/trunk/Addons

Experimental Addons

Addons which are in the development stage/unfinished but can be used as a quick view of addon functionality

Ideas

Hooking into features using legacy OpenGL code

See also Unifying the 2D rendering backend via canvas.

In 09/2018, James suggested that legacy features using raw OpenGL calls (e.g. HUD/2D panels) could be easily replaced via scripted Canvas/Nasal solutions at the mere cost of providing a mechanism to hook into the legacy code implementing these features (namely, the HUD/instrumentation subsystems) [20] [21]

Catalog & Package Manager support

if this works with more complex, pre-existing addons such as Bombable, where the file layout is a replica of the old FGData layout, these types of mature addons might be better as SourceForge FlightGear sub-projects rather than being copied into FGAddon. Maybe the config file and nasal script could be used to automate the installation process ?[22] The Bombable addon is one of the most popular addons out there, and a large number of aircraft in FGAddon have bombable support, so it is worth not forgetting about. Especially if the addon system one day becomes automated through a catalog.xml type system[23]

References

References
  1. ↑ Torsten  (Jul 19th, 2017).  Re: New Feature: Addon - "API" .
  2. ↑ 2.0 2.1 2.2 2.3 Torsten  (Jul 18th, 2017).  New Feature: Addon - "API" .
  3. ↑ Torsten  (Jul 23rd, 2017).  Re: Spoken .
  4. ↑ Torsten  (Jul 19th, 2017).  Re: Spoken ATC .
  5. ↑ Hooray  (Jun 11th, 2016).  Re: Whatever happened to radom radio .
  6. ↑ Hooray  (Jun 11th, 2016).  Re: Whatever happened to radom radio .
  7. ↑ zakalawe  (Oct 26th, 2013).  Re: NavCache:init failed:Sqlite error:Sqlite API abuse .
  8. ↑ https://sourceforge.net/p/flightgear/mailman/message/36146017/
  9. ↑ https://sourceforge.net/p/flightgear/mailman/message/36150159/
  10. ↑ https://sourceforge.net/p/flightgear/mailman/message/36150444/
  11. ↑ Roman Ludwicki (PlayeRom)  (Aug 14th, 2022).  Re: Aerotow Everywhere .
  12. ↑ Wayne Bragg (wlbragg) .  Re: Cargo Towing Addon .
  13. ↑ wkitty42  (Aug 13th, 2017).  Re: .
  14. ↑ Unknown, HHS (Nov 1th, 2018).  Re: .
  15. ↑ Stefan Frank  (Aug 8th, 2021).  Re: .
  16. ↑ ThomasS  (Aug 12th, 2017).  Re: .
  17. ↑ Roman Ludwicki (PlayeRom)  (Dec 11th, 2022).  Re: Logbook Add-on .
  18. ↑ RedGriffin  (Jan 6th, 2020).  Re: .
  19. ↑ Torsten  (Jul 10th, 2017).  Re: .
  20. ↑ https://sourceforge.net/p/flightgear/mailman/message/36399261/
  21. ↑ https://sourceforge.net/p/flightgear/mailman/message/36399261/
  22. ↑ Edward d'Auvergne  (Jul 19th, 2017).  Re: [Flightgear-devel] Simple API for creating FlightGear addons/plugins .
  23. ↑ Edward d'Auvergne  (Jul 19th, 2017).  Re: [Flightgear-devel] Simple API for creating FlightGear addons/plugins .

Related content

Wiki articles

Forum topics

Readme files

Source code

FGAddon

FGData

FlightGear

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