Aircraft Center

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This article describes content/features that may not yet be available in the latest stable version of FlightGear (2020.3).
You may need to install some extra components, use the latest development (Git) version or even rebuild FlightGear from source, possibly from a custom topic branch using special build settings: .

This feature is scheduled for FlightGear 4.x. 50}% completed

If you'd like to learn more about getting your own ideas into FlightGear, check out Implementing new features for FlightGear.

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Canvas dialog showing the prototype for an Aircraft Center for directly downloading/installing/managing -and switching between- aircraft from within FlightGear, an upcoming experimental feature scheduled for FlightGear 3.2, currently being developed by TheTom and Zakalawe


Cquote1.png Recently I've also been mulling the possibility of selecting aircraft from an "in program" dialog similar to Fly II where you can climb up to 35,000 feet in a 747 and then switch to a C172 :-) Seriously, even if we did a full reset, it'd be nice to switch aircraft (3D models as well) and fdm's on the fly (pun not intended).
— David Megginson ( Fri, 08 Nov 2002 18:01:41 -0800). starting the XML GUI; early implementors needed.
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Background

Cquote1.png The "built-in" GUI/launcher is one of the longest-standing feature requests - but it's not just about the GUI (which is rather straightforward in comparison), but about the simulator never having been developed with this requirement, i.e. run-time reinitialization, in mind - thus, things like "fgrun" (and a plethora of other external launchers) were developed, which acted as a front-end on top of FG, so that FG itself wouldn't need to be changed - i.e. kind of a "remote control" using command line arguments. So it's there for a reason - fgrun uses the FLTK GUI library, which while relatively simple, is much more powerful than our legacy GUI engine, PUI.


Still, people have been asking for this for years, and it's thanks to pretty much a single person, Zakalawe, that switching aircraft is going to become possible pretty soon - he handled all the ugly work of cleaning up the simulator internals to make this happen - it's not exactly glamorous work, you gotta touch a ton of places, and you inevitably introduce a ton of regressions along the way.


— Hooray (Thu Jun 26). Re: About FlightGear being user-friendly or not.
(powered by Instant-Cquotes)
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Cquote1.png And yes, even the legacy FG GUI is entirely based on XML and configurable through just editiing XML files - but the collection of "widgets" (GUI controls like buttons, checkboxes, labels etc) is extremely small and very inflexible.


This is something that is currently being addressed by TheTom and Zakalawe, who've both been working on a new Canvas GUI, and a new Canvas GUI dialog called "Aircraft Center", which -while still experimental- is intended to eventually allow end-users to easily download/install aircraft right within the simulator, and also switch between aircraft at run-time without having to exit/restart the simulator.

Thus, adopting Canvas is going to address a number of long-standing issues, but it's obviously a process that only just got started, and it will not happen overnight - 2-3 release cycles are not far-fetched, that's how long the whole migration could very well take, unless there are more people interested in helping.


— Hooray (Thu Jun 26). Re: About FlightGear being user-friendly or not.
(powered by Instant-Cquotes)
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The FlightGear Frontend Debacle

Note  This is currently being addressed via the Canvas system, see ticket #1295 and Aircraft Center.


That in fact many users do feel a need to improve the current situation, can be seen by the multitude of GUI frontends that have been developed for FlightGear during the last couple of years.

In fact, in 2006 there were reported to be at least five different GUI launchers available for FlightGear [1]:

All of which supporting different functionality/features, having different library/system dependencies and being different code bases, with little -if any- reuse of existing code, all of which serving however the very same purpose of providing: a GUI frontend for FlightGear.

Furthermore, plans to develop even more new frontends in addition to the plethora of existing ones are still being discussed [4].

As has been pointed out in the original discussion [5], this pattern is a not only a very unfortunate one, but also a recurring one - which is also likely to drain development resources from FlightGear itself - simply because a number of developers and potential contributors spend time developing redundant software that wouldn't need to be developed in the first place if the FlightGear design were to be fixed so that the key facilities provided by existing launchers would be directly supported by FlightGear itself.


While it was pointed out in one case that the reason for yet another FlightGear GUI frontend, was motivated by non-technical reasons (such as native/platform "look & feel"), all other remaining reasons for developing these launchers were indeed technical ones, meaning:

None of these standalone frontends would likely need to be in existence today if FlightGear itself featured a native, built-in GUI frontend

Indeed, FlightGear's cross-platform nature obviously provides additional challenges for developing standalone launchers, so that some launchers may only work on specific platforms.

So, the most natural thing to do would be to directly integrate these facilities into FlightGear, where they can make use of extensive FlightGear APIs that are known to compile and work across all supported FlightGear platforms.

Status

Cquote1.png I've pushed now a first version of an aircraft install/removal dialog.

Was a lot more effort than expected, but now there are a lot of
improvements available useful for every type of dialog.


— Thomas Geymayer (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png The dialog is available in the menu (File > Aircraft Center) and shows

a list of the 100 first aircrafts available to install/remove. I've
chosen to limit the number, because with showing all aircrafts at once
I got a delay of a few seconds on opening the dialog. I will
investigate into this more later. You can use the according buttons to
install/remove aircrafts - which I have already done successfully.
Currently the dialog does not indicate any progress and needs to be
reopened to update the buttons.

As the feature freeze is already approaching, I won't be able to add
too much features for this release. So I think there won't be any
keyboard input/searching for this release. I want to support different
tabs to show a list of eg. just the installed aircrafts and do a
simple cache for all the downloaded images, to have them visible
faster on opening the dialog.


— Thomas Geymayer (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png Thomas Geymayer and I are working on it, I am not sure where’s he go to with the UI, the backend pieces are mostly there but will need some intensive testing. There is a #define flag you can toggle (in HTTPClient.cxx) to enable the code including the Nasal API; it will download / refresh a catalog, which is generated by the scripts I committed to fgmeta a week ago. Then you can access the package system from pkg.root in the Nasal console, using the API defined at the bottom of HTTPClient.cxx.


If you are crazy enough to enable this code, and run it, be aware it downloads zips, unpacks them, makes calls to unlink files, renames directories, and so on. I would recommend some caution, and especially, don’t run it as root - while developing it I had it extract a few zips to ‘/‘ or worse due to screwed up path logic.

Equally, I would welcome a code review of the code in simgear/package/Install.cxx to check any security issues or dangerous behaviour. The code /tries/ to be ‘safe’ - extract zip to a temporary folder, and uses rename/unlink to atomically update if the zip extraction succeeds. But it’s only had one pair of eyes on it so far.


— James Turner (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png My next objective will be actually switching to an aircraft, and setting up the correct paths so that dependencies work; this is more or less orthogonal, I will make a new command to select an aircraft (and reset the sim) based on an aircraft ID or fully-qualified ID. (Again to allow catalogs with ID collisions, such as org.flightgear.default.747-400 and nl.gijs-hangar.beta.747-400)


If anyone wishes to start adding tags or more meta-data to aircraft in FGdata, please let me know, especially to keep the tag space coherent and hence useful for searching.


— James Turner (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
Cquote2.png
Cquote1.png the whole thing is still pretty experimental, it’s probably not at the ‘this text should be a little to the left’ point. We’re more at the ‘it didn’t erase your C drive? Great!’ stage….
— James Turner (2014-06-13). Re: [Flightgear-devel] Notes on Aircraft Center....
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Cquote1.png The layout and widget systems is now maturing, so I think after 3.2 I

can start with porting PUI. Just one major component is missing, namely
keyboard input and the according input focus.

I guess this will take one or two more releases.


— Thomas Geymayer (2014-06-13). Re: [Flightgear-devel] Notes on Aircraft Center....
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Tagging

Cquote1.png Related to this, does anyone know how standardised the <status> values are? If there is a defined list of values I will add query support and expose them as an enum to Nasal.


And, if anyone who has a custom hangar would like to start maintaining a catalog, please let me know - there is no UI in FG to add additional catalogs yet but it would help with testing. If you already have a web server with zip files of aircraft, you only need to serve one extra XML file to run a ‘package-ified’ hangar. The catalog XML can be hand written or generated using any technology you like - there’s Python scripts in fgmeta, but PHP / shell-script / etc will all work too.


— James Turner (2014-06-11). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png have updated my script with to restrict tags to the set I original wrote on the wiki some time ago:


http://wiki.flightgear.org/Catalog_metadata

I am going to do make a drive-by assault on fgdata/Aircraft adding tags - hopefully no maintainer feels this is problematic since it’s purely adding metadata to make the UI more functional. I am sure I will get some entries ‘wrong’ and the tags themselves are still up for discussion, but we have a version control system, and most of the tags are very non-controversial.

The ‘nicer’ Nasal tags syntax is added now too. (Part of the motivation for adding tags to fgdata is to test it better(


— James Turner (2014-06-12). Re: [Flightgear-devel] select/download aircraft.
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Variants

Cquote1.png I don’t think there’s any pathological examples with more than eight -set.xml. Designating the ‘main’ -set.xml is still an issue.


What I will do is include the set-file and description in a ‘variants’ list, with the first entry being the default. So in the catalog XML, something like:

<package>
<variant>
<id>747-400-FO</id>
<name>747-400 First-officer mode</name>
</variant>
...
</package>

On Package I’ll expose this as string_list of variants() with a nameForVariant(std::string variant) helper. For Nasal I can return a dictionary.

Variant IDs will need to be unique within the Catalog, and I’ll update the search logic to accept /any/ variant ID as matching the package - this will make the aircraft-startup part of everything work, and keeps thing close to how it behaves with unpackaged aircraft.


— James Turner (2014-06-13). Re: [Flightgear-devel] select/download aircraft.
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Development

Cquote1.png I thought about adding a cache add Canvas::Image or rather at the

HTTPRequest level to cache all HTTP requests/files which have not set
a no-cache header.


— Thomas Geymayer (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png for a first step I want to limit it only to the

HTTPMemoryRequest which is mainly used for downloading canvas images. So
it should not affect too many parts.
Someday we should probably add a cache limit - but not now ;-) I will
also need this for displaying tilemaps.


— Thomas Geymayer (2014-06-10). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png A semi-related small thing: I'd like to have saved-between-sessions

"default aircraft/starting airport" properties (/sim/default-aircraft,
/sim/default-airport ?), set by a "make this default" check box in Go To
Airport and the new aircraft dialog, so those who prefer something other
than c172p@... don't have to select it on every startup. I should be
able to implement this, but comments would be appreciated.


— Rebecca N. Palmer (2014-05-30). Re: [Flightgear-devel] select/download aircraft.
Cquote2.png
Cquote1.png Currently box layouts are available. Once they fully

work I'll start thinking of other layouts and widgets.


— Thomas Geymayer (2014-06-13). Re: [Flightgear-devel] Notes on Aircraft Center....
Cquote2.png
Cquote1.png I want

to implement a cache to speed it up after the first time, but not for
3.2. If an image fails to load there should be a message in the terminal.
"No thumbnail available" is shown if there is no image specified in the
catalog.


— Thomas Geymayer (2014-06-13). Re: [Flightgear-devel] Notes on Aircraft Center....
Cquote2.png
Cquote1.png what I’d want is tabs at the top for ‘installed aircraft’, ‘available updates’ and so on. But again the question is really what UI we can build in the time available.
— James Turner (2014-06-13). Re: [Flightgear-devel] Notes on Aircraft Center....
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Known Issues

Cquote1.png Prior to a reset, if you edit /sim/aircraft, it works as you would expect. However there are some quirks related to aircraft-specific menu items / dialogs, at least on Mac (the custom menu for previous aircraft is not removed).


There may be other bugs, since this feature is not used by anyone yet.


— James Turner (2014-05-30). Re: [Flightgear-devel] select/download aircraft.
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Cquote1.png If you've created a grid control for Canvas, it would be nice to see the

FDM, Systems, Cockpit and Model ratings broken out into individual columns
so you could sort by them. :)

If you get to the point where you can change aircraft from this dialog,
you might want to include a checkbox that will limit the list to installed
aircraft.

If the Aircraft Center dialog is open, other dialogs don't appear to work
- I tried exiting via File->Exit and none of the items were selectable.
Hitting ESC brings up the Exit dialog, but the buttons were not clickable.

Dismissing the Aircraft Center dialog allowed the other dialogs to operate
properly.


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