PUI: Difference between revisions

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=== 2018 ===
=== 2018 ===
{{See also|QtQuick use in FlightGear}}
According to James, we have to accept that changes like testing or making [[PUI]] a modular thing or moving the JS code tend to have an immediate pain for some people (because strange stuff gets broken, and takes some time to get fixed), whereas the payoff in terms of improved joystick handling or replacing the UI or testing of all subsystems will take some months or years to be felt.<ref>https://sourceforge.net/p/flightgear/mailman/message/36323240/</ref>
According to James, we have to accept that changes like testing or making [[PUI]] a modular thing or moving the JS code tend to have an immediate pain for some people (because strange stuff gets broken, and takes some time to get fixed), whereas the payoff in terms of improved joystick handling or replacing the UI or testing of all subsystems will take some months or years to be felt.<ref>https://sourceforge.net/p/flightgear/mailman/message/36323240/</ref>



Revision as of 18:25, 4 August 2020

Caution  The feature documented below, in its current form, is currently being scheduled/expected (or discussed) to be significantly updated, or phased out, in future FlightGear versions + (rough estimate). This should be taken into account if you're interested in working on the feature or developing it further. If in doubt, please get in touch via the devel list first.

(PUI is likely to be removed to help improve compatibility with OSG/OpenGL 3.x and improve performance by phasing out legacy OpenGL code. Therefore, people should be careful when using/extending the PUI based legacy GUI engine[1][2] and coordinate any related work with the devel mailing list-this applies particularly to adding any additional hard-coded PUI widgets.)

FlightGear GUI dialog (exit.xml)stored in $FG_ROOT/gui/dialogs


Custom-autopilot-dialog.png

PUI is the standard GUI engine used in FlightGear, it is part of PLIB and is using raw, fixed-pipeline, OpenGL code internally (no OpenSceneGraph). PUI provides a fairly basic, but robust, set of widgets. PUI is also used for rendering the Menubar:

Menubar2.jpg

Replacement status

2020

As of 03/2020, the PLIB replacement was reported to be in the backlog [3].

With PLIB replacement work likely being re-scheduled for post 2020.2 LTS [4].

In 08/2020, James stated that he was still working (exceptionally slowly!) on replacing PUI (as part of removing legacy OpenGL code (PUI, HUD, 2d panels, porting Canvas away form ShivaVG), so we can switch to Vulkan/VSG at some point (ideally at some point before Apple turn off OpenGL support…)), and that he doesn't think /any/ of us *want* to be working on these features particularly, but projects like these need to be done before anyone can have fun with VSG or Vulkan (personally James would be very enthusiastic about working on VSG support (being on macOS, I also have the most to lose / gain from it)). Sometimes that’s just how it goes. Equally they will all benefit the project ultimately, but the payoff both for the individual and the project is very drawn out. [5]

2019

The new GUI has been incubating for a few years, but there's apparently been a lot of progress as of 10/2019.

It is likely the new GUI will be a user opt-in feature - at least initially. The sunset of the PLIB library _could_ happen relatively soon, but people will need to see the new GUI and react to it before we could commit to PLIB removal [6].

In 02/2019, James stated that the new UI is coming quite soon. [7]

2018

According to James, we have to accept that changes like testing or making PUI a modular thing or moving the JS code tend to have an immediate pain for some people (because strange stuff gets broken, and takes some time to get fixed), whereas the payoff in terms of improved joystick handling or replacing the UI or testing of all subsystems will take some months or years to be felt.[8]

James said he was in the middle of porting the launcher’s final tab (location) to the new UI scheme, once that’s done he will start sketching out the ‘in sim’ settings UI using the same pieces. He’ll send a request for contributions around about that in the next three-four weeks, once he has enough templates & examples that there is a clear pattern to follow.[9]

James announced that the launcher is now feature complete with the QtQuick UI, he’ll keep making bug-fixes of course as people report them, but my todo list for the core features is now done[10].

2017

In 10/2017, James said he was getting really close to having the PUI replacement UI suitable for beta-testing.[11]


Originally, James was hoping to land the PUI replacement GUI in the last dev cycle in 2017 (at least as a proof-of-concept, probably not as the default UI), so wouldn’t expend lots of effort on things like collapsible sections which might be a lot of work with the current PUI/Canvas approaches, but are trivial with the new QtQuick based UI scheme.[12]


Once the basic new UI is in place we can experiment with different re-arrangements easily, without being limited by PUI. (James expects PUI to live on as the default / alternate UI while this happens)[13]

Technically, this entails replacing dialog.cxx with some code which builds up some special ‘PUI-Emulation’ QtQuick controls, so that existing dialogs (especially from Aircraft) continue to work. This mode will look somewhat ugly but hopefully no more ugly than PUI! And it helps that the set of widgets we have in PUI is limited, and the ‘tricky’ widgets (map, scrolling list, etc) are in the dialogs will will replace with new ones first.[14]

This PUI emulation isn't going to use any code from PLIB[15], so what will remain from it in FG afterwards will be the FNT and JS components (reworked).[16]

Background

In FlightGear, PUI dialogs are standard PropertyList XML Files that are stored in $FG_ROOT/gui/dialogs, they can contain the widgets mentioned in $FG_ROOT/Docs/README.gui, using a simple layout engine discussed in $FG_ROOT/Docs/README.layout, and bindings using a combination of so called fgcommands operating on properties (see $FG_ROOT/Docs/README.commands) and custom Nasal (FlightGear scripting) code.

In addition, each PUI/XML dialog may contain Nasal script sections that are executed when opening/closing the dialog, a feature which is commonly used for procedurally creating/updating widgets using the cmdarg() API, which allows the dialog tree to be traversed and manipulated prior to the dialog being rendered. Widgets can be conditionally hidden/shown using a wrapper for SGCondition in props.nas The canvas widget also supports its own embedded Nasal code section to execute arbitrary widget specific Nasal code upon opening/closing the dialog/widget.

PUI/XML dialogs can be loaded, dynamically created, updated and closed using a handful of fgcommands:

  • dialog-new
  • dialog-show
  • dialog-update
  • dialog-apply
  • dialog-close


PUI related OpenGL code is particularly infamous for causing rendering artifacts for people on AMD/ATI and Intel hardware (especially in combination with certain fonts/styles and effects/shaders), see ticket #2213.

PUI is also known to affect rendering performance quite significantly (see forum search for anthrax+gui FlightGear Forum), while also preventing FlightGear from using a more recent version of OpenGL[17][18].

However, improving the frame-rate and modernised 3D rendering, can’t be worked on until the PUI code, 2D panels and Shiva are removed, but doing so is a frustrating slow path[19]

Besides, while most people seem to agree PUI needs to be replaced, it sounds as if the fallout from doing so would be more painful (cumulatively) than the pain its existence causes.[20]

But given that with many graphics drivers PUI doesn't render correctly when higher shader quality is on, graphics folks are also convinced it needs to be replaced.[21]


In addition, OpenSceneGraph (OSG) can obviously not help optimize any PUI related GL code and PUI widgets are generally considered to be pretty archaic and not easy to extend[22][23][24].

Note  We use the GUI code from PLIB, which doesn't know anything about OSG. See the SGPuDrawable class in $FG_SRC/Viewer/renderer.cxx for the implementation. The one catch is that OSG has a strong notion of separation between the update of a "scene" and its rendering, and that might not play well with arbitrary existing OpenGL code.

For these reasons, we're hoping to phase out PUI in FlightGear. One of the lowest hanging fruits is re-implementing the Menubar by using a Nasal/Canvas translator

Canvas-menubar-jabberwocky-09-2014.png


As of late 2015, there is heavy activity towards providing alternatives to a PUI-based UI:

References

References
  1. https://sourceforge.net/p/flightgear/mailman/message/34921495/
  2. Torsten Dreyer  (Jun 14th, 2016).  Re: [Flightgear-devel] GUI options (Was: Aircraft center) .
  3. Scott Giese  (Mar 18th, 2020). Re: [Flightgear-devel] C++ and/or OSG question .
  4. James Turner  (April 18th, 2020). Re: [Flightgear-devel] Working Group Proposal - Boost and PLIB replacement - Delegation and Teamwork .
  5. https://sourceforge.net/p/flightgear/mailman/message/37077158/
  6. Scott Giese  (Oct 14th, 2019). Re: [Flightgear-devel] in Flightgear/Simgear C++ Code: What needs Doing? What are YOU Doing? What would you do if you had the time? .
  7. James Turner  (Feb 17th, 2019).  Re: [Flightgear-devel] Lagging .
  8. https://sourceforge.net/p/flightgear/mailman/message/36323240/
  9. https://sourceforge.net/p/flightgear/mailman/flightgear-devel/thread/2d10f16c-ddc8-07f3-07e7-eca2a0a0d55f%40zaretto.com/#msg36293586
  10. https://sourceforge.net/p/flightgear/mailman/message/36355833/
  11. James Turner  (Oct 7th, 2017).  Re: [Flightgear-devel] PLIB features in plib svn but not in any release .
  12. James Turner  (Oct 1st, 2017).  Re: [Flightgear-devel] Canvas MapLayer for OpenStreetMap, OpenAIP, VFR Sectionals .
  13. James Turner  (Oct 2nd, 2017).  Re: [Flightgear-devel] FGFS macOS Menubar .
  14. James Turner  (Oct 8th, 2017).  Re: [Flightgear-devel] PLIB features in plib svn but not in any release .
  15. https://sourceforge.net/p/flightgear/mailman/message/36985303/
  16. Florent Rougon  (Oct 8th, 2017).  Re: [Flightgear-devel] PLIB features in plib svn but not in any release .
  17. http://sourceforge.net/p/flightgear/mailman/message/34532040/
  18. http://forum.flightgear.org/viewtopic.php?f=71&t=24046
  19. James Turner  (Jan 24th, 2017).  Re: [Flightgear-devel] canvas non svg-elements broken .
  20. James Turner  (Jan 24th, 2017).  Re: [Flightgear-devel] canvas non svg-elements broken .
  21. Thorsten Renk  (Jan 25th, 2017).  Re: [Flightgear-devel] canvas non svg-elements broken .
  22. http://sourceforge.net/p/flightgear/mailman/message/26832164/
  23. http://sourceforge.net/p/flightgear/mailman/message/10587120/
  24. http://sourceforge.net/p/flightgear/mailman/message/10587272/