Unifying the 2D rendering backend via canvas

Canvas - the FlightGear 2D drawing API
Canvas - Main Page Canvas News - for the latest developments Shiva Alternatives - ongoing work for Core Profile support Canvas Efforts - projects using the Canvas system Canvas FAQs - frequently asked questions Canvas - Getting started Canvas Development (core) Canvas Troubleshooting (core) Canvas Sandbox (core) PUI2Canvas (PUI/XML Parser) Canvas GUI Canvas Widgets Canvas Maps Canvas Snippets
RFC
Canvas Instancing Howto:New Canvas Execution Model Canvas SVG Canvas Popout Windows Canvas Scenery Overlays
Frameworks
Canvas Map API (soon deprecated!) Canvas MapStructure Canvas MapStructure Layers MapStructure Snippets Canvas Radar Canvas Animation Framework (WIP) Canvas Plotting Framework (WIP) Canvas MFD Framework Canvas ND Framework Canvas PFD Framework Canvas MCDU Framework Canvas EFB Framework Canvas Wrappers Canvas Glass Cockpit Efforts
Tutorials
Howto:Getting started with Canvas Howto: Canvas Troubleshooting Howto:Adding a canvas to a GUI dialog (PUI!) Howto:Creating a Canvas GUI dialog file (New) Howto:Dynamic Liveries via Canvas (new) Howto:Creating a Canvas GUI Widget Howto:Add a 2D canvas instrument to your aircraft Howto:Parsing 2D Instruments using the Canvas Howto:Creating fullscreen Canvas applications Howto:Use SVG inside a Canvas Howto:Extend the Canvas SVG module Howto:Serializing a Canvas to SVG Howto:Canvas applications as Nasal submodules Howto:Using raster images and nested canvases Canvas HUD Howto:Project 3D to 2D coordinates on desktop canvas
Reference
Canvas Element Group Image Map Path Text Canvas Nasal API MessageBox Layout System Canvas GUI API Canvas draw library Event Handling
Related
Canvas Properties Unifying the 2D rendering backend via canvas Howto:Use a Camera View in an Instrument Howto:Extending Canvas to support rendering 3D models Howto:Extending Canvas to support MathGL
To be ported
Navigation display Map FGCanvas Canvas Nasal/JavaScript Subset
Deprecated by Canvas
Complex Glass Cockpit Avionics
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Background

The long term idea is to eventually port some other 2D elements to this backend (eg the HUD and 2D panels) so they use OSG (and osgText) natively, and hence reduce the amount of C++ code we have for these jobs. (And increase our chances of working with never OpenGL versions that forbid old style GL calls) Long-term here means 'after 2.8 at least'. — James Turner

The Canvas subsystem is flexible enough to re-implement existing 2D rendering related features, such as the HUD system or the 2D panel system, in scripting space, so that legacy C++ code can be incrementally replaced with a more accessible and more maintainable version in scripting space, i.e. as part of the base package - while ensuring that the 2D rendering backend is increasingly unified, as part of the Canvas subsystem.

The idea is to provide Nasal wrappers for these systems, which implement the existing behavior using the canvas system, so that the old C++ code can be eventually phased out. In particular, this means that wrappers for the following systems will be added:

• HUD: https://gitorious.org/fg/flightgear/trees/next/src/Instrumentation/HUD
• 2D PANEL: https://gitorious.org/fg/flightgear/blobs/next/src/Cockpit/
• GUI: https://gitorious.org/fg/flightgear/blobs/next/src/GUI/FGPUIDialog.cxx#line709

Initially, the main focus will be on providing the infrastructure to enable people to develop widgets entirely in Nasal space. Once that is working, it will be possible to increasingly re-implement native PUI widgets in Canvas/Nasal space, so that PUI usage is increasingly reduced.

To ensure that the Canvas/GUI wrapper is flexible enough, we need to take a look at existing hard coded PUI dialogs/widgets, and make sure that these can be theoretically reimplemented using Canvas/Nasal, and add any missing hooks as required:

• property list widget: https://gitorious.org/fg/flightgear/blobs/next/src/GUI/property_list.cxx
• waypoint list widget: https://gitorious.org/fg/flightgear/blobs/next/src/GUI/WaypointList.cxx
• map widget: https://gitorious.org/fg/flightgear/blobs/next/src/GUI/MapWidget.cxx

This automatically means that PUI callbacks must be forwarded to Nasal, so that they can be implemented as Nasal callbacks.

Also, the Canvas subsystem should be powerful enough to allow re-implementing existing hard-coded od_gauge instruments, such as:

• dclgps: https://gitorious.org/fg/flightgear/blobs/next/src/Instrumentation/dclgps.cxx
• kln89: https://gitorious.org/fg/flightgear/trees/next/src/Instrumentation/KLN89
• groundradar: https://gitorious.org/fg/flightgear/blobs/next/src/Instrumentation/groundradar.cxx
• wxRadar: https://gitorious.org/fg/flightgear/blobs/next/src/Instrumentation/wxradar.cxx
• agradar: https://gitorious.org/fg/flightgear/blobs/next/src/Instrumentation/agradar.cxx
• NavDisplay: https://gitorious.org/fg/flightgear/blobs/next/src/Instrumentation/NavDisplay.cxx

As of 07/2012 the navdb is fully exposed as part of the NasalPositioned module $FG_SRC/Scripting.