Canvas wrappers

Canvas - the FlightGear 2D drawing API
Canvas - Main Page Canvas News - for the latest developments Shiva Alternatives - ongoing work for Core Profile support 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: 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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The canvas subsystem is entirely implemented on top of the property tree, so it does not depend on Nasal scripting. However, it is Nasal scripting which makes the Canvas system really flexible and powerful.

Currently, there are a number of efforts being discussed to unify the 2D rendering backends in FlightGear (2D panel, HUD, GUI etc) to ensure that the Canvas system is the common backend for all these needs, which will reduce the amount of legacy C++ code that we have in FlightGear for these things, while also paving the way towards better overall OpenGL compatibility, better maintainability and more optimization opportunities.

Directly working with the canvas via the property tree is possible but tedious, that's why there is a special generic Nasal wrapper to simplify working with canvases. However, to cater for more specific 2D drawing needs, there are going to be additional wrappers provided on top of the main canvas.nas module.

The purpose of this page is to determine the requirements for each wrapper.

HUDs

The HUD module will be specifically targeted at developing HUDs.

2D Instruments parser

The 2D panel module will reimplement the existing 2D panel functionality in Canvas/Nasal space, so that the legacy C++ code can be slowly phased out:

I'm even more convinced now that we should move the 2D panel and HUD rendering over to this approach, since that would get rid of all the legacy OpenGL code besides the GUI. — James Turner

Also see Howto:Parsing 2D Instruments using the Canvas

We need to reimplement the 2D panel code in $FG_SRC/Cockpit/

• panel_io.cxx
• panel.cxx
• $FG_ROOT/Docs/README.xmlpanel

Note that the FGPanel code is a bit cleaner than the old code, i.e. see [1].

Write a Nasal module that will take our existing instruments in $FG_AIRCRAFT/Instruments and turn them into canvases. Namely, that means, parsing:

• params
• layers
• transformations
• conditions
• actions

Basically, we should already have all building blocks in place, because:

• PropertyList-XML parsing support via io.nas
• we have support for raster images: Canvas Image
• Texture maps are also supported Howto:Using_raster_images_and_nested_canvases#Texture_Maps
• event handling: Canvas - Event Handling
• SGCondition bindings in Nasal (props.nas)
• support for layers via Canvas groups
• transformation can be directly handled through manipulation the tf properties
• bindings/actions would be directly turned into Nasal callbacks

In fact, the combination of Nasal and the Canvas is so much more flexible than our existing panel code, that it is foreseeable that it will see useful additions, which is why it'd be a good idea to introduce an optional version tag, so that new instruments can directly use canvas features.