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 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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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.

GUI Widgets

The widget module will allow implementing custom GUI widgets using the Canvas system and Nasal, this will make it possible to re-implement existing PUI widgets as fully interactive "Nasal canvases", so that usage of PUI is increasingly reduced, facilitating phasing out of PUI eventually.

The Canvas/GUI integration is implemented such that none of the existing code is touched, i.e. the old behavior remains fully supported. In addition, new widgets can be shared and reused by adding them to the $FG_ROOT/Nasal directory.

Also, we also don't need to duplicate the existing C++ code and the dialog XML parsing.

Everything keeps as working as it is, adding new widgets (and USING them) can be purely done by modifying stuff in the base package, without touching the C++ code again.

In order to start using any custom Canvas-widgets, you only need to change the widget type to "canvas" and specify the name of the widget to be instantiated. For example:

 <type>canvas</type>
 <name>button</name>

This is fully supported by Nasal code, as well as XML files.

For example, if someone creates a new Canvas-based widget, say a "button" - all that is needed to start using it in FG, would be modifying the corresponding GUI XML files, and replacing the

<type>button</type>

with this instead:

<type>canvas</type> <widget>button</widget>

(i.e. rename type and add a new "widget" node)

This can be done automatically within seconds using XSLT for XML files in $FG_ROOT - and all of a sudden, the PUI button class would no longer be used - no need to touch any C++.

MFD

The MFD module will provide a wrapper on top of the canvas system specifically designed for building MFD-type displays (PFD, ND, EICAS etc). The MFD module will be largely inspired on the hard coded displays currently available in FlightGear, in particular the NavDisplay: Navigation display. What about CDUs, shall these be also covered by this module, or separately?

2D Panels

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.