Canvas EFIS framework

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Foreword

The canvas EFIS framework (created by jsb) is by-product of the EFIS development done for the CRJ700 family, which uses Rockwell Collins Proline. It is published as a separate framework in the hope that it is useful for other aircraft as well, however some features may be rather specific. The biggest motivation and primary design goal was to support "near optimal" performance but that does not come automatically of course.

For the bigger picture see also Howto:Add an EFIS to your aircraft.

Introduction and Overview

An EFIS usually comprises multiple display units (DU for short; CRT or LCD screens) to show all the information relevant to the pilot (e.g. 2x PFD, 2x MFD, 2x EICAS in the CRJ700). Some displays like an EICAS / ECAM may show different pages for the systems of the aircraft, they can be select by the pilot via a corresponding control panel. Furthermore, displays can be swapped in case of a DU fault. In the CRJ700 the pilot can select display sources by turning the corresponding knobs.

The EFIS framework provides Nasal classes to handle the following:

Display unit

reference to a 3D object in the cockpit ("display unit") on which the canvas texture shall be displayed
power switch property
image source (canvas reference)

Note: Dimming of display can be done by defining an animation in the XML going with the 3D model of the DU. See example below.

Image source (EFISCanvas)

base class for EFIS/EICAS pages handling some SVG stuff
can load a SVG file and create clipping from <name>_clip elements
allows to register multiple update functions with individual update intervals
update functions can be en-/disabled by a single property that should reflect the visibility of the canvas (e.g. do not waste CPU with updating pages that are not currently displayed)
several listener factories for common animations like show/hide, translation, rotation

Display selectors / routing

Handle input events from cockpit knobs to switch displays / pages

EICAS Message system

Handle EICAS messages efficiently without eating up to much frame rate
Message queue: decouple canvas updates from message arrival

Thoughts on implementation

Design goal: EFIS framework should support best performance by offering different update methods and update rates for efficency.

Update rates

The EFIS/EICAS basically monitors the whole aircraft so it will have to read lots of properties. For efficiency the properties must be grouped into different classes already in the design phase, that is, the aircraft developer shall carefully think about how often a property changes. Some props are written to at frame rate by property rules but that does not mean the value changes every time. Furthermore, not every change has the same relevance, not everything needs to be displayed real time (= frame rate).

update rate	Interval	comment
2	0.500s	low performance needs
10	0.100s	low to med. performance but no fluent animation
20	0.050s
30	0.033s	smooth canvas animation but possibly high performance need
60	0.017s

Some examples:

PFD contains many "real-time" elements like attitude indicator, speed, altitude etc. They should be updated probably at frame rate (min. 25 Hz) Other elements like radio frequency may be ok to update after 100ms or even 0.5s
An EICAS page displaying the door status maybe just fine with one update per second as doors move slowly and you won't see the door from outside and EICAS display inside the cockpit at the same time so a delay of one second does not matter

Update methods

Simple approach is to write an update loop that reads all relevant props, calculates the needed updates and updates the canvas elements (which in the end means writing properties) -> tends to be inefficient.
Property read/write is somehow "expensive" and can cost you a lot of frame rate. So the next better idea could be to limit the rate at which the update function is called - usually by a timer with some sensible interval.
If an animation is triggered only by one property and that property is unlikely to change often, remove the prop / animation from the update loop and use a listener instead. The listener may read other props as needed. A listener does not consume any CPU unless the property it listens to has changed, in which case the listener function is run.

Framework API documentation

The following sections document the framework classes and their methods.

Class EFIS

This is the top level class which ties together the different parts like display units, sources and cockpit controls.

new()

new(display_names, object_names, canvas_settings=nil);

Returns a new EFIS object

display_names: Vector of display names
object_names: Vector of 3D object names for canvas placement.
canvas_settings: Optional config hash for canvas that is merged with default settings of EFIS class

setPowerProp()

setPowerProp(path);

Creates listener for property path. Power on will start all display update functions, power of will stop them.

path: Property path to EFIS power property (bool).

setWindowSize()

setWindowSize(window_size);

Sets default size for canvas windows

window_size: Vector [size_x, size_y]

setDUPowerProps()

setDUPowerProps(power_props, minimum_power=0);

Sets default size for canvas windows

power_props: Vector of property paths, must be of same size as display_names given to new().
minimum_power: Passed to DisplayUnit.setPowerSource()

addSource()

addSource(efis_canvas);

Adds a EFISCanvas as display source, returns source ID to be used in mappings.

efis_canvas: A EFISCanvas instance created with EFISCanvas.new()

addDisplaySwapControl()

addDisplaySwapControl(ctrl, mappings, callback=nil);

Adds a listener for "ctrl", activates new source-display-mapping on change. Use this to implement a display swap knob in the cockpit.

ctrl: property path to integer prop, e.g. some selector knob in the cockpit
mappings: vector of display mappings, one mapping per value of ctrl
callback: optional function that will be called with current ctrl value

addSourceSelector()

addSourceSelector(selected, target, sources=nil);

Adds a listener for "selected" which will read the target DU from "target" and sets its source according to "selected". Use this e.g. for a EICAS / ECAM page select panel.

selected: property (node or path); source number (index to sources vector)
target: property (node or path); DU number to which the source will be mapped
sources: optional vector; selected -> source ID (as returned by addSource), defaults to all registered sources

setDefaultMapping()

setDefaultMapping(mapping);

Sets and activates a default mapping of sources to display units.

mapping: Vector [source_id1, source_id2, ...] or hash {DisplayName: source_id}

displayWindow()

displayWindow(id);

Opens display unit as canvas window.

id: Index of display

Class EFISCanvas

EFISCanvas manages a single canvas for you. It offers a bunch of little helpers to make the live of an aircraft developer easier. These helpers mostly do animation and update stuff on canvas elements in an efficient way.

new()

new(name, svgfile);

Returns a new EFISCanvas

name: Used e.g. in window title (see below)
svgfile: Filename of a SVG to load. (see also: loadsvg)

getPath()

returns path of canvas

getCanvas()

returns canvas instance

getRoot()

returns root group of the canvas

setUpdateN()

setUpdateN(node);

set a node that is checked in all registered update functions, they will only be run, if the value of this node is true

node: props.node object

loadsvg()

loadsvg(file);

Parses the given SVG file into the root group of the EFISCanvas. Clipping is setup for elements that have a corresponding element with the same name extended by "_clip".

file: filepath passed to canvas.parsesvg

addUpdateFunction()

addUpdateFunction(f, interval);

Creates a timer with given interval that runs the given function if the value of the update node is true.

f: Nasal function to run
interval: Interval in seconds

startUpdates()

Start all update timers.

stopUpdates()

Stop all update timers.

getInstr()

When updating EFIS displays, there is a need to access properties under /instrumentation very often. To avoid the rather expensive append operator ("~") and property path lookups, you should use this little helper. It creates node objects (only once) to access properties like "/instrumentation/"~sys~"["~id~"]/"~prop,

getInstr(sys, prop, default=0, id=nil);

Helper to quickly access instrumentation properties with this name schema: "/instrumentation/"~sys~"["~id~"]/"~prop

sys: the system name under /instrumentation
prop
default: Optional default value to return, if getValue() returns nil
id: Optional override the id of the current EFISCanvas obj (me.id)

updateTextElement()

updateTextElement(svgkey, text, color=nil);

Updates a single text element and optionally sets its color.

svgkey: Name of the text element to update.
text: new text, passed to setText()
color: Vector [r,g,b] or valid color name from EFISCanvas.colors

_updateClip()

private function that sets clipping for an element, if there is another element with the same name extended by "_clip".

Listener factories

Note

The following listener factories will return a function. The general usage is setlistener("/some/property/name", _makeListener_xxx(parameters), 1, 0);

As usual, the listened-to node is passed into the listener function as first argument and the function will getValue() and do something meaningful with the value.

The first argument to the listener factory functions is always svgkey which can be either a string naming one canvas element or a vector of such strings.

_makeListener_showHide()

_makeListener_showHide(svgkey, value=nil);

Returns listener to show/hide element(s).

svgkey: String or vector; the element(s) to update.
value: optional value to trigger show(); otherwise node.value will be implicitly treated as bool.

_makeListener_rotate()

_makeListener_rotate(svgkey, factors=nil);

Returns listener to rotate one or more canvas element(s) by property value. If svgkey is a vector, factors must be a hash having each elemnent in svgkey as a key and the corresponding factor.

svgkey: String or vector; the element(s) to update.
factors=nil: Factor for setRotation(value * factor); defaults to 1 if not given

_makeListener_translate()

_makeListener_translate(svgkey, fx, fy);

Returns listener to translate one or more canvas element(s) by property value. If svgkey is a vector, fx and fy must be hashes having each elemnent in svgkey as a key and the corresponding factor for translation.

svgkey: String or vector; the element(s) to update.
fx: Factor for translation in x direction
fy: Factor for translation in y direction

_makeListener_setColor()

_makeListener_setColor(svgkey, color_true, color_false);

Returns generic listener to change element color. Both color arguments can be either a vector [r,g,b] or a valid name (hash key) for EFISCanvas.colors;

svgkey: String or vector; element(s) on which to call setColor().
color_true: Color to use, if getValue() is true.
color_false: Color to use, if getValue() is false.

_makeListener_updateText()

_makeListener_updateText(svgkey, format="%s", default="");

Returns listener to update a canvas text element from property value.

svgkey: The element to update.
format: A valid format string for printf()
default: Value to use, if getValue() returns nil or false.

Class DisplayUnit

This class is used by the EFIS class. DisplayUnit creates and places a canvas to a 3D object specified in new().

new()

new(name, canvas_settings, screen_obj, parent_obj = nil);

Configure the nasal file to load.

name: Used e.g. in window title (see below)
canvas_settings: passed to canvas.new()
screen_obj: used for canvas placement
parent_obj: used for canvas placement

setSource()

display_unit.setSource(path);

Select a canvas to show on the display unit.

path: A valid canvas path as returned by the canvas.getPath() method.

setPowerSource()

display_unit.setPowerSource(prop, min);

Sets a listener to prop. Display will show only if property value >= min

prop: Path to property that represents display power supply.
min: Minimum value of property to show display.

Example

var my_display_unit = DisplayUnit.new("PFD1");
# display turns on when DC power is >= 24 volts
my_display_unit.setPowerSource("/systems/DC/outputs/pfd1", 24);

asWindow()

display_unit.asWindow(window_size);

Opens the display in a canvas window.

window_size: Vector [size_x, size_y]; passed to canvas.Window.new().

EICAS message system

The message system decouples the update of canvas text elements (e.g. message lines) from the handling of messages. It is configured with the necessary message classes (e.g. warnings, caution messages, status messages) and a list of all possible messages. For each message a corresponding property can be defined that controls whether or not the message is shown. Alternatively, a message can be shown or hidden via the Nasal methods (see also the HOWTO section for examples and best practices).

Class MessageSystem

new()

new(page_length, prop_path);

Creates a new message system.

page_length: Maximum page length. Page length can be changed at runtime but not exceed this initial value.
prop_path: Property path, some config and data of the message system will be put here.

setPowerProp()

setPowerProp(prop_path);

Sets a listener to the "power switch" property. Will call init() if property changes to true.

prop_path: Path to a bool property representing the EFIS power state.

addMessageClass()

addMessageClass(class_name, paging, color = nil);

Sets the number of lines per page.

lines: Number of lines per page

addMessages()

addMessages(class, messages);

Add message definitions to a class. Setup listeners according to message definitions that call setMessage() accordingly.

class: Class identifier returned by addMessageClass()
messages: Vector of message definitions. See below for format.

Caution Use setSoundPath() before addAuralAlert() or addAuralAlerts().

setSoundPath()

setSoundPath(path);

Set aural alert configuration hash

path: Default path for aural alert audio files.

Example

var sound_dir = getprop("sim/aircraft-dir")~"/Sounds/auralalerts/";
myMessageSystem..setSoundPath(sound_dir);

addAuralAlert()

addAuralAlert(id, filename, volume=1.0, path=nil);

Add a single aural alert.

id: Name of aural alert referenced in the message definitions or the auralAlert() method.
filename: Name of the sound file, e.g. "alert.wav"
volume: Sound volume for this alert, defaults to 1.0
path: Optional, override default path set with setSoundPath() before(!).

Note If you want to store the alerts in a single hash you can pass this to the message system by calling addAuralAlerts(). Note the 's' at the end.

Warning addAuralAlerts() overwrites any previous alert config. If you want to add single alerts with addAuralAlert() this has to be done after calling addAuralAlerts().

addAuralAlerts()

addAuralAlerts(alert_hash);

Set aural alert configuration hash

alert_hash: Hash

Example

var sound_dir = getprop("sim/aircraft-dir")~"/Sounds/auralalerts/";
# you can add aural alerts one by one...
myMessageSystem.addAuralAlert("firebell", "firebell.wav");
# ... or you can define everything in one hash and pass it to addAuralAlerts (mind the trailing 's')
var Alerts = {
    overspeed: {path: "/Sounds", file: "overspeed.wav", volume: 1.0 },
    alert1: {file: "sound.wav", volume: 0.8 },
    alert2: "sound2.wav",
};
myMessageSystem.setSoundPath(sound_dir);
myMessageSystem.addAuralAlerts(Alerts);

setMessage()

setMessage(class, msg_id, visible=1);

Show or hide a message, optional trigger aural alert on show. Does nothing if message is already in desired state.

class: Class identifier returned by addMessageClass()
msg_id: see getMessageID()
visible: bool; 0 = hide, otherwise show

auralAlert()

auralAlert(id);

Plays an aural alert.

id: Identifier of the aural alert (see addAuralAlert() ).

init()

init();

Used on power up to check for active messages. Enables sound queue for aural alerts.

hasUpdate()

hasUpdate();

Returns update flag.

setPageLength()

setPageLength(length);

Change page length. Length cannot exceed initial page length (see new())

length: New number of lines per page.

getPageLength()

getPageLength();

Returns current page length.

getFirstUpdateIndex()

getFirstUpdateIndex();

Returns the index of the first line that has changed.

getActiveMessages()

getActiveMessages();

Returns message queue and clears the hasUpdate flag.

getMessageID()

getMessageID(class, msg_text);

Returns numeric id for a message in given class.

class: Class identifier returned by addMessageClass()
msg_text: Message string to search for.

disableMessage()

disableMessage(class, msg_id);

Inhibit message (or all messages in class if no msg_id is given).

class: Class identifier returned by addMessageClass()
msg_id: see getMessageID()

enableMessage()

enableMessage(class, msg_id);

Re-enable message (or all messages in class if no id is given).

class: Class identifier returned by addMessageClass()
msg_id: see getMessageID()

-- following methods are for message output on a canvas --

setCanvasGroup()

setCanvasGroup(group);

Set an existing canvas group to create text elements on.

group: A valid canvas group element

createCanvasTextLines()

createCanvasTextLines(left, top, line_spacing, font_size);

Show or hide a message, optional trigger aural alert on show. Does nothing if message is already in desired state.

left, top: Position of text element.
line_spacing: see getMessageID()
font_size: Font size.

createPageIndicator()

createPageIndicator(left, top, font_size, format_string = nil);

Creates a text element for a page indicator on the canvas group set with setCanvasGroup().

left, top: Position of text element
font_size: Font size.
format_string: Optional printf format string, defaults to "Page %2d/%2d"

updateCanvas()

updateCanvas();

Call this regularly to update text lines on canvas with the content of the message queue.

updatePageIndicator()

updatePageIndicator(current, total);

Updates the page indicator text element.

current: Currently displayed page.
total: Total number of pages.

Format for message definitions

MessageSystem.addMessages() expects a vector of message definitions. A message definition is a hash with the keys msg, prop, aural, condition (only msg is required, the rest is optional).

prop shall be used if

the visibility of a message depends on only one property
this property does NOT change frequently

The optional condition element reqires prop and is again a hash where you can define up to four compare values. For each existing key a listener to prop will be created performing the selected comparision. It is up to the developer to provide a reasonable configuration here.

The optional aural element can be any key of the aural configuration hash passed to MessageSystem.addAuralAlerts(). If the

{
    msg: "Message Text",
    prop: "/some/bool/trigger", # optional
    aural: "sound_name",        # optional
    condition: {                # optional
        eq: "foo",
        ne: "bar",
        lt: 21, # "less than",
        gt: 42, # "greater than",
    },
}
# example:
var EICASMessages = [
    {msg: "APU FIRE", prop: "engines/engine[2]/on-fire", aural: "firebell"},
    {msg: "AC 1 AUTOXFER", prop: "systems/AC/system[1]/serviceable", condition: {eq: 0} },
    {msg: "AC BUS 1", prop: "systems/AC/outputs/bus1", condition: {lt: 100} },
    {msg: "ELT ON", prop: ""},
];

Class MessageClass

Helper class for MessageSystem. Stores configuration data for a message class.

Class Pager

Helper class for MessageSystem. The pager class takes a vector of messages and splits it into pages (sub vectors of defined length). It can be configured via the Nasal methods described below or via some properties on the fly.

Config nodes

property name	Type and access	Description
page_length	(INT, r/w)	maximum number of lines per page.
page	(INT, r/w)	currently selected page.
pages	(INT, r/o)	number of pages according to last run of the page() method.

new()

new(page_length, prop_path);

Configure the nasal file to load.

page_length: Maximum lines per page.
prop_path: Property base path; pager configuration nodes will be created under this path.

page()

page(lines);

Return lines of current page; sticky messages will not be paged.

lines: Vector of messages

pageChanged()

pageChanged();

Return the page-changed flag and resets it to false, so calling this method again will return false unless another page has been selected in the meantime.

setPageLength()

setPageLength(lines);

Update the value of the page_length node (the number of lines per page).

lines: Number of lines per page

setPage()

setPage(page);

Update the value of page node used by page() to return the right lines.

page: Selected page

getPageCount()

Returns total number of pages, according to last run of page()

getCurrentPage()

Returns current page, according to last run of page()

HOWTO and Examples

to be written / reference implementation in CRJ700 familiy to be published after framework is published.