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Canvas ND framework: Difference between revisions
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If you are primarily interested in porting/adding new '''mapping''' layers (such as e.g. waypoints, route, weather etc), please see the [[MapStructure]] article for details. | If you are primarily interested in porting/adding new '''mapping''' layers (such as e.g. waypoints, route, weather etc), please see the [[MapStructure]] article for details. | ||
Otherwise, this section is focused on dealing with non-mapping aspects, i.e. ND-specific SVG symbols and animating them via properties and calculations. Typically, a new symbol will require 10-20 lines of code added to navdisplay.mfd - it will typically take 5-10 minutes to add a new animated symbol to the ND.}} | Otherwise, this section is focused on dealing with non-mapping aspects, i.e. ND-specific SVG symbols and animating them via properties and calculations. Typically, a new symbol will require 10-20 lines of code added to navdisplay.mfd - it will typically take 5-10 minutes to add a new animated symbol to the ND.}} | ||
If you want to add new features to the navdisplay. | If you want to add new features to the navdisplay.styles code, you need to open that file and map an existing SVG element to a Nasal callback routine - that's how everything is working currently. A straightforward examples can be found in the implementation of the '''planArcs''' symbol animation: | ||
<syntaxhighlight lang="nasal"> | |||
{ | |||
id:'planArcs', | |||
impl: { | |||
init: func(nd,symbol), | |||
predicate: func(nd) nd.in_mode('toggle_display_mode', ['PLAN']), | |||
is_true: func(nd) nd.symbols.planArcs.show(), | |||
is_false: func(nd) nd.symbols.planArcs.hide(), | |||
}, | |||
}, | |||
</syntaxhighlight> | |||
This is hash entry, linked to the SVG element whose id is '''planArcs'''. The embedded hash named '''impl''' contains 4 fields: | |||
* '''init()''': a Nasal function that will be invoked to initialize the symbol | |||
* '''predicate()''': a Nasal function that will be invoked to check some condition (predicate) | |||
* '''is_true()''': the Nasal function that will be executed if the condition is true | |||
* '''is_false()''': the Nasal function that will be executed if the condition is false | |||
Except for the init() callback, all others get passed a single argument called '''nd''' which is the instance of the current nd, i.e. the equivalent of '''me''', Nasal's '''this''' pointer. In the future, we're hoping to generalize this a little better and also use the init signature, which should make for shorter/more readable code. | |||
In this case, the predicate will merely determine in which mode a certain switch is and hide/show the symbol (SVG element) accordingly. Here, it's checking that the '''display-mode''' switch is set to '''PLAN''' mode, and otherwise hide the symbol. | |||
Switches are configured at the top of the navdisplay.mfd file, but will usually be overridden by each ND.nas, i.e. by the aircraft developer. For now, modes are hard-coded and people should refer to the code to see what's supported there. | |||
There's a "configuration hash" called "NDStyles" at the top of the file. Each aircraft can have its own entry in NDStyles, such as NDStyles["B747-400"] or NavDisplay["777"]. Then, all the required canvas callbacks are listed there, i.e. the font mapper etc. | There's a "configuration hash" called "NDStyles" at the top of the file. Each aircraft can have its own entry in NDStyles, such as NDStyles["B747-400"] or NavDisplay["777"]. Then, all the required canvas callbacks are listed there, i.e. the font mapper etc. | ||