fgdata/Nasal/canvas/design.txt

Nothing set in stone yet, we'll document things once the API becomes more stable and once it has been used in several dialogs and instruments

At the moment, this implements the notion of a "LayeredMap", a LayeredMap is a conventional Canvas Map which has support for easily managing "Layers",
which are internally mapped to Canvas Groups. Each Group's "visible" property is managed by the LayeredMap, so that layers can be easily
toggled on/off, i.e. via checkboxes.

Basically, the idea is this, we'll have a MVC (Model/View/Controller) setup, where:
	- the Model is mapped to the drawable's meta information (i.e. position)
	- the View is mapped to a conventional canvas group
	- the Controller is mapped to a bunch of property/timer callbacks to control the Model/View


Model = PositionedSource
View =  Canvas
Controller = control properties (zoom, range etc)

LayerElement = callback to create a canvas group
Layer = canvas.Group

Map -> LayeredMap -> GenericMap -> AirportMap
Canvas Scripting Layer (Mapping): - first stab at refactoring the map.nas module, and trying to let the API evolve according to our requirements - split up the module into separate files (some of them will disappear soon) - split up the "drawing" loops into separate functions so that they can be individually called - move actual "drawing" to map_layers.nas - introduce some OOP helpers to prepare a pure Layer-based design - prepare helpers: LayeredMap, GenericMap, AirportMap (TODO: use a real "Layer" class) - move airport features (taxiways, runways, parking, tower) to separate layers (i.e. canvas groups) - avoid using a single update callback and use different layer-specific callbacks to update individual layers more efficiently - add some boilerplate hashes to prepare the MVC design - allow lazy updating of layers, where canvas groups are only populated on demand, to save some time during instantiation, i.e. loading an airport without "parking" selected, will only populate the layer once the checkbox is checked - extend the original code such that it supports showing multiple airports at once - add some proof of concept "navaid" layer using SVG files for navaid symbols (added only NDB symbol from wikimedia commons) regressions: - runway highlighting needs to be re-implemented - parking highlighting will be done differently - enforcing a specific drawing order for layers is currently not explicitly supported, so that taxiways may be rendered on top of runways Also: - integrated with the latest changes in git/master (HEAD) -i.e. metar support - further generalized map.nas - partially moved instantiation from Nasal space to XML space (WIP) - create "toggle layer" checkboxes procedurally in Nasal space - prepared the code to be better reusable in other dialogs (e.g. route manager, map dialog etc) - completely removed the "highlighting" (runway/parking) feature for now, because we talked about re-implementing it anyhow 2012-09-20 23:49:17 +00:00			`Nothing set in stone yet, we'll document things once the API becomes more stable and once it has been used in several dialogs and instruments`

			`At the moment, this implements the notion of a "LayeredMap", a LayeredMap is a conventional Canvas Map which has support for easily managing "Layers",`
			`which are internally mapped to Canvas Groups. Each Group's "visible" property is managed by the LayeredMap, so that layers can be easily`
			`toggled on/off, i.e. via checkboxes.`

			`Basically, the idea is this, we'll have a MVC (Model/View/Controller) setup, where:`
			`- the Model is mapped to the drawable's meta information (i.e. position)`
			`- the View is mapped to a conventional canvas group`
			`- the Controller is mapped to a bunch of property/timer callbacks to control the Model/View`




			`Model = PositionedSource`
			`View = Canvas`
			`Controller = control properties (zoom, range etc)`

			`LayerElement = callback to create a canvas group`
			`Layer = canvas.Group`

			`Map -> LayeredMap -> GenericMap -> AirportMap`