🎨 implementing mapbox style compiler, turning filter into call chains

LabelBuffer.coffee

@@ -1,39 +0,0 @@
-###
-  termap - Terminal Map Viewer
-  by Michael Strassburger <codepoet@cpan.org>
-
-  Using 2D spatial indexing to avoid overlapping labels and markers
-  Future: to detect collision on mouse interaction
-###
-
-rbush = require 'rbush'
-
-module.exports = class LabelBuffer
-  tree: null
-  margin: 5
-
-  constructor: (@width, @height) ->
-    @tree = rbush()
-
-  clear: ->
-    @tree.clear()
-
-  project: (x, y) ->
-    [Math.floor(x/2), Math.floor(y/4)]
-
-  writeIfPossible: (text, x, y) ->
-    point = @project x, y
-
-    if @_hasSpace text, point[0], point[1]
-      @tree.insert @_calculateArea text, point[0], point[1]
-    else
-      false
-
-  _hasSpace: (text, x, y) ->
-    not @tree.collides @_calculateArea text, x, y, 0
-
-  _calculateArea: (text, x, y, margin = @margin) ->
-    minX: x-margin
-    minY: y-margin
-    maxX: x+margin+text.length
-    maxY: y+margin

README.md

@@ -3,7 +3,7 @@
 No web browser around? No worries - discover the planet in your console!
 
 * Use your mouse or keys to navigate
-* Discover the globe or zoom in to learn about house numbers
+* Discover the globe or zoom in to explore your neighbourhood
 * See Point-of-Interest around any given location
 * Use an online map server or work offline with VectorTile/MBTiles
 * Highly customizable styling (colors, feature visibility, ...)
@@ -46,8 +46,11 @@ No web browser around? No worries - discover the planet in your console!
 ### TODOs
 * [ ] cli linking
 * [ ] mapping of view to tiles to show
+* [x] abstracted MapBox style JSON support
+* [ ] giving render priority to features across layers (collect before render vs. direct)?
 * [ ] line drawing
   * [ ] support for stroke width
+  * [ ] support for dashed/dotted lines?
 * [ ] label drawing
   * [x] support for point labels
   * [x] dynamic decluttering of labels
@@ -63,6 +66,8 @@ No web browser around? No worries - discover the planet in your console!
 * [ ] lat/lng-center + zoom based viewport
   * [ ] bbox awareness
   * [ ] zoom -> scale calculation
+* [ ] Tile parsing
+  * [ ] directly throw away features that aren't covered by any style
 * [ ] TileSource class (abstracting URL, mbtiles, single vector tile source)
 * [ ] tile request system
   * [ ] from local mbtiles
@@ -75,8 +80,7 @@ No web browser around? No worries - discover the planet in your console!
 * [x] start with zoom level which shows full vector tile
 * [x] accurate mouse drag&drop
 * [x] handle console resize
-* [ ] styling
-  * [ ] abstracted MapBox style JSON support
+* [x] styling
 * [ ] turn this into a [`blessed-contrib`](https://github.com/yaronn/blessed-contrib) widget
 
 ## License

src/Renderer.coffee

@@ -20,7 +20,7 @@ module.exports = class Renderer
     fillPolygons: true
     language: 'de'
 
-    drawOrder: ["admin", "water", "building", "road", "poi_label", "place_label", "housenum_label"]
+    drawOrder: ["admin", "building", "road", "water", "poi_label", "place_label", "housenum_label"]
 
     icons:
       car: "🚗"
@@ -42,29 +42,15 @@ module.exports = class Renderer
       cinema: "C" #"🎦"
 
     layers:
-      housenum_label:
-        minZoom: 1.5
-        color: 8
-      building:
-        minZoom: 3.8
-        color: 8
+      housenum_label: minZoom: 1.5
+      building: minZoom: 3.8
 
-      place_label:
-        color: "yellow"
+      place_label: true
+      poi_label: minZoom: 3
 
-      poi_label:
-        minZoom: 3
-        color: "yellow"
-
-      road:
-        color: 15
-
-      landuse:
-        color: "green"
-      water:
-        color: "blue"
-      admin:
-        color: "red"
+      road: true
+      water: true
+      admin: true
 
   isDrawing: false
   lastDrawAt: 0
@@ -108,6 +94,8 @@ module.exports = class Renderer
     @isDrawing = true
     @lastDrawAt = Date.now()
 
+    @notify "rendering..."
+
     @labelBuffer.clear()
 
     # TODO: better way for background color instead of setting filling FG?
@@ -122,16 +110,17 @@ module.exports = class Renderer
     @_drawLayers()
     @canvas.restore()
 
-    @write @canvas._canvas.frame()
+    @_write @canvas._canvas.frame()
 
     @isDrawing = false
 
-  write: (output) ->
+  _write: (output) ->
     process.stdout.write output
 
   _drawLayers: ->
     drawn = []
     for layer in @config.drawOrder
+      @notify "rendering #{layer}..."
       scale = Math.pow 2, @zoom
       continue unless @features?[layer]
 
@@ -240,3 +229,6 @@ module.exports = class Renderer
     point.x+@view[0]<@width-4 and
     point.y+@view[1]>=0 and
     point.y+@view[1]<@height
+
+  notify: (text) ->
+    @_write "\r\x1B[K"+text

src/Styler.coffee

@@ -5,8 +5,8 @@
   Minimalistic parser and compiler for Mapbox (Studio) Map Style files
   See: https://www.mapbox.com/mapbox-gl-style-spec/
 
-  Verrrrry MVP implementation
-  TODO: should be optimized by compiling the json to method&cb based filters
+  Compiles layer filter instructions into a chain of true/false returning
+  anonymous functions to improve rendering speed compared to realtime parsing.
 ###
 
 fs = require 'fs'
@@ -19,47 +19,48 @@ module.exports = class Styler
     json = JSON.parse fs.readFileSync(file).toString()
     @styleName = json.name
 
-    for layer in json.layers
-      continue if layer.ref
-      style = layer
+    for style in json.layers
+      continue if style.ref
 
-      @styleByLayer[layer['source-layer']] ?= []
-      @styleByLayer[layer['source-layer']].push style
+      style.appliesTo = @_compileFilter style.filter
 
-      @styleById[layer.id] = style
+      @styleByLayer[style['source-layer']] ?= []
+      @styleByLayer[style['source-layer']].push style
+
+      @styleById[style.id] = style
 
   getStyleFor: (layer, feature, zoom) ->
+    # Skip all layers that don't have any styles set
     return false unless @styleByLayer[layer]
 
     for style in @styleByLayer[layer]
-      return style unless style.filter
-
-      if @_passesFilter feature, style.filter
-        return style
+      return style if style.appliesTo feature
 
     false
 
-  _passesFilter: (feature, filter) ->
+  _compileFilter: (filter) ->
+    if not filter or not filter.length
+      return -> true
+
     switch filter[0]
       when "all"
-        for subFilter in filter[1..]
-          return false unless @_passesFilter feature, subFilter
+        filters = (@_compileFilter subFilter for subFilter in filter[1..])
+        (feature) ->
+          return false for appliesTo in filters when not appliesTo feature
           true
 
       when "=="
-        feature.properties[filter[1]] is filter[2]
+        (feature) -> feature.properties[filter[1]] is filter[2]
 
       when "!="
-        feature.properties[filter[2]] isnt filter[2]
+        (feature) -> feature.properties[filter[1]] isnt filter[2]
 
       when "in"
-        field = filter[1]
-        for value in filter[2..]
-          return true if feature.properties[field] is value
+        (feature) ->
+          return true for value in filter[2..] when feature.properties[filter[1]] is value
           false
 
       when "!in"
-        field = filter[1]
-        for value in filter[2..]
-          return false if feature.properties[field] is value
+        (feature) ->
+          return false for value in filter[2..] when feature.properties[filter[1]] is value
           true

src/Termap.coffee

@@ -119,7 +119,7 @@ module.exports = class Termap
 
   _draw: ->
     @renderer.draw @view, @zoom
-    @renderer.write @_getFooter()
+    @renderer.notify @_getFooter()
 
   _getBBox: ->
     [x, y] = mercator.forward [@center.lng, @center.lat]
@@ -132,10 +132,6 @@ module.exports = class Termap
     "center: [#{utils.digits @center.lat, 2}, #{utils.digits @center.lng, 2}] zoom: #{utils.digits @zoom, 2}"
     # bbox: [#{@_getBBox().map((z) -> utils.digits(z, 2)).join(',')}]"
 
-  notify: (text) ->
-    return if @renderer.isDrawing
-    @renderer.write "\r\x1B[K#{@_getFooter()} #{text}"
-
   zoomBy: (step) ->
     return unless @scale+step > 0