CanvasRenderer class
A renderer which renders map tiles on a Canvas element.
class CanvasRenderer extends Renderer {
CanvasElement _canvas;
CanvasRenderingContext2D get _context {
if (_canvas == null) return null;
return _canvas.context2D;
}
List<Tile> _tiles = [];
CanvasRenderer(TileLayer layer): super(layer);
_clear() {
if (_context == null) return;
_context
..save()
..setTransform(1, 0, 0, 1, 0, 0)
..clearRect(0, 0, _canvas.width, _canvas.height)
..restore();
_tiles.forEach((t) => t.detach());
_tiles.clear();
}
@override
void beforeRender() {
if (_layer.map == null) {
_canvas = null;
} else {
if (_canvas == null) {
_canvas = new Element.tag("canvas");
_layer.container.children.add(_canvas);
_canvas.style
..width="100%"
..height="100%"
..top="0px"
..left="0px"
..position="relative"
..zIndex = "inherit";
}
_updateSize();
_clear();
}
}
_updateSize() {
var vs = _layer.map.viewportSize;
// make sure the _canvas size is equal to the map
// size
if (vs.width != _canvas.width || vs.height != _canvas.height) {
_canvas
..width=vs.width
..height=vs.height;
}
}
@override
void renderTile(Point2D tileCoord) {
Tile t = new Tile(tileCoord, _canvas, _layer);
_tiles.add(t);
t.load();
}
/* ------------- rendering the tile border - for debugging --- */
bool renderTileBorders = false;
}
Extends
Renderer > CanvasRenderer
Methods
void afterRender() #
inherited from Renderer
Invoked after the tile grid is rendered using renderTileGrid.
Default implementation is empty. Override in subclasses if
necessary.
void afterRender(){}
void beforeRender() #
Invoked before the tile grid is rendered using renderTileGrid.
Default implementation is empty. Override in subclasses if
necessary.
docs inherited from Renderer
@override
void beforeRender() {
if (_layer.map == null) {
_canvas = null;
} else {
if (_canvas == null) {
_canvas = new Element.tag("canvas");
_layer.container.children.add(_canvas);
_canvas.style
..width="100%"
..height="100%"
..top="0px"
..left="0px"
..position="relative"
..zIndex = "inherit";
}
_updateSize();
_clear();
}
}
void render() #
inherited from Renderer
Invoked by a TileLayer to render itself
void render() {
beforeRender();
renderTileGrid();
afterRender();
}
void renderTile(Point2D tileCoord) #
Renders the tile at position tileCoord in the current tile plane.
docs inherited from Renderer
@override
void renderTile(Point2D tileCoord) {
Tile t = new Tile(tileCoord, _canvas, _layer);
_tiles.add(t);
t.load();
}
void renderTileGrid() #
inherited from Renderer
Renders the tile grid
void renderTileGrid() {
var map = _layer._map;
var tileSize = _layer.tileSize;
var centerOnZoomPlane = map.mapToZoomPlane(map.earthToMap(map.center));
var vshalf = (map.viewportSize / 2).toInt();
var topLeftOnZoomPlane = new Point2D(
centerOnZoomPlane.x - vshalf.width,
centerOnZoomPlane.y - vshalf.height
);
var viewportOnZoomPlaneBounds = new Bounds(
topLeftOnZoomPlane,
topLeftOnZoomPlane + map.viewportSize
);
tileIntersectsWithViewport(Point2D t) {
var tl = t.scale(sx:tileSize.width, sy:tileSize.height);
var tileBounds = new Bounds(
tl,
tl + tileSize
);
return viewportOnZoomPlaneBounds.intersects(tileBounds);
}
// the tile covering the map center
var tile = new Point2D(
centerOnZoomPlane.x ~/ tileSize.width,
centerOnZoomPlane.y ~/ tileSize.height
);
// find the first tile to be rendered
while(true) {
var candidate = tile.translate(dx:-1);
if (candidate.x < 0) break;
if (! tileIntersectsWithViewport(candidate)) break;
tile = candidate;
}
while(true) {
var candidate = tile.translate(dy:-1);
if (candidate.y < 0) break;
if (! tileIntersectsWithViewport(candidate)) break;
tile = candidate;
}
// render the tile grid intersecting with the viewport
var maxTileX = (1 << map.zoom);
var maxTileY = (1 << map.zoom);
var cur = new Point2D.from(tile);
while(cur.x < maxTileX && tileIntersectsWithViewport(cur)) {
while(cur.y < maxTileY && tileIntersectsWithViewport(cur)) {
renderTile(cur);
cur = cur.translate(dy:1);
}
cur = new Point2D(cur.x + 1, tile.y);
}
}