openlayers/src/ol/renderer/canvas/TileLayer.js

/**
 * @module ol/renderer/canvas/TileLayer
 */
import {getUid, inherits} from '../../index.js';
import LayerType from '../../LayerType.js';
import TileRange from '../../TileRange.js';
import TileState from '../../TileState.js';
import ViewHint from '../../ViewHint.js';
import {createCanvasContext2D} from '../../dom.js';
import {containsExtent, createEmpty, equals, getIntersection, isEmpty} from '../../extent.js';
import RendererType from '../Type.js';
import IntermediateCanvasRenderer from '../canvas/IntermediateCanvas.js';
import {create as createTransform, compose as composeTransform} from '../../transform.js';

/**
 * @constructor
 * @extends {ol.renderer.canvas.IntermediateCanvas}
 * @param {module:ol/layer/Tile~TileLayer|module:ol/layer/VectorTile~VectorTile} tileLayer Tile layer.
 * @api
 */
const CanvasTileLayerRenderer = function(tileLayer) {

  IntermediateCanvasRenderer.call(this, tileLayer);

  /**
   * @protected
   * @type {CanvasRenderingContext2D}
   */
  this.context = this.context === null ? null : createCanvasContext2D();

  /**
   * @private
   * @type {number}
   */
  this.oversampling_;

  /**
   * @private
   * @type {module:ol/extent~Extent}
   */
  this.renderedExtent_ = null;

  /**
   * @protected
   * @type {number}
   */
  this.renderedRevision;

  /**
   * @protected
   * @type {!Array.<module:ol/Tile~Tile>}
   */
  this.renderedTiles = [];

  /**
   * @protected
   * @type {module:ol/extent~Extent}
   */
  this.tmpExtent = createEmpty();

  /**
   * @private
   * @type {module:ol/TileRange~TileRange}
   */
  this.tmpTileRange_ = new TileRange(0, 0, 0, 0);

  /**
   * @private
   * @type {module:ol/transform~Transform}
   */
  this.imageTransform_ = createTransform();

  /**
   * @protected
   * @type {number}
   */
  this.zDirection = 0;

};

inherits(CanvasTileLayerRenderer, IntermediateCanvasRenderer);


/**
 * Determine if this renderer handles the provided layer.
 * @param {ol.renderer.Type} type The renderer type.
 * @param {module:ol/layer/Layer~Layer} layer The candidate layer.
 * @return {boolean} The renderer can render the layer.
 */
CanvasTileLayerRenderer['handles'] = function(type, layer) {
  return type === RendererType.CANVAS && layer.getType() === LayerType.TILE;
};


/**
 * Create a layer renderer.
 * @param {ol.renderer.Map} mapRenderer The map renderer.
 * @param {module:ol/layer/Layer~Layer} layer The layer to be rendererd.
 * @return {ol.renderer.canvas.TileLayer} The layer renderer.
 */
CanvasTileLayerRenderer['create'] = function(mapRenderer, layer) {
  return new CanvasTileLayerRenderer(/** @type {module:ol/layer/Tile~TileLayer} */ (layer));
};


/**
 * @private
 * @param {module:ol/Tile~Tile} tile Tile.
 * @return {boolean} Tile is drawable.
 */
CanvasTileLayerRenderer.prototype.isDrawableTile_ = function(tile) {
  const tileState = tile.getState();
  const useInterimTilesOnError = this.getLayer().getUseInterimTilesOnError();
  return tileState == TileState.LOADED ||
      tileState == TileState.EMPTY ||
      tileState == TileState.ERROR && !useInterimTilesOnError;
};

/**
 * @inheritDoc
 */
CanvasTileLayerRenderer.prototype.prepareFrame = function(frameState, layerState) {

  const pixelRatio = frameState.pixelRatio;
  const size = frameState.size;
  const viewState = frameState.viewState;
  const projection = viewState.projection;
  const viewResolution = viewState.resolution;
  const viewCenter = viewState.center;

  const tileLayer = this.getLayer();
  const tileSource = /** @type {ol.source.Tile} */ (tileLayer.getSource());
  const sourceRevision = tileSource.getRevision();
  const tileGrid = tileSource.getTileGridForProjection(projection);
  const z = tileGrid.getZForResolution(viewResolution, this.zDirection);
  const tileResolution = tileGrid.getResolution(z);
  let oversampling = Math.round(viewResolution / tileResolution) || 1;
  let extent = frameState.extent;

  if (layerState.extent !== undefined) {
    extent = getIntersection(extent, layerState.extent);
  }
  if (isEmpty(extent)) {
    // Return false to prevent the rendering of the layer.
    return false;
  }

  const tileRange = tileGrid.getTileRangeForExtentAndZ(extent, z);
  const imageExtent = tileGrid.getTileRangeExtent(z, tileRange);

  const tilePixelRatio = tileSource.getTilePixelRatio(pixelRatio);

  /**
   * @type {Object.<number, Object.<string, module:ol/Tile~Tile>>}
   */
  const tilesToDrawByZ = {};
  tilesToDrawByZ[z] = {};

  const findLoadedTiles = this.createLoadedTileFinder(
    tileSource, projection, tilesToDrawByZ);

  const tmpExtent = this.tmpExtent;
  const tmpTileRange = this.tmpTileRange_;
  let newTiles = false;
  let tile, x, y;
  for (x = tileRange.minX; x <= tileRange.maxX; ++x) {
    for (y = tileRange.minY; y <= tileRange.maxY; ++y) {
      tile = tileSource.getTile(z, x, y, pixelRatio, projection);
      if (tile.getState() == TileState.ERROR) {
        if (!tileLayer.getUseInterimTilesOnError()) {
          // When useInterimTilesOnError is false, we consider the error tile as loaded.
          tile.setState(TileState.LOADED);
        } else if (tileLayer.getPreload() > 0) {
          // Preloaded tiles for lower resolutions might have finished loading.
          newTiles = true;
        }
      }
      if (!this.isDrawableTile_(tile)) {
        tile = tile.getInterimTile();
      }
      if (this.isDrawableTile_(tile)) {
        const uid = getUid(this);
        if (tile.getState() == TileState.LOADED) {
          tilesToDrawByZ[z][tile.tileCoord.toString()] = tile;
          const inTransition = tile.inTransition(uid);
          if (!newTiles && (inTransition || this.renderedTiles.indexOf(tile) === -1)) {
            newTiles = true;
          }
        }
        if (tile.getAlpha(uid, frameState.time) === 1) {
          // don't look for alt tiles if alpha is 1
          continue;
        }
      }

      const childTileRange = tileGrid.getTileCoordChildTileRange(
        tile.tileCoord, tmpTileRange, tmpExtent);
      let covered = false;
      if (childTileRange) {
        covered = findLoadedTiles(z + 1, childTileRange);
      }
      if (!covered) {
        tileGrid.forEachTileCoordParentTileRange(
          tile.tileCoord, findLoadedTiles, null, tmpTileRange, tmpExtent);
      }

    }
  }

  const renderedResolution = tileResolution * pixelRatio / tilePixelRatio * oversampling;
  const hints = frameState.viewHints;
  const animatingOrInteracting = hints[ViewHint.ANIMATING] || hints[ViewHint.INTERACTING];
  if (!(this.renderedResolution && Date.now() - frameState.time > 16 && animatingOrInteracting) && (
    newTiles ||
        !(this.renderedExtent_ && containsExtent(this.renderedExtent_, extent)) ||
        this.renderedRevision != sourceRevision ||
        oversampling != this.oversampling_ ||
        !animatingOrInteracting && renderedResolution != this.renderedResolution
  )) {

    const context = this.context;
    if (context) {
      const tilePixelSize = tileSource.getTilePixelSize(z, pixelRatio, projection);
      const width = Math.round(tileRange.getWidth() * tilePixelSize[0] / oversampling);
      const height = Math.round(tileRange.getHeight() * tilePixelSize[1] / oversampling);
      const canvas = context.canvas;
      if (canvas.width != width || canvas.height != height) {
        this.oversampling_ = oversampling;
        canvas.width = width;
        canvas.height = height;
      } else {
        if (this.renderedExtent_ && !equals(imageExtent, this.renderedExtent_)) {
          context.clearRect(0, 0, width, height);
        }
        oversampling = this.oversampling_;
      }
    }

    this.renderedTiles.length = 0;
    /** @type {Array.<number>} */
    const zs = Object.keys(tilesToDrawByZ).map(Number);
    zs.sort(function(a, b) {
      if (a === z) {
        return 1;
      } else if (b === z) {
        return -1;
      } else {
        return a > b ? 1 : a < b ? -1 : 0;
      }
    });
    let currentResolution, currentScale, currentTilePixelSize, currentZ, i, ii;
    let tileExtent, tileGutter, tilesToDraw, w, h;
    for (i = 0, ii = zs.length; i < ii; ++i) {
      currentZ = zs[i];
      currentTilePixelSize = tileSource.getTilePixelSize(currentZ, pixelRatio, projection);
      currentResolution = tileGrid.getResolution(currentZ);
      currentScale = currentResolution / tileResolution;
      tileGutter = tilePixelRatio * tileSource.getGutter(projection);
      tilesToDraw = tilesToDrawByZ[currentZ];
      for (const tileCoordKey in tilesToDraw) {
        tile = tilesToDraw[tileCoordKey];
        tileExtent = tileGrid.getTileCoordExtent(tile.getTileCoord(), tmpExtent);
        x = (tileExtent[0] - imageExtent[0]) / tileResolution * tilePixelRatio / oversampling;
        y = (imageExtent[3] - tileExtent[3]) / tileResolution * tilePixelRatio / oversampling;
        w = currentTilePixelSize[0] * currentScale / oversampling;
        h = currentTilePixelSize[1] * currentScale / oversampling;
        this.drawTileImage(tile, frameState, layerState, x, y, w, h, tileGutter, z === currentZ);
        this.renderedTiles.push(tile);
      }
    }

    this.renderedRevision = sourceRevision;
    this.renderedResolution = tileResolution * pixelRatio / tilePixelRatio * oversampling;
    this.renderedExtent_ = imageExtent;
  }

  const scale = this.renderedResolution / viewResolution;
  const transform = composeTransform(this.imageTransform_,
    pixelRatio * size[0] / 2, pixelRatio * size[1] / 2,
    scale, scale,
    0,
    (this.renderedExtent_[0] - viewCenter[0]) / this.renderedResolution * pixelRatio,
    (viewCenter[1] - this.renderedExtent_[3]) / this.renderedResolution * pixelRatio);
  composeTransform(this.coordinateToCanvasPixelTransform,
    pixelRatio * size[0] / 2 - transform[4], pixelRatio * size[1] / 2 - transform[5],
    pixelRatio / viewResolution, -pixelRatio / viewResolution,
    0,
    -viewCenter[0], -viewCenter[1]);


  this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
  this.manageTilePyramid(frameState, tileSource, tileGrid, pixelRatio,
    projection, extent, z, tileLayer.getPreload());
  this.scheduleExpireCache(frameState, tileSource);

  return this.renderedTiles.length > 0;
};


/**
 * @param {module:ol/Tile~Tile} tile Tile.
 * @param {module:ol/PluggableMap~FrameState} frameState Frame state.
 * @param {module:ol/layer/Layer~State} layerState Layer state.
 * @param {number} x Left of the tile.
 * @param {number} y Top of the tile.
 * @param {number} w Width of the tile.
 * @param {number} h Height of the tile.
 * @param {number} gutter Tile gutter.
 * @param {boolean} transition Apply an alpha transition.
 */
CanvasTileLayerRenderer.prototype.drawTileImage = function(tile, frameState, layerState, x, y, w, h, gutter, transition) {
  const image = tile.getImage(this.getLayer());
  if (!image) {
    return;
  }
  const uid = getUid(this);
  const alpha = transition ? tile.getAlpha(uid, frameState.time) : 1;
  if (alpha === 1 && !this.getLayer().getSource().getOpaque(frameState.viewState.projection)) {
    this.context.clearRect(x, y, w, h);
  }
  const alphaChanged = alpha !== this.context.globalAlpha;
  if (alphaChanged) {
    this.context.save();
    this.context.globalAlpha = alpha;
  }
  this.context.drawImage(image, gutter, gutter,
    image.width - 2 * gutter, image.height - 2 * gutter, x, y, w, h);

  if (alphaChanged) {
    this.context.restore();
  }
  if (alpha !== 1) {
    frameState.animate = true;
  } else if (transition) {
    tile.endTransition(uid);
  }
};


/**
 * @inheritDoc
 */
CanvasTileLayerRenderer.prototype.getImage = function() {
  const context = this.context;
  return context ? context.canvas : null;
};


/**
 * @function
 * @return {module:ol/layer/Tile~TileLayer|module:ol/layer/VectorTile~VectorTile}
 */
CanvasTileLayerRenderer.prototype.getLayer;


/**
 * @inheritDoc
 */
CanvasTileLayerRenderer.prototype.getImageTransform = function() {
  return this.imageTransform_;
};
export default CanvasTileLayerRenderer;