jrtechs-vis/lib/network/modules/components/shared/Label.js

let util = require('../../../../util');


/**
 * Internal helper class used for splitting a label text into lines.
 *
 * This has been moved away from the label processing code for better undestanding upon reading.
 *
 * @private
 */
class LabelAccumulator {
  constructor(measureText) {
    this.measureText = measureText;  // callback to determine text dimensions, using the parent label settings.
    this.current = 0;
    this.width   = 0;
    this.height  = 0;
    this.lines   = [];
  }


  /**
   * Append given text to the given line.
   *
   * @param {number}  l    index of line to add to
   * @param {string}  text string to append to line
   * @param {'bold'|'ital'|'boldital'|'mono'|'normal'} [mod='normal']
   * @private
   */
  _add(l, text, mod = 'normal') { 
    if (text === undefined || text === "") return;

    if (this.lines[l] === undefined) {
      this.lines[l] = {
        width : 0,
        height: 0,
        blocks: []
      };
    }

    // Determine width and get the font properties
    let result = this.measureText(text, mod);
    let block = Object.assign({}, result.values);
    block.text  = text;
    block.width = result.width;
    block.mod   = mod;

    this.lines[l].blocks.push(block);

    // Update the line width. We need this for
    // determining if a string goes over max width
    this.lines[l].width += result.width;
  }


  /**
   * Returns the width in pixels of the current line.
   *
   * @returns {number}
   */
  curWidth() {
    let line = this.lines[this.current];
    if (line === undefined) return 0;

    return line.width;
  }


   /**
    * Add text in block to current line
    *
    * @param {string} text
    * @param {'bold'|'ital'|'boldital'|'mono'|'normal'} [mod='normal']
    */
   append(text, mod = 'normal') { 
     this._add(this.current, text, mod);
   }


  /**
   * Add text in block to current line and start a new line
   *
   * @param {string} text
   * @param {'bold'|'ital'|'boldital'|'mono'|'normal'} [mod='normal']
   */
  newLine(text, mod = 'normal') {
    this._add(this.current, text, mod);
    this.current++;
  }


  /**
   * Set the sizes for all lines and the whole thing.
   *
   * @returns {{width: (number|*), height: (number|*), lines: Array}}
   */
  finalize() {
    // console.log(JSON.stringify(this.lines, null, 2));

    // Determine the heights of the lines
    // Note that width has already been set
    for (let k = 0; k < this.lines.length; k++) {
      let line   = this.lines[k];
      let height = 0;

      for (let l = 0; l < line.blocks.length; l++) {
        let block =  line.blocks[l];
        height += block.height;
      }
  
      line.height = height;
    }

    // Determine the full label size
    let width  = 0;
    let height = 0;
    for (let k = 0; k < this.lines.length; k++) {
      let line   = this.lines[k];

      if (line.width > width) {
        width = line.width;
      }
      height += line.height;
    }

    this.width  = width;
    this.height = height;

    // Return a simple hash object for further processing.
    return {
      width : this.width,
      height: this.height,
      lines : this.lines
    }
  }
} 

/**
 * A Label to be used for Nodes or Edges.
 *
 * @param {Object} options
 * @param {Object} body
 * @param {boolean} [edgeLabel=false]
 * @constructor Label
 */
class Label {
  constructor(body, options, edgelabel = false) {
    this.body = body;

    this.pointToSelf = false;
    this.baseSize = undefined;
    this.fontOptions = {};
    this.setOptions(options);
    this.size = {top: 0, left: 0, width: 0, height: 0, yLine: 0}; // could be cached
    this.isEdgeLabel = edgelabel;
  }

  setOptions(options, allowDeletion = false) {
    this.elementOptions = options;

    // We want to keep the font options separated from the node options.
    // The node options have to mirror the globals when they are not overruled.
    this.fontOptions = util.deepExtend({},options.font, true);

    if (options.label !== undefined) {
      this.labelDirty = true;
    }

    if (options.font !== undefined) {
      Label.parseOptions(this.fontOptions, options, allowDeletion);
      if (typeof options.font === 'string') {
        this.baseSize = this.fontOptions.size;
      }
      else if (typeof options.font === 'object') {
        if (options.font.size !== undefined) {
          this.baseSize = options.font.size;
        }
      }
    }
  }

  static parseOptions(parentOptions, newOptions, allowDeletion = false) {
    if (Label.parseFontString(parentOptions, newOptions.font)) {
      parentOptions.vadjust = 0;
    }
    else if (typeof newOptions.font === 'object') {
      util.fillIfDefined(parentOptions, newOptions.font, allowDeletion);
    }
    parentOptions.size    = Number(parentOptions.size);
    parentOptions.vadjust = Number(parentOptions.vadjust);
  }


  /**
   * If in-variable is a string, parse it as a font specifier.
   *
   * Note that following is not done here and have to be done after the call:
   * - No number conversion (size)
   * - Not all font options are set (vadjust, mod)
   *
   * @param {Object} outOptions  out-parameter, object in which to store the parse results (if any)
   * @param {Object} inOptions  font options to parse
   * @return {boolean} true if font parsed as string, false otherwise
   */
  static parseFontString(outOptions, inOptions) {
    if (!inOptions || typeof inOptions !== 'string') return false;

    let newOptionsArray = inOptions.split(" ");

    outOptions.size  = newOptionsArray[0].replace("px",'');
    outOptions.face  = newOptionsArray[1];
    outOptions.color = newOptionsArray[2];

    return true;
  }


  // set the width and height constraints based on 'nearest' value
  constrain(elementOptions, options, defaultOptions) {
    this.fontOptions.constrainWidth = false;
    this.fontOptions.maxWdt = -1;
    this.fontOptions.minWdt = -1;

    let pile = [options, elementOptions, defaultOptions];

    let widthConstraint = util.topMost(pile, 'widthConstraint');
    if (typeof widthConstraint === 'number') {
      this.fontOptions.maxWdt = Number(widthConstraint);
      this.fontOptions.minWdt = Number(widthConstraint);
    } else if (typeof widthConstraint === 'object') {
      let widthConstraintMaximum = util.topMost(pile, ['widthConstraint', 'maximum']);
      if (typeof widthConstraintMaximum === 'number') {
        this.fontOptions.maxWdt = Number(widthConstraintMaximum);
      }
      let widthConstraintMinimum = util.topMost(pile, ['widthConstraint', 'minimum'])
      if (typeof widthConstraintMinimum === 'number') {
        this.fontOptions.minWdt = Number(widthConstraintMinimum);
      }
    }

    this.fontOptions.constrainHeight = false;
    this.fontOptions.minHgt = -1;
    this.fontOptions.valign = 'middle';

    let heightConstraint = util.topMost(pile, 'heightConstraint');
    if (typeof heightConstraint === 'number') {
      this.fontOptions.minHgt = Number(heightConstraint);
    } else if (typeof heightConstraint === 'object') {
      let heightConstraintMinimum = util.topMost(pile, ['heightConstraint', 'minimum']);
      if (typeof heightConstraintMinimum === 'number') {
        this.fontOptions.minHgt = Number(heightConstraintMinimum);
      }
      let heightConstraintValign = util.topMost(pile, ['heightConstraint', 'valign']);
      if (typeof heightConstraintValign === 'string') {
        if ((heightConstraintValign === 'top')||(heightConstraintValign === 'bottom')) {
            this.fontOptions.valign = heightConstraintValign;
        }
      }
    }
  }

  // set the selected functions based on 'nearest' value
  choosify(elementOptions, options, defaultOptions) {
    this.fontOptions.chooser = true;

    let pile = [options, elementOptions, defaultOptions];

    let chosen = util.topMost(pile, 'chosen');
    if (typeof chosen === 'boolean') {
      this.fontOptions.chooser = chosen;
    } else if (typeof chosen === 'object') {
      let chosenLabel = util.topMost(pile, ['chosen', 'label']);
      if ((typeof chosenLabel === 'boolean') || (typeof chosenLabel === 'function')) {
        this.fontOptions.chooser = chosenLabel;
      }
    }
  }

  // When margins are set in an element, adjust sizes is called to remove them
  // from the width/height constraints. This must be done prior to label sizing.
  adjustSizes(margins) {
    let widthBias =  (margins) ? (margins.right + margins.left) : 0;
    if (this.fontOptions.constrainWidth) {
      this.fontOptions.maxWdt -= widthBias;
      this.fontOptions.minWdt -= widthBias;
    }
    let heightBias = (margins) ? (margins.top + margins.bottom)  : 0;
    if (this.fontOptions.constrainHeight) {
      this.fontOptions.minHgt -= heightBias;
    }
  }


  /**
   * Collapse the font options for the multi-font to single objects, from
   * the chain of option objects passed.
   *
   * If an option for a specific multi-font is not present, the parent
   * option is checked for the given option.
   *
   * NOTE: naming of 'groupOptions' is a misnomer; the actual value passed
   *       is the new values to set from setOptions().
   *
   * @param {Object} options
   * @param {Object} groupOptions
   * @param {Object} defaultOptions
   */
  propagateFonts(options, groupOptions, defaultOptions) {
    if (!this.fontOptions.multi) return;

    /**
     * Resolve the font options path.
     * If valid, return a reference to the object in question.
     * Otherwise, just return null.
     *
     * @param {Object} options base object to determine path from
     * @param {'bold'|'ital'|'boldital'|'mono'|'normal'} [mod=undefined] if present, sub path for the mod-font
     * @returns {Object|null}
     */
    var pathP = function(options, mod) {
       if (!options || !options.font) return null;

      var opt = options.font;

      if (mod) {
        if (!opt[mod]) return null;
        opt = opt[mod];
      }

      return opt;
    };


    /**
     * Get property value from options.font[mod][property] if present.
     * If mod not passed, use property value from options.font[property].
     *
     * @param {vis.Label.options} options
     * @param {'bold'|'ital'|'boldital'|'mono'|'normal'} mod
     * @param {string} property
     * @return {*|null} value if found, null otherwise.
     */
    var getP = function(options, mod, property) {
      let opt = pathP(options, mod);

      if (opt && opt.hasOwnProperty(property)) {
         return opt[property];
      }

      return null;
    };


    let mods = [ 'bold', 'ital', 'boldital', 'mono' ];
    for (const mod of mods) {
      let modOptions  = this.fontOptions[mod];
      let modDefaults = defaultOptions.font[mod];

      if (Label.parseFontString(modOptions, pathP(options, mod))) {
        modOptions.vadjust = this.fontOptions.vadjust;
        modOptions.mod = modDefaults.mod;
      } else {

        // We need to be crafty about loading the modded fonts. We want as
        // much 'natural' versatility as we can get, so a simple global
        // change propagates in an expected way, even if not stictly logical.

        // 'face' has a special exception for mono, since we probably
        // don't want to sync to the base font face.
         modOptions.face =
          getP(options     ,  mod, 'face')          || 
          getP(groupOptions,  mod, 'face')          ||
           (mod === 'mono'? modDefaults.face:null ) ||
          getP(groupOptions, null, 'face')          ||
          this.fontOptions.face
        ;

        // 'color' follows the standard flow
         modOptions.color =
          getP(options     ,  mod, 'color') ||
          getP(groupOptions,  mod, 'color') ||
          getP(groupOptions, null, 'color') ||
          this.fontOptions.color
        ;

        // 'mode' follows the standard flow
        modOptions.mod =
          getP(options     ,  mod, 'mod') ||
          getP(groupOptions,  mod, 'mod') ||
          getP(groupOptions, null, 'mod') ||
          modDefaults.mod
        ;


        // It's important that we size up defaults similarly if we're
        // using default faces unless overriden. We want to preserve the
        // ratios closely - but if faces have changed, all bets are off.
        let ratio;

        // NOTE: Following condition always fails, because modDefaults
        //       has no explicit font property. This is deliberate, see
        //       var's 'NodesHandler.defaultOptions.font[mod]'.
        //       However, I want to keep the original logic while refactoring;
        //       it appears to be working fine even if ratio is never set.
        // TODO: examine if this is a bug, fix if necessary.
        //
        if ((modOptions.face === modDefaults.face) &&
            (this.fontOptions.face === defaultOptions.font.face)) {

          ratio = this.fontOptions.size / Number(defaultOptions.font.size);
        }


        modOptions.size =
          getP(options     ,  mod, 'size')        ||
          getP(groupOptions,  mod, 'size')        ||
          (ratio? modDefaults.size * ratio: null) || //   Scale the mod size using the same ratio
          getP(groupOptions, null, 'size')        ||
          this.fontOptions.size
        ;

        modOptions.vadjust =
          getP(options     , mod, 'vadjust')                     ||
          getP(groupOptions, mod, 'vadjust')                     ||
          (ratio? modDefaults.vadjust * Math.round(ratio): null) || // Scale it using the same ratio
          this.fontOptions.vadjust
        ;

      }

      modOptions.size    = Number(modOptions.size);
      modOptions.vadjust = Number(modOptions.vadjust);
    }
  }


  /**
   * Main function. This is called from anything that wants to draw a label.
   * @param {CanvasRenderingContext2D} ctx
   * @param {number} x
   * @param {number} y
   * @param {boolean} selected
   * @param {boolean} hover
   * @param {string} [baseline='middle']
   */
  draw(ctx, x, y, selected, hover, baseline = 'middle') {
    // if no label, return
    if (this.elementOptions.label === undefined)
      return;

    // check if we have to render the label
    let viewFontSize = this.fontOptions.size * this.body.view.scale;
    if (this.elementOptions.label && viewFontSize < this.elementOptions.scaling.label.drawThreshold - 1)
      return;

    // update the size cache if required
    this.calculateLabelSize(ctx, selected, hover, x, y, baseline);

    // create the fontfill background
    this._drawBackground(ctx);
    // draw text
    this._drawText(ctx, selected, hover, x, y, baseline);
  }

  /**
   * Draws the label background
   * @param {CanvasRenderingContext2D} ctx
   * @private
   */
  _drawBackground(ctx) {
    if (this.fontOptions.background !== undefined && this.fontOptions.background !== "none") {
      ctx.fillStyle = this.fontOptions.background;

      let lineMargin = 2;

      if (this.isEdgeLabel) {
        switch (this.fontOptions.align) {
          case 'middle':
            ctx.fillRect(-this.size.width * 0.5, -this.size.height * 0.5, this.size.width, this.size.height);
            break;
          case 'top':
            ctx.fillRect(-this.size.width * 0.5, -(this.size.height + lineMargin), this.size.width, this.size.height);
            break;
          case 'bottom':
            ctx.fillRect(-this.size.width * 0.5, lineMargin, this.size.width, this.size.height);
            break;
          default:
            ctx.fillRect(this.size.left, this.size.top - 0.5*lineMargin, this.size.width, this.size.height);
            break;
        }
      } else {
        ctx.fillRect(this.size.left, this.size.top - 0.5*lineMargin, this.size.width, this.size.height);
      }
    }
  }


  /**
   *
   * @param {CanvasRenderingContext2D} ctx
   * @param {boolean} selected
   * @param {boolean} hover
   * @param {number} x
   * @param {number} y
   * @param {string} [baseline='middle']
   * @private
   */
  _drawText(ctx, selected, hover, x, y, baseline = 'middle') {
    let fontSize = this.fontOptions.size;
    let viewFontSize = fontSize * this.body.view.scale;
    // this ensures that there will not be HUGE letters on screen by setting an upper limit on the visible text size (regardless of zoomLevel)
    if (viewFontSize >= this.elementOptions.scaling.label.maxVisible) {
      // TODO: Does this actually do anything?
      fontSize = Number(this.elementOptions.scaling.label.maxVisible) / this.body.view.scale;
    }

    let yLine = this.size.yLine;
    [x, yLine] = this._setAlignment(ctx, x, yLine, baseline);

    ctx.textAlign = 'left';
    x = x - this.size.width / 2; // Shift label 1/2-distance to the left
    if ((this.fontOptions.valign) && (this.size.height > this.size.labelHeight)) {
      if (this.fontOptions.valign === 'top') {
        yLine -= (this.size.height - this.size.labelHeight) / 2;
      }
      if (this.fontOptions.valign === 'bottom') {
        yLine += (this.size.height - this.size.labelHeight) / 2;
      }
    }

    // draw the text
    for (let i = 0; i < this.lineCount; i++) {
      if (this.lines[i] && this.lines[i].blocks) {
        let width = 0;
        if (this.isEdgeLabel || this.fontOptions.align === 'center') {
          width += (this.size.width - this.lines[i].width) / 2
        } else if (this.fontOptions.align === 'right') {
          width += (this.size.width - this.lines[i].width)
        }
        for (let j = 0; j < this.lines[i].blocks.length; j++) {
          let block = this.lines[i].blocks[j];
          ctx.font = block.font;
          let [fontColor, strokeColor] = this._getColor(block.color, viewFontSize, block.strokeColor);
          if (block.strokeWidth > 0) {
            ctx.lineWidth = block.strokeWidth;
            ctx.strokeStyle = strokeColor;
            ctx.lineJoin = 'round';
          }
          ctx.fillStyle = fontColor;

          if (block.strokeWidth > 0) {
            ctx.strokeText(block.text, x + width, yLine + block.vadjust);
          }
          ctx.fillText(block.text, x + width, yLine + block.vadjust);
          width += block.width;
        }
        yLine += this.lines[i].height;
      }
    }
  }

  /**
   *
   * @param {CanvasRenderingContext2D} ctx
   * @param {Number} x
   * @param {Number} yLine
   * @param {String} baseline
   * @returns {Array<Number>}
   * @private
   */
  _setAlignment(ctx, x, yLine, baseline) {
    // check for label alignment (for edges)
    // TODO: make alignment for nodes
    if (this.isEdgeLabel && this.fontOptions.align !== 'horizontal' && this.pointToSelf === false) {
      x = 0;
      yLine = 0;

      let lineMargin = 2;
      if (this.fontOptions.align === 'top') {
        ctx.textBaseline = 'alphabetic';
        yLine -= 2 * lineMargin; // distance from edge, required because we use alphabetic. Alphabetic has less difference between browsers
      }
      else if (this.fontOptions.align === 'bottom') {
        ctx.textBaseline = 'hanging';
        yLine += 2 * lineMargin;// distance from edge, required because we use hanging. Hanging has less difference between browsers
      }
      else {
        ctx.textBaseline = 'middle';
      }
    }
    else {
      ctx.textBaseline = baseline;
    }
    return [x,yLine];
  }

  /**
   * fade in when relative scale is between threshold and threshold - 1.
   * If the relative scale would be smaller than threshold -1 the draw function would have returned before coming here.
   *
   * @param {string} color  The font color to use
   * @param {number} viewFontSize
   * @param {string} initialStrokeColor
   * @returns {Array<string>} An array containing the font color and stroke color
   * @private
   */
  _getColor(color, viewFontSize, initialStrokeColor) {
    let fontColor = color || '#000000';
    let strokeColor = initialStrokeColor || '#ffffff';
    if (viewFontSize <= this.elementOptions.scaling.label.drawThreshold) {
      let opacity = Math.max(0, Math.min(1, 1 - (this.elementOptions.scaling.label.drawThreshold - viewFontSize)));
      fontColor = util.overrideOpacity(fontColor, opacity);
      strokeColor = util.overrideOpacity(strokeColor, opacity);
    }
    return [fontColor, strokeColor];
  }

  /**
   *
   * @param {CanvasRenderingContext2D} ctx
   * @param {boolean} selected
   * @param {boolean} hover
   * @returns {{width: number, height: number}}
   */
  getTextSize(ctx, selected = false, hover = false) {
    this._processLabel(ctx, selected, hover);
    return {
      width: this.size.width,
      height: this.size.height,
      lineCount: this.lineCount
    };
  }


  /**
   *
   * @param {CanvasRenderingContext2D} ctx
   * @param {boolean} selected
   * @param {boolean} hover
   * @param {number} [x=0]
   * @param {number} [y=0]
   * @param {'middle'|'hanging'} [baseline='middle']
   */
  calculateLabelSize(ctx, selected, hover, x = 0, y = 0, baseline = 'middle') {
    if (this.labelDirty === true) {
      this._processLabel(ctx, selected, hover);
    }
    this.size.left = x - this.size.width * 0.5;
    this.size.top = y - this.size.height * 0.5;
    this.size.yLine = y + (1 - this.lineCount) * 0.5 * this.fontOptions.size;
    if (baseline === "hanging") {
      this.size.top += 0.5 * this.fontOptions.size;
      this.size.top += 4;   // distance from node, required because we use hanging. Hanging has less difference between browsers
      this.size.yLine += 4; // distance from node
    }
    this.labelDirty = false;
  }

  /**
   * normalize the markup system
   *
   * @param {boolean|'md'|'markdown'|'html'} markupSystem
   * @returns {string}
   */
  decodeMarkupSystem(markupSystem) {
    let system = 'none';
    if (markupSystem === 'markdown' || markupSystem === 'md') {
      system = 'markdown';
    } else if (markupSystem === true || markupSystem === 'html') {
      system = 'html'
    }
    return system;
  }

  /**
   * Explodes a piece of text into single-font blocks using a given markup
   * @param {string} text
   * @param {boolean|'md'|'markdown'|'html'} markupSystem
   * @returns {Array<{text: string, mod: string}>}
   */
  splitBlocks(text, markupSystem) {
    let system = this.decodeMarkupSystem(markupSystem);
    if (system === 'none') {
      return [{
        text: text,
        mod: 'normal'
      }]
    } else if (system === 'markdown') {
      return this.splitMarkdownBlocks(text);
    } else if (system === 'html') {
      return this.splitHtmlBlocks(text);
    }
  }

  splitMarkdownBlocks(text) {
    let blocks = [];
    let s = {
      bold: false,
      ital: false,
      mono: false,
      beginable: true,
      spacing: false,
      position: 0,
      buffer: "",
      modStack: []
    };
    s.mod = function() {
      return (this.modStack.length === 0) ? 'normal' : this.modStack[0];
    };
    s.modName = function() {
      if (this.modStack.length === 0)
        return 'normal';
      else if (this.modStack[0] === 'mono')
        return 'mono';
      else {
        if (s.bold && s.ital) {
          return 'boldital';
        } else if (s.bold) {
          return 'bold';
        } else if (s.ital) {
          return 'ital';
        }
      }
    };
    s.emitBlock = function(override=false) {  // eslint-disable-line no-unused-vars
      if (this.spacing) {
        this.add(" ");
        this.spacing = false;
      }
      if (this.buffer.length > 0) {
        blocks.push({ text: this.buffer, mod: this.modName() });
        this.buffer = "";
      }
    };
    s.add = function(text) {
      if (text === " ") {
        s.spacing = true;
      }
      if (s.spacing) {
        this.buffer += " ";
        this.spacing = false;
      }
      if (text != " ") {
        this.buffer += text;
      }
    };
    while (s.position < text.length) {
      let ch = text.charAt(s.position);
      if (/[ \t]/.test(ch)) {
        if (!s.mono) {
          s.spacing = true;
        } else {
          s.add(ch);
        }
        s.beginable = true
      } else if (/\\/.test(ch)) {
        if (s.position < text.length+1) {
          s.position++;
          ch = text.charAt(s.position);
          if (/ \t/.test(ch)) {
            s.spacing = true;
          } else {
            s.add(ch);
            s.beginable = false;
          }
        }
      } else if (!s.mono && !s.bold && (s.beginable || s.spacing) && /\*/.test(ch)) {
        s.emitBlock();
        s.bold = true;
        s.modStack.unshift("bold");
      } else if (!s.mono && !s.ital && (s.beginable || s.spacing) && /\_/.test(ch)) {
        s.emitBlock();
        s.ital = true;
        s.modStack.unshift("ital");
      } else if (!s.mono && (s.beginable || s.spacing) && /`/.test(ch)) {
        s.emitBlock();
        s.mono = true;
        s.modStack.unshift("mono");
      } else if (!s.mono && (s.mod() === "bold") && /\*/.test(ch)) {
        if ((s.position === text.length-1) || /[.,_` \t\n]/.test(text.charAt(s.position+1))) {
          s.emitBlock();
          s.bold = false;
          s.modStack.shift();
        } else {
          s.add(ch);
        }
      } else if (!s.mono && (s.mod() === "ital") && /\_/.test(ch)) {
        if ((s.position === text.length-1) || /[.,*` \t\n]/.test(text.charAt(s.position+1))) {
          s.emitBlock();
          s.ital = false;
          s.modStack.shift();
        } else {
          s.add(ch);
        }
      } else if (s.mono && (s.mod() === "mono") && /`/.test(ch)) {
        if ((s.position === text.length-1) || (/[.,*_ \t\n]/.test(text.charAt(s.position+1)))) {
          s.emitBlock();
          s.mono = false;
          s.modStack.shift();
        } else {
          s.add(ch);
        }
      } else {
        s.add(ch);
        s.beginable = false;
      }
      s.position++
    }
    s.emitBlock();
    return blocks;
  }

  splitHtmlBlocks(text) {
    let blocks = [];
    let s = {
      bold: false,
      ital: false,
      mono: false,
      spacing: false,
      position: 0,
      buffer: "",
      modStack: []
    };
    s.mod = function() {
      return (this.modStack.length === 0) ? 'normal' : this.modStack[0];
    };
    s.modName = function() {
      if (this.modStack.length === 0)
        return 'normal';
      else if (this.modStack[0] === 'mono')
        return 'mono';
      else {
        if (s.bold && s.ital) {
          return 'boldital';
        } else if (s.bold) {
          return 'bold';
        } else if (s.ital) {
          return 'ital';
        }
      }
    };
    s.emitBlock = function(override=false) {  // eslint-disable-line no-unused-vars
      if (this.spacing) {
        this.add(" ");
        this.spacing = false;
      }
      if (this.buffer.length > 0) {
        blocks.push({ text: this.buffer, mod: this.modName() });
        this.buffer = "";
      }
    };
    s.add = function(text) {
      if (text === " ") {
        s.spacing = true;
      }
      if (s.spacing) {
        this.buffer += " ";
        this.spacing = false;
      }
      if (text != " ") {
        this.buffer += text;
      }
    };
    while (s.position < text.length) {
      let ch = text.charAt(s.position);
      if (/[ \t]/.test(ch)) {
        if (!s.mono) {
          s.spacing = true;
        } else {
          s.add(ch);
        }
      } else if (/</.test(ch)) {
        if (!s.mono && !s.bold && /<b>/.test(text.substr(s.position,3))) {
          s.emitBlock();
          s.bold = true;
          s.modStack.unshift("bold");
          s.position += 2;
        } else if (!s.mono && !s.ital && /<i>/.test(text.substr(s.position,3))) {
          s.emitBlock();
          s.ital = true;
          s.modStack.unshift("ital");
          s.position += 2;
        } else if (!s.mono && /<code>/.test(text.substr(s.position,6))) {
          s.emitBlock();
          s.mono = true;
          s.modStack.unshift("mono");
          s.position += 5;
        } else if (!s.mono && (s.mod() === 'bold') && /<\/b>/.test(text.substr(s.position,4))) {
          s.emitBlock();
          s.bold = false;
          s.modStack.shift();
          s.position += 3;
        } else if (!s.mono && (s.mod() === 'ital') && /<\/i>/.test(text.substr(s.position,4))) {
          s.emitBlock();
          s.ital = false;
          s.modStack.shift();
          s.position += 3;
        } else if ((s.mod() === 'mono') && /<\/code>/.test(text.substr(s.position,7))) {
          s.emitBlock();
          s.mono = false;
          s.modStack.shift();
          s.position += 6;
        } else {
          s.add(ch);
        }
      } else if (/&/.test(ch)) {
        if (/&lt;/.test(text.substr(s.position,4))) {
          s.add("<");
          s.position += 3;
        } else if (/&amp;/.test(text.substr(s.position,5))) {
          s.add("&");
          s.position += 4;
        } else {
          s.add("&");
        }
      } else {
        s.add(ch);
      }
      s.position++
    }
    s.emitBlock();
    return blocks;
  }

  getFormattingValues(ctx, selected, hover, mod) {
    var getValue = function(fontOptions, mod, option) {
      if (mod === "normal") {
        if (option === 'mod' ) return "";
        return fontOptions[option];
      }

      if (fontOptions[mod][option]) {
        return fontOptions[mod][option];
      } else {
        // Take from parent font option
        return fontOptions[option];
      }
    };

    let values = {
      color  : getValue(this.fontOptions, mod, 'color'  ),
      size   : getValue(this.fontOptions, mod, 'size'   ),
      face   : getValue(this.fontOptions, mod, 'face'   ),
      mod    : getValue(this.fontOptions, mod, 'mod'    ),
      vadjust: getValue(this.fontOptions, mod, 'vadjust'),
      strokeWidth: this.fontOptions.strokeWidth,
      strokeColor: this.fontOptions.strokeColor
    };
    if (selected || hover) {
      if (mod === "normal" && (this.fontOptions.chooser === true) && (this.elementOptions.labelHighlightBold)) {
          values.mod = 'bold';
      } else {
        if (typeof this.fontOptions.chooser === 'function') {
          this.fontOptions.chooser(values, this.elementOptions.id, selected, hover);
        }
      }
    }
    ctx.font = (values.mod + " " + values.size + "px " + values.face).replace(/"/g, "");
    values.font = ctx.font;
    values.height = values.size;
    return values;
  }

  differentState(selected, hover) {
    return ((selected !== this.fontOptions.selectedState) && (hover !== this.fontOptions.hoverState));
  }
   

  /**
   * This explodes the passed text into lines and determines the width, height and number of lines.
   *
   * @param {CanvasRenderingContext2D} ctx
   * @param {boolean} selected
   * @param {boolean} hover
   * @param {String} text  the text to explode
   * @returns {{width, height, lines}|*}
   * @private
   */
  _processLabelText(ctx, selected, hover, text) {
    let self = this;


    /**
     * Callback to determine text width; passed to LabelAccumulator instance
     *
     * @param  {String} text string to determine width of
     * @param  {String} mod  font type to use for this text
     * @return {Object} { width, values} width in pixels and font attributes
     */
    let textWidth = function(text, mod) {
      if (text === undefined) return 0;

      // TODO: This can be done more efficiently with caching
      let values = self.getFormattingValues(ctx, selected, hover, mod);

      let width = 0;
      if (text !== '') {
        // NOTE: The following may actually be *incorrect* for the mod fonts!
        //       This returns the size with a regular font, bold etc. may
        //       have different sizes.
        let measure = ctx.measureText(text);
        width = measure.width;
      }

      return {width, values: values};
    };


    let lines = new LabelAccumulator(textWidth);

    if (text === undefined || text === "") {
      return lines.finalize();
    }


    let overMaxWidth = function(text) {
      let width = ctx.measureText(text).width;
      return (lines.curWidth() + width > self.fontOptions.maxWdt);
    };


    /**
     * Determine the longest part of the sentence which still fits in the 
     * current max width.
     * 
     * @param {Array} words Array of strings signifying a text lines
     * @return {number} index of first item in string making string go over max
     */
    let getLongestFit = function(words) {
      let text = '';
      let w = 0;

      while (w < words.length) {
        let pre = (text === '') ? '' : ' ';
        let newText = text + pre + words[w];

        if (overMaxWidth(newText)) break;
        text = newText;
        w++;
      }

      return w;
    };

    /**
     * Determine the longest part of the string which still fits in the
     * current max width.
     * 
     * @param {Array} words Array of strings signifying a text lines
     * @return {number} index of first item in string making string go over max
     */
    let getLongestFitWord = function(words) {
      let w = 0;

      while (w < words.length) {
        if (overMaxWidth(words.slice(0,w))) break;
        w++;
      }

      return w;
    };


    let splitStringIntoLines = function(str, mod = 'normal', appendLast = false) {
      let words = str.split(" ");

      while (words.length > 0) {
        let w = getLongestFit(words);

        if (w === 0) {
          // Special case: the first word may already
          // be larger than the max width.
          let word = words[0];

          // Break the word to the largest part that fits the line
          let x = getLongestFitWord(word);
          lines.newLine(word.slice(0, x), mod);

          // Adjust the word, so that the rest will be done next iteration
          words[0] = word.slice(x);
        } else {
          let text = words.slice(0, w).join(" ");

          if (w == words.length && appendLast) {
            lines.append(text, mod); 
          } else {
            lines.newLine(text, mod); 
          }

          words = words.slice(w);
        }
      }
    };


    let nlLines = String(text).split('\n');
    let lineCount = nlLines.length;

    if (this.elementOptions.font.multi) {
      // Multi-font case: styling tags active
      for (let i = 0; i < lineCount; i++) {
        let blocks = this.splitBlocks(nlLines[i], this.elementOptions.font.multi);
        if (blocks === undefined) continue;

        if (blocks.length === 0) {
          lines.newLine("");
          continue;
        }

        if (this.fontOptions.maxWdt > 0) {
          // widthConstraint.maximum defined
          //console.log('Running widthConstraint multi, max: ' + this.fontOptions.maxWdt);
          for (let j = 0; j < blocks.length; j++) {
            let mod  = blocks[j].mod;
            let text = blocks[j].text;
            splitStringIntoLines(text, mod, true);
          }
        } else {
          // widthConstraint.maximum NOT defined
          for (let j = 0; j < blocks.length; j++) {
            let mod  = blocks[j].mod;
            let text = blocks[j].text;
            lines.append(text, mod); 
          }
        }

        lines.newLine();
      }
    } else {
      // Single-font case
      if (this.fontOptions.maxWdt > 0) {
        // widthConstraint.maximum defined
        // console.log('Running widthConstraint normal, max: ' + this.fontOptions.maxWdt);
        for (let i = 0; i < lineCount; i++) {
          splitStringIntoLines(nlLines[i]);
        }
      } else {
        // widthConstraint.maximum NOT defined
        for (let i = 0; i < lineCount; i++) {
          lines.newLine(nlLines[i]); 
        }
      }
    }
   
    return lines.finalize();
  }


  /**
   * This explodes the label string into lines and sets the width, height and number of lines.
   * @param {CanvasRenderingContext2D} ctx
   * @param {boolean} selected
   * @param {boolean} hover
   * @private
   */
  _processLabel(ctx, selected, hover) {
    let state = this._processLabelText(ctx, selected, hover, this.elementOptions.label);

    if ((this.fontOptions.minWdt > 0) && (state.width < this.fontOptions.minWdt)) {
      state.width = this.fontOptions.minWdt;
    }

    this.size.labelHeight =state.height;
    if ((this.fontOptions.minHgt > 0) && (state.height < this.fontOptions.minHgt)) {
      state.height = this.fontOptions.minHgt;
    }

    this.lines = state.lines;
    this.lineCount = state.lines.length;
    this.size.width = state.width;
    this.size.height = state.height;
    this.selectedState = selected;
    this.hoverState = hover;
  }
}

export default Label;