fix(symbol): fix emphasis.scale can't be reset and specified values may not be respected

src/chart/helper/Symbol.ts

@@ -27,7 +27,7 @@ import { ColorString, BlurScope, AnimationOption, ZRColor, AnimationOptionMixin
 import SeriesModel from '../../model/Series';
 import { PathProps } from 'zrender/src/graphic/Path';
 import { SymbolDrawSeriesScope, SymbolDrawItemModelOption } from './SymbolDraw';
-import { extend, isNumber } from 'zrender/src/core/util';
+import { extend } from 'zrender/src/core/util';
 import { setLabelStyle, getLabelStatesModels } from '../../label/labelStyle';
 import ZRImage from 'zrender/src/graphic/Image';
 import { saveOldStyle } from '../../animation/basicTransition';
@@ -336,11 +336,19 @@ class Symbol extends graphic.Group {
  symbolPath.ensureState('select').style = selectItemStyle;
  symbolPath.ensureState('blur').style = blurItemStyle;
 
- if (hoverScale) {
- const scaleRatio = Math.max(isNumber(hoverScale) ? hoverScale : 1.1, 3 / this._sizeY);
- emphasisState.scaleX = this._sizeX * scaleRatio;
- emphasisState.scaleY = this._sizeY * scaleRatio;
- }
+ // null / undefined / true means to use default strategy.
+ // 0 / false / negative number / NaN / Infinity means no scale.
+ const scaleRatio =
+ hoverScale == null || hoverScale === true
+ ? Math.max(1.1, 3 / this._sizeY)
+ // PENDING: restrict hoverScale > 1? It seems unreasonable to scale down
+ : isFinite(hoverScale as number) && hoverScale > 0
+ ? +hoverScale
+ : 1;
+ // always set scale to allow resetting
+ emphasisState.scaleX = this._sizeX * scaleRatio;
+ emphasisState.scaleY = this._sizeY * scaleRatio;
+
  this.setSymbolScale(1);
 
  toggleHoverEmphasis(this, focus, blurScope, emphasisDisabled);