added functionality to apply cutOffY value on below or above bar area,

and for sure changed BelowBarData to BarAreaData to reuse it for both areas, fixed issue #62

lib/src/chart/line_chart/line_chart_data.dart

@@ -166,8 +166,11 @@ class LineChartBarData {
 
  final bool isStrokeCapRound;
 
- /// to fill space below the bar line,
- final BelowBarData belowBarData;
+ /// to fill space below the bar line
+ final BarAreaData belowBarData;
+
+ /// to fill space above the bar line
+ final BarAreaData aboveBarData;
 
  /// to show dot spots upon the line chart
  final FlDotData dotData;
@@ -182,15 +185,16 @@ class LineChartBarData {
  this.curveSmoothness = 0.35,
  this.preventCurveOverShooting = false,
  this.isStrokeCapRound = false,
- this.belowBarData = const BelowBarData(),
+ this.belowBarData = const BarAreaData(),
+ this.aboveBarData = const BarAreaData(),
  this.dotData = const FlDotData(),
  });
 
  static LineChartBarData lerp(LineChartBarData a, LineChartBarData b, double t) {
  return LineChartBarData(
  show: b.show,
  barWidth: lerpDouble(a.barWidth, b.barWidth, t),
- belowBarData: BelowBarData.lerp(a.belowBarData, b.belowBarData, t),
+ belowBarData: BarAreaData.lerp(a.belowBarData, b.belowBarData, t),
  curveSmoothness: b.curveSmoothness,
  isCurved: b.isCurved,
  isStrokeCapRound: b.isStrokeCapRound,
@@ -203,10 +207,9 @@ class LineChartBarData {
  }
 }
 
-/***** BelowBarData *****/
-
-/// This class holds data about draw on below space of the bar line,
-class BelowBarData {
+/***** BarAreaData *****/
+/// This class holds data about draw on below or above space of the bar line,
+class BarAreaData {
  final bool show;
 
  /// if you pass just one color, the solid color will be used,
@@ -227,55 +230,65 @@ class BelowBarData {
  /// stop points of the gradient.
  final List<double> gradientColorStops;
 
- /// holds data for drawing a line from each spot the the bottom of the chart
- final BelowSpotsLine belowSpotsLine;
+ /// holds data for drawing a line from each spot the the bottom, or top of the chart
+ final BarAreaSpotsLine spotsLine;
 
- const BelowBarData({
- this.show = true,
+ /// cut the drawing below or above area to this y value
+ final double cutOffY;
+
+ /// determines should or shouldn't apply cutOffY
+ final bool applyCutOffY;
+
+ const BarAreaData({
+ this.show = false,
  this.colors = const [Colors.blueGrey],
  this.gradientFrom = const Offset(0, 0),
  this.gradientTo = const Offset(1, 0),
  this.gradientColorStops,
- this.belowSpotsLine = const BelowSpotsLine(),
- });
+ this.spotsLine = const BarAreaSpotsLine(),
+ this.cutOffY,
+ this.applyCutOffY = false,
+ }) : assert(applyCutOffY == true ? cutOffY != null : true);
 
- static BelowBarData lerp(BelowBarData a, BelowBarData b, double t) {
- return BelowBarData(
+ static BarAreaData lerp(BarAreaData a, BarAreaData b, double t) {
+ return BarAreaData(
  show: b.show,
  gradientFrom: Offset.lerp(a.gradientFrom, b.gradientFrom, t),
  gradientTo: Offset.lerp(a.gradientTo, b.gradientTo, t),
- belowSpotsLine: BelowSpotsLine.lerp(a.belowSpotsLine, b.belowSpotsLine, t),
+ spotsLine: BarAreaSpotsLine.lerp(a.spotsLine, b.spotsLine, t),
  colors: lerpColorList(a.colors, b.colors, t),
  gradientColorStops: lerpDoubleList(a.gradientColorStops, b.gradientColorStops, t),
+ cutOffY: lerpDouble(a.cutOffY, b.cutOffY, t),
+ applyCutOffY: b.applyCutOffY,
  );
  }
 }
 
-typedef CheckToShowSpotBelowLine = bool Function(FlSpot spot);
+typedef CheckToShowSpotLine = bool Function(FlSpot spot);
 
 bool showAllSpotsBelowLine(FlSpot spot) {
  return true;
 }
 
-class BelowSpotsLine {
+class BarAreaSpotsLine {
  final bool show;
 
  /// determines style of the line
  final FlLine flLineStyle;
 
- /// a function to determine whether to show or hide the below line on the given spot
- final CheckToShowSpotBelowLine checkToShowSpotBelowLine;
+ /// a function to determine whether to show or hide the below or above line on the given spot
+ final CheckToShowSpotLine checkToShowSpotLine;
 
- const BelowSpotsLine({
+ const BarAreaSpotsLine({
  this.show = false,
  this.flLineStyle = const FlLine(),
- this.checkToShowSpotBelowLine = showAllSpotsBelowLine,
+ this.checkToShowSpotLine = showAllSpotsBelowLine,
  });
 
- static BelowSpotsLine lerp(BelowSpotsLine a, BelowSpotsLine b, double t) {
- return BelowSpotsLine(
+ static BarAreaSpotsLine lerp(BarAreaSpotsLine a, BarAreaSpotsLine b, double t) {
+ return BarAreaSpotsLine(
  show: b.show,
- checkToShowSpotBelowLine: b.checkToShowSpotBelowLine,
+ checkToShowSpotLine: b.checkToShowSpotLine,
  flLineStyle: FlLine.lerp(a.flLineStyle, b.flLineStyle, t),
  );
  }