Added gradient to FlLine

CHANGELOG.md

@@ -1,3 +1,6 @@
+## nextVersion
+* **FEATURE** (by @Dartek12): Added gradient to [FlLine](https://github.com/imaNNeo/fl_chart/blob/master/repo_files/documentations/base_chart.md#FlLine) 
+
 ## 0.64.0
 * **BUGFIX** (by @Anas35) Fix Tooltip not displaying when value from BackgroundBarChartRodData is less than zero. #1345.
 * **BUGFIX** (by @imaNNeo) Fix Negative BarChartRodStackItem are not drawn correctly bug, #1347

lib/src/chart/base/axis_chart/axis_chart_data.dart

@@ -664,13 +664,18 @@ class FlLine with EquatableMixin {
   /// For example, the array `[5, 10]` would result in dashes 5 pixels long
   /// followed by blank spaces 10 pixels long.
   const FlLine({
-    this.color = Colors.black,
+    Color? color,
+    this.gradient,
     this.strokeWidth = 2,
     this.dashArray,
-  });
+  }) : color = color ??
+            ((color == null && gradient == null) ? Colors.black : null);
 
   /// Defines color of the line.
-  final Color color;
+  final Color? color;
+
+  /// Defines the gradient of the line.
+  final Gradient? gradient;
 
   /// Defines thickness of the line.
   final double strokeWidth;
@@ -685,7 +690,8 @@ class FlLine with EquatableMixin {
   /// Lerps a [FlLine] based on [t] value, check [Tween.lerp].
   static FlLine lerp(FlLine a, FlLine b, double t) {
     return FlLine(
-      color: Color.lerp(a.color, b.color, t)!,
+      color: Color.lerp(a.color, b.color, t),
+      gradient: Gradient.lerp(a.gradient, b.gradient, t),
       strokeWidth: lerpDouble(a.strokeWidth, b.strokeWidth, t)!,
       dashArray: lerpIntList(a.dashArray, b.dashArray, t),
     );
@@ -695,11 +701,13 @@ class FlLine with EquatableMixin {
   /// and replaces provided values.
   FlLine copyWith({
     Color? color,
+    Gradient? gradient,
     double? strokeWidth,
     List<int>? dashArray,
   }) {
     return FlLine(
       color: color ?? this.color,
+      gradient: gradient ?? this.gradient,
       strokeWidth: strokeWidth ?? this.strokeWidth,
       dashArray: dashArray ?? this.dashArray,
     );
@@ -709,6 +717,7 @@ class FlLine with EquatableMixin {
   @override
   List<Object?> get props => [
         color,
+        gradient,
         strokeWidth,
         dashArray,
       ];

lib/src/chart/base/axis_chart/axis_chart_painter.dart

@@ -73,20 +73,28 @@ abstract class AxisChartPainter<D extends AxisChartData>
         if (!data.gridData.checkToShowVerticalLine(axisValue)) {
           continue;
         }
-        final flLineStyle = data.gridData.getDrawingVerticalLine(axisValue);
-        _gridPaint
-          ..color = flLineStyle.color
-          ..strokeWidth = flLineStyle.strokeWidth
-          ..transparentIfWidthIsZero();
-
         final bothX = getPixelX(axisValue, viewSize, holder);
         final x1 = bothX;
         const y1 = 0.0;
         final x2 = bothX;
         final y2 = viewSize.height;
+        final from = Offset(x1, y1);
+        final to = Offset(x2, y2);
+
+        final flLineStyle = data.gridData.getDrawingVerticalLine(axisValue);
+        _gridPaint
+          ..setColorOrGradientForLine(
+            flLineStyle.color,
+            flLineStyle.gradient,
+            from: from,
+            to: to,
+          )
+          ..strokeWidth = flLineStyle.strokeWidth
+          ..transparentIfWidthIsZero();
+
         canvasWrapper.drawDashedLine(
-          Offset(x1, y1),
-          Offset(x2, y2),
+          from,
+          to,
           _gridPaint,
           flLineStyle.dashArray,
         );
@@ -111,19 +119,28 @@ abstract class AxisChartPainter<D extends AxisChartData>
           continue;
         }
         final flLine = data.gridData.getDrawingHorizontalLine(axisValue);
-        _gridPaint
-          ..color = flLine.color
-          ..strokeWidth = flLine.strokeWidth
-          ..transparentIfWidthIsZero();
 
         final bothY = getPixelY(axisValue, viewSize, holder);
         const x1 = 0.0;
         final y1 = bothY;
         final x2 = viewSize.width;
         final y2 = bothY;
+        final from = Offset(x1, y1);
+        final to = Offset(x2, y2);
+
+        _gridPaint
+          ..setColorOrGradientForLine(
+            flLine.color,
+            flLine.gradient,
+            from: from,
+            to: to,
+          )
+          ..strokeWidth = flLine.strokeWidth
+          ..transparentIfWidthIsZero();
+
         canvasWrapper.drawDashedLine(
-          Offset(x1, y1),
-          Offset(x2, y2),
+          from,
+          to,
           _gridPaint,
           flLine.dashArray,
         );
@@ -229,7 +246,12 @@ abstract class AxisChartPainter<D extends AxisChartData>
 
       if (!isLineOutsideOfChart) {
         _extraLinesPaint
-          ..color = line.color
+          ..setColorOrGradientForLine(
+            line.color,
+            line.gradient,
+            from: from,
+            to: to,
+          )
           ..strokeWidth = line.strokeWidth
           ..transparentIfWidthIsZero()
           ..strokeCap = line.strokeCap;
@@ -316,7 +338,12 @@ abstract class AxisChartPainter<D extends AxisChartData>
 
       if (!isLineOutsideOfChart) {
         _extraLinesPaint
-          ..color = line.color
+          ..setColorOrGradientForLine(
+            line.color,
+            line.gradient,
+            from: from,
+            to: to,
+          )
           ..strokeWidth = line.strokeWidth
           ..transparentIfWidthIsZero()
           ..strokeCap = line.strokeCap;

lib/src/chart/line_chart/line_chart_data.dart

@@ -1195,7 +1195,7 @@ List<TouchedSpotIndicatorData> defaultTouchedIndicators(
       lineColor = _defaultGetDotColor(barData.spots[index], 0, barData);
     }
     const lineStrokeWidth = 4.0;
-    final flLine = FlLine(color: lineColor!, strokeWidth: lineStrokeWidth);
+    final flLine = FlLine(color: lineColor, strokeWidth: lineStrokeWidth);
 
     var dotSize = 10.0;
     if (barData.dotData.show) {

lib/src/chart/line_chart/line_chart_painter.dart

@@ -411,16 +411,22 @@ class LineChartPainter extends AxisChartPainter<LineChartData> {
         }
       }
 
+      final indicatorLine = indicatorData.indicatorBelowLine;
       _touchLinePaint
-        ..color = indicatorData.indicatorBelowLine.color
-        ..strokeWidth = indicatorData.indicatorBelowLine.strokeWidth
+        ..setColorOrGradientForLine(
+          indicatorLine.color,
+          indicatorLine.gradient,
+          from: lineStart,
+          to: lineEnd,
+        )
+        ..strokeWidth = indicatorLine.strokeWidth
         ..transparentIfWidthIsZero();
 
       canvasWrapper.drawDashedLine(
         lineStart,
         lineEnd,
         _touchLinePaint,
-        indicatorData.indicatorBelowLine.dashArray,
+        indicatorLine.dashArray,
       );
 
       /// Draw the indicator dot
@@ -752,17 +758,22 @@ class LineChartPainter extends AxisChartPainter<LineChartData> {
             );
           }
 
+          final lineStyle = barData.belowBarData.spotsLine.flLineStyle;
           _barAreaLinesPaint
-            ..color = barData.belowBarData.spotsLine.flLineStyle.color
-            ..strokeWidth =
-                barData.belowBarData.spotsLine.flLineStyle.strokeWidth
+            ..setColorOrGradientForLine(
+              lineStyle.color,
+              lineStyle.gradient,
+              from: from,
+              to: to,
+            )
+            ..strokeWidth = lineStyle.strokeWidth
             ..transparentIfWidthIsZero();
 
           canvasWrapper.drawDashedLine(
             from,
             to,
             _barAreaLinesPaint,
-            barData.belowBarData.spotsLine.flLineStyle.dashArray,
+            lineStyle.dashArray,
           );
         }
       }
@@ -841,17 +852,22 @@ class LineChartPainter extends AxisChartPainter<LineChartData> {
             );
           }
 
+          final lineStyle = barData.aboveBarData.spotsLine.flLineStyle;
           _barAreaLinesPaint
-            ..color = barData.aboveBarData.spotsLine.flLineStyle.color
-            ..strokeWidth =
-                barData.aboveBarData.spotsLine.flLineStyle.strokeWidth
+            ..setColorOrGradientForLine(
+              lineStyle.color,
+              lineStyle.gradient,
+              from: from,
+              to: to,
+            )
+            ..strokeWidth = lineStyle.strokeWidth
             ..transparentIfWidthIsZero();
 
           canvasWrapper.drawDashedLine(
             from,
             to,
             _barAreaLinesPaint,
-            barData.aboveBarData.spotsLine.flLineStyle.dashArray,
+            lineStyle.dashArray,
           );
         }
       }

lib/src/extensions/paint_extension.dart

@@ -18,4 +18,14 @@ extension PaintExtension on Paint {
       shader = null;
     }
   }
+
+  void setColorOrGradientForLine(
+    Color? color,
+    Gradient? gradient, {
+    required Offset from,
+    required Offset to,
+  }) {
+    final rect = Rect.fromPoints(from, to);
+    setColorOrGradient(color, gradient, rect);
+  }
 }

test/extensions/paint_extension_test.dart

@@ -36,4 +36,20 @@ void main() {
     expect(paint.color, MockData.color0);
     expect(paint.shader, isNull);
   });
+
+  test('test setColorOrGradientForLine', () {
+    final paint = Paint()
+      ..color = MockData.color0
+      ..setColorOrGradientForLine(
+        null,
+        MockData.gradient1,
+        from: MockData.rect1.topLeft,
+        to: MockData.rect1.bottomRight,
+      );
+    expect(paint.shader, isNotNull);
+
+    paint.setColorOrGradient(MockData.color0, null, MockData.rect1);
+    expect(paint.color, MockData.color0);
+    expect(paint.shader, isNull);
+  });
 }