Add shadow to line chart's tooltip

[Sosssen]

hi:)

this PR resolves #1767

i've added 3 params to LineTouchTooltipData for tooltip shadow:

• shadowColor - color of the shadow
• shadowBlur - sigma value of mask filter blur (how much will shadow be blurred)
• shadowOffset - offset of the shadow (related to tooltip)

please check the image below to see example of changes:)

and the code code of LineTouchTooltipData from example image:

LineTouchData get lineTouchData => LineTouchData(
        touchTooltipData: LineTouchTooltipData(
          getTooltipColor: (touchedSpot) => Colors.black,
          shadowColor: Colors.white.withOpacity(0.25),
          shadowBlur: 4,
          shadowOffset: const Offset(0, 4),
        ),
      );

[seniorb]

Would be great if this could be added to the barchart tooltip as well!

[imaNNeo]

Hi, thanks for your details description.
We already have a shadow feature in our line chart, that works like a simple shadow property (that uses the Shadow class from flutter).

Can you please use the same naming and method of drawing shadow, this way we keep the consistency in the project.

Look at the below code:

fl_chart/lib/src/chart/line_chart/line_chart_data.dart

Lines 359 to 360 in 0e75570

	/// Drops a shadow behind the bar line.
	final Shadow shadow;

fl_chart/lib/src/chart/line_chart/line_chart_painter.dart

Lines 911 to 938 in 0e75570

	if (!barData.show || barData.shadow.color.opacity == 0.0) {
	return;
	}
	if (barPath.computeMetrics().isEmpty) {
	return;
	}
	_barPaint
	..strokeCap = barData.isStrokeCapRound ? StrokeCap.round : StrokeCap.butt
	..strokeJoin =
	barData.isStrokeJoinRound ? StrokeJoin.round : StrokeJoin.miter
	..color = barData.shadow.color
	..shader = null
	..strokeWidth = barData.barWidth
	..color = barData.shadow.color
	..maskFilter = MaskFilter.blur(
	BlurStyle.normal,
	Utils().convertRadiusToSigma(barData.shadow.blurRadius),
	);
	barPath = barPath.toDashedPath(barData.dashArray);
	barPath = barPath.shift(barData.shadow.offset);
	canvasWrapper.drawPath(
	barPath,
	_barPaint,
	);