Change pie chart color

[hypolas]

Hello,

I try to set color to pie chart serie.

In my case, I need, for exemple, to set color "red" (for error data) and green (for valide data) .

That seems don't work.  I try with:

	p, err := charts.PieRender(
		values,
		charts.TitleOptionFunc(charts.TitleOption{
			Text:    "Rainfall vs Evaporation",
			Subtext: "Fake Data",
			Left:    charts.PositionCenter,
		}),
		charts.PaddingOptionFunc(charts.Box{
			Top:    20,
			Right:  20,
			Bottom: 10,
			Left:   20,
		}),
		charts.LegendOptionFunc(charts.LegendOption{
			Orient: charts.OrientVertical,
			Data: []string{
				"tests",
				"failures",
				"errors",
			},
			Left: charts.PositionLeft,
		}),
		charts.PieSeriesShowLabel(),
		func(opt *charts.ChartOption) {
			opt.SeriesList[1].Style.FillColor = drawing.ColorRed
			opt.SeriesList[2].Style.FillColor = drawing.ColorRed
		},
	)

[jentfoo]

Thank you for opening this issue @hypolas. This fork has been re-evaluating the chart configuration options and the series Style has not yet been considered.

Looking at the implementation, it looks like setting the FillColor currently only functions on Bar charts. This could be easily extended to also support Pie Charts, but there ends up being a weird side effect that the Legend does not have a reference to the series (also true for bar charts), and thus it's colors are not updated, for example:

One goal of this fork is to make themes more straight forward. We don't require themes to be globally registered (they are passed in with the chart configuration). Would a suitable alternative be to take a theme you like, and then replace the SeriesColors with the colors you want represented? I still want to make theme mutations easier, it would look something like this:

	baseTheme := charts.GetTheme(ThemeVividLight)
	var seriesColors []charts.Color
	for i := range series {
		if red {
			seriesColors = append(seriesColors, drawing.ColorRed)
		} else {
			seriesColors = append(seriesColors, baseTheme.GetSeriesColor(i))
		}
	}
	customTheme := baseTheme.WithSeriesColors(seriesColors)
	// or possibly
	customTheme := baseTheme.WithOptions(ThemeOption{SeriesColors: seriesColors})

Then your pie chart would be constructed like this:

	p, err := charts.PieRender(
		values,
		charts.ThemeOptionFunc(customTheme),
		charts.TitleOptionFunc(charts.TitleOption{
			Text:    "Rainfall vs Evaporation",
			Subtext: "Fake Data",
			Left:    charts.PositionCenter,
		}),
		charts.PaddingOptionFunc(charts.Box{
			Top:    20,
			Right:  20,
			Bottom: 10,
			Left:   20,
		}),
		charts.LegendOptionFunc(charts.LegendOption{
			Orient: charts.OrientVertical,
			Data: []string{
				"tests",
				"failures",
				"errors",
			},
			Left: charts.PositionLeft,
		}),
		charts.PieSeriesShowLabel(),
	)

I believe that having a single method of setting the theme for the series would be more straight forward, but I would appreciate your feedback before we make any changes. Thank you!

[jentfoo]

@hypolas, I just submitted a PR which removes the series Style you were configuring and instead introduces the ergonomics around changing the series colors of the theme: #15

Let me know your thoughts on moving forward with a change like this, or if you think there is a good reason to leave this style configuration at the series level. Thank you!

[hypolas]

Hello.

Than you for your very fast answer.

For solve my problem quikly, I had modified my code like this :

func (g Graph) buildGraph() {
	p, err := charts.PieRender(
		g.Values,
		g.makeDefaultTheme(),
		charts.TitleOptionFunc(charts.TitleOption{
			Text:    g.Text,
			Subtext: g.Subtext,
			Left:    charts.PositionCenter,
		}),
		charts.PaddingOptionFunc(charts.Box{
			Top:    20,
			Right:  20,
			Bottom: 20,
			Left:   20,
		}),
		charts.LegendOptionFunc(charts.LegendOption{
			Orient: charts.OrientVertical,
			Data:   g.Legends,
			Top:    "5%",
			Left:   charts.PositionLeft,
		}),
		charts.PieSeriesShowLabel(),
	)

	if err != nil {
		panic(err)
	}

	if buf, err := p.Bytes(); err != nil {
		panic(err)
	} else if err = writeFile(buf); err != nil {
		panic(err)
	}
}

func (g Graph) makeDefaultTheme() charts.OptionFunc {
	th := charts.ThemeOptionFunc(charts.MakeTheme(charts.ThemeOption{
		SeriesColors:    g.Colors,
		TextColor:       drawing.ColorFromHex("555555"),
		BackgroundColor: drawing.ColorWhite,
	}))

	return th
}

g.Color is a slice of color previously generated with this code.

func colorSwitch(result string) drawing.Color {
	switch result {
	case "failed":
		return drawing.ColorRed
	case "failure":
		return drawing.ColorRed
	case "passed":
		return drawing.ColorLime
	case "ok":
		return drawing.ColorLime
	case "errors":
		colorError := drawing.Color{
			R: 244,
			G: 100,
			B: 100,
			A: 255,
		}

		return colorError
	}
	return drawing.ColorWhite
}

If this can help somebody ;)

[jentfoo]

Thank you for the feedback @hypolas, I am glad to hear that the custom theme options is a workable solution for you.

I went ahead and polished PR #15 further, making sure that Font configuration (which is broadly used and common) is encapsulated in the FontStyle struct instead of needing the broader Style struct (which could lead to similar confusion as you had here). Feel free to give the PR a look if you have interest, I would appreciate any feedback you might have.

Once merged I plan to release this under version 0.2.0. Although you have a good solution here, the primary benefit to you will be the WithSeriesColors which could allow you to easily only change the series colors.

Let me know if you have questions or thoughts, thank you again!

[jentfoo]

These changes were just pushed under the v0.2.0 tag. Let me know if you have any questions or further recommendations. Thank you!