Add the ability to underline text

[kodawah]

If I get things correctly, there is no way to draw underlined text, as https://godoc.org/github.com/llgcode/draw2d#FontStyle shows only Bold and Italics

Is there a way to underline text via the API? What about mixed styles, such as Boldltalics? Would it be possible to implement these features in some way? thanks

[llgcode]

I thought you would combine bold and italic like this style = FontStyleBold | FontStyleItalic need more test on this. For underline I'm not sure it's a property of a font that we could set. Otherwise drawing a line underneath a text could be sufficient.

[kodawah]

Thanks, I confirm combining the values work, I've documented it here http://sprunge.us/PdIK

I had thought about just drawing a line below the text for underlined style, but the size, the width, the strokes are dependent on the font, and style applied. I think it'd be nicer if this is done in the library rather than the user application.

[llgcode]

Thx for testing Yes, For underline, it will be nicer to have it implemented in draw2d or freetype but I was thinking of a utility function. I'm not sure I wanted to see as a font style.

[redstarcoder]

To clarify this issue in its present state, I believe it should be renamed to "Add the ability to underline text" and have the label changed to "Enhancement".

To add to discussion, I believe adding underline as a style would be how most users would expect underlining to be done, so that's how we should do it. A utility function should be fine too though as most text functions return the width anyways (and the font size is usually the height of the glyphs) so I don't believe it'd be difficult. I just think isolating it to a utility function will make text styling code look inconsistent.

[xeoncross]

It's been a while, but this is still a desired feature. Based on what I read here, I'm going to look at matching text width while keeping line-height and font-size in mind for wrapping text.

[llgcode]

Hi @Xeoncross, yes you can use the length returned by FillString to draw the line that you need underneet the text.

[llgcode]

I've prototyped the function you need , Is it something like this? https://play.golang.org/p/MuxKhec9G9H

[xeoncross]

Thanks @llgcode! I'm going to play with what you posted. I actually ended up playing with the http://github.com/fogleman/gg library for underline text but was never able to calculate the correct line-height for multi-line text.

Here is some partial code I was looking at but my calculations are incorrect.

dc := gg.NewContext(W, H)

// ...

err := dc.LoadFontFace(fontPath, 16);

// ...

var maxTextWidth float64 = 120

dc.DrawStringWrapped("Hello world ...", P, H/2, 0, 0.5, maxTextWidth, 2, gg.AlignLeft)

// Trying to calculate the line height of each row so we can add an underline!

var lineStrokeWidth float64 = .5
var lineSpacing float64 = 2

// How many lines does the text take-up?
textWidth, textHeight := dc.MeasureMultilineString(strings.Join(lines, "\n"), lineSpacing)
lineHeight := textHeight / float64(len(lines))

dc.SetLineWidth(lineStrokeWidth)

baseTextOffset := H/2 - (textHeight / 2)
for i := 1; i <= len(lines); i++ {
	textY := float64(i) * lineHeight
	dc.DrawLine(P, baseTextOffset+textY, P+textWidth, baseTextOffset+textY)
}
dc.Stroke()

dc.SavePNG("out.png")