Text and fonts

A tale of two APIs

There are two ways to draw text in Luxor. You can use either the so-called 'toy' API or the 'pro' API. Both have their advantages and disadvantages. Also, font selection and availability varies a lot across the three operating systems. You may have to experiment to find code patterns that work for you.

The Toy API

Use:

  • text(string, [position]) to place text at a position, otherwise at 0/0, and optionally specify the horizontal and vertical alignment
  • fontface(fontname) to specify the fontname
  • fontsize(fontsize) to specify the fontsize
fontsize(16)
fontface("Georgia-Bold")
text("Georgia: a serif typeface designed in 1993 by Matthew Carter.", halign=:center)

text placement

(If the specified font is unavailable on the current system configuration, the default, usually Times/Helvetica or DejaVu, is used.)

The label function also uses the Toy API.

The Pro API

Use:

  • setfont(fontname, fontsize) to specify the fontname and size
  • settext(text, [position]) to place the text at a position, and optionally specify horizontal and vertical alignment, rotation (in degrees counterclockwise!), and the presence of any pseudo-Pango-flavored markup.
setfont("Georgia Bold", 16)
settext("Georgia: a serif typeface designed in 1993 by Matthew Carter.", halign="center")

text placement

Specifying the font ("Toy" API)

Use fontface(fontname) to choose a font, and fontsize(n) to set the font size. get_fontsize finds the current font size.

Specifying the font ("Pro" API)

To select a font in the Pro text API, use setfont and supply both the font name and a size.

Placing text ("Toy" API)

Use text to place text.

pt1 = Point(-100, 0)
pt2 = Point(0, 0)
pt3 = Point(100, 0)
sethue("black")
text("1",  pt1, halign=:left,   valign = :bottom)
text("2",  pt2, halign=:center, valign = :bottom)
text("3",  pt3, halign=:right,  valign = :bottom)
text("4",  pt1, halign=:left,   valign = :top)
text("5", pt2, halign=:center, valign = :top)
text("6",  pt3, halign=:right,  valign = :top)
sethue("red")
map(p -> circle(p, 4, :fill), [pt1, pt2, pt3])

text placement

fontsize(10)
fontface("Georgia")
[text(string(θ), Point(40cos(θ), 40sin(θ)), angle=θ) for θ in 0:π/12:47π/24]

text rotation

Placing text ("Pro" API)

Use settext to place text. You can include some pseudo-HTML markup with the keyword argument markup=true.

rulers()
sethue("black")
settext("<span font='26' background ='green' foreground='red'> Hey</span>
    <i>italic</i> <b>bold</b> <sup>superscript</sup>
    <tt>monospaced</tt>",
    halign="center",
    markup=true,
    angle=10) # degrees counterclockwise!

pro text placement

Notes on fonts

Fonts are loaded when you first start using Luxor/Cairo in a Julia session. This partly explains why starting a Luxor/Cairo session can take a few seconds.

On macOS, the fontname required by the Toy API's fontface should be the PostScript name of a currently activated font. You can find this out using, for example, the FontBook application.

On macOS, a list of currently activated fonts can be found (after a while) with the shell command:

system_profiler SPFontsDataType

Fonts currently activated by a Font Manager can be found and used by the Toy API but not by the Pro API (at least on my macOS computer currently).

On macOS, you can obtain a list of fonts that fontconfig considers are installed and available for use (via the Pro Text API with setfont) using the shell command:

fc-list | cut -f 2 -d ":"

although typically this lists only those fonts in /System/Library/Fonts and /Library/Fonts, and not ~/Library/Fonts.

(There is a Julia interface to fontconfig at Fontconfig.jl. See also FreeTypeAbstraction.jl)

In the Pro API, the default font is Times Roman (on macOS). In the Toy API, the default font is Helvetica (on macOS).

One difference between settext and text (on macOS) is that many more missing Unicode glyphs are automatically substituted by other fonts when you use the former.

Cairo.jl (and hence Luxor.jl) doesn't support emoji currently. 😢

Text is rasterized (converted from outlines to pixels) only when you output to the PNG format. For SVG formats, text is converted to outlines (curves and lines). For PDF and EPS formats, the fonts you use are stored inside the output file ("embedded"), and the text is displayed using that font only when the file is viewed.

For PNG files, the appearance of fonts when output is controlled to some extent by the operating system. For example, on Windows, if ClearType is active, differently-colored pixels are used to display fonts, because of the use of subpixel rendering. These colored pixels will be visible in the PNG output.

Text to paths

textoutlines(string, position) converts the text into graphic path(s), places them starting at position, and applies the action.

fontface("Times-Roman")
fontsize(500)
setline(4)
sethue("maroon2")
textoutlines("&", O, :path, valign=:middle, halign=:center)
fillpreserve()
sethue("black")
strokepath()

text outlines

textpath converts the text into graphic paths suitable for further manipulation.

Text and font dimensions ("Toy" API only)

The textextents(str) function returns the dimensions of the string str, given the current font. There has to be a current drawing before this function is called.

width and height are stored in elements 3 and 4. The first two elements are the offsets ("bearings") from the reference point (green) to the bounding box. The last two elements determine where the next ("advance") character should start (blue).

textextents

Note

There is currently no equivalent of this function for the "Pro" API.

Labels

The label function places text relative to a specific point, and you can use compass points or angles to indicate where it should be. So :N (for North) places a text label directly above the point, as does 3π/2.

sethue("black")
fontsize(15)
octagon = ngon(O, 100, 8, 0, vertices=true)

compass = [:SE, :S, :SW, :W, :NW, :N, :NE, :E, :SE]

for i in 1:8
    circle(octagon[i], 5, :fill)
    label(string(compass[i]), compass[i], octagon[i], leader=true, leaderoffsets=[0.2, 0.9], offset=50)
end

labels

Text on a curve

Use textcurve(str) to draw a string str on a circular arc or spiral.

fontsize(7)
fontface("Menlo")
textstring = join(names(Base), " ")
textcurve("this spiral contains every word in julia names(Base): " * textstring,
    -π/2,
    350, 0, 0,
    spiral_in_out_shift = -8.0,
    letter_spacing = 0,
    spiral_ring_step = 0)
fontsize(35)
fontface("Avenir-Black")
textcentered("julia names(Base)", 0, 0)

text on a curve or spiral

For shorter strings, textcurvecentered tries to place the text on a circular arc by its center point.

fontface("Arial-Black")
circle(O, 100, :stroke)
textcurvecentered("hello world", -π/2, 100, O;
    clockwise = true,
    letter_spacing = 0,
    baselineshift = -20
    )
textcurvecentered("hello world", π/2, 100, O;
    clockwise = false,
    letter_spacing = 0,
    baselineshift = 10
    )

text centered on curve

Text clipping

You can use newly-created text paths as a clipping region - here the text paths are filled with names of randomly chosen Julia functions:

text clipping

using Luxor

currentwidth = 1250 # pts
currentheight = 800 # pts
Drawing(currentwidth, currentheight, "/tmp/text-path-clipping.png")

origin()
background("darkslategray3")

fontsize(600)                             # big fontsize to use for clipping
fontface("Agenda-Black")
str = "julia"                             # string to be clipped
w, h = textextents(str)[3:4]              # get width and height

translate(-(currentwidth/2) + 50, -(currentheight/2) + h)

textpath(str)                             # make text into a path
setline(3)
setcolor("black")
fillpreserve()                            # fill but keep
clip()                                    # and use for clipping region

fontface("Monaco")
fontsize(10)
namelist = map(x->string(x), names(Base)) # get list of function names in Base.

let
    x = -20
    y = -h
    while y < currentheight
        sethue(rand(7:10)/10, rand(7:10)/10, rand(7:10)/10)
        s = namelist[rand(1:end)]
        text(s, x, y)
        se = textextents(s)
        x += se[5]                            # move to the right
        if x > w
            x = -20                            # next row
            y += 10
        end
    end
end

finish()
preview()

Text blocks, boxes, and wrapping

Longer lines of text can be made to wrap inside an imaginary rectangle with textwrap. Specify the required width of the rectangle, and the location of the top left corner.

fontface("Georgia")

loremipsum = """Lorem ipsum dolor sit amet, consectetur
adipiscing elit. Nunc placerat lorem ullamcorper,
sagittis massa et, elementum dui. Sed dictum ipsum vel
commodo pellentesque. Aliquam erat volutpat. Nam est
dolor, vulputate a molestie aliquet, rutrum quis lectus.
Sed lectus mauris, tristique et tempor id, accumsan
pharetra lacus. Donec quam magna, accumsan a quam
quis, mattis hendrerit nunc. Nullam vehicula leo ac
leo tristique, a condimentum tortor faucibus."""

setdash("dot")
box(O, 200, 200, :stroke)
textwrap(loremipsum, 200, O - (200/2, 200/2))

text wrapping

textwrap accepts a function that allows you to insert code that responds to the next line's linenumber, contents, position, and height.

fontface("Georgia")

loremipsum = """Lorem ipsum dolor sit amet, consectetur
adipiscing elit. Nunc placerat lorem ullamcorper,
sagittis massa et, elementum dui. Sed dictum ipsum vel
commodo pellentesque. Aliquam erat volutpat. Nam est
dolor, vulputate a molestie aliquet, rutrum quis lectus.
Sed lectus mauris, tristique et tempor id, accumsan
pharetra lacus. Donec quam magna, accumsan a quam
quis, mattis hendrerit nunc. Nullam vehicula leo ac
leo tristique, a condimentum tortor faucibus."""

textwrap(loremipsum, 200, O - (200/2, 200/2),
    (lnumber, str, pt, l) -> begin
        sethue(Colors.HSB(rescale(lnumber, 1, 15, 0, 360), 1, 1))
        text(string("line ", lnumber), pt - (50, 0))
    end)

text wrapped

The textbox function also draws text inside a box, but doesn't alter the lines, and doesn't force the text to a specific width. Supply an array of strings and the top left position. The leading argument specifies the distance between the lines, so should be set relative to the current font size (as set with fontsize).

This example counts the number of characters drawn, using a simple closure. The function returns the position of the start of what would have been the next line.

fontface("Georgia")
fontsize(30)

loremipsum = """Lorem ipsum dolor sit amet, consectetur
adipiscing elit. Nunc placerat lorem ullamcorper,
sagittis massa et, elementum dui. Sed dictum ipsum vel
commodo pellentesque. Aliquam erat volutpat. Nam est
dolor, vulputate a molestie aliquet, rutrum quis lectus.
Sed lectus mauris, tristique et tempor id, accumsan
pharetra lacus. Donec quam magna, accumsan a quam
quis, mattis hendrerit nunc. Nullam vehicula leo ac
leo tristique, a condimentum tortor faucibus."""

_counter() = (a = 0; (n) -> a += n)
counter = _counter()

translate(boxtopleft(BoundingBox()))
fontface("Georgia")
fontsize(20)

finishpos = textbox(filter(!isempty, split(loremipsum, "\n")),
    O + (5, 0),
    leading = 28,
    linefunc = (lnumber, str, pt, h) -> begin
        text(string(lnumber), pt - (30, 0))
        counter(length(str))
    end)

fontsize(10)
text(string(counter(0), " characters"), finishpos)

textbox

Text tracking

Use texttrack to track or letter-space text, i.e. vary the spacing between every letter. ("Kerning" is when you do this for just a pair of letters.)

The tracking units depend on the current font size. In a 12‑point font, 1 em equals 12 points. A point is about 0.35mm, so a 1000 units of tracking for 12 point text produces about 4.2mm of space between each character.

function text_tracking_example()
    fonts = [
        "Verdana",
        "TrebuchetMS",
        "Times-Roman",
        "Georgia",
        "Monaco"]
    fsize = 16
    grid = GridRect(boxtopleft(BoundingBox() * 0.9), 0, 20)
    tracking = 50
    for f in fonts
        fontsize(fsize)
        fontface(f)
        texttrack("This is some text in $(f): it’s been tracked by +$(tracking)",
            nextgridpoint(grid), tracking, fsize)
        text("This is some text in $(f): it’s not been tracked",
            nextgridpoint(grid))
        texttrack("This is some text in $(f): it’s been tracked by -$(tracking)",
            nextgridpoint(grid), -tracking, fsize)
    end

end

text_tracking_example()

textbox