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.

Luxor.fontsizeFunction
fontsize(n)

Set the font size to n units. The default size is 10 units. (Toy API)

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Luxor.get_fontsizeFunction
get_fontsize()

Return the font size set by fontsize or. more precisely. the y-scale of the Cairo font matrix if Cairo.set_font_matrix is used directly. (Toy API)

This only works if Cairo is at least at v1.0.5.

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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.

Luxor.setfontFunction
setfont(family, fontsize)

Select a font and specify the size.

Example:

setfont("Helvetica", 24)
settext("Hello in Helvetica 24 using the Pro API", Point(0, 10))
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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

Luxor.textFunction
text(str)
text(str, pos)
text(str, pos, angle=pi/2)
text(str, x, y)
text(str, pos, halign=:left)
text(str, valign=:baseline)
text(str, valign=:baseline, halign=:left)
text(str, pos, valign=:baseline, halign=:left)

Draw the text in the string str at x/y or pt, placing the start of the string at the point. If you omit the point, it's placed at the current 0/0.

angle specifies the rotation of the text relative to the current x-axis.

Horizontal alignment halign can be :left, :center, (also :centre) or :right. Vertical alignment valign can be :baseline, :top, :middle, or :bottom.

The default alignment is :left, :baseline.

This uses textextents() to query the dimensions of the text. This returns values of the built in to the font. You can't find

This uses Cairo's Toy text API.

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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

Luxor.settextFunction
settext(text, pos;
    halign = "left",
    valign = "bottom",
    angle  = 0, # degrees!
    markup = false)

settext(text;
    kwargs)

Draw the text at pos (if omitted defaults to 0/0). If no font is specified, on macOS the default font is Times Roman.

To align the text, use halign, one of "left", "center", or "right", and valign, one of "top", "center", or "bottom".

angle is the rotation - in counterclockwise degrees, rather than Luxor's default clockwise (+x-axis to +y-axis) radians.

If markup is true, then the string can contain some HTML-style markup. Supported tags include:

<b>, <i>, <s>, <sub>, <sup>, <small>, <big>, <u>, <tt>, and <span>

The <span> tag can contains things like this:

<span font='26' background='green' foreground='red'>unreadable text</span>
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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 to paths

textoutlines(string, position, action) 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

Luxor.textoutlinesFunction
textoutlines(s::AbstractString, pos::Point=O, action::Symbol=:none;
    halign=:left,
    valign=:baseline,
    startnewpath=true)

Convert text to a graphic path and apply action.

By default this function discards any current path, unless you use startnewpath=false

See also textpath().

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

Luxor.textpathFunction
textpath(t)

Convert the text in string t and adds closed paths to the current path, for subsequent filling/stroking etc...

Typically you'll have to use pathtopoly() or getpath() or getpathflat() then work through the one or more path(s). Or use textoutlines().

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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

Luxor.textextentsFunction
textextents(str)

Return an array of six Float64s containing the measurements of the string str when set using the current font settings (Toy API):

1 x_bearing

2 y_bearing

3 width

4 height

5 x_advance

6 y_advance

The x and y bearings are the displacement from the reference point to the upper-left corner of the bounding box. It is often zero or a small positive value for x displacement, but can be negative x for characters like "j"; it's almost always a negative value for y displacement.

The width and height then describe the size of the bounding box. The advance takes you to the suggested reference point for the next letter. Note that bounding boxes for subsequent blocks of text can overlap if the bearing is negative, or the advance is smaller than the width would suggest.

Example:

textextents("R")

returns

[1.18652; -9.68335; 8.04199; 9.68335; 9.74927; 0.0]
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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

Luxor.labelFunction
label(txt::AbstractString, alignment::Symbol=:N, pos::Point=O;
    offset=5,
    leader=false,
    leaderoffsets=[0.0, 1.0])

Add a text label at a point, positioned relative to that point, for example, :N signifies North and places the text directly above that point.

Use one of :N, :S, :E, :W, :NE, :SE, :SW, :NW to position the label relative to that point.

label("text")          # positions text at North (above), relative to the origin
label("text", :S)      # positions text at South (below), relative to the origin
label("text", :S, pt)  # positions text South of pt
label("text", :N, pt, offset=20)  # positions text North of pt, offset by 20

The default offset is 5 units.

If leader is true, draw a line as well.

leaderoffsts uses normalized fractions (see between()) to specify the gap between the designated points and the start and end of the lines.

TODO: Negative offsets don't give good results.

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label(txt::AbstractString, rotation::Float64, pos::Point=O;
    offset=5,
    leader=false,
    leaderoffsets=[0.0, 1.0])

Add a text label at a point, positioned relative to that point, for example, 0.0 is East, pi is West.

label("text", pi)          # positions text to the left of the origin
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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

Luxor.textcurveFunction
textcurve(the_text, start_angle, start_radius, x_pos = 0, y_pos = 0;
      # optional keyword arguments:
      spiral_ring_step = 0,    # step out or in by this amount
      letter_spacing = 0,      # tracking/space between chars, tighter is (-), looser is (+)
      spiral_in_out_shift = 0, # + values go outwards, - values spiral inwards
      clockwise = true
      )

Place a string of text on a curve. It can spiral in or out.

start_angle is relative to +ve x-axis, arc/circle is centered on (x_pos,y_pos) with radius start_radius.

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Luxor.textcurvecenteredFunction
textcurvecentered(the_text, the_angle, the_radius, center::Point;
      clockwise = true,
      letter_spacing = 0,
      baselineshift = 0

This version of the textcurve() function is designed for shorter text strings that need positioning around a circle. (A cheesy effect much beloved of hipster brands and retronauts.)

letter_spacing adjusts the tracking/space between chars, tighter is (-), looser is (+)). baselineshift moves the text up or down away from the baseline.

textcurvecentred (UK spelling) is a synonym

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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

Luxor.textwrapFunction
textwrap(s::T where T<:AbstractString, width::Real, pos::Point;
    rightgutter=5,
    leading=0)
textwrap(s::T where T<:AbstractString, width::Real, pos::Point, linefunc::Function;
    rightgutter=5,
    leading=0)

Draw the string in s by splitting it at whitespace characters into lines, so that each line is no longer than width units. The text starts at pos such that the first line of text is drawn entirely below a line drawn horizontally through that position. Each line is aligned on the left side, below pos.

See also textbox().

Optionally, before each line, execute the function linefunc(linenumber, linetext, startpos, leading).

If you don't supply a value for leading, the font's built-in extents are used.

Text with no whitespace characters won't wrap. You can write a simple chunking function to split a string or array into chunks:

chunk(x, n) = [x[i:min(i+n-1,length(x))] for i in 1:n:length(x)]

For example:

textwrap(the_text, 300, boxtopleft(BoundingBox()) + 20,
    (ln, lt, sp, ht) -> begin
        c = count(t -> occursin(r"[[:punct:]]", t), split(lt, ""))
        @layer begin
            fontface("Menlo")
            sethue("darkred")
            text(string("[", c, "]"), sp + (310, 0))
        end
    end)

puts a count of the number of punctuation characters in each line at the end of the line.

Returns the position of what would have been the next line.

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Luxor.textboxFunction
textbox(lines::Array, pos::Point=O;
    leading = 12,
    linefunc::Function = (linenumber, linetext, startpos, height) -> (),
    alignment=:left)

Draw the strings in the array lines vertically downwards. leading controls the spacing between each line (default 12), and alignment determines the horizontal alignment (default :left).

Optionally, before each line, execute the function linefunc(linenumber, linetext, startpos, height).

Returns the position of what would have been the next line.

See also textwrap(), which modifies the text so that the lines fit into a specified width.

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textbox(s::AbstractString, pos::Point=O;
    leading = 12,
    linefunc::Function = (linenumber, linetext, startpos, height) -> (),
    alignment=:left)
source
Luxor.splittextFunction
splittext(s)

Split the text in string s into an array, but keep all the separators attached to the preceding word.

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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 units are 1/1000 em, so the actual distance of "50 units of tracking" varies depending on the current font size.

But really, don’t track text unless you have to.

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

Luxor.texttrackFunction
texttrack(txt, pos, tracking, fontsize=12;
    action=:fill,
    halign=:left,
    valign=:baseline,
    startnewpath=true)

Place the text in txt at pos, left-justified, and letter space ('track') the text using the value in tracking.

The tracking units depend on the current font size! 1 is 1/1000 em. In a 6‑point font, 1 em equals 6 points; in a 10‑point font, 1 em equals 10 points.

A value of -50 would tighten the letter spacing noticeably. A value of 50 would make the text more open.

The text drawing action applied to each character defaults to textoutlines(... :fill).

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