Unicode symbols as arrowheads in Makie

Specific Domains Visualization
1

Is it possible to use other Symbols for the arrowheads in Makie? According to the docs, the arrowhead attribute is set by default to automatic, which is in 2D the symbol "▲". To use something like arrowhead="△" could be very useful but throws an error when trying to display the figure.

MWE

This works fine:

using CairoMakie
positions = Point2f.(rand(5), rand(5))
directions = Vec2f.(rand(5), rand(5))
arrows(positions, directions, arrowsize=15)

test
test800×600 10 KB

But this throws an error:

using CairoMakie
positions = Point2f.(rand(5), rand(5))
directions = Vec2f.(rand(5), rand(5))
arrows(positions, directions, arrowsize=15, arrowhead="△")

ERROR: MethodError: no method matching draw_marker(::Cairo.CairoContext, ::String, ::Vec{2, Float32}, ::Vec{2, Float32}, ::ColorTypes.RGBA{Float32}, ::Float32, ::Vec{2, Float32}, ::Quaternionf)
Closest candidates are:
draw_marker(::Any, ::Circle, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any) at ~/.julia/packages/CairoMakie/F9l4g/src/primitives.jl:278
draw_marker(::Any, ::GeometryBasics.HyperRectangle, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any) at ~/.julia/packages/CairoMakie/F9l4g/src/primitives.jl:292
draw_marker(::Any, ::Char, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any) at ~/.julia/packages/CairoMakie/F9l4g/src/primitives.jl:228
2

use a Char like '△' not "△"

1 Like
3

Thanks a lot!

using CairoMakie
positions = Point2f.(rand(5), rand(5))
directions = Vec2f.(rand(5), rand(5))
arrows(positions, directions, arrowsize=15, arrowhead='△')

test
test800×600 7.01 KB

4

Thanks, wile the solution was simple, and I understand the concept of Char*, would it be appropriate for that package (and most or all others), to also allow 1-letter strings? For the benefit of people coming from e.g. Python where there is no Char, and ‘△’ not “△” would mean the same, a string happens to be 1 Char long.

* Char may actually be a bad idea, in Swift since it’s based on grapeme-clusters, they’re “chars” are actually strings, often 1 Char as in Julia, but not always.