[BUG] Arrows not showing correctly when using `yscale = :log10`

[dermesser]

Details

Arrowheads (e.g. created with plot(...; arrow = arrow(:closed))) are butchered when using a semi-log scale, using GR.

This is correct (lin-lin scale):

This is wrong (lin-log scale):

Backends

This bug occurs on ( insert x below )

(at least gr)

Backend	yes	no	untested
gr (default)	x
pythonplot			x
plotlyjs		x (doesn't show any arrows)
pgfplotsx		x (doesn't support arrows)
unicodeplots		x (doesn't show any arrows)
inspectdr		x (doesn't show any arrows)
gaston		x (doesn't show any arrows)

Versions

Plots.jl version: [91a5bcdd] Plots v1.38.8 Backend version (]st -m <backend(s)>): [28b8d3ca] GR v0.71.8 Output of versioninfo():

Julia Version 1.9.0-rc1
Commit 3b2e0d8fbc (2023-03-07 07:51 UTC)
Platform Info:
  OS: Linux (x86_64-redhat-linux)
  CPU: 4 × Intel(R) Core(TM) i5-7300U CPU @ 2.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, skylake)
  Threads: 1 on 4 virtual cores
Environment:
  JULIA_IMAGE_THREADS = 1

[ivan-boikov]

Can confirm, arrows indeed are botched in logscale, both semi and full.

• For GR gr_drawarrow is called through GR.jl, so it's a bug for GR framework. Looks like arrows are drawn assuming linear scale https://github.com/sciapp/gr/blob/eff7161c08df40e298cb16ac429bbaeae13cb3b1/lib/gr/gr.c#L10865.
• For PGFPlotsX it does not work at all since pgfplots LaTeX package does not implement quiver plot in logscale, so also not a Plots.jl bug.

Can't test other backends, have trouble with their precompilation.