Fix CairoMakie line color bug #3704

[jkrumbiegel]

Fix #3704, a logic bug for the case where a line contains the same color multiple times. In this case, the drawing should be delayed to have as few separate draw calls as possible, but of course the whole line should not be drawn with the following color gradient. Curious that this didn't come up earlier because it's very obviously wrong.

lines(1:10, sin, color = [fill(0, 9); fill(1, 1)], linewidth = 3, colormap = [:red, :cyan])

Before:

After:

[MakieBot]

Compile Times benchmark

Note, that these numbers may fluctuate on the CI servers, so take them with a grain of salt. All benchmark results are based on the mean time and negative percent mean faster than the base branch. Note, that GLMakie + WGLMakie run on an emulated GPU, so the runtime benchmark is much slower. Results are from running:

using_time = @ctime using Backend
# Compile time
create_time = @ctime fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @ctime Makie.colorbuffer(display(fig))
# Runtime
create_time = @benchmark fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @benchmark Makie.colorbuffer(fig)

	using	create	display	create	display
GLMakie	3.32s (3.30, 3.38) 0.03+-	162.82ms (161.85, 164.86) 1.01+-	463.38ms (461.83, 464.78) 1.09+-	7.28ms (7.17, 7.35) 0.06+-	25.44ms (25.37, 25.58) 0.07+-
master	3.32s (3.29, 3.36) 0.02+-	164.24ms (161.48, 172.58) 3.80+-	466.12ms (459.42, 477.82) 5.77+-	7.22ms (7.13, 7.27) 0.05+-	25.40ms (25.38, 25.42) 0.02+-
evaluation	1.00x invariant, 0.0s (0.06d, 0.91p, 0.03std)	1.01x invariant, -1.41ms (-0.51d, 0.37p, 2.41std)	1.01x invariant, -2.74ms (-0.66d, 0.26p, 3.43std)	0.99x slower X, 0.07ms (1.18d, 0.05p, 0.06std)	1.00x invariant, 0.04ms (0.77d, 0.19p, 0.04std)
CairoMakie	3.05s (2.97, 3.11) 0.06+-	176.89ms (166.61, 197.99) 11.73+-	108.79ms (100.71, 129.50) 9.88+-	7.42ms (7.27, 7.50) 0.08+-	886.94μs (882.12, 893.26) 3.63+-
master	3.04s (3.02, 3.06) 0.02+-	170.12ms (165.94, 175.22) 3.29+-	105.50ms (101.49, 111.95) 4.48+-	7.25ms (7.13, 7.36) 0.09+-	880.98μs (873.95, 887.11) 4.72+-
evaluation	1.00x invariant, 0.01s (0.15d, 0.79p, 0.04std)	0.96x invariant, 6.77ms (0.79d, 0.19p, 7.51std)	0.97x invariant, 3.29ms (0.43d, 0.44p, 7.18std)	0.98x slower X, 0.18ms (2.01d, 0.00p, 0.09std)	0.99x slower X, 5.96μs (1.42d, 0.02p, 4.18std)
WGLMakie	3.61s (3.56, 3.66) 0.04+-	373.91ms (368.10, 382.83) 6.04+-	8.61s (8.50, 8.93) 0.15+-	9.47ms (9.11, 10.12) 0.36+-	72.88ms (68.30, 97.07) 10.67+-
master	3.59s (3.55, 3.70) 0.05+-	228.78ms (163.11, 376.48) 98.04+-	8.74s (8.50, 9.03) 0.20+-	9.36ms (9.12, 9.78) 0.22+-	68.75ms (67.86, 70.14) 0.78+-
evaluation	1.00x invariant, 0.01s (0.32d, 0.57p, 0.05std)	0.61x slower❌, 145.13ms (2.09d, 0.01p, 52.04std)	1.02x invariant, -0.13s (-0.74d, 0.19p, 0.17std)	0.99x invariant, 0.1ms (0.35d, 0.53p, 0.29std)	0.94x noisy🤷‍♀️, 4.13ms (0.55d, 0.35p, 5.73std)