Fixes for WGLMakie

[SimonDanisch]

Closes #3781

[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	4.32s (4.28, 4.34) 0.02+-	110.55ms (107.37, 118.25) 3.85+-	487.86ms (484.53, 493.31) 3.34+-	8.59ms (8.49, 8.65) 0.07+-	26.07ms (25.97, 26.20) 0.07+-
master	4.33s (4.30, 4.37) 0.03+-	108.50ms (106.57, 111.24) 1.75+-	490.14ms (483.72, 496.14) 3.96+-	8.65ms (8.55, 8.70) 0.05+-	26.06ms (26.00, 26.16) 0.05+-
evaluation	1.00x invariant, -0.01s (-0.46d, 0.41p, 0.03std)	0.98x invariant, 2.05ms (0.68d, 0.23p, 2.80std)	1.00x invariant, -2.28ms (-0.62d, 0.27p, 3.65std)	1.01x invariant, -0.06ms (-1.00d, 0.09p, 0.06std)	1.00x invariant, 0.01ms (0.11d, 0.84p, 0.06std)
CairoMakie	3.96s (3.72, 4.14) 0.17+-	124.86ms (112.93, 137.95) 8.03+-	148.59ms (139.75, 156.90) 5.08+-	9.03ms (8.75, 9.13) 0.13+-	1.02ms (1.00, 1.04) 0.02+-
master	3.78s (3.68, 3.84) 0.06+-	125.48ms (118.12, 132.73) 5.06+-	144.40ms (141.90, 147.54) 2.14+-	8.74ms (8.27, 9.01) 0.27+-	1.02ms (0.98, 1.04) 0.02+-
evaluation	0.95x slower X, 0.18s (1.44d, 0.03p, 0.11std)	1.00x invariant, -0.62ms (-0.09d, 0.87p, 6.55std)	0.97x invariant, 4.19ms (1.07d, 0.08p, 3.61std)	0.97x slower X, 0.29ms (1.36d, 0.03p, 0.20std)	1.00x invariant, 0.0ms (0.12d, 0.82p, 0.02std)
WGLMakie	4.70s (4.57, 4.85) 0.09+-	116.42ms (108.77, 125.20) 6.73+-	9.70s (9.29, 10.10) 0.28+-	9.82ms (9.57, 10.04) 0.16+-	71.42ms (70.24, 73.15) 1.06+-
master	4.58s (4.47, 4.79) 0.12+-	113.27ms (106.27, 117.59) 4.13+-	9.51s (9.29, 9.82) 0.18+-	10.06ms (9.18, 13.27) 1.44+-	71.47ms (70.28, 73.20) 0.99+-
evaluation	0.97x invariant, 0.12s (1.17d, 0.05p, 0.10std)	0.97x invariant, 3.15ms (0.56d, 0.32p, 5.43std)	0.98x invariant, 0.18s (0.78d, 0.18p, 0.23std)	1.02x invariant, -0.23ms (-0.23d, 0.68p, 0.80std)	1.00x invariant, -0.05ms (-0.05d, 0.93p, 1.02std)

[SimonDanisch]

I also found the problem for:
#3752
Turns out we weren't discarding transparent pixel for picking, so that the whole text quad is rendered, most of it overwriting anything below with 0.
I added a debug function to get the picking buffer, should have done that first, since without seeing the buffer its impossible to debug^^

[SimonDanisch]

May need: SimonDanisch/Bonito.jl#215