Add drag threshold to improve click experience

[jkrumbiegel]

It has been a problem for a long time which I've also seen in many user recordings that a drag starts when any distance is travelled by the mouse after mouse down. This means that for a click to register, the mouse has to stay perfectly still between mouse down and up. That's hard to do with precision input devices like my Macbook's trackpad. When implementing this code, I frequently see difference values like 0.1 or 0.2 pixels, you don't even see the cursor move (as it's snapped to the pixel grid) but no click is happening.

This PR adds a small threshold in pixels that the mouse has to travel before a drag starts. Until then, if the mouse goes up, a click will be registered. For me this is immediately noticeable in usability. The threshold value 2 that I chose is kind of arbitrary but seemed to work well enough, at some point higher values feel weird as dragging a slider, for example, seems to start too late.

[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	4.50s (4.44, 4.57) 0.04+-	110.84ms (105.77, 120.70) 6.12+-	485.39ms (472.96, 504.51) 11.31+-	9.43ms (9.01, 9.68) 0.27+-	26.43ms (26.05, 26.89) 0.27+-
master	4.53s (4.44, 4.66) 0.10+-	111.30ms (105.63, 126.97) 7.27+-	485.17ms (471.15, 514.94) 16.63+-	9.46ms (8.75, 9.85) 0.34+-	26.29ms (26.02, 26.64) 0.25+-
evaluation	1.01x invariant, -0.03s (-0.40d, 0.47p, 0.07std)	1.00x invariant, -0.45ms (-0.07d, 0.90p, 6.70std)	1.00x invariant, 0.22ms (0.02d, 0.98p, 13.97std)	1.00x invariant, -0.03ms (-0.10d, 0.86p, 0.31std)	0.99x invariant, 0.15ms (0.56d, 0.31p, 0.26std)
CairoMakie	4.24s (4.18, 4.34) 0.05+-	109.58ms (107.35, 111.62) 1.57+-	172.71ms (168.58, 176.39) 2.45+-	9.81ms (9.72, 9.94) 0.08+-	1.17ms (1.13, 1.19) 0.02+-
master	4.22s (4.19, 4.25) 0.02+-	112.98ms (107.84, 117.80) 3.34+-	175.95ms (169.35, 185.93) 6.28+-	9.82ms (9.67, 10.05) 0.16+-	1.18ms (1.14, 1.21) 0.03+-
evaluation	1.00x invariant, 0.01s (0.35d, 0.53p, 0.04std)	1.03x faster ✓, -3.4ms (-1.30d, 0.04p, 2.46std)	1.02x invariant, -3.24ms (-0.68d, 0.24p, 4.36std)	1.00x invariant, -0.01ms (-0.09d, 0.87p, 0.12std)	1.01x invariant, -0.01ms (-0.28d, 0.61p, 0.03std)
WGLMakie	4.72s (4.65, 4.78) 0.05+-	108.17ms (105.63, 112.83) 2.35+-	9.47s (9.25, 9.68) 0.13+-	11.71ms (11.35, 12.41) 0.35+-	124.94ms (116.28, 162.97) 16.83+-
master	4.75s (4.70, 4.80) 0.03+-	109.68ms (107.16, 113.78) 2.11+-	9.47s (9.32, 9.69) 0.12+-	11.61ms (11.51, 11.81) 0.11+-	119.37ms (114.83, 121.18) 2.22+-
evaluation	1.01x invariant, -0.03s (-0.61d, 0.28p, 0.04std)	1.01x invariant, -1.51ms (-0.67d, 0.23p, 2.23std)	1.00x invariant, -0.0s (-0.01d, 0.98p, 0.13std)	0.99x invariant, 0.11ms (0.42d, 0.46p, 0.23std)	0.96x invariant, 5.56ms (0.46d, 0.42p, 9.52std)