GR performance: SVG, not HTML, and use PNG for large plots

[fonsp]

Implemented:

• For Plots.Plot{Plots.GRBackend} objects, disable HTML to render as SVG instead: fix Blank frames make reactive Pluto plots look choppy #577 using idea 1 in Blank frames make reactive Pluto plots look choppy #577 (comment)
• For Plots.Plot{Plots.GRBackend} objects, when there are more than 8000 data points (count function), also disable SVG to render to PNG: fix SVG output from Plots can cause browser tab to consume large amounts of memory #911. Yes that number is arbitrary; no it won't be configurable ❤️

Hide whitespace in the diff: https://github.com/fonsp/Pluto.jl/pull/1090/files?diff=split&w=1

Try it out!

julia> ]
pkg> activate --temp
pkg> add Pluto#plots-performance
julia> import Pluto; Pluto.run()

[fonsp]

@daschw @jheinen FYI: Pluto will now skip the HTML MIME type for outputs of type Plots.Plot{Plots.GRBackend}. I improvised a function to count the 'complexity' of a given plot, and when there are too many datapoints, SVG is also disabled, leaving PNG.

@jheinen the interactive GR mode still works, since that is not the Plots.jl type. What I was not sure about is whether you can get the Pluto-interactive GR mode as part of a Plots.Plot? If so, is there a way for Pluto to check whether that is being used for a given Plots.Plot, so that we can re-enable HTML for that plot?

[jheinen]

Right now, you can't use the GR JS backend within Plots.jl. We (only) have an idea, how this could be managed - but there's still a lot of things to do.

[fonsp]

Okay! @jheinen please let me know when that happens, I will need to re-enable HTML output for GR JS plots. Important is that Pluto can use a function:

prefers_html(::Plots.Plot)::Bool

to decide whether or not HTML should be enabled. Pluto-managed SVG and PNG output has significant performance benefits over SVG-inside-HTML or PNG-inside-HTML.

[pankgeorg]

#1111

The size of the surface plot in the above issue is calculated to be 201, while the SVG size is about 700MB, and it crashes the browser
An idea is to default to PNG for all surfaces or for all plots in general (and allow opt-in SVG using DisplayAs)

Another idea is to default to PNG, but respect an explicit Plots.jl option, if it exists.

[jheinen]

To which surface plot do you refer? MWE?

[pankgeorg]

To which surface plot do you refer? MWE?

From the issue I've linked: #1111

x_range = -10:0.01:10
surface(x_range, x_range, (x, y)->sin(x)+cos(y), fillalpha=0.5, color=:coolwarm)

[jheinen]

It seems that Plots doesn't use GR's software renderer to create 3d surface plots. The SVG size of the following plain GR example is about 400K.

using GR
x_range = -10:0.01:10
surface(x_range, x_range, (x, y)->sin(x)+cos(y))