The sequence chooser loads very slowly for certain visualizers

[Vectornaut]

When I click the name of the current sequence, or equivalently the Change sequence button, while viewing a Factor Histogram or Turtle visualization, the sequence chooser window takes about 250–500 ms to appear. The delay is noticeable and frustrating.

I suspect the issue is related to the p5's WebGL backend, because neither Chaos nor Mod Fill has a noticeable delay.

My sequence chooser contains nine sequences.

[gwhitney]

I can verify that there is a noticeable difference in the amount of time the Change Sequence dialogue takes to pop up between say Factor Histogram (slow) and Factor Fence (fast), although I didn't try to time it precisely in either case. I would say the problem is not severe in that in both cases the dialogue showed up before I was wondering if it wasn't working etc. Hence my assigning this a beta milestone. My initial hunch - no more than that - is we need to find a way to get the SwitcherModal popup to be willing to show before its SpecimenCards have started rendering. I think the user experience would be improved if it popped instantly with the window and the spaces for the visualizations and the text descriptions, and then they started to draw after the 250-500ms that Aaron estimates that it currently takes the popup to appear.

[katestange]

I don't know if this is the same performance issue or another, but if you are looking at VFib Snowflake and you move your mouse, it noticeably slows the rotation while the mouse is moving, before speeding up again. [UPDATE: this may not be an issue on ui2, it might be PR 484 I'm having trouble with]