image and heatmap traces jump/flash on Firefox and Safari

[jonmmease]

The new image trace seems to have a flashing/jumping behavior when zoomed in and panning on Firefox and Safari. (Firefox version 69.0, Safari version 13.0.3)

Example from https://plot.ly/python/imshow/

This jumping does not happen on Chrome but I do see it on Firefox/Safari. Not sure if it's related, but in all three browsers, the tooltip also seems to jump to another location when the pan is completed.

[antoinerg]

@jonmmease I think the issue also occurs on heatmap (https://plot.ly/python/heatmap/). Could you rename the issue to reflect that?

The problem stems from reinjecting an image when pan operation is completed. I thought this pattern was safe since it's been used for a long time in heatmap. Maybe this issue only affects newer versions of Firefox 🤔 ?

[jonmmease]

Could you rename the issue to reflect that?

Done, thanks!

[etpinard]

Hmm. I can't replicate in FF 70

[jonmmease]

Hmm, I am seeing it in FF 70 on Ubuntu. @antoinerg were you able to reproduce?

[antoinerg]

Hmm, I am seeing it in FF 70 on Ubuntu. @antoinerg were you able to reproduce?

I can reproduce it in FF 70.0.1 (64-bit) on Linux (NixOS distro).

[firasm]

I can also reproduce in Safari 13.0.3 on macOS 10.15.1.

On the same system, the problem does not appear in Chrome Version 78.0.3904.108.

[etpinard]

@antoinerg do you think there's an "easy" way to fix this bug?

Or do you think our canvas -> pixels -> img inside the _paper SVG is fundamentally flawed and FF does behaves as expected?

[antoinerg]

Or do you think our canvas -> pixels -> img inside the _paper SVG is fundamentally flawed and FF does behaves as expected?

It's hard to say which one behaves right and I suspect the specification may not be clear in this regard.

do you think there's an "easy" way to fix this bug?

Idea for an easy fix: have two images (A and B) and alternate between the two. Once you pan, image B content is updated and moved in front of image A (so no flash in principle). Then if you pan again, image A content is updated and moved in front and so on. Hopefully, this approach works.

If we only target a fix for FF: leverage image-rendering: pixelated, draw the image only once and things will fly 🐎.

[alexcjohnson]

So we're reverting the drag, then redrawing with the new view... and it seems like even if we do this synchronously, some browsers will do two repaints (if that's it, there will be async edge cases in other browsers too). I wonder if we can just not revert the drag, and tweak the redraw process if necessary so it still works right. I think it's this call that's doing it:

plotly.js/src/plots/cartesian/dragbox.js

Lines 770 to 774 in 4ab3b49

	function dragTail() {
	// put the subplot viewboxes back to default (Because we're going to)
	// be repositioning the data in the relayout. But DON'T call
	// ticksAndAnnotations again - it's unnecessary and would overwrite `updates`
	updateSubplots([0, 0, pw, ph]);

updateSubplots seems to modify some internal state as well as adjusting viewboxes, we still may need the internal state even if we don't change anything visible.

[antoinerg]

This may be a problem with Firefox itself: Images are flashing when updates by img.src[]=url in Firefox >= 8.0

Potential solution: https://stackoverflow.com/questions/14704796/image-reload-causes-flicker-only-in-firefox/14711272#14711272