[BUG] Blurry plots with WebGL about bokeh

[ianthomas23]

Are you using a Retina display here, or maybe a hybrid setup with one Retina display and an external monitor that is not Retina?

We effectively scale the antialiasing distance by the pixel ratio of the screen, which is 2 for a Retina display. So the antialiasing distance on a Retina display is twice as much in physical pixels which means it is correct in CSS pixels (i.e. expected "human eye" pixels). So the antialiasing should be similar for canvas and webgl backends, which is evidently not the situation here.

From a purely practical point of view I do not currently have access to a Retina display (or any display with a pixel ratio far from 1) so I am not able to check that what we currently do is what I expect us to do.

[Yura52]

Yes, this issue is observed of my MacBook Pro: 14.2-inch (diagonal) Liquid Retina XDR display; 3024-by-1964 native resolution at 254 pixels per inch

[ianthomas23]

Thanks. Could you try with a different browser, ideally Chrome, to confirm that it is not a browser-specific problem?

[Yura52]

Thanks. Could you try with a different browser, ideally Chrome, to confirm that it is not a browser-specific problem?

I reproduced the issue in Safari and in one Blink/Chromium-based browser (unfortunately, I cannot install Chrome on my machine).

[mattpap]

I don't see any difference between different pixel densities in Chromium's devtools (all my screens are natively 1:1), but I see a clear differences when scaling the viewport (blurring seems to increase with scaling).

At 100% zoom:

At 250% zoom (need to open this image in a new tab to see it in full resolution and see the blurring):

(both use 1:1 DPI). When testing this, note that you have to reload the page for zoom to take effect in bokehjs.

[Yura52]

Not sure if this is an additional context for Bokeh developers or a suggestion to check the zoom-related things on my side :) So just in case I did the following:

• I turned off the native system-wide macOS scaling.
• I reset the browser scaling.

And after those changes, the issue is still there.