[Vega] PDF reports do not have good dimensions compared to PNG reports

[rshen91]

Kibana version: 8.15.0 local

Browser: Chrome Version 124.0.6367.201 (Official Build) (arm64)

Describe the bug: Vega reports only for PDFs have strange dimensions: [Logs] Visitors Map (5).pdf

Same vega report but a PNG:

We believe it might have something to do with the screenshotting plugin or the dimensions are not be respected for PDFs.

Steps to reproduce:

1. Load sample data - web logs has a vega map but any vega visualization shows this issue
2. Go to vega and hit share and then PDF and export file
3. Once the PDF report finishes you can see that the dimensions are very squished.

Expected behavior: I would expect that the PDF would look similar to the PNG example and be more human readable.

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[petrklapka]

I've asked the Viz folks to take a look at their specific reporting code first and volley it back to us if they don't find anything. Sticking this in "discussion" and "soon" for us so we don't loose track of it.

[markov00]

@petrklapka @rshen91 a couple of observations:

• this doesn't happen only when printing a Vega chart, but also a Lens (is also worst in Lens), TSVB and a Visualize one.
• this happens only when you click share as PDF from within each editor, not when sharing from the dashboard.
• The problem seems to be caused by the fact that in these cases we are taking a "screenshot" of the chart DOM element and then we are stretching this screenshot into a PDF page that seems, in most case, in landscape mode. For squared charts like the vega map o some Lens charts, this results in a stretched image (below some examples).
• Because the PNG seems to have, at least, the correct aspect ratio, I believe the problem is on the way each image is attached to the PDF page.
• if you play around with the PNG and with the browser page sizing, you can also notice that the resulting PDF/PNG image size depends a bit on the current browser size, but also depends on other factors that seems to be unpredictable. This is also another factor to check when considering the final chart aspect ratio.

[petrklapka]

Thanks for taking a look @markov00 ! We'll take this one back then and prioritize at next triage.
cc: @rshen91 & @tsullivan

[tsullivan]

I'm moving this to the icebox since this is an internally-reported issue and PDF reports from the visualize app do not seem to be used very much.