Empty png in report

[KochankovID]

Bug description

1. I set up reporting dash to my email
2. For some reason, report was sent, but in email I got empty png
3. This happens regulary for every report

Why the report was not failed with error?

I know the reason of this thing was one of the chart, which was "legacy" bar chart, but my problem, is that I can't determine when report was sent correct and when not correct (cause no error in logs at all) and on report UI everything is green

Screenshots/recordings

And also with another dash I have same problem sometimes:

And sometimes is OK:

And again no error in logs and UI

Superset version

5.0.0

Python version

3.11

Node version

Not applicable

Browser

Not applicable

Additional context

I'm using Trino as SQL engine

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot]

This is a recognized pain point — Superset's report validation checks whether the screenshot capture returned bytes, but it does not verify that the image actually contains meaningful content [1]. A blank/white PNG is still a valid image file, so it passes all checks and gets sent with a green status. That's why you see no errors.

Why legacy charts make this worse: Legacy charts have a unique code path where they may lack a saved query context, triggering a fallback screenshot to generate it. This extra step introduces additional failure points that can result in a blank render without raising an error [1].

Things to try:

1. Replace the legacy bar chart with the modern ECharts bar chart — this is the most reliable fix if a legacy viz type is the root cause.

2. Increase screenshot timeout values in your superset_config.py, since charts may not finish rendering before the screenshot is taken:

   SCREENSHOT_SELENIUM_HEADSTART = 5
   SCREENSHOT_LOCATE_WAIT = 20
   SCREENSHOT_LOAD_WAIT = 120
   SCREENSHOT_SELENIUM_ANIMATION_WAIT = 10

3. Enable tiled screenshots if your dashboard is large or has many charts — this addresses a known issue where Chromium unmounts/redraws elements mid-capture on tall pages [2]:

   SCREENSHOT_TILED_ENABLED = True
   SCREENSHOT_TILED_CHART_THRESHOLD = 15
   SCREENSHOT_TILED_HEIGHT_THRESHOLD = 4000

4. Try Playwright instead of Selenium, which may be more reliable for screenshot capture:

   FEATURE_FLAGS = {
       "PLAYWRIGHT_REPORTS_AND_THUMBNAILS": True
   }

5. Check your logs for this warning: "No query context found, taking a screenshot to generate it" — it indicates a legacy chart is hitting the fallback path [1].

As for your core question about why the report doesn't fail with an error — this is essentially a gap in Superset's validation. There are related issues tracking this: #25187 and #14351. Content-aware validation (detecting blank images before sending) hasn't been implemented yet.

To reply, just mention @dosu.

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[KochankovID]

More context:

1. I used playwrite
2. I have very big screenshot timeout:
   SCREENSHOT_LOAD_WAIT = 6000
   SCREENSHOT_PLAYWRIGHT_DEFAULT_TIMEOUT = 6000000

[dosubot]

Thanks for the extra context. Since you're already using Playwright with very large timeouts, the timeout itself likely isn't the issue — if the charts don't render properly, waiting longer won't help. The core problem is that Superset doesn't validate whether the captured PNG actually has content; a blank white image is still a valid PNG, so the report succeeds silently [1].

Two things worth checking given your setup:

1. Enable tiled screenshots — This was introduced specifically to fix blank screenshots on large dashboards caused by Chromium unmounting/redrawing UI elements mid-capture [2]. If your dashboards are tall or have many charts, this is likely the fix:

SCREENSHOT_TILED_ENABLED = True
SCREENSHOT_TILED_CHART_THRESHOLD = 20  # or lower if your dashboards have fewer charts
SCREENSHOT_TILED_HEIGHT_THRESHOLD = 5000

2. Legacy NVD3 charts have async rendering via nv.addGraph() [3] that may complete after loading indicators disappear. The Playwright wait strategy detects .loading elements being removed but doesn't know about NVD3's internal rendering queue. Increasing the animation wait may help as a band-aid:

SCREENSHOT_SELENIUM_ANIMATION_WAIT = 10  # default is 5

But the most reliable fix is to replace the legacy bar chart with the modern ECharts bar chart. Legacy chart types use a deprecated API path [4] and have fundamentally different rendering behavior that the screenshot system wasn't designed to handle well.

Also, your SCREENSHOT_PLAYWRIGHT_DEFAULT_TIMEOUT = 6000000 is 6,000 seconds (~100 minutes) — that's almost certainly higher than needed. The default of 60,000ms (60 seconds) should be sufficient; if the chart hasn't rendered by then, waiting longer won't resolve it.

To reply, just mention @dosu.

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