Affected versions

• 84.0b2
• 85.0a1 (2020-11-18)

Affected platforms

• Windows 10
• Windows 7
• macOS 10.15
• Ubuntu 20.04

Steps to reproduce

1. Launch Firefox with a clean profile
2. Make sure print.tab_modal.enabled is set on true
3. Hit CTRL + P on a long page (eg. https://en.wikipedia.org/wiki/University_of_Oxford)
4. Select Custom option from Pages
5. Set a scale value above the default one
6. Observe the Custom interval and the total sheets of paper

Expected result

• The total sheets of paper is updated to reflect the scale change

Actual result

• The custom page interval is stuck on the previous set value

Regression range

• Not a regression

Additional notes

• This issue is also visible on paper size changing, the custom page interval update is working if the total number of pages is lower than the one set initially, but not viceversa
• No error is trigger if I manually change the custom interval max value above the limit set initially but below the limit that should be reflected by the new set scale level
• Print preview refreshes, the scale level is applied, but the number of pages remains as it was before the scale change
• Issue reproducible regardless the destination

Suggested severity

• S3

Hey :Anca, thanks for filing. This is actually the expected behavior. If the number of pages change and the end range is now out of range (meaning the number of pages decreased), we update the end range to the new number of pages. If the number of pages increase, we keep whatever the value was.

We're also planning on replacing the start/end range format in Bug 499640, which should land this week.