Page Settings: switching to inches distorts staff space
Tested in version 2.1 and 3.0. Steps to reproduce:
1) create a new score of any kind
2) go to Layout/Page Settings... and verify that the Staff space (sp) value is 1.764
3) switch Units from mm to in
4) click OK
5) open the Layout/Page Settings dialog again
6) switch the Unit to mm, and now the Staff space value is 1.753
It may seem like a small difference, but it makes a big difference. Clearly it is what happened in this issue:
I imagine this is a rounding error of some kind. It also rings a bell, like I submitted this same bug a few years ago. I can't remember how it was resolved.
edit - Yes, definitely a rounding error when rounding the staff space value to 3 decimal places for inches. I just did the math. You can round the display for inches, but you cannot round the internal number or it will modify the staff space value inadvertently. You have to keep it all at 4 decimal places, at least 4 decimal places.
edit - I just changed my branch to use 5 decimals, but the mm value starts at 1.76400. It is being rounded elsewhere from 1.76388889. This is funky! Rounding really screws this up. Maybe there is no solution for this, and there was no solution a few years ago when this came up. That's probably one of the reasons why I tried to make Points/Pixels an available unit in this dialog, so that the spatium could be kept at exactly 25.000.
If this is not fixable, then I will submit an issue to increase the page width max to be greater than its current value of 2,000. If maintaining a clean spatium value requires using mm units, then I and others need pages wider then 2,000mm in order to do piano-roll-style horizontally scrolling scores. I have set my branch's max to 20,000 in the Width spinbox on the pagesettings.ui. That seems like a reasonable max at this time, though it could definitely go as high as 99,999, keeping it at 5 digits. I don't think 9,999 is enough, though it will probably suffice for now if you want to limit it to 4 digits to the left of the decimal.