Ebook-viewer: "Zoom step size" values less than 10 don't seem to work

[etc205]

1. Open a book in the viewer, press Esc and click on "Preferences -> Fonts".
2. Set "Zoom step size (%)" to 1 and "Minimum font size (px)" also to 1 there, click on "OK", press Esc.
3. Hit Ctrl+0 to set zoom to 100%.
4. Press Ctrl+- repeatedly. Notice that it takes only around 10 presses to set zoom to its minimum value, while with the "Zoom step size" set to 1 it should probably take around 100 presses.

Calibre version: 7.21,
OS: Windows 10 Home.

[etc205 (etc205)]

I observe the same behavior (Ctrl+- decrements zoom value in about 10% steps) if I set "Zoom step size (%)" at step 2 to any value from 1 to 9.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

[etc205 (etc205)]

Just tried calibre 8.1.1, the issue isn't gone for me - if I set "Zoom step size (%)" to "1", the viewer decrements/increments zoom value in around 10% steps.

[Kovid Goyal (kovid)]

Yes 10% is the minimum increment size. The control was changed to
disallow values below 10, but I guess you can still manually type a
small value, this is really a bug in HTML, I guess I can at least
prevent the small value from being saved.