Support shift and page keyboard steps in NumberSpinner, NumberPicker, and FineCoarseSpinner

[jessegreenberg]

From slack, @pixelzoom asked:

Does NumberSpinner not support keyboardStep and shiftKeyboardStep? Or am I looking in the wrong place?

It currently does not. NumberSpinner sets keyboardStep, shiftKeyboardStep, and pageKeyboardStep to 0 so that all arrow-key input goes through synthetic arrow-button clicks and uses deltaValue. This was our intentional design many years ago.

That makes keyboard input slow for small deltaValue values, and is different from NumberControl. For NumberControl, all keyboard step options are available (although that component has an actual slider).

Should we revisit this design? Should NumberSpinner support keyboardStep and shiftKeyboardStep? If so, what should the arrow buttons look like when keyboard input changes the value by a different amount than clicking the button?

[jessegreenberg]

Discussed with @terracoda -

In agreement with @pixelzoom , NumberSpinner, NumberPicker, and FineCoarseSpinner should support all typical keyboard step options of AccessibleValueHandler. The value changes do not need to be reflected by button presses visually for the various components, but it is icing on the cake so lets keep it when possible.

[jessegreenberg]

For NumberPicker and NumberSpinner, the arrow buttons are likely the smallest delta we would want because that is the precision the user is allowed with mouse presses. So I think the deltaValue should be the value for shiftKeyboardStep. And optionally, you can make keyboardStep and pageKeyboardStep larger.

[jessegreenberg]

Another complexity is the incrementFunction / decrementFunction options. If we modify by alternative keyboard steps, we bypass callbacks. Any rounding or side effects would be skipped. I think that actually blocks this issue. This is already a problem for home/end and could be buggy.

One way around it could be to change the behavior to this:

• make deltaValue and incrementFunction/decrementFunction callbacks mutually exclusive.
• If incrementFunction/decrementFunction callbacks are provided, all key presses use them and you cannot have different steps for page/shift. Home and end are disabled.
• If deltaValue is provided, this is used as the value for shiftKeyboardStep. You can also provide custom keyboardStep and pageKeyboardStep values.

A smaller change for now could be to add page up/page down to the list of keys that trigger the arrow buttons. At least they would do something (even if they do not have a different step size).

@pixelzoom do you have a recommendation for how to proceed with this issue?

[pixelzoom]

Sorry I haven't gotten back to you on this @jessegreenberg. I have a higher-priority QBS deadline, so I'm unlikely to have time for this until >= 8/3/26.