[scrollable_positioned_list] Scroll by mouse wheel speedup for desktop apps

[nikitatg]

Description

In desktop app (Windows and Linux) scrolling with mouse wheel was too slow. There is option to add some extra scroll speed that will be applied to any scroll tick. This is handled in the body of the scroll listener _ScrollablePositionedListState._speedUpScrollListener() which in turn assigned to both primary.scrollController and secondary.scrollController

When scrolling is done on touchscreen mentioned method just do return; and does not affect kinetic scrolling (tested on Windows notebook's touchscreen).

Scrolling device is recognized by Listener at line 371.

• Handler onPointerHover intended to detect that it's NOT touchscreen because is called only when cursor hovers over view which is only possible with mouse (and maybe trackpad).
• Empirically found that onPointerMove called only when dragging view with a finger and therefore are a good way to detect touchscreen.

The disadvantage for now is that there is no way to recognize if the touchpad or mouse caused scrolling (both are PointerDeviceKind.mouse) and therefore scrolling with touchpad became too fast (but only when extraScrollSpeed was passed).

Related Issues

#406

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[AmirhosseinShk]

Hi , dear google we need this feature ASAP , our customers really need speed up scroll on message list with mouse wheel. we hope this branch merge ASAP.
best regards

[nikitatg]

After update Flutter to 3.3.* there appears a little issue with scrolling by notebook's touchpad. Difficult to explain but sometimes touchpad still recognized as mouse, and sometimes as trackpad. But it not makes this PR unusable.

If it's important for your project(s) better try this feature on some notebook for a test

[nikitatg]

I've fixed mentioned above but tested only on Flutter 3.3.5. Now should not be felt changing scroll devices

Sadly, haven't enough time to test this on earlier Flutter versions