scrolling fast on web show bad index item

[rmasarovic]

Hi i try your example and when i scroll fast with mouse on web i see different item on screen and different values are printing on observer update

this is screen

and this is last print on console
firstChild.index -- 14
displaying -- [14]
item - 14 - -20 - 456
visible -- true
firstChild.index -- 24
displaying -- [24]
item - 24 - -20 - 456

any idea what is wrong?

[LinXunFeng]

Thx for feedback, please upgrade to version 1.13.1, or pull the latest code.

[rmasarovic]

i try it and when i using mouse wheel this index dont work

firstChild.index -- 51
displaying -- [51, 52, 53, 54, 55, 56, 57, 58]
item - 51 - -8.336594410433463 - 474.33659441043346
item - 52 - 46.66340558956654 - 389.33659441043346
item - 53 - 131.66340558956654 - 334.33659441043346
item - 54 - 186.66340558956654 - 249.33659441043346
item - 55 - 271.66340558956654 - 194.33659441043346
item - 56 - 326.66340558956654 - 109.33659441043346
item - 57 - 411.66340558956654 - 54.33659441043346
item - 58 - 466.66340558956654 - -30.663405589566537

[LinXunFeng]

It works fine on macos, this problem seems to only occur on windows. 🧐

[rmasarovic]

hm i try it on mac and some

i think this edge-case depence when use mouse wheel scroller

[LinXunFeng]

I have tried to fix this problem on the fix_observe_web branch and tested it, you can try it again after pulling the code.

[rmasarovic]

I tried it and out of 100 attempts, it failed 1 time, but I haven't find the pattern yet, but still it's perfect now.

What else did I notice when I scroll a lot and then I go away from the page, the observer keeps printing values to console. it normal behavior?

[LinXunFeng]

Yes, this is normal behavior, because there was a lot of printing in the Example, and the IDE did not process it in time.

This bug is caused by scrolling in Flutter Web with mouse wheel is not smooth.

Related issues:

• #78708
• #78634

The problem has not been solved yet, so for now, i use delay to solve it.

The key code is here: observer_widget.dart#L148

Future.delayed(const Duration(microseconds: 1), () {

Could you please replace microseconds with milliseconds in this line of code, and try it again?

Future.delayed(const Duration(milliseconds: 1), () {

[rmasarovic]

i try it and maybe this is the best solution for now

[LinXunFeng]

Thank you, version 1.13.2 has been released to fix the above issues.