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[WIP/POC] Libscroll Integration #766

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[WIP/POC] Libscroll Integration #766

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32d3a8c
Initial add libscroll
szbergeron Feb 22, 2020
9b80ce6
Merge branch 'master' of https://github.com/revery-ui/revery
szbergeron Feb 22, 2020
fef8273
Push temp changes for input
szbergeron Feb 26, 2020
81223fe
More changes to figure out why build fails
szbergeron Feb 26, 2020
d538a89
Get building with new fields
szbergeron Feb 28, 2020
110bd8f
Precise scroll now (sort of) works
szbergeron Feb 28, 2020
d349008
Change event makeup to be more ideomatic
szbergeron Feb 28, 2020
52c120e
Add changes before pulling in latest master
szbergeron Mar 7, 2020
9e15386
Merge branch 'master' of https://github.com/revery-ui/revery into lib…
szbergeron Mar 7, 2020
f5451c1
Merge branch 'master' of https://github.com/revery-ui/revery into lib…
szbergeron Apr 13, 2020
06c7a9d
Merge branch 'master' of https://github.com/revery-ui/revery into lib…
szbergeron Apr 15, 2020
a1bbd2e
Mostly working
szbergeron Apr 21, 2020
2a12b58
Idle+animating+sampling+bounds/geometry
szbergeron Apr 23, 2020
7acd3f1
cleanup
szbergeron Apr 23, 2020
8863d53
Cleanup
szbergeron Apr 27, 2020
b03b8a3
Avoid libscroll panicking on non-pan-supporting platforms
szbergeron Apr 28, 2020
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3 changes: 2 additions & 1 deletion package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,8 @@
"timber": "glennsl/timber#ae065bb",
"libscroll": "link:../libscroll-re",
"reason-sdl2": "revery-ui/reason-sdl2#a52eee7",
"esy-sdl2": "revery-ui/esy-sdl2#13ac578"
"esy-sdl2": "link:../esy-sdl2",
"reason-sdl2": "link:../reason-sdl2"
},
"devDependencies": {
"ocaml": "~4.8",
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31 changes: 31 additions & 0 deletions src/UI_Components/ScrollView.re
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Expand Up @@ -180,10 +180,41 @@ let%component make =
}
}*/

let scrollForFrameFlip = (timestamp: int) => {
// call into libscroll to sample new position
}

let scroll = (wheelEvent: NodeEvents.mouseWheelEventParams) => {
switch (scrollViewRef^) {
| Some(scrollview) => {//Libscroll.push_pan(scrollview, Libscroll.Axis.Vertical, 10.0, 0)
Log.info("Scrollview existed");

Libscroll.set_source(scrollview, wheelEvent.source);

switch(wheelEvent.deltaX) {
| Some(delta) => {
Libscroll.push_pan(scrollview, Libscroll.Axis.Horizontal, delta, wheelEvent.timestamp);
}
| None => ()
};
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Why is this an option? Wouldn't a delta of 0 be "neutral" and effectively do nothing anyway?

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If it wasn't doing interpolation/prediction then yes, but with both enabled it would mean that acceleration goes to infinity and velocity drops to zero, which would cause weird stuttering if event ordering isn't consistent (and also make it so that fling sometimes wouldn't work)

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@glennsl glennsl Mar 8, 2020 •
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Can you not just weed out the 0s from the interpolation? Or does the None have some other significance?

Like, if it was not an option, would this not be equivalent?

if (wheelEvent.deltaX != 0) {
  Libscroll.push_pan(scrollview, Libscroll.Axis.Horizontal, wheelEvent.deltaX, wheelEvent.timestamp);
}

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Probably, at least on Wayland I never seem to get a zero delta. I still need to figure out how to drag prediction toward zero if velocity drops but no zero event or fling event comes in.

It seems semantically odd to special case zero delta to me but it might be fine

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I find it odd that it needs to be special-cased too, but I would consider both using an option and weeding out 0s special-casing. A delta of 0 seems completely normal to me, so I'm wondering if the problem is somewhere else in the model. Unless you work with imperfect sensor data, which of course happens sometimes.

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If these were polymorphic variants, you wouldn't even need to do the mapping. It's a good use case for it.

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Hm, how would that work? Am not super familiar with them

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Polymorphic variants are the structurally typed equivalents of ordinary variants. Their identity is derived from the type itself, not from any definition. In this case specifically that means SDL and libscroll can share a polymorphic variant type without either library knowing about the other.

By example, it looks like this:

let functionTakingPolyVariant = (poly: [`Number(int) | `Text(string)]) =>
  switch (poly) {
  | `Number(num) => "Number: " ++ string_of_int(num)
  | `Text(text) => "Text: " ++ text
  };

let str = functionTakingPolyVariant(`Number(42));

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Something I'm also remembering here, is that wayland sends events for when the source axis changes for a pan, and that contains an undefined delta. I probably need a way of excluding the delta as well. Might make sense to have a more general axis enum indicating horizontal, vertical, or undefined (undefined meaning the delta is meaningless, and shouldn't be interpreted)

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Looking at how this interacts with scroll stop events makes me want to bring back the guard, for single accesses.

Effectively what I want to encode is the variant/enum

Info(Source)
Fling(Axis, Source) |
Interrupt(Axis, Source) |
Pan(Axis, Source, delta)

in a way that is fairly ideomatic in c and translates well across to reasonml/rust code. What are your opinions on doing that nicely?

I might be overfitting for the linux way of handling input, but afaik it's pretty similar on OSX and can be fully described for the Windows model (just compose multiple events)


switch(wheelEvent.deltaY) {
| Some(delta) => {
Libscroll.push_pan(scrollview, Libscroll.Axis.Vertical, delta, wheelEvent.timestamp);
}
| None => ()
};

switch(wheelEvent.isFling) {
| true => Libscroll.push_fling(scrollview, wheelEvent.timestamp);
| false => ()
};
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@glennsl glennsl Mar 8, 2020 •
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Don't use pattern matching for boolean conditionals. That's what if expressions are for. They communicate intent better, are less noisy, and also shorter in cases like this where you can skip the else branch:

Suggested change
switch(wheelEvent.isFling) {
| true => Libscroll.push_fling(scrollview, wheelEvent.timestamp);
| false => ()
};
if (wheelEvent.isFling) {
Libscroll.push_fling(scrollview, wheelEvent.timestamp);
};

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Ok, will change


switch(wheelEvent.isInterrupt) {
| true => Libscroll.push_interrupt(scrollview, wheelEvent.timestamp);
| false => ()
};

}
| None => Log.error("Scrollview not present on event dispatch");
}
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