Unified origin

[xarvic]

This PR removes the viewport_offset property of WidgetPod and changes the ClipBox implementation to use WidgetPod::set_origin instead. This will fix incorrect hot state when scrolling.

TODOs:

• find a way to merge WidgetPod::set_origin and WidgetPod::set_origin_dyn
• decide when hot state should change. I think the current implementation, which is doing it during layout is wrong, since we don't know the new origin in layout.
• change TextBox implementation to use scroll_to_view and LifeCycle::ViewContextChanged instead of manually managing its Scroll widget

[jpochyla]

Hi @xarvic, do you think this is ready to be merged?

[xarvic]

I am still waiting for awnser, how to make WidgetPod::set_origin callable from multiple contexts. TextBox for an example updates its scroll position when it recieves LifeCycle::FocusChanged. Which would otherwise be imposible.
set_viewportoffset solved this by requiering no context at all but this leads to a buggy hot state.
If we could merge #1611, doing this should be straitforward.

[xarvic]

Apart from that the PR is ready for review.

[jpochyla]

I think #1611 was missing a use-case inside Druid, and this is a compelling one!

[xarvic]

@jpochyla the PR is now ready for review.

[liias]

FWIW: I tested this on macOS and this fixes the incorrect hot state while scrolling.

[xStrom]

Thanks for taking this on and sorry for letting it sit so long!

Given that this changes quite a bit of code it's going to take several rounds of review. I'm going to start off with a simple surface level review of small stuff that stuck out as I went over the changes.

Next I will dig deeper to understand what is even going on here. 😄

[xStrom]

Thanks for investing your time into making the adjustments. I have reviewed the latest commit and have a few more minor notes.

I've also been playing around with the code a bit, but a more thorough review of the substance here isn't ready yet.

[xStrom]

Okay, here's my first pass on the code. One interesting thing is that it's looking like there's increasingly fewer reasons to have the context trait changes. We'll see about that, for now can just look over the stuff I commented in this batch.

[xStrom]

Thanks for your continued effort on this! I think this is ready for merge.

[xarvic]

And thank you for the thorough review :)

[jpochyla]

Thanks a lot Kaur!