This commit is based on a patch by Elias that improved drag scrolling
on the scrollbar by locking some parameters of the math at the start
of the scroll event.
I discovered while playing with that implementation that there was
an even simpler approach within his changeset. You can actually
use no information other than the delta between the current and
previous frame's scroll position to compute the scroll distance.
By simplifying the math to rely on no other inputs, the jitter that
we've been fighting simply disappears (it came from other inputs).
Turns out my attempts to make the logic smart were the problem.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit fixes a problem that could force the scroll indicator to
lay itself out outside of its configured bounds. This occurred when
the scroll indicator size was increased to meet the minimum size
configured on the style type while the scrollbar was near the end
of the list. The increased size did not take the start position
of the scroll indicator into account, which made the indicator begin
in the correct place, but extend beyond the end of its track.
This commit alters the logic to ensure that the scroll indicator can
never extend beyond the end of its track.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
Previously, it was possible for fromListPosition to return
an end coordinate greater than 1, which would make scroll
indicators using those coordinates render beyond the
boundaries of their scroll tracks. One could argue that
this is a bug in the scroll indicator, but I don't think
this method should return data outside of its documented
range.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit ensures that the dimensions returned by material.List
include the size of the scrollbar when the scrollbar is set to
the Occupy AnchorStrategy.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This change ensures that the scrollbar anchors to the proper edge of the
content even when the list was drawn with a zero minimum constraint.
Without this, the layout.Direction used to anchor the scrollbar will choose
to use the minimum size and anchor it to the opposite edge of the content.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
The scrollbar implementation prior to this change only adjusted
list.Position.Offset. This works in all circumstances except when
list.Position.BeforeEnd=false. If the position indicates that the
scroll position is at the end of the list, the offset is ignored.
This change ensures that manually dragging the scrollbar always
causes BeforeEnd to be set to true. If the drag ends with the
scrollbar at the end of the list, BeforeEnd will be set
automatically by the next list.Layout call, so this doesn't
prevent the list from optimizing for that case in general.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
To use these lists instead of layout.List, callers simply need to
change declarations of layout.List to widget.List, and to change
calls to layout.List.Layout to material.List(th,&list).Layout.
So this:
var list layout.List
list.Layout(gtx, 10, func(gtx C, index int) D {
return material.Body1(th, fmt.Sprintf("%d", index)).Layout(gtx)
})
Becomes:
var list widget.List
material.List(th, &list).Layout(gtx, 10, func(gtx C, index int) D {
return material.Body1(th, fmt.Sprintf("%d", index)).Layout(gtx)
})
Naturally, the material.ListStyle type supports tweaking the scrollbar's
appearance and behavior.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
Elias Naur