c417df08a512adab3f36579a093504952b20b613 — Chris Waldon 4 months ago 3777c48
list: make Manager respect List.ScrollToEnd

This commit adds support for sticking to the end of
the list content across asynchronous insertions of data.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
1 files changed, 14 insertions(+), 0 deletions(-)

M list/manager.go
M list/manager.go => list/manager.go +14 -0
@@ 290,6 290,9 @@ func (m *Manager) Layout(gtx layout.Context, index int) layout.Dimensions {
// the state of the ListManager and List prior to layout. This method should
// be called to provide a layout.List with the length of the underlying list,
// and the layout.List should be passed in as a parameter.
// If the provided layout.List has its ScrollToEnd field set to true, the
// Manager will attempt to respect that when handling content inserted
// asynchronously with Modify() (and similar methods).
func (m *Manager) UpdatedLen(list *layout.List) int {
	// Update the state of the manager in response to any loads.
	select {

@@ 315,11 318,22 @@ func (m *Manager) UpdatedLen(list *layout.List) int {
					newStartIndex, ok = su.SerialToIndex[startSerial]
			// Check whether the final list element is visible before modifying
			// the list's position.
			lastElementVisible := list.Position.First+list.Position.Count == len(m.elements.Elements)

			// Update the list position to match the new set of elements.
			list.Position.First = newStartIndex

			if !su.PreserveListEnd {
				// Ensure that the list considers the possibility that new content
				// has changed the end of the list.
				list.Position.BeforeEnd = true
			} else if lastElementVisible && list.ScrollToEnd {
				// If we are attempting to preserve the end of the list, and the
				// end is currently on the final element, jump to the new final
				// element.
				list.Position.BeforeEnd = false
		m.elements = su.Synthesis