b96205cac1
* Use a VStack for the timeline. Replace edge publishers with a binding. * Allow both top and bottom edges to be detected. * Fix scrolling with frame changes.
77 lines
2.8 KiB
Swift
77 lines
2.8 KiB
Swift
//
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// Copyright 2022 New Vector Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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import SwiftUI
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struct VisibleEdgesKey: PreferenceKey {
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static var defaultValue: [VerticalEdge] = []
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static func reduce(value: inout [VerticalEdge], nextValue: () -> [VerticalEdge]) {
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value = nextValue()
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}
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}
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/// A SwiftUI scroll view with the following customisations for a room timeline
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/// - The content is laid out starting at the bottom.
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/// - Top and bottom edge visibility detection for triggering other behaviours.
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struct TimelineScrollView<Content: View>: View {
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@Binding var visibleEdges: [VerticalEdge]
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@ViewBuilder var content: () -> Content
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/// A small threshold added to the edge detection to allow a bit of leniency.
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private let edgeDetectionThreshold: CGFloat = 15
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var body: some View {
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GeometryReader { scrollViewGeometry in
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ScrollView {
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VStack(alignment: .leading, spacing: 0) {
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Spacer()
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content()
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}
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.frame(minHeight: scrollViewGeometry.size.height)
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.background {
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GeometryReader { contentGeometry in
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Color.clear
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.preference(key: VisibleEdgesKey.self,
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value: visibleEdges(of: contentGeometry, in: scrollViewGeometry))
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}
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.onPreferenceChange(VisibleEdgesKey.self) {
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visibleEdges = $0
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}
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}
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}
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}
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}
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func visibleEdges(of contentGeometry: GeometryProxy, in scrollViewGeometry: GeometryProxy) -> [VerticalEdge] {
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let frame = contentGeometry.frame(in: .global)
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let isTopVisible = scrollViewGeometry.frame(in: .global).contains(CGPoint(x: frame.midX, y: frame.minY + edgeDetectionThreshold))
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let isBottomVisible = scrollViewGeometry.frame(in: .global).contains(CGPoint(x: frame.midX, y: frame.maxY - edgeDetectionThreshold))
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switch (isTopVisible, isBottomVisible) {
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case (false, false):
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return []
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case (true, false):
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return [.top]
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case (false, true):
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return [.bottom]
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case (true, true):
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return [.top, .bottom]
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}
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}
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}
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