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Merge pull request #1 from swiftui-library/feat/snap-to-center
Feat/snap to center
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‎README.md

+26-17
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@@ -6,47 +6,56 @@ https://user-images.githubusercontent.com/8763719/131393666-6af82d2a-998e-4dba-a
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## Getting Started
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Using `SnapToScroll` is straightforward. There's only two requirements:
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Using `SnapToScroll` is straightforward. There's just three steps.
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1. Replace `HStack` with `HStackSnap`
12-
2. Add `GeometryReaderOverlay` to your view.
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1. Import `SnapToScroll`
12+
2. Replace `HStack` with `HStackSnap`
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3. Add `.snapAlignmentHelper` to your view.
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An example:
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```swift
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import SnapToScroll // Step 1
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...
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HStackSnap(leadingOffset: 16) {
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HStackSnap(alignment: .center(32)) { // Step 2
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ForEach(modelArray) { viewModel in
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ForEach(myModels) { viewModel in
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myView(viewModel: viewModel)
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.frame(maxWidth: 250)
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.overlay(GeometryReaderOverlay(id: viewModel.id))
25-
}
26-
}
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MyView(
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selectedIndex: $selectedIndex,
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viewModel: viewModel
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)
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.snapAlignmentHelper(id: viewModel.id) // Step 3
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}
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}
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```
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For more examples, see `SnapToScrollDemo/ContentView.swift`.
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## Options
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## Configuration
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`HStackSnap` comes with two customizable properties:
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- `leadingOffset`: The leading padding you'd like each element to snap to.
37-
- `coordinateSpace`: Option to set custom name for the coordinate space, in the case you're using multiple `HStackSnap`s of various sizes.
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- `alignment`: The way you'd like your elements to be arranged.
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- `leading(CGFloat)`: Aligns your child views to the leading edge of `HStackSnap`. This configuration supports elements of various sizes, so long as they don't take up all available horizontal space (which would extend beyond the screen). Use the value to set the size of the left offset.
42+
- `center(CGFloat)`: Automatically aligns your child view to the center of the screen, using the offset value you've provided. This is accomplished with inside of the `.snapAlignmentHelper` which sets the frame width based on the available space. Note that setting your own width elsewhere may produce unexpected layouts.
43+
- `coordinateSpace`: Option to set custom name for the coordinate space, in the case you're using multiple `HStackSnap`s of various sizes. If you use this, set the same value in `.snapAlignmentHelper`.
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`.snapAlignmentHelper` comes with two options as well:
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- `id`: Required. A unique ID for the element.
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- `coordinateSpace`: Same as above.
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## Limitations
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1. If your child views are designed to take up all available horizontal space, they'll expand beyond the visible view. Prevent this with `.frame(maxWidth: x)`
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2. `HStackSnap` is currently designed to work with static content.
43-
3. At the moment, `HStackSnap` offers snapping to the leading edge only. If you'd like to offer a PR that adds support for `.center` and / or `.trailing`, I'd love to look it over!
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- `HStackSnap` is currently designed to work with static content.
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## How it Works
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At render, `HStackSnap` reads the frame data of each child element and calculates the `scrollOffset` each element should use. Then, on `DragGesture.onEnded`, the nearest snap location is calculated, and the scroll offset is set to this point.
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Read through `HStackSnap` for more details.
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Read through `HStackSnap.swift` and `Views/HStackSnapCore.swift` for more details.
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## Credits
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‎SnapToScrollDemo/SnapToScrollDemo.xcodeproj/project.pbxproj

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objects = {
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/* Begin PBXBuildFile section */
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840130AF26DFB8DD00E4A8A3 /* GettingStartedModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840130AE26DFB8DC00E4A8A3 /* GettingStartedModel.swift */; };
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840130B126DFB93400E4A8A3 /* GettingStartedView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840130B026DFB93400E4A8A3 /* GettingStartedView.swift */; };
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840130B326DFC27700E4A8A3 /* Example3ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840130B226DFC27700E4A8A3 /* Example3ContentView.swift */; };
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840130B526DFC2FB00E4A8A3 /* Example2ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840130B426DFC2FB00E4A8A3 /* Example2ContentView.swift */; };
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840130B726DFC33100E4A8A3 /* Example1ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840130B626DFC33100E4A8A3 /* Example1ContentView.swift */; };
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841B0F8326DD39A4008A436B /* TripTupleView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 841B0F8226DD39A4008A436B /* TripTupleView.swift */; };
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84B568D926DD271000D37CF2 /* TagView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84B568D826DD271000D37CF2 /* TagView.swift */; };
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84B568DB26DD309400D37CF2 /* Example1HeaderView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84B568DA26DD309400D37CF2 /* Example1HeaderView.swift */; };
@@ -23,6 +28,11 @@
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/* End PBXBuildFile section */
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/* Begin PBXFileReference section */
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840130AE26DFB8DC00E4A8A3 /* GettingStartedModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GettingStartedModel.swift; sourceTree = "<group>"; };
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840130B026DFB93400E4A8A3 /* GettingStartedView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GettingStartedView.swift; sourceTree = "<group>"; };
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840130B226DFC27700E4A8A3 /* Example3ContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Example3ContentView.swift; sourceTree = "<group>"; };
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840130B426DFC2FB00E4A8A3 /* Example2ContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Example2ContentView.swift; sourceTree = "<group>"; };
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840130B626DFC33100E4A8A3 /* Example1ContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Example1ContentView.swift; sourceTree = "<group>"; };
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841B0F8226DD39A4008A436B /* TripTupleView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TripTupleView.swift; sourceTree = "<group>"; };
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84B568D826DD271000D37CF2 /* TagView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TagView.swift; sourceTree = "<group>"; };
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84B568DA26DD309400D37CF2 /* Example1HeaderView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Example1HeaderView.swift; sourceTree = "<group>"; };
@@ -52,9 +62,20 @@
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/* End PBXFrameworksBuildPhase section */
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/* Begin PBXGroup section */
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840130AD26DFB8C800E4A8A3 /* Example3 */ = {
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isa = PBXGroup;
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children = (
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840130B226DFC27700E4A8A3 /* Example3ContentView.swift */,
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840130AE26DFB8DC00E4A8A3 /* GettingStartedModel.swift */,
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840130B026DFB93400E4A8A3 /* GettingStartedView.swift */,
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);
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path = Example3;
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sourceTree = "<group>";
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};
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84B568D626DD26A800D37CF2 /* Example1 */ = {
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isa = PBXGroup;
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children = (
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840130B626DFC33100E4A8A3 /* Example1ContentView.swift */,
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84C99CD726D99BA100C1D5C4 /* TagModel.swift */,
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84B568D826DD271000D37CF2 /* TagView.swift */,
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84B568DA26DD309400D37CF2 /* Example1HeaderView.swift */,
@@ -68,6 +89,7 @@
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84B568DD26DD351900D37CF2 /* TripModel.swift */,
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84B568DF26DD37A600D37CF2 /* TripView.swift */,
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841B0F8226DD39A4008A436B /* TripTupleView.swift */,
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840130B426DFC2FB00E4A8A3 /* Example2ContentView.swift */,
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);
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path = "Example 2";
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sourceTree = "<group>";
@@ -97,6 +119,7 @@
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84D9FA3526D9753600F87EF5 /* AppDelegate.swift */,
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84B568D626DD26A800D37CF2 /* Example1 */,
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84B568DC26DD311F00D37CF2 /* Example 2 */,
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840130AD26DFB8C800E4A8A3 /* Example3 */,
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84D9FA3726D9753600F87EF5 /* SceneDelegate.swift */,
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84D9FA3926D9753600F87EF5 /* ContentView.swift */,
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);
@@ -204,10 +227,15 @@
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files = (
205228
84B568DB26DD309400D37CF2 /* Example1HeaderView.swift in Sources */,
206229
84D9FA3626D9753600F87EF5 /* AppDelegate.swift in Sources */,
230+
840130AF26DFB8DD00E4A8A3 /* GettingStartedModel.swift in Sources */,
207231
841B0F8326DD39A4008A436B /* TripTupleView.swift in Sources */,
232+
840130B726DFC33100E4A8A3 /* Example1ContentView.swift in Sources */,
208233
84B568D926DD271000D37CF2 /* TagView.swift in Sources */,
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840130B326DFC27700E4A8A3 /* Example3ContentView.swift in Sources */,
209235
84B568E026DD37A600D37CF2 /* TripView.swift in Sources */,
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840130B526DFC2FB00E4A8A3 /* Example2ContentView.swift in Sources */,
210237
84B568DE26DD351900D37CF2 /* TripModel.swift in Sources */,
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840130B126DFB93400E4A8A3 /* GettingStartedView.swift in Sources */,
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84D9FA3826D9753600F87EF5 /* SceneDelegate.swift in Sources */,
212240
84D9FA3A26D9753600F87EF5 /* ContentView.swift in Sources */,
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84C99CD826D99BA100C1D5C4 /* TagModel.swift in Sources */,

‎SnapToScrollDemo/Sources/ContentView.swift

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@@ -5,55 +5,28 @@ import SwiftUI
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66
struct ContentView: View {
77

8-
@State var items = [("one", 1), ("two", 2), ("three", 3), ("four", 4), ("five", 5), ("six", 6)]
9-
108
var body: some View {
119
VStack {
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ScrollView {
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1513
VerticalSpace
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17-
VStack {
18-
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LargeHeader(text: "Example 1")
20-
21-
Example1HeaderView()
22-
23-
// Don't forget to attach GeometryReaderOverlay!
24-
HStackSnap(leadingOffset: 16) {
25-
26-
ForEach(TagModel.exampleModels) { viewModel in
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28-
TagView(viewModel: viewModel)
29-
.overlay(GeometryReaderOverlay(id: viewModel.id))
30-
}
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}.padding(.top, 4)
32-
}
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LargeHeader(text: "Example 1")
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17+
Example1ContentView()
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3419
VerticalSpace
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36-
VStack {
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38-
LargeHeader(text: "Example 2")
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40-
Text("Explore Nearby")
41-
.font(.system(size: 22, weight: .semibold, design: .rounded))
42-
.frame(maxWidth: .infinity, alignment: .leading)
43-
.padding([.top, .leading], 16)
44-
45-
HStackSnap(leadingOffset: 16) {
46-
47-
ForEach(TripTupleModel.exampleModels) { viewModel in
21+
LargeHeader(text: "Example 2")
22+
23+
Example2ContentView()
24+
25+
VerticalSpace
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49-
TripTupleView(viewModel: viewModel)
50-
.frame(maxWidth: 250)
51-
.overlay(GeometryReaderOverlay(id: viewModel.id))
52-
}
53-
}
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.frame(height: 200)
55-
.padding(.top, 4)
56-
}
27+
LargeHeader(text: "Example 3")
28+
29+
Example3ContentView()
5730
}
5831
}
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.preferredColorScheme(.light)

‎SnapToScrollDemo/Sources/Example 2/Example2ContentView.swift

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import SwiftUI
2+
import SnapToScroll
3+
4+
// MARK: - Example2ContentView
5+
6+
struct Example2ContentView: View {
7+
var body: some View {
8+
9+
VStack {
10+
11+
Text("Explore Nearby")
12+
.font(.system(size: 22, weight: .semibold, design: .rounded))
13+
.frame(maxWidth: .infinity, alignment: .leading)
14+
.padding([.top, .leading], 16)
15+
16+
HStackSnap(alignment: .leading(16)) {
17+
18+
ForEach(TripTupleModel.exampleModels) { viewModel in
19+
20+
TripTupleView(viewModel: viewModel)
21+
.frame(maxWidth: 250)
22+
.snapAlignmentHelper(id: viewModel.id)
23+
}
24+
} onSwipe: { index in
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26+
print(index)
27+
}
28+
.frame(height: 130)
29+
.padding(.top, 4)
30+
}
31+
}
32+
}
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34+
// MARK: - Example2ContentView_Previews
35+
36+
struct Example2ContentView_Previews: PreviewProvider {
37+
static var previews: some View {
38+
Example2ContentView()
39+
}
40+
}

‎SnapToScrollDemo/Sources/Example1/Example1ContentView.swift

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//
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// Example2ContentView.swift
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// Example2ContentView
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//
5+
// Created by Trent Guillory on 9/1/21.
6+
//
7+
8+
import SwiftUI
9+
import SnapToScroll
10+
11+
struct Example1ContentView: View {
12+
var body: some View {
13+
14+
VStack {
15+
16+
Example1HeaderView()
17+
18+
// Don't forget to attach snapAlignmentHelper!
19+
HStackSnap(alignment: .leading(16)) {
20+
21+
ForEach(TagModel.exampleModels) { viewModel in
22+
23+
TagView(viewModel: viewModel)
24+
.snapAlignmentHelper(id: viewModel.id)
25+
}
26+
}.padding(.top, 4)
27+
}
28+
}
29+
}
30+
31+
struct Example1ContentView_Previews: PreviewProvider {
32+
static var previews: some View {
33+
Example2ContentView()
34+
}
35+
}

‎SnapToScrollDemo/Sources/Example3/Example3ContentView.swift

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import SnapToScroll
2+
import SwiftUI
3+
4+
// MARK: - Example3ContentView
5+
6+
struct Example3ContentView: View {
7+
8+
// MARK: Internal
9+
10+
var body: some View {
11+
12+
VStack {
13+
14+
Text("Getting Started")
15+
.font(.system(size: 22, weight: .semibold, design: .rounded))
16+
.foregroundColor(.white)
17+
.frame(maxWidth: .infinity, alignment: .leading)
18+
.padding([.top, .leading], 32)
19+
20+
HStackSnap(alignment: .center(32)) {
21+
22+
ForEach(GettingStartedModel.exampleModels) { viewModel in
23+
24+
GettingStartedView(
25+
selectedIndex: $selectedGettingStartedIndex,
26+
viewModel: viewModel)
27+
.snapAlignmentHelper(id: viewModel.id)
28+
}
29+
} onSwipe: { index in
30+
31+
selectedGettingStartedIndex = index
32+
}
33+
.frame(height: 200)
34+
.padding(.top, 4)
35+
}
36+
.padding([.top, .bottom], 64)
37+
.background(LinearGradient(
38+
colors: [Color("Cream"), Color("LightPink")],
39+
startPoint: .top,
40+
endPoint: .bottom))
41+
}
42+
43+
// MARK: Private
44+
45+
@State private var selectedGettingStartedIndex: Int = 0
46+
}
47+
48+
// MARK: - Example3ContentView_Previews
49+
50+
struct Example3ContentView_Previews: PreviewProvider {
51+
static var previews: some View {
52+
Example3ContentView()
53+
}
54+
}

‎SnapToScrollDemo/Sources/Example3/GettingStartedModel.swift

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1+
import Foundation
2+
3+
struct GettingStartedModel: Identifiable {
4+
5+
static let exampleModels: [GettingStartedModel] = [
6+
.init(
7+
id: 0,
8+
systemImage: "camera.aperture",
9+
title: "Snap a Pic",
10+
body: "We feature the viewfinder front and center in this throwback app."),
11+
.init(
12+
id: 1,
13+
systemImage: "camera.filters",
14+
title: "Filter it Up",
15+
body: "Add filters - from detailed colorization to film effects."),
16+
.init(
17+
id: 2,
18+
systemImage: "paperplane",
19+
title: "Send It",
20+
body: "Share your photos with your contacts. Or the entire world."),
21+
.init(
22+
id: 3,
23+
systemImage: "sparkles",
24+
title: "Be Awesome",
25+
body: "You're clearly already doing this. Just wanted to remind you. 😉"),
26+
]
27+
28+
let id: Int
29+
let systemImage: String
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let title: String
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let body: String
32+
}

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