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Merge pull request #49 from PureSwift/feature/focus-state
Add @focusstate and .focused
2 parents ebbcaae + e7004fb commit 1f889b5

5 files changed

Lines changed: 264 additions & 2 deletions

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‎AndroidSwiftUICore/Sources/AndroidSwiftUICore/FocusState.swift‎

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//
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// FocusState.swift
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// AndroidSwiftUICore
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//
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// Keyboard focus as bindable state. `@FocusState` stores its value in the same
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// persisted box `@State` uses, so it survives re-evaluation; `.focused(_:)`
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// links a field to it, driving focus when Swift writes the value and reporting
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// back when the user moves focus themselves.
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//
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/// A property wrapper holding which field (if any) currently has focus.
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///
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/// Use `Bool` for a single field, or an optional `Hashable` to arbitrate
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/// between several: `@FocusState private var focused: Field?`.
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@propertyWrapper
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public struct FocusState<Value: Hashable>: DynamicProperty {
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internal let box: StateBox<Value>
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public init(wrappedValue value: Value) {
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self.box = StateBox(value)
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}
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public var wrappedValue: Value {
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get { box.value }
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nonmutating set { box.value = newValue }
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}
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public var projectedValue: Binding {
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Binding(box: box)
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}
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/// The `$`-projection `.focused(_:)` accepts. Distinct from `SwiftUI.Binding`
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/// so only focus state can be bound to a field's focus.
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@propertyWrapper
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public struct Binding {
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internal let box: StateBox<Value>
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public var wrappedValue: Value {
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get { box.value }
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nonmutating set { box.value = newValue }
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}
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public var projectedValue: Binding { self }
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}
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}
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public extension FocusState where Value == Bool {
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init() { self.init(wrappedValue: false) }
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}
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public extension FocusState where Value: ExpressibleByNilLiteral {
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init() { self.init(wrappedValue: nil) }
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}
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extension FocusState: _StatePropertyReflectable {
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public var _box: AnyObject { box }
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}
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// MARK: - focused
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public struct _FocusedModifier: RenderModifier, _CallbackModifier {
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/// Whether this field is the one the focus state currently names.
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let isFocused: Bool
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/// Called by the interpreter as the field gains (true) or loses (false) focus.
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let setFocused: (Bool) -> Void
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public var _modifierNode: ModifierNode { ModifierNode(kind: "focused") }
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public func _callbackNode(in context: ResolveContext) -> ModifierNode {
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let id = context.callbacks.register(.bool(setFocused))
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return ModifierNode(kind: "focused", args: [
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"isFocused": .bool(isFocused),
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"onChange": .int(Int(id)),
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])
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}
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}
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public extension View {
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/// Binds this field's focus to a `Bool` focus state.
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func focused(_ condition: FocusState<Bool>.Binding) -> ModifiedContent<Self, _FocusedModifier> {
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modifier(_FocusedModifier(
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isFocused: condition.wrappedValue,
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setFocused: { gained in
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if gained {
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condition.wrappedValue = true
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} else if condition.wrappedValue {
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condition.wrappedValue = false
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}
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}
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))
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}
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/// Binds this field's focus to `value` within a shared focus state.
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func focused<V: Hashable>(
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_ binding: FocusState<V?>.Binding,
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equals value: V
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) -> ModifiedContent<Self, _FocusedModifier> {
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modifier(_FocusedModifier(
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isFocused: binding.wrappedValue == value,
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setFocused: { gained in
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if gained {
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binding.wrappedValue = value
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} else if binding.wrappedValue == value {
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// only surrender focus if it is still ours — a sibling that
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// just took focus must not be cleared by our blur
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binding.wrappedValue = nil
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}
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}
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))
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}
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}

‎AndroidSwiftUICore/Tests/AndroidSwiftUICoreTests/ControlTests.swift‎

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@@ -48,6 +48,64 @@ struct ControlTests {
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#expect(node.props["text"] == .string("Coleman"))
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}
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@Test("focused drives a field's focus and adopts focus the user gives it")
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func focusState() {
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struct Screen: View {
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@State var name = ""
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@FocusState var focused = false
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var body: some View {
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TextField("Name", text: $name).focused($focused)
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}
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}
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let host = ViewHost(Screen())
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var node = host.evaluate()
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#expect(isFocused(node) == false)
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guard let callback = focusCallback(node) else {
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Issue.record("missing focus callback"); return
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}
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// the user tapping the field reports focus back into the state
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host.callbacks.invokeBool(callback, true)
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node = host.evaluate()
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#expect(isFocused(node) == true)
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// and blurring clears it
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host.callbacks.invokeBool(focusCallback(node) ?? callback, false)
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node = host.evaluate()
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#expect(isFocused(node) == false)
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}
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@Test("focused(equals:) arbitrates between fields and a sibling's blur can't steal focus")
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func focusStateEquals() {
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enum Field: Hashable { case first, second }
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struct Screen: View {
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@State var a = ""
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@State var b = ""
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@FocusState var focus: Field? = nil
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var body: some View {
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VStack {
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TextField("A", text: $a).focused($focus, equals: .first)
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TextField("B", text: $b).focused($focus, equals: .second)
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}
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}
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}
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let host = ViewHost(Screen())
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var node = host.evaluate()
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#expect(isFocused(node.children[0]) == false)
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#expect(isFocused(node.children[1]) == false)
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guard let firstCallback = focusCallback(node.children[0]),
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let secondCallback = focusCallback(node.children[1]) else {
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Issue.record("missing focus callbacks"); return
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}
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// second field takes focus
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host.callbacks.invokeBool(secondCallback, true)
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node = host.evaluate()
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#expect(isFocused(node.children[0]) == false)
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#expect(isFocused(node.children[1]) == true)
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// the first field's late blur must NOT clear the second field's focus
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host.callbacks.invokeBool(firstCallback, false)
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node = host.evaluate()
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#expect(isFocused(node.children[1]) == true)
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}
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@Test("Picker emits tagged children and maps the selection string back")
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func picker() {
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struct Screen: View {
@@ -215,3 +273,17 @@ struct ControlTests {
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#expect(node.props["millis"] == .double(changed.timeIntervalSince1970 * 1000))
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}
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}
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/// Whether a field's `focused` modifier currently claims focus.
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private func isFocused(_ node: RenderNode) -> Bool? {
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guard let mod = node.modifiers.first(where: { $0.kind == "focused" }),
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case .bool(let value)? = mod.args["isFocused"] else { return nil }
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return value
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}
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/// The callback a field's `focused` modifier reports focus changes through.
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private func focusCallback(_ node: RenderNode) -> Int64? {
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guard let mod = node.modifiers.first(where: { $0.kind == "focused" }),
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case .int(let id)? = mod.args["onChange"] else { return nil }
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return Int64(id)
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}

‎Demo/App.swiftpm/Sources/Catalog.swift‎

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@@ -30,6 +30,7 @@ struct CatalogEntry: Identifiable {
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CatalogEntry(id: "toggle", title: "Toggle", screen: AnyCatalogScreen(TogglePlayground())),
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CatalogEntry(id: "slider", title: "Slider", screen: AnyCatalogScreen(SliderPlayground())),
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CatalogEntry(id: "textfield", title: "TextField", screen: AnyCatalogScreen(TextFieldPlayground())),
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CatalogEntry(id: "focus", title: "FocusState", screen: AnyCatalogScreen(FocusPlayground())),
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CatalogEntry(id: "picker", title: "Picker", screen: AnyCatalogScreen(PickerPlayground())),
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CatalogEntry(id: "progress", title: "ProgressView", screen: AnyCatalogScreen(ProgressViewPlayground())),
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CatalogEntry(id: "morecontrols", title: "More Controls", screen: AnyCatalogScreen(MoreControlsPlayground())),

‎Demo/App.swiftpm/Sources/FocusPlaygrounds.swift‎

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#if canImport(AndroidSwiftUI)
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import AndroidSwiftUI
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#else
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import SwiftUI
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#endif
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struct FocusPlayground: View {
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private enum Field: Hashable { case name, email }
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@State private var name = ""
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@State private var email = ""
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@FocusState private var focus: Field?
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private var focusLabel: String {
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switch focus {
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case .name: return "Name"
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case .email: return "Email"
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case nil: return "none"
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}
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}
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var body: some View {
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ScrollView {
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VStack(alignment: .leading, spacing: 16) {
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Text("Focused field: \(focusLabel)")
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TextField("Name", text: $name)
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.focused($focus, equals: .name)
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TextField("Email", text: $email)
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.focused($focus, equals: .email)
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// driving focus from Swift
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Button("Focus name") { focus = .name }
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Button("Focus email") { focus = .email }
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Button("Dismiss keyboard") { focus = nil }
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}
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.padding()
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}
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.navigationTitle("FocusState")
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}
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}

‎Demo/swiftui/src/commonMain/kotlin/com/pureswift/swiftui/Render.kt‎

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@@ -131,6 +131,10 @@ import androidx.compose.ui.draw.scale
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import androidx.compose.ui.draw.shadow
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import androidx.compose.ui.graphics.Brush
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import androidx.compose.ui.graphics.Color
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import androidx.compose.ui.focus.FocusRequester
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import androidx.compose.ui.focus.focusRequester
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import androidx.compose.ui.focus.onFocusChanged
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import androidx.compose.ui.platform.LocalFocusManager
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import androidx.compose.ui.graphics.RectangleShape
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import androidx.compose.ui.graphics.vector.ImageVector
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import androidx.compose.foundation.shape.CircleShape
@@ -434,6 +438,27 @@ private fun RenderTextField(node: ViewNode) {
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local = TextFieldValue(swiftText, selection = androidx.compose.ui.text.TextRange(swiftText.length))
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lastSent = swiftText
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}
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// `.focused` binding: Swift drives focus through `isFocused`, and the field
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// reports back when the user moves focus themselves.
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val focus = node.modifiers.firstOrNull { it.kind == "focused" }
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val shouldFocus = focus?.args?.string("isFocused") == "true"
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val onFocusChange = focus?.args?.long("onChange")
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val requester = remember(node.id) { FocusRequester() }
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val focusManager = LocalFocusManager.current
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var hasFocus by remember(node.id) { mutableStateOf(false) }
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var fieldModifier = node.composeModifiers().fillMaxWidth()
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if (focus != null) {
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fieldModifier = fieldModifier
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.focusRequester(requester)
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.onFocusChanged { state ->
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if (state.isFocused != hasFocus) {
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hasFocus = state.isFocused
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onFocusChange?.let { SwiftBridge.sink.invokeBool(it, state.isFocused) }
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}
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}
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}
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OutlinedTextField(
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value = local,
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onValueChange = { v ->
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label = { Text(node.string("placeholder") ?: "") },
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enabled = node.isEnabled(),
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visualTransformation = if (node.bool("secure") == true) PasswordVisualTransformation() else VisualTransformation.None,
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modifier = node.composeModifiers().fillMaxWidth(),
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modifier = fieldModifier,
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)
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if (focus != null) {
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LaunchedEffect(shouldFocus) {
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if (shouldFocus && !hasFocus) requester.requestFocus()
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else if (!shouldFocus && hasFocus) focusManager.clearFocus()
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}
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}
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}
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// Label, then − / + edge buttons pushed to the trailing side.
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"scale", "opacity", "border", "shadow", "clipShape", "onTapGesture", "disabled",
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"font", "fontWeight", "italic", "foregroundColor", "lineLimit", "multilineTextAlignment",
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"tint", "onAppear", "onDisappear", "task", "onChange", "animation", "tag", "tabItem",
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"transition",
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"transition", "focused",
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)
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// Folds a frame entry: fixed size, fill (maxWidth/Height .infinity), bounded

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