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Adds bridged SwiftUI body Observation via withObservationTracking #251

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Adds bridged SwiftUI body Observation via withObservationTracking #251

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040fc72
Adds brdiged SwiftUI body Observation via withObservationTracking
woodymelling May 21, 2026
bbff959
Render bridged SwiftUI views atomically
woodymelling May 21, 2026
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75 changes: 65 additions & 10 deletions Sources/SkipSyntax/Kotlin/KotlinBridgeToKotlinVisitor.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ final class KotlinBridgeToKotlinVisitor {
private let includesUI: Bool
private var swiftDefinitions: [SwiftDefinition] = []
private var cdeclFunctions: [CDeclFunction] = []
private var needsObservationImport = false

init?(for syntaxTree: KotlinSyntaxTree, options: KotlinBridgeOptions, translator: KotlinTranslator) {
guard syntaxTree.isBridgeFile, !syntaxTree.root.isInIfSkipBlock, let codebaseInfo = translator.codebaseInfo else {
Expand Down Expand Up @@ -121,8 +122,12 @@ final class KotlinBridgeToKotlinVisitor {
}
let swiftDefinitions = self.swiftDefinitions
let cdeclFunctions = self.cdeclFunctions
let needsObservationImport = self.needsObservationImport
let outputNode = SwiftDefinition { output, indentation, _ in
output.append("import SkipBridge\n\n")
if needsObservationImport, !importDeclarations.contains(where: { $0.modulePath == ["Observation"] }) {
output.append("import Observation\n")
}
for importDeclaration in importDeclarations {
let path = importDeclaration.modulePath.joined(separator: ".")
output.append(indentation).append("import ").append(path).append("\n")
Expand Down Expand Up @@ -1047,6 +1052,9 @@ final class KotlinBridgeToKotlinVisitor {
}

classDeclaration.inherits = mappedInherits
if swiftUIType == .view {
classDeclaration.inherits.append(.named("skip.ui.Renderable", []))
}
classDeclaration.extras = Self.bridgeExtras(classDeclaration.extras)
if clearSuperclassCall {
classDeclaration.superclassCall = nil
Expand Down Expand Up @@ -1757,10 +1765,34 @@ final class KotlinBridgeToKotlinVisitor {
private func swiftUIBodyImplementation(_ swiftUIType: TypeSignature.SwiftUIType, for classDeclaration: KotlinClassDeclaration, visibility: Modifiers.Visibility) -> (statements: [KotlinStatement], swift: [String], cdeclFunctions: [CDeclFunction]) {
let classType = ClassType(classDeclaration)
let externalName = "Swift_composableBody"
let externalParameters = swiftUIType == .view || swiftUIType == .toolbarContent ? classType.peerExternalParameter : "\(classType.peerExternalParameter), content: skip.ui.View"
var externalParameters = swiftUIType == .view || swiftUIType == .toolbarContent ? classType.peerExternalParameter : "\(classType.peerExternalParameter), content: skip.ui.View"
externalParameters += ", onChange: () -> Unit"
let externalArguments = swiftUIType == .view || swiftUIType == .toolbarContent ? classType.peerExternalArgument : "\(classType.peerExternalArgument), content"
let externalSourceCode = "private external fun \(externalName)(\(externalParameters)): skip.ui.View?"
let functionSourceCode = "return skip.ui.ComposeBuilder { composectx: skip.ui.ComposeContext -> \(externalName)(\(externalArguments))?.Compose(composectx) ?: skip.ui.ComposeResult.ok }"
let bodyFunctionSourceCode: [String]
let renderFunctionSourceCode: [String]?
if swiftUIType == .view {
bodyFunctionSourceCode = [
"return skip.ui.ComposeBuilder { composectx: skip.ui.ComposeContext ->",
" Render(composectx)",
" skip.ui.ComposeResult.ok",
"}",
]
renderFunctionSourceCode = [
"val observationInvalidation = androidx.compose.runtime.remember { androidx.compose.runtime.mutableStateOf(0) }",
"observationInvalidation.value",
"\(externalName)(\(externalArguments), onChange = { observationInvalidation.value += 1 })?.Compose(context)",
]
} else {
bodyFunctionSourceCode = [
"return skip.ui.ComposeBuilder { composectx: skip.ui.ComposeContext ->",
" val observationInvalidation = androidx.compose.runtime.remember { androidx.compose.runtime.mutableStateOf(0) }",
" observationInvalidation.value",
" \(externalName)(\(externalArguments), onChange = { observationInvalidation.value += 1 })?.Compose(composectx) ?: skip.ui.ComposeResult.ok",
"}",
]
renderFunctionSourceCode = nil
}
let externalFunctionDeclaration = KotlinRawStatement(sourceCode: externalSourceCode)

let functionDeclaration = KotlinFunctionDeclaration(name: "body")
Expand All @@ -1770,10 +1802,25 @@ final class KotlinBridgeToKotlinVisitor {
functionDeclaration.returnType = .skipUIView
functionDeclaration.modifiers = Modifiers(visibility: .public, isOverride: true)
functionDeclaration.extras = .singleNewline
functionDeclaration.body = KotlinCodeBlock(statements: [KotlinRawStatement(sourceCode: functionSourceCode)])
functionDeclaration.body = KotlinCodeBlock(statements: bodyFunctionSourceCode.map { KotlinRawStatement(sourceCode: $0) })
functionDeclaration.body?.disallowSingleStatementAppend = true
functionDeclaration.parent = classDeclaration

let renderFunctionDeclaration: KotlinFunctionDeclaration?
if let renderFunctionSourceCode {
let declaration = KotlinFunctionDeclaration(name: "Render")
declaration.parameters = [Parameter<KotlinExpression>(externalLabel: "context", declaredType: .named("skip.ui.ComposeContext", []))]
declaration.modifiers = Modifiers(visibility: .public, isOverride: true)
declaration.attributes.attributes.append(Attribute(signature: .named("androidx.compose.runtime.Composable", [])))
declaration.extras = .singleNewline
declaration.body = KotlinCodeBlock(statements: renderFunctionSourceCode.map { KotlinRawStatement(sourceCode: $0) })
declaration.body?.disallowSingleStatementAppend = true
declaration.parent = classDeclaration
renderFunctionDeclaration = declaration
} else {
renderFunctionDeclaration = nil
}

var swift: [String] = []
let visibilityString = visibility.swift(suffix: " ")
if swiftUIType == .view || swiftUIType == .toolbarContent {
Expand All @@ -1789,30 +1836,38 @@ final class KotlinBridgeToKotlinVisitor {
if swiftUIType != .view && swiftUIType != .toolbarContent {
cdeclParameters.append(TypeSignature.Parameter(label: "content", type: .javaObjectPointer))
}
cdeclParameters.append(TypeSignature.Parameter(label: "onChange", type: .javaObjectPointer))
let cdeclSignature: TypeSignature = .function(cdeclParameters, .optional(.javaObjectPointer), APIFlags(), nil)
var cdeclSource = classType.peerSwiftAssignment(to: classDeclaration, optionsString: "[]")
let bodyInvocation: String
let bodyExpression: String
if swiftUIType == .view || swiftUIType == .toolbarContent {
if classType == .generic {
bodyInvocation = "let body = \(classType.peerSwiftTarget).body()"
bodyExpression = "\(classType.peerSwiftTarget).body()"
} else {
bodyInvocation = "let body = \(classType.peerSwiftTarget).body"
bodyExpression = "\(classType.peerSwiftTarget).body"
}
} else {
cdeclSource.append("let content_swift = JavaBackedView(content)!")
if classType == .generic {
bodyInvocation = "let body = \(classType.peerSwiftTarget).body(content_swift)"
bodyExpression = "\(classType.peerSwiftTarget).body(content_swift)"
} else {
bodyInvocation = "let body = \(classType.peerSwiftTarget).body(content: content_swift)"
bodyExpression = "\(classType.peerSwiftTarget).body(content: content_swift)"
}
}
needsObservationImport = true
cdeclSource.append("let onChange_swift = SwiftClosure0.closure(forJavaObject: onChange, options: [])! as @Sendable () -> Void")
cdeclSource.append("return SkipBridge.assumeMainActorUnchecked {")
cdeclSource.append(1, bodyInvocation)
cdeclSource.append(1, "let body = withObservationTracking {")
cdeclSource.append(2, "return \(bodyExpression)")
cdeclSource.append(1, "} onChange: {")
cdeclSource.append(2, "onChange_swift()")
cdeclSource.append(1, "}")
cdeclSource.append(1, "return ((body as? SkipUIBridging)?.Java_view as? JConvertible)?.toJavaObject(options: [])")
cdeclSource.append("}")
let cdeclFunction = CDeclFunction(name: cdeclName, cdecl: cdecl, signature: cdeclSignature, body: cdeclSource)

return ([functionDeclaration, externalFunctionDeclaration], swift, [cdeclFunction])
let declarations = [functionDeclaration] + (renderFunctionDeclaration.map { [$0] } ?? []) + [externalFunctionDeclaration]
return (declarations, swift, [cdeclFunction])
}
}

Expand Down
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