OpenSwiftUI
OpenSwiftUI is an OpenSource implementation of Apple's SwiftUI DSL (Domain-specific language).
The project's goal is to stay close to the original API as possible.
Currently, this project is in early development.
Background
Apple introduced SwiftUI at WWDC 19. Since then, developing applications with graphical user interfaces became more comfortable to read, write, and maintain. Unfortunately, the principle "Learn once, apply anywhere" works on Apple platforms, only.
Swift runs on Apple platforms, the web, Linux, Windows, and even on embedded devices.
Wouldn't it be great if you could write GUI based applications with SwiftUI on platforms that run Swift?
SwiftUI on your platform
OpenSwiftUI provides the API — other projects can implement the actual rendering of UI elements for different platforms like Linux, Windows, Embedded, and many more.
SwiftUIEmbedded is one of the first projects that make use of OpenSwiftUI (Demo).
Contributing
Over time and collective guesswork, it should be possible to re-create the complete SwiftUI API from Apple.
Check the Status overview to see what's missing or needs to be completed.
A good starting point is to get familiar with the SwiftUI interface, focus on certain functionality, and try to re-implement it.
A helpful tool is to use reflection (Mirror(reflecting: …)
) to peek into SwiftUI types and instances. This reveals the internal structure of instances (properties, types, names and inheritance).
Once you implemented a missing piece, please feel free to contribute a pull request.
Please note:
Private methods and properties of SwiftUI should be prefixed by an _
(underscore) and marked as public in OpenSwiftUI.
Doing this is necessary because the frontend might need access.
Xcode 11.2 or higher is required.
Status
Views and Controls
Essentials
Status |
Name |
Notes |
✅ |
protocol View |
|
Text
Status |
Name |
Notes |
✅ |
struct Text |
|
❌ |
struct TextField |
|
❌ |
struct SecureField |
|
✅ |
struct Font |
|
Images
Status |
Name |
Notes |
⚠️ |
struct Image |
CGImage not supported |
Buttons
Status |
Name |
Notes |
✅ |
struct Button |
|
❌ |
struct NavigationLink |
|
❌ |
struct MenuButton |
|
❌ |
struct EditButton |
|
❌ |
struct PasteButton |
|
Value Selectors
Status |
Name |
Notes |
❌ |
struct Toggle |
|
⚠️ |
struct Picker |
|
❌ |
struct DatePicker |
|
❌ |
struct Slider |
|
⚠️ |
struct Stepper |
|
Supporting Types
Status |
Name |
Notes |
✅ |
struct ViewBuilder |
|
✅ |
protocol ViewModifier |
|
View Layout and Presentation
Stacks
Status |
Name |
Notes |
✅ |
struct HStack |
|
✅ |
struct VStack |
|
✅ |
struct ZStack |
|
Lists and Scroll Views
Status |
Name |
Notes |
❌ |
struct List |
|
❌ |
protocol DynamicViewContent |
|
✅ |
protocol Identifiable |
Provided by Swift. |
✅ |
struct ForEach |
|
❌ |
struct ScrollView |
|
⚠️ |
enum Axis |
|
Container Views
Status |
Name |
Notes |
❌ |
struct Form |
|
⚠️ |
struct Group |
|
❌ |
struct GroupBox |
|
❌ |
struct Section |
|
Spacer and Dividers
Status |
Name |
Notes |
✅ |
struct Spacer |
|
✅ |
struct Divider |
|
Architectural Views
Status |
Name |
Notes |
❌ |
struct NavigationView |
|
❌ |
struct TabView |
|
❌ |
struct HSplitView |
|
❌ |
struct VSplitView |
|
Presentations
Status |
Name |
Notes |
❌ |
struct Alert |
|
❌ |
struct ActionSheet |
|
Conditionally Visible Items
Status |
Name |
Notes |
✅ |
struct EmptyView |
|
❌ |
struct EquatableView |
|
Infrequently Used Views
Status |
Name |
Notes |
⚠️ |
struct AnyView |
init?(_fromValue value: Any) missing. |
✅ |
struct TupleView |
|
Drawing and Animation
Essentials
Status |
Name |
Notes |
⚠️ |
protocol Shape |
|
Animation
Status |
Name |
Notes |
❌ |
struct Animation |
|
❌ |
protocol Animatable |
|
❌ |
protocol AnimatableModifier |
|
❌ |
func withAnimation<Result>(Animation?, () -> Result) -> Result |
|
❌ |
struct AnimationPair |
|
❌ |
struct EmptyAnimationData |
|
❌ |
struct AnyTransition |
|
Shapes
Status |
Name |
Notes |
⚠️ |
struct Rectangle |
|
✅ |
enum Edge |
|
❌ |
struct RoundedRectangle |
|
⚠️ |
struct Circle |
|
❌ |
struct Ellipse |
|
❌ |
struct Capsule |
|
❌ |
struct Path |
|
Transformed Shapes
Status |
Name |
Notes |
❌ |
protocol InsettableShape |
|
❌ |
struct ScaledShape |
|
❌ |
struct RotatedShape |
|
❌ |
struct OffsetShape |
|
❌ |
struct TransformedShape |
|
Paints, Styles, and Gradients
Status |
Name |
Notes |
✅ |
struct Color |
|
❌ |
struct ImagePaint |
|
❌ |
struct Gradient |
|
❌ |
struct LinearGradient |
|
❌ |
struct AngularGradient |
|
❌ |
struct RadialGradient |
|
❌ |
struct ForegroundStyle |
|
❌ |
struct FillStyle |
|
❌ |
protocol ShapeStyle |
|
❌ |
enum RoundedCornerStyle |
|
❌ |
struct SelectionShapeStyle |
|
❌ |
struct SeparatorShapeStyle |
|
❌ |
struct StrokeStyle |
|
Geometry
Status |
Name |
Notes |
❌ |
struct GeometryProxy |
|
❌ |
struct GeometryReader |
|
❌ |
protocol GeometryEffect |
|
❌ |
struct Angle |
|
❌ |
struct Anchor |
|
❌ |
struct UnitPoint |
|
❌ |
enum CoordinateSpace |
|
❌ |
struct ProjectionTransform |
|
❌ |
protocol VectorArithmetic |
|
State and Data Flow
Bindings
Status |
Name |
Notes |
⚠️ |
struct Binding |
|
Data-Dependent Views
Status |
Name |
Notes |
✅ |
struct State |
|
❌ |
struct ObservedObject |
|
❌ |
struct EnvironmentObject |
|
❌ |
struct FetchRequest |
|
❌ |
struct FetchedResults |
|
⚠️ |
protocol DynamicProperty |
func update() missing. |
Environment Values
Status |
Name |
Notes |
✅ |
struct Environment |
|
✅ |
struct EnvironmentValues |
|
Preferences
Status |
Name |
Notes |
❌ |
protocol PreferenceKey |
|
❌ |
struct LocalizedStringKey |
|
Transactions
Status |
Name |
Notes |
❌ |
struct Transaction |
|
Gestures
Basic Gestures
Status |
Name |
Notes |
❌ |
struct TapGesture |
|
❌ |
struct LongPressGesture |
|
❌ |
struct DragGesture |
|
❌ |
struct MagnificationGesture |
|
❌ |
struct RotationGesture |
|
Combined Gestures
Status |
Name |
Notes |
❌ |
struct SequenceGesture |
|
❌ |
struct SimultaneousGesture |
|
❌ |
struct ExclusiveGesture |
|
Custom Gesture
Status |
Name |
Notes |
❌ |
protocol Gesture |
|
❌ |
struct AnyGesture |
|
Dynamic View Properties
Status |
Name |
Notes |
❌ |
struct GestureState |
|
❌ |
struct GestureStateGesture |
|
Gesture Support
Status |
Name |
Notes |
❌ |
struct GestureMask |
|
❌ |
struct EventModifiers |
|
Legend
Symbol |
Description |
✅ |
Done |
❌ |
Open |
⚠️ |
Incomplete |
Resources
SwiftUI Interface
Compared to what you can see in Xcode, this gist shows you more than just the public interfaces.
It shows private properties, and the body of @inlinable
marked properties, functions, and initializers.
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/SwiftUI.framework/Versions/A/Modules/SwiftUI.swiftmodule/x86_64.swiftinterface
SwiftWebUI
SwiftWebUI is an implementation of SwiftUI for the web by Helge Heß.
This project's goal is focused exclusively on the web.
It deviates a little bit from SwiftUI by taking some shortcuts here and there -- but looks quite complete in functionality and is great for inspiration.
SwiftUI symbols
This command prints the symbol table of SwiftUI via the llvm-mn
utility.
nm -gUj /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/System/Library/Frameworks/SwiftUI.framework/SwiftUI | swift-demangle | sed 's/SwiftUI.//g' | sed 's/Swift.//g'
You can also have a look at this gist instead.
Links
Special thanks
I want to give special thanks to Helge Heß. He created SwiftWebUI, contributed many suggestions to OpenSwiftUI, and helped with insights of his findings.
Contact
License
OpenSwiftUI is released under the MIT License.