Create a Gtk3Backend for legacy systems

Currently missing window resizing support, pickers, split views, and probably more.

Author: stackotter

Package.swift

@@ -104,6 +104,7 @@ let package = Package(
         .library(name: "CursesBackend", type: libraryType, targets: ["CursesBackend"]),
         .library(name: "QtBackend", type: libraryType, targets: ["QtBackend"]),
         .library(name: "GtkBackend", type: libraryType, targets: ["GtkBackend"]),
+        .library(name: "Gtk3Backend", type: libraryType, targets: ["Gtk3Backend"]),
         .library(name: "DefaultBackend", type: libraryType, targets: ["DefaultBackend"]),
         .library(name: "Gtk", type: libraryType, targets: ["Gtk"]),
         .executable(name: "GtkExample", targets: ["GtkExample"]),
@@ -191,6 +192,10 @@ let package = Package(
             name: "GtkBackend",
             dependencies: ["SwiftCrossUI", "Gtk", "CGtk"]
         ),
+        .target(
+            name: "Gtk3Backend",
+            dependencies: ["SwiftCrossUI", "Gtk3", "CGtk3"]
+        ),
         .systemLibrary(
             name: "CGtk",
             pkgConfig: "gtk4",

Sources/AppKitBackend/AppKitBackend.swift

@@ -230,8 +230,13 @@ public final class AppKitBackend: AppBackend {
         container.removeSubview(child)
     }
 
-    public func setBackgroundColor(ofContainer widget: Widget, to color: Color) {
+    public func createColorableRectangle() -> Widget {
+        let widget = NSView()
         widget.wantsLayer = true
+        return widget
+    }
+
+    public func setColor(ofColorableRectangle widget: Widget, to color: Color) {
         widget.layer?.backgroundColor = color.nsColor.cgColor
     }
 
@@ -560,7 +565,19 @@ public final class AppKitBackend: AppBackend {
         return imageView
     }
 
-    public func updateImageView(_ imageView: Widget, rgbaData: [UInt8], width: Int, height: Int) {
+    public func updateImageView(
+        _ imageView: Widget,
+        rgbaData: [UInt8],
+        width: Int,
+        height: Int,
+        targetWidth: Int,
+        targetHeight: Int,
+        dataHasChanged: Bool
+    ) {
+        guard dataHasChanged else {
+            return
+        }
+
         let imageView = imageView as! NSImageView
         var rgbaData = rgbaData
         let context = CGContext(

Sources/DefaultBackend/DefaultBackend.swift

@@ -4,18 +4,18 @@
 #elseif canImport(GtkBackend)
     import GtkBackend
     public typealias DefaultBackend = GtkBackend
-#elseif canImport(QtBackend)
-    import QtBackend
-    public typealias DefaultBackend = QtBackend
+#elseif canImport(Gtk3Backend)
+    import Gtk3Backend
+    public typealias DefaultBackend = Gtk3Backend
 #elseif canImport(WinUIBackend)
     import WinUIBackend
     public typealias DefaultBackend = WinUIBackend
+#elseif canImport(QtBackend)
+    import QtBackend
+    public typealias DefaultBackend = QtBackend
 #elseif canImport(CursesBackend)
     import CursesBackend
     public typealias DefaultBackend = CursesBackend
-#elseif canImport(LVGLBackend)
-    import LVGLBackend
-    public typealias DefaultBackend = LVGLBackend
 #else
     #error("Unknown backend selected")
 #endif

Sources/Gtk3/Generated/Entry.swift

@@ -892,6 +892,10 @@ public class Entry: Widget, CellEditable, Editable {
 
     @GObjectProperty(named: "max-length") public var maxLength: Int
 
+    /// The text that will be displayed in the #GtkEntry when it is empty
+    /// and unfocused.
+    @GObjectProperty(named: "placeholder-text") public var placeholderText: String
+
     @GObjectProperty(named: "text") public var text: String
 
     @GObjectProperty(named: "visibility") public var visibility: Bool

Sources/Gtk3/Pixbuf.swift

@@ -3,26 +3,17 @@ import CGtk3
 public struct Pixbuf {
     public let pointer: OpaquePointer
 
-    private class DestructorContext {
-        let bufferLength: Int
+    public init(rgbaData: [UInt8], width: Int, height: Int) {
+        let buffer = UnsafeMutableBufferPointer<UInt8>.allocate(capacity: rgbaData.count)
+        memcpy(buffer.baseAddress!, rgbaData, rgbaData.count)
 
-        init(bufferLength: Int) {
-            self.bufferLength = bufferLength
-        }
-    }
-
-    public init(rgbaData: [UInt8], width: Int, height: Int, format: Int, stride: Int) {
-        let bufferLength = rgbaData.count
-        let destructorContext = DestructorContext(
-            bufferLength: bufferLength
-        )
-        let buffer = UnsafeMutableBufferPointer<UInt8>.allocate(capacity: bufferLength)
         let width = gint(width)
         let height = gint(height)
         let hasAlpha = true.toGBoolean()
         let bitsPerSample: gint = 8
         let channels: gint = 4
         let rowStride = channels * gint(width)
+
         pointer = gdk_pixbuf_new_from_data(
             buffer.baseAddress,
             GDK_COLORSPACE_RGB,
@@ -31,15 +22,24 @@ public struct Pixbuf {
             width,
             height,
             rowStride,
-            { buffer, context in
-                let context = Unmanaged<DestructorContext>.fromOpaque(context!).takeRetainedValue()
-                let buffer = UnsafeMutableBufferPointer<UInt8>(
-                    start: buffer,
-                    count: context.bufferLength
-                )
-                buffer.deallocate()
+            { buffer, _ in
+                buffer?.deallocate()
             },
-            Unmanaged.passRetained(destructorContext).toOpaque()
+            nil
+        )
+    }
+
+    private init(pointer: OpaquePointer) {
+        self.pointer = pointer
+    }
+
+    public func scaled(toWidth width: Int, andHeight height: Int) -> Pixbuf {
+        let newPointer = gdk_pixbuf_scale_simple(
+            pointer,
+            gint(width),
+            gint(height),
+            GDK_INTERP_BILINEAR
         )
+        return Pixbuf(pointer: newPointer!)
     }
 }

Sources/Gtk3/Utility/GObjectProperty.swift

@@ -18,7 +18,9 @@ import CGtk3
         wrapped _: ReferenceWritableKeyPath<EnclosingSelf, Value>,
         storage storageKeyPath: ReferenceWritableKeyPath<EnclosingSelf, Self>
     ) -> Value {
-        get { instance.getProperty(named: instance[keyPath: storageKeyPath].name) }
+        get {
+            instance.getProperty(named: instance[keyPath: storageKeyPath].name)
+        }
         set {
             instance.setProperty(named: instance[keyPath: storageKeyPath].name, newValue: newValue)
         }

Sources/Gtk3/Widgets/Label+ManualAdditions.swift

@@ -13,4 +13,13 @@ extension Label {
             gtk_label_set_line_wrap_mode(castedPointer(), newValue.toPangoWrapMode())
         }
     }
+
+    public var wrap: Bool {
+        get {
+            self.getProperty(named: "wrap")
+        }
+        set {
+            self.setProperty(named: "wrap", newValue: newValue)
+        }
+    }
 }