Add canvas detection (devicekit#303)

* Add canvas detection

* Move isCanvas to include it on tvOS and watchOS.

* Remove additional whitespace.

* Add optional return value to isCanvas and return nil if the current instance isn't the current device.

* Fix broken test on non iOS/iPadOS platforms.

Co-authored-by: Zandor Smith <info@zsinfo.nl>

Source/Device.generated.swift

@@ -1055,6 +1055,16 @@ public enum Device {
     }
   #endif
 
+  /// Returns whether the current device is a SwiftUI preview canvas
+  public var isCanvas: Bool? {
+    guard isCurrent else { return nil }
+    #if DEBUG
+      return ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1"
+    #else
+      return false
+    #endif
+  }
+
   /// All real devices (i.e. all devices except for all simulators)
   public static var allRealDevices: [Device] {
     #if os(iOS)

Source/Device.swift.gyb

@@ -680,6 +680,16 @@ public enum Device {
     }
   #endif
 
+  /// Returns whether the current device is a SwiftUI preview canvas
+  public var isCanvas: Bool? {
+    guard isCurrent else { return nil }
+    #if DEBUG
+      return ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1"
+    #else
+      return false
+    #endif
+  }
+
   /// All real devices (i.e. all devices except for all simulators)
   public static var allRealDevices: [Device] {
     #if os(iOS)

Tests/Tests.swift

@@ -32,6 +32,18 @@ class DeviceKitTests: XCTestCase {
       || device.description.contains("TV"))
   }
 
+  func testIsCanvas() {
+    #if os(iOS)
+    let otherDevice: Device = device == .iPhone14Pro ? .iPhone14ProMax : .iPhone14Pro
+    #elseif os(tvOS)
+    let otherDevice: Device = device == .appleTVHD ? .appleTV4K : .appleTVHD
+    #elseif os(watchOS)
+    let otherDevice: Device = device == .appleWatchUltra ? .appleWatchSeries8_41mm : .appleWatchUltra
+    #endif
+    XCTAssertEqual(otherDevice.isCanvas, nil)
+    XCTAssertEqual(device.isCanvas, false)
+  }
+
   #if os(iOS) || os(tvOS)
   func testDeviceCPU() {
   #if os(iOS)