Add additional options to list layout

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### Added
 
+- [Added additional layout configuration options](https://github.com/kyleve/Listable/pull/173/): `headerToFirstSectionSpacing` and `lastSectionToFooterSpacing` now let you control the spacing between the list header and content, and the content and the list footer.
+
 - [Add support for snapshot testing `Item`s](https://github.com/kyleve/Listable/pull/171) via the `ItemPreviewView` class. This is a view type which takes in some configuration options, and an `Item`, which you can then use in snapshot tests to verify the appearance of your `Item` and `ItemContent` .
 
   ```
@@ -42,6 +44,8 @@
 
 - Update `Item` callbacks to [allow for providing more info to the callback parameters](https://github.com/kyleve/Listable/pull/160).
 
+- [`ListAppearance.Layout.padding` is now applied around all content in the list](https://github.com/kyleve/Listable/pull/173/), not only around sections. To regain the previous behavior, use `headerToFirstSectionSpacing` and `lastSectionToFooterSpacing`.
+
 ### Misc
 
 # Past Releases

Internal Pods/Snapshot/Sources/Snapshot.swift

@@ -19,7 +19,23 @@ public struct Snapshot<Iteration:SnapshotIteration>
     internal var onFail : OnFail = XCTFail
 
     public init(
-        iterations : [Iteration],
+        for iteration: Iteration ,
+        settings : SnapshotSettings = .init(),
+        input : Iteration.RenderingFormat
+    ) {
+        self.init(for: [iteration], settings : settings) { _ in input }
+    }
+
+    public init(
+        for iterations: [Iteration] ,
+        settings : SnapshotSettings = .init(),
+        input : Iteration.RenderingFormat
+    ) {
+        self.init(for: iterations, settings : settings) { _ in input }
+    }
+
+    public init(
+        for iterations : [Iteration],
         settings : SnapshotSettings = .init(),
         test : @escaping Test
     ) {
@@ -56,10 +72,13 @@ public struct Snapshot<Iteration:SnapshotIteration>
                 functionName: functionName.description,
                 iteration: iteration.name
             )
+
+            var onFailData : Data? = nil
 
             do {
                 let rendering = iteration.prepare(render: try self.test(iteration))
                 let data = try OutputFormat.snapshotData(with: rendering)
+                onFailData = data
 
                 let existingData = try self.existingData(at: url)
 
@@ -74,7 +93,29 @@ public struct Snapshot<Iteration:SnapshotIteration>
                     try data.write(to: url)
                 }
             } catch {
-                self.onFail("Snapshot test '\(iteration.name)' with format '\(OutputFormat.self)' failed with error: \(error).", testFilePath, line)
+                let data : String = {
+                    if let onFailData = onFailData {
+                        return onFailData.base64EncodedString()
+                    } else {
+                        return "Error generating snapshotData."
+                    }
+                }()
+
+                self.onFail(
+                    """
+                    Snapshot test '\(iteration.name)' with format '\(OutputFormat.self)' failed.
+
+                    Error: \(error).
+
+                    File extension: '.\(output.outputInfo.fileExtension)'.
+
+                    Base64 Data (pass this to `Data.saveBase64(toPath: "~/Development/etc ...", content: "...")` to inspect locally):
+
+                    '\(data)'.
+
+                    """,
+                    testFilePath, line
+                )
             }            
         }
     }
@@ -124,6 +165,29 @@ public struct Snapshot<Iteration:SnapshotIteration>
 }
 
 
+public extension Data
+{
+    static func saveBase64(toPath path : String, content : String) -> Bool
+    {
+        let url = URL(fileURLWithPath: (path as NSString).expandingTildeInPath)
+
+        guard let data = Data(base64Encoded: content) else {
+            print("Could not create data from base64 string.")
+            return false
+        }
+
+        do {
+            try data.write(to: url)
+        } catch {
+            print("Could not write data to disk. Error: \(error)")
+            return false
+        }
+
+        return true
+    }
+}
+
+
 public enum SnapshotValidationError : Error
 {
     case notMatching
@@ -144,8 +208,16 @@ public protocol SnapshotOutputFormat
 
 public struct SnapshotOutputInfo : Equatable
 {
-    var directoryName : String
-    var fileExtension : String
+    public var directoryName : String
+    public var fileExtension : String
+
+    public init(
+        directoryName : String,
+        fileExtension : String
+    ) {
+        self.directoryName = directoryName
+        self.fileExtension = fileExtension
+    }
 }
 
 

Internal Pods/Snapshot/Sources/ViewHierarchySnapshot.swift

@@ -8,13 +8,13 @@
 import UIKit
 
 
-public struct ViewHierarchySnapshot : SnapshotOutputFormat
+public struct ViewHierarchySnapshot<ViewType:UIView> : SnapshotOutputFormat
 {
     // MARK: SnapshotOutputFormat
 
-    public typealias RenderingFormat = UIView
+    public typealias RenderingFormat = ViewType
 
-    public static func snapshotData(with renderingFormat : UIView) throws -> Data
+    public static func snapshotData(with renderingFormat : ViewType) throws -> Data
     {
         let hierarchy = renderingFormat.textHierarchy
         let string = hierarchy.stringValue
@@ -29,7 +29,7 @@ public struct ViewHierarchySnapshot : SnapshotOutputFormat
         )
     }
 
-    public static func validate(render view: UIView, existingData : Data) throws
+    public static func validate(render view: ViewType, existingData : Data) throws
     {
         let textHierarchy = try ViewHierarchySnapshot.snapshotData(with: view)
 

Internal Pods/Snapshot/Sources/ViewImageSnapshot.swift

@@ -8,13 +8,13 @@
 import UIKit
 
 
-public struct ViewImageSnapshot : SnapshotOutputFormat
+public struct ViewImageSnapshot<ViewType:UIView> : SnapshotOutputFormat
 {
     // MARK: SnapshotOutputFormat
 
-    public typealias RenderingFormat = UIView
+    public typealias RenderingFormat = ViewType
 
-    public static func snapshotData(with renderingFormat : UIView) throws -> Data
+    public static func snapshotData(with renderingFormat : ViewType) throws -> Data
     {
         return renderingFormat.toImage.pngData()!
     }
@@ -26,7 +26,7 @@ public struct ViewImageSnapshot : SnapshotOutputFormat
         )
     }
 
-    public static func validate(render newView : UIView, existingData: Data) throws
+    public static func validate(render newView : ViewType, existingData: Data) throws
     {
         let existing = try ViewImageSnapshot.image(with: existingData)
         let new = newView.toImage
@@ -79,10 +79,69 @@ extension UIView
 }
 
 
+/// Image diffing copied from Point Free (https://github.com/pointfreeco/swift-snapshot-testing/blob/master/Sources/SnapshotTesting/Snapshotting/UIImage.swift)
+/// with some changes. Notably, we base the
 extension UIImage
 {
     static func compareImages(lhs : UIImage, rhs : UIImage) -> Bool
     {
         return lhs.pngData() == rhs.pngData()
     }
+
+    private func compare(_ old: UIImage, _ new: UIImage, precision: Float) -> Bool {
+      guard let oldCgImage = old.cgImage else { return false }
+      guard let newCgImage = new.cgImage else { return false }
+      guard oldCgImage.width != 0 else { return false }
+      guard newCgImage.width != 0 else { return false }
+      guard oldCgImage.width == newCgImage.width else { return false }
+      guard oldCgImage.height != 0 else { return false }
+      guard newCgImage.height != 0 else { return false }
+      guard oldCgImage.height == newCgImage.height else { return false }
+
+      // Values between images may differ due to padding to multiple of 64 bytes per row,
+      // because of that a freshly taken view snapshot may differ from one stored as PNG.
+      // At this point we're sure that size of both images is the same, so we can go with minimal `bytesPerRow` value
+      // and use it to create contexts.
+      let minBytesPerRow = min(oldCgImage.bytesPerRow, newCgImage.bytesPerRow)
+      let byteCount = minBytesPerRow * oldCgImage.height
+
+      var oldBytes = [UInt8](repeating: 0, count: byteCount)
+      guard let oldContext = context(for: oldCgImage, bytesPerRow: minBytesPerRow, data: &oldBytes) else { return false }
+      guard let oldData = oldContext.data else { return false }
+      if let newContext = context(for: newCgImage, bytesPerRow: minBytesPerRow), let newData = newContext.data {
+        if memcmp(oldData, newData, byteCount) == 0 { return true }
+      }
+      let newer = UIImage(data: new.pngData()!)!
+      guard let newerCgImage = newer.cgImage else { return false }
+      var newerBytes = [UInt8](repeating: 0, count: byteCount)
+      guard let newerContext = context(for: newerCgImage, bytesPerRow: minBytesPerRow, data: &newerBytes) else { return false }
+      guard let newerData = newerContext.data else { return false }
+      if memcmp(oldData, newerData, byteCount) == 0 { return true }
+      if precision >= 1 { return false }
+      var differentPixelCount = 0
+      let threshold = 1 - precision
+      for byte in 0..<byteCount {
+        if oldBytes[byte] != newerBytes[byte] { differentPixelCount += 1 }
+        if Float(differentPixelCount) / Float(byteCount) > threshold { return false}
+      }
+      return true
+    }
+
+    private func context(for cgImage: CGImage, bytesPerRow: Int, data: UnsafeMutableRawPointer? = nil) -> CGContext? {
+      guard
+        let space = cgImage.colorSpace,
+        let context = CGContext(
+          data: data,
+          width: cgImage.width,
+          height: cgImage.height,
+          bitsPerComponent: cgImage.bitsPerComponent,
+          bytesPerRow: bytesPerRow,
+          space: space,
+          bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
+        )
+        else { return nil }
+
+      context.draw(cgImage, in: CGRect(x: 0, y: 0, width: cgImage.width, height: cgImage.height))
+      return context
+    }
 }

Internal Pods/Snapshot/Sources/ViewIterations.swift

@@ -47,9 +47,19 @@ public struct SizedViewIteration<ViewType:UIView> : SnapshotIteration
 
     public func prepare(render : ViewType) -> ViewType
     {
-        render.frame.origin = .zero
-        render.frame.size = self.size
+        render.frame = CGRect(origin: .zero, size: self.size)
+        render.layoutIfNeeded()
+
+        // Some views, like UICollectionView, do not lay out properly
+        // without spinning the runloop once, in order to update the onscreen cells.
+        self.waitForOneRunloop()
 
         return render
     }
+
+    private func waitForOneRunloop()
+    {
+        let runloop = RunLoop.main
+        runloop.run(mode: .default, before: Date(timeIntervalSinceNow: 0.001))
+    }
 }

Internal Pods/Snapshot/Tests/SnapshotTests.swift

@@ -14,7 +14,7 @@ class SnapshotTests : XCTestCase
 {
     fileprivate func newSnapshot(with test : @escaping Snapshot<TestIteration>.Test) -> Snapshot<TestIteration>
     {
-        return Snapshot(iterations: [TestIteration(name: "Test")], test: test)
+        return Snapshot(for: [TestIteration(name: "Test")], test: test)
     }
 
     func test_no_asset_writes_and_passes()
@@ -106,7 +106,7 @@ class SnapshotTests : XCTestCase
             SizedViewIteration(size: CGSize(width: 300.0, height: 300.0)),
         ]
 
-        let snapshot = Snapshot(iterations: iterations) { iteration in
+        let snapshot = Snapshot(for: iterations) { iteration in
             let root = ViewType1(frame: .init(origin: .zero, size: .init(width: 150.0, height: 150.0)))
             root.backgroundColor = .init(white: 0.8, alpha: 1.0)