UI: support showing basic context & window menus

This change adds support for basic context menus (attached to a `View` instance) and window title menus.

Examples/UICatalog/UICatalog.swift

@@ -110,6 +110,14 @@ final class UICatalog: ApplicationDelegate, SceneDelegate {
     window.addSubview(self.tableview)
     window.addSubview(self.imageview)
 
+    window.rootViewController?.titleMenu = Menu(children: [
+      Menu(title: "Application", children: [
+        MenuElement(title: "Quit")
+      ]),
+    ])
+
+    self.progress.addInteraction(ContextMenuInteraction(delegate: self))
+
     self.label.font = Font(name: "Consolas", size: 10)!
 
     self.button.addTarget(self, action: UICatalog.pressMe(_:),
@@ -184,3 +192,15 @@ extension UICatalog: TableViewDataSource {
     return cell
   }
 }
+
+extension UICatalog: ContextMenuInteractionDelegate {
+  public func contextMenuInteraction(_ interaction: ContextMenuInteraction,
+                                     configurationForMenuAtLocation location: Point) -> ContextMenuConfiguration? {
+    return ContextMenuConfiguration(identifier: nil, previewProvider: nil) { suggestedElements -> Menu? in
+      Menu(children: [
+        MenuElement(title: "Popup!"),
+        MenuElement(title: "2nd Element"),
+      ])
+    }
+  }
+}

Sources/SwiftWin32/Support/WindowsHandle+UIExtensions.swift

@@ -38,3 +38,14 @@ extension HBITMAP__: HandleValue {
   }
 }
 internal typealias BitmapHandle = ManagedHandle<HBITMAP__>
+
+extension HMENU: HandleValue {
+  typealias HandleType = HMENU
+  internal static func release(_ hMenu: HandleType?) {
+    if let hMenu = hMenu {
+      DestroyMenu(hMenu)
+    }
+  }
+}
+
+internal typealias MenuHandle = ManagedHandle<HMENU>

Sources/SwiftWin32/UI/ContextMenuConfiguration.swift

@@ -44,4 +44,8 @@ public class ContextMenuConfiguration {
 
   private var previewProvider: ContextMenuContentPreviewProvider
   private var actionProvider: ContextMenuActionProvider?
+
+  internal func provideActions() -> Menu? {
+    actionProvider?([]) // TODO suggest default actions
+  }
 }

Sources/SwiftWin32/UI/ContextMenuInteraction.swift

@@ -19,7 +19,7 @@ extension ContextMenuInteraction {
   }
 }
 
-public class ContextMenuInteraction {
+public class ContextMenuInteraction: Interaction {
   // MARK - Creating a Context Menu Interaction Object
 
   /// Creates a context menu interaction object with the specified delegate

Sources/SwiftWin32/UI/Interaction.swift

@@ -0,0 +1,9 @@
+/**
+ * Copyright © 2020 Saleem Abdulrasool <[email protected]>
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ **/
+
+public protocol Interaction {
+}

Sources/SwiftWin32/UI/Menu.swift

@@ -5,6 +5,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  **/
 
+import WinSDK
+
 extension Menu {
   /// Constants for identifying an application's standard menus.
   public struct Identifier: Equatable, Hashable, RawRepresentable {
@@ -275,12 +277,38 @@ extension Menu.Options {
 /// A container for grouping related menu elements in an application menu or
 /// contextual menu.
 public class Menu: MenuElement {
+  internal let children: [MenuElement]
+
   /// Creating a Menu Object
 
   /// Creates a new menu with the specified values.
   public init(title: String = "", image: Image? = nil,
               identifier: Menu.Identifier? = nil, options: Menu.Options = [],
               children: [MenuElement] = []) {
+    self.children = children
     super.init(title: title, image: image)
   }
 }
+
+internal class Win32Menu {
+  internal let hMenu: MenuHandle
+  private let children: [Win32MenuElement]
+
+  private init(hMenu: HMENU, children: [MenuElement]) {
+    self.hMenu = MenuHandle(owning: hMenu)
+    self.children = children.map { Win32MenuElement.of($0) }
+    for (index, child) in self.children.enumerated() {
+      InsertMenuItemW(hMenu,
+                      UINT(index), true,
+                      &(child.info))
+    }
+  }
+
+  internal static func ofContextMenu(_ menu: Menu) -> Win32Menu {
+    Win32Menu(hMenu: CreatePopupMenu(), children: menu.children)
+  }
+
+  internal static func ofWindowMenu(_ menu: Menu) -> Win32Menu {
+    Win32Menu(hMenu: CreateMenu(), children: menu.children)
+  }
+}

Sources/SwiftWin32/UI/MenuElement.swift

@@ -5,6 +5,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  **/
 
+import WinSDK
+
 extension MenuElement {
   /// Attributes that determine the style of the menu element.
   public struct Attributes: OptionSet {
@@ -67,3 +69,48 @@ public class MenuElement {
     self.image = image
   }
 }
+
+internal class Win32MenuElement {
+  internal var info: MENUITEMINFOW
+  private var titleW: [WCHAR]
+  private let subMenu: Win32Menu?
+
+  private init(title: String, subMenu: Win32Menu?, fType: Int32) {
+    self.titleW = title.LPCWSTR
+    let titleSize = titleW.count
+
+    self.subMenu = subMenu
+    self.info = titleW.withUnsafeMutableBufferPointer {
+      MENUITEMINFOW(cbSize: UINT(MemoryLayout<MENUITEMINFOW>.size),
+                    fMask: UINT(MIIM_FTYPE | MIIM_STATE | MIIM_ID | MIIM_STRING | MIIM_SUBMENU | MIIM_DATA),
+                    fType: UINT(fType),
+                    fState: UINT(MFS_ENABLED),
+                    wID: UInt32.random(in: .min ... .max),
+                    hSubMenu: subMenu?.hMenu.value,
+                    hbmpChecked: nil,
+                    hbmpUnchecked: nil,
+                    dwItemData: 0,
+                    dwTypeData: $0.baseAddress,
+                    cch: UINT(titleSize),
+                    hbmpItem: nil)
+    }
+  }
+
+  internal static func of(_ element: MenuElement) -> Win32MenuElement {
+    let subMenu: Win32Menu?
+    if let menu = element as? Menu {
+      subMenu = Win32Menu.ofContextMenu(menu)
+    } else {
+      subMenu = nil
+    }
+    return Win32MenuElement(title: element.title, subMenu: subMenu, fType: MFT_STRING)
+  }
+
+  internal static func ofSeparator() -> Win32MenuElement {
+    return Win32MenuElement(title: "", subMenu: nil, fType: MFT_SEPARATOR)
+  }
+
+  internal var isSeparator: Bool {
+    info.fType == MFT_SEPARATOR
+  }
+}

Sources/SwiftWin32/UI/View.swift

@@ -11,8 +11,26 @@ private let SwiftViewProc: SUBCLASSPROC = { (hWnd, uMsg, wParam, lParam, uIdSubc
   let view: View? = unsafeBitCast(dwRefData, to: AnyObject.self) as? View
   switch uMsg {
   case UINT(WM_CONTEXTMENU):
-    // TODO handle popup menu events
+    guard let view = view,
+          let menuInteraction = view.interactions.first(where: { $0 is ContextMenuInteraction })
+            as? ContextMenuInteraction else { break }
+    let x = Int16(truncatingIfNeeded: lParam)
+    let y = Int16(truncatingIfNeeded: lParam >> 16)
+    let point = Point(x: Int(x), y: Int(y))
+    let menuConfiguration = menuInteraction.delegate?.contextMenuInteraction(menuInteraction,
+                                                                             configurationForMenuAtLocation: point)
+    if let menu = menuConfiguration?.provideActions() {
+      view.win32ContextMenu = Win32Menu.ofContextMenu(menu)
+    } else {
+      view.win32ContextMenu = nil
+    }
+    let hMenu = view.win32ContextMenu?.hMenu.value
+    TrackPopupMenu(hMenu, UINT(TPM_RIGHTBUTTON),
+                   Int32(x), Int32(y), 0, view.hWnd, nil)
     return 0
+  case UINT(WM_COMMAND):
+    // TODO handle menu actions
+    break
   default:
     break
   }
@@ -202,6 +220,13 @@ public class View: Responder {
     set { _ = EnableWindow(self.hWnd, newValue) }
   }
 
+  public private(set) var interactions: [Interaction] = []
+  internal var win32ContextMenu: Win32Menu? = nil
+
+  public func addInteraction(_ interaction: Interaction) {
+    interactions.append(interaction)
+  }
+
   // MARK - Managing the View Hierarchy
 
   public private(set) var superview: View?

Sources/SwiftWin32/UI/ViewController.swift

@@ -57,6 +57,19 @@ public class ViewController: Responder {
     set(value) { _ = SetWindowTextW(view.hWnd, value?.LPCWSTR) }
   }
 
+  /// Menu bar shown below the window title
+  public var titleMenu: Menu? {
+    didSet {
+      if let newValue = titleMenu {
+        win32TitleMenu = Win32Menu.ofWindowMenu(newValue)
+      } else {
+        win32TitleMenu = nil
+      }
+      SetMenu(view.hWnd, win32TitleMenu?.hMenu.value)
+    }
+  }
+  private var win32TitleMenu: Win32Menu? = nil
+
   /// The preferred size for the view controller's view.
   public var preferredContentSize: Size {
     fatalError("not yet implemented")