Makes first attempt to connect up an in-machine open panel.

OSBindings/Mac/Clock Signal/Base.lproj/MainMenu.xib

@@ -116,6 +116,11 @@
                                     <action selector="saveScreenshot:" target="-1" id="7ky-xD-tip"/>
                                 </connections>
                             </menuItem>
+                            <menuItem title="Insert..." keyEquivalent="O" id="qQa-kh-4nz">
+                                <connections>
+                                    <action selector="insertMedia:" target="-1" id="9Hs-9J-dlY"/>
+                                </connections>
+                            </menuItem>
                             <menuItem isSeparatorItem="YES" id="rXU-KX-GkZ"/>
                             <menuItem title="Page Setup…" enabled="NO" keyEquivalent="P" id="qIS-W8-SiK">
                                 <modifierMask key="keyEquivalentModifierMask" shift="YES" command="YES"/>

OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift

@@ -213,6 +213,7 @@ class MachineDocument:
 		}
 	}
 
+	// MARK: Runtime media insertion.
 	final func openGLView(_ view: CSOpenGLView, didReceiveFileAt URL: URL) {
 		let mediaSet = CSMediaSet(fileAt: URL)
 		if let mediaSet = mediaSet {
@@ -220,6 +221,16 @@ class MachineDocument:
 		}
 	}
 
+	@IBAction final func insertMedia(_ sender: AnyObject!) {
+		let panel = NSOpenPanel()
+		self.openGLView.window!.beginSheet(panel) { (response) in
+			if response == .OK {
+				Swift.print("An animal")
+			}
+			Swift.print("\(response)")
+		}
+	}
+
 	// MARK: NSDocument overrides
 	override func data(ofType typeName: String) throws -> Data {
 		throw NSError(domain: NSOSStatusErrorDomain, code: unimpErr, userInfo: nil)