Attempts to support insertion of states into existing windows.

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

@@ -137,6 +137,9 @@ class MachineDocument:
 	func configureAs(_ analysis: CSStaticAnalyser) {
 		self.machineDescription = analysis
 
+		actionLock.lock()
+		drawLock.lock()
+
 		let missingROMs = NSMutableArray()
 		if let machine = CSMachine(analyser: analysis, missingROMs: missingROMs) {
 			self.machine = machine
@@ -147,9 +150,11 @@ class MachineDocument:
 			// Store the selected machine and list of missing ROMs, and
 			// show the missing ROMs dialogue.
 			self.missingROMs = missingROMs.map({$0 as! CSMissingROM})
-
 			requestRoms()
 		}
+
+		actionLock.unlock()
+		drawLock.unlock()
 	}
 
 	enum InteractionMode {
@@ -280,8 +285,7 @@ class MachineDocument:
 
 	/// Delegate message to receive drag and drop files.
 	final func scanTargetView(_ view: CSScanTargetView, didReceiveFileAt URL: URL) {
-		let mediaSet = CSMediaSet(fileAt: URL)
-		mediaSet.apply(to: self.machine)
+		insertFile(URL)
 	}
 
 	/// Action for the insert menu command; displays an NSOpenPanel and then segues into the same process
@@ -292,13 +296,30 @@ class MachineDocument:
 		openPanel.beginSheetModal(for: self.windowControllers[0].window!) { (response) in
 			if response == .OK {
 				for url in openPanel.urls {
-					let mediaSet = CSMediaSet(fileAt: url)
-					mediaSet.apply(to: self.machine)
+					self.insertFile(url)
 				}
 			}
 		}
 	}
 
+	private func insertFile(_ URL: URL) {
+		// Try to insert media.
+		let mediaSet = CSMediaSet(fileAt: URL)
+		if !mediaSet.empty {
+			mediaSet.apply(to: self.machine)
+			return
+		}
+
+		// Failing that see whether a new machine is required.
+		// TODO.
+		if let newMachine = CSStaticAnalyser(fileAt: URL) {
+			machine?.stop()
+			self.interactionMode = .notStarted
+			self.scanTargetView.willChangeScanTargetOwner()
+			configureAs(newMachine)
+		}
+	}
+
 	// MARK: - Input Management.
 
 	/// Upon a resign key, immediately releases all ongoing input mechanisms — any currently pressed keys,

OSBindings/Mac/Clock Signal/Machine/StaticAnalyser/CSStaticAnalyser.h

@@ -114,6 +114,8 @@ typedef int Kilobytes;
 - (instancetype)initWithFileAtURL:(NSURL *)url;
 - (void)applyToMachine:(CSMachine *)machine;
 
+@property(nonatomic, readonly) BOOL empty;
+
 @end
 
 NS_ASSUME_NONNULL_END

OSBindings/Mac/Clock Signal/Machine/StaticAnalyser/CSStaticAnalyser.mm

@@ -309,4 +309,8 @@ static Analyser::Static::ZX8081::Target::MemoryModel ZX8081MemoryModelFromSize(K
 	[machine applyMedia:_media];
 }
 
+- (BOOL)empty {
+	return _media.empty();
+}
+
 @end

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.h

@@ -22,4 +22,6 @@
 
 - (nonnull NSBitmapImageRep *)imageRepresentation;
 
+- (void)willChangeOwner;
+
 @end

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm

@@ -1143,6 +1143,10 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	return &_scanTarget;
 }
 
+- (void)willChangeOwner {
+	_scanTarget.ScanTarget::will_change_owner();
+}
+
 - (NSBitmapImageRep *)imageRepresentation {
 	// Create an NSBitmapRep as somewhere to copy pixel data to.
 	NSBitmapImageRep *const result =

OSBindings/Mac/Clock Signal/Views/CSScanTargetView.h

@@ -162,4 +162,10 @@
 */
 @property(nonatomic, readonly, nonnull) CSScanTarget *scanTarget;
 
+/*!
+	Indicates that the enclosed scan target is about to be handed off to a new owner;
+	exactly identical to calling scanTarget.will_change_owner().
+*/
+- (void)willChangeScanTargetOwner;
+
 @end

OSBindings/Mac/Clock Signal/Views/CSScanTargetView.m

@@ -129,6 +129,10 @@ static CVReturn DisplayLinkCallback(__unused CVDisplayLinkRef displayLink, const
 	return _scanTarget;
 }
 
+- (void)willChangeScanTargetOwner {
+	[_scanTarget willChangeOwner];
+}
+
 - (void)updateBacking {
 	[_scanTarget updateFrameBuffer];
 }