Causes GUI LEDs to reflect their underlying activity.

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

@@ -28,7 +28,7 @@
                         <constraints>
                             <constraint firstAttribute="width" secondItem="ySY-ir-hzb" secondAttribute="height" multiplier="1:1" id="UX0-hT-7Td"/>
                         </constraints>
-                        <levelIndicatorCell key="cell" alignment="left" doubleValue="1" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="DhQ-Di-tRT"/>
+                        <levelIndicatorCell key="cell" alignment="left" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="DhQ-Di-tRT"/>
                     </levelIndicator>
                     <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="Tah-UQ-vdf">
                         <rect key="frame" x="44" y="94" width="59" height="17"/>
@@ -43,7 +43,7 @@
                         <constraints>
                             <constraint firstAttribute="width" secondItem="ncQ-wN-C61" secondAttribute="height" multiplier="1:1" id="176-v3-mVW"/>
                         </constraints>
-                        <levelIndicatorCell key="cell" alignment="left" doubleValue="1" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="jlb-bk-FPd"/>
+                        <levelIndicatorCell key="cell" alignment="left" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="jlb-bk-FPd"/>
                     </levelIndicator>
                     <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="14O-Lq-Npx">
                         <rect key="frame" x="44" y="69" width="61" height="17"/>
@@ -58,7 +58,7 @@
                         <constraints>
                             <constraint firstAttribute="width" secondItem="0rV-Th-Zwt" secondAttribute="height" multiplier="1:1" id="Ai8-b3-Nn5"/>
                         </constraints>
-                        <levelIndicatorCell key="cell" alignment="left" doubleValue="1" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="CJy-Jn-eCL"/>
+                        <levelIndicatorCell key="cell" alignment="left" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="CJy-Jn-eCL"/>
                     </levelIndicator>
                     <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="Acy-tT-OFH">
                         <rect key="frame" x="44" y="44" width="61" height="17"/>
@@ -73,7 +73,7 @@
                         <constraints>
                             <constraint firstAttribute="width" secondItem="bvH-EJ-TYb" secondAttribute="height" multiplier="1:1" id="cKc-q1-2Q4"/>
                         </constraints>
-                        <levelIndicatorCell key="cell" alignment="left" doubleValue="1" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="eoN-hl-30l"/>
+                        <levelIndicatorCell key="cell" alignment="left" maxValue="1" warningValue="2" criticalValue="2" levelIndicatorStyle="continuousCapacity" id="eoN-hl-30l"/>
                     </levelIndicator>
                     <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="R0g-Oa-VB5">
                         <rect key="frame" x="44" y="19" width="62" height="17"/>

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

@@ -304,7 +304,15 @@ class MachineDocument:
 	}
 
 	// MARK: Activity display.
-	fileprivate var activityLevelIndicators: [String: NSLevelIndicator] = [:]
+	class LED {
+		let levelIndicator: NSLevelIndicator
+		init(levelIndicator: NSLevelIndicator) {
+			self.levelIndicator = levelIndicator
+		}
+		var isLit = false
+		var isBlinking = false
+	}
+	fileprivate var leds: [String: LED] = [:]
 	func setupActivityDisplay() {
 		var leds = machine.leds
 		if leds.count > 0 {
@@ -337,9 +345,39 @@ class MachineDocument:
 				activityIndicators[c].removeFromSuperview()
 			}
 
-			// Apply labels.
+			// Apply labels and create leds entries.
 			for c in 0 ..< leds.count {
 				textFields[c].stringValue = leds[c]
+				self.leds[leds[c]] = LED(levelIndicator: activityIndicators[c])
+			}
+		}
+	}
+
+	func machine(_ machine: CSMachine, ledShouldBlink ledName: String) {
+		// If there is such an LED, switch it off for 0.03 of a second; if it's meant
+		// to be off at the end of that, leave it off. Don't allow the blinks to
+		// pile up — allow there to be only one in flight at a time.
+		if let led = leds[ledName] {
+			DispatchQueue.main.async {
+				if !led.isBlinking {
+					led.levelIndicator.floatValue = 0.0
+					led.isBlinking = true
+
+					DispatchQueue.main.asyncAfter(deadline: .now() + 0.03) {
+						led.levelIndicator.floatValue = led.isLit ? 1.0 : 0.0
+						led.isBlinking = false
+					}
+				}
+			}
+		}
+	}
+
+	func machine(_ machine: CSMachine, led ledName: String, didChangeToLit isLit: Bool) {
+		// If there is such an LED, switch it appropriately.
+		if let led = leds[ledName] {
+			DispatchQueue.main.async {
+				led.levelIndicator.floatValue = isLit ? 1.0 : 0.0
+				led.isLit = isLit
 			}
 		}
 	}

OSBindings/Mac/Clock Signal/Machine/CSMachine.h

@@ -16,6 +16,8 @@
 @class CSMachine;
 @protocol CSMachineDelegate
 - (void)machineSpeakerDidChangeInputClock:(nonnull CSMachine *)machine;
+- (void)machine:(nonnull CSMachine *)machine led:(nonnull NSString *)led didChangeToLit:(BOOL)isLit;
+- (void)machine:(nonnull CSMachine *)machine ledShouldBlink:(nonnull NSString *)led;
 @end
 
 typedef NS_ENUM(NSInteger, CSMachineVideoSignal) {

OSBindings/Mac/Clock Signal/Machine/CSMachine.mm

@@ -61,9 +61,11 @@ struct ActivityObserver: public Activity::Observer {
 	}
 
 	void set_led_status(const std::string &name, bool lit) override {
+		[machine.delegate machine:machine led:[NSString stringWithUTF8String:name.c_str()] didChangeToLit:lit];
 	}
 
 	void announce_drive_event(const std::string &name, DriveEvent event) override {
+		[machine.delegate machine:machine ledShouldBlink:[NSString stringWithUTF8String:name.c_str()]];
 	}
 
 	void set_drive_motor_status(const std::string &name, bool is_on) override {