[macos] Implement getOpacity & setOpacity methods #37

Author: lijy91

example/lib/pages/home.dart

@@ -39,6 +39,7 @@ class _HomePageState extends State<HomePage> with WindowListener {
   bool _isAlwaysOnTop = false;
   bool _isSkipTaskbar = false;
   bool _hasShadow = true;
+  double _opacity = 1;
 
   @override
   void initState() {
@@ -447,6 +448,35 @@ class _HomePageState extends State<HomePage> with WindowListener {
                 setState(() {});
               },
             ),
+            PreferenceListItem(
+              title: Text('getOpacity / setOpacity'),
+              onTap: () async {
+                double opacity = await windowManager.getOpacity();
+                BotToast.showText(
+                  text: 'opacity: $opacity',
+                );
+              },
+              accessoryView: Row(
+                children: [
+                  CupertinoButton(
+                    child: Text('1'),
+                    onPressed: () async {
+                      _opacity = 1;
+                      windowManager.setOpacity(_opacity);
+                      setState(() {});
+                    },
+                  ),
+                  CupertinoButton(
+                    child: Text('0.5'),
+                    onPressed: () async {
+                      _opacity = 0.5;
+                      windowManager.setOpacity(_opacity);
+                      setState(() {});
+                    },
+                  ),
+                ],
+              ),
+            ),
             PreferenceListItem(
               title: Text('createSubWindow'),
               onTap: () async {

lib/src/window_manager.dart

@@ -349,6 +349,19 @@ class WindowManager {
     await _channel.invokeMethod('setHasShadow', arguments);
   }
 
+  /// Returns double - between 0.0 (fully transparent) and 1.0 (fully opaque). On Linux, always returns 1.
+  Future<double> getOpacity() async {
+    return await _channel.invokeMethod('getOpacity');
+  }
+
+  /// Sets the opacity of the window.
+  Future<void> setOpacity(double opacity) async {
+    final Map<String, dynamic> arguments = {
+      'opacity': opacity,
+    };
+    await _channel.invokeMethod('setOpacity', arguments);
+  }
+
   Future<void> startDragging() async {
     await _channel.invokeMethod('startDragging');
   }

macos/Classes/WindowManager.swift

@@ -348,6 +348,15 @@ public class WindowManager: NSObject, NSWindowDelegate {
         mainWindow.invalidateShadow();
     }
 
+    public func getOpacity() -> CGFloat {
+        return mainWindow.alphaValue
+    }
+    
+    public func setOpacity(_ args: [String: Any]) {
+        let opacity: CGFloat = CGFloat(truncating: args["opacity"] as! NSNumber)
+        mainWindow.alphaValue = opacity
+    }
+    
     public func startDragging() {
         DispatchQueue.main.async {
             let window: NSWindow  = self.mainWindow

macos/Classes/WindowManagerPlugin.swift

@@ -187,6 +187,13 @@ public class WindowManagerPlugin: NSObject, FlutterPlugin {
             windowManager.setHasShadow(args)
             result(true)
             break
+        case "getOpacity":
+            result(windowManager.getOpacity())
+            break
+        case "setOpacity":
+            windowManager.setOpacity(args)
+            result(true)
+            break
         case "startDragging":
             windowManager.startDragging()
             result(true)