[windows] Implement getOpacity & setOpacity methods #45

Author: lijy91

windows/window_manager.cpp

@@ -37,6 +37,7 @@ class WindowManager
 
     bool is_frameless = false;
     std::string title_bar_style = "default";
+    double opacity = 1;
 
     // The minimum size set by the platform channel.
     POINT minimum_size = {0, 0};
@@ -80,6 +81,8 @@ class WindowManager
     void WindowManager::SetSkipTaskbar(const flutter::EncodableMap &args);
     bool WindowManager::HasShadow();
     void WindowManager::SetHasShadow(const flutter::EncodableMap &args);
+    double WindowManager::GetOpacity();
+    void WindowManager::SetOpacity(const flutter::EncodableMap &args);
     void WindowManager::StartDragging();
 
   private:
@@ -541,6 +544,20 @@ void WindowManager::SetSkipTaskbar(const flutter::EncodableMap &args)
     }
 }
 
+double WindowManager::GetOpacity()
+{
+    return this->opacity;
+}
+
+void WindowManager::SetOpacity(const flutter::EncodableMap &args)
+{
+    this->opacity = std::get<double>(args.at(flutter::EncodableValue("opacity")));
+    HWND hWnd = GetMainWindow();
+    long gwlExStyle = GetWindowLong(hWnd, GWL_EXSTYLE);
+    SetWindowLong(hWnd, GWL_EXSTYLE, gwlExStyle | WS_EX_LAYERED);
+    SetLayeredWindowAttributes(hWnd, 0, static_cast<int8_t>(255 * this->opacity), 0x02);
+}
+
 void WindowManager::StartDragging()
 {
     ReleaseCapture();

windows/window_manager_plugin.cpp

@@ -405,6 +405,17 @@ void WindowManagerPlugin::HandleMethodCall(const flutter::MethodCall<flutter::En
         window_manager->SetSkipTaskbar(args);
         result->Success(flutter::EncodableValue(true));
     }
+    else if (method_name.compare("getOpacity") == 0)
+    {
+        double value = window_manager->GetOpacity();
+        result->Success(flutter::EncodableValue(value));
+    }
+    else if (method_name.compare("setOpacity") == 0)
+    {
+        const flutter::EncodableMap &args = std::get<flutter::EncodableMap>(*method_call.arguments());
+        window_manager->SetOpacity(args);
+        result->Success(flutter::EncodableValue(true));
+    }
     else if (method_name.compare("startDragging") == 0)
     {
         window_manager->StartDragging();