Alpha premultiplied backbuffer Windows (#429)

* Alpha premultiplied backbuffer Windows

* submodule update

Author: CedricGuillemet

Modules/@babylonjs/react-native-iosandroid/submodules/BabylonNative

@@ -183,7 +183,7 @@ namespace winrt::BabylonReactNative::implementation {
             if (propertyName == "isTransparent")
             {
                 bool isTransparent = propertyValue.AsBoolean();
-                this->CompositeMode(isTransparent ? ElementCompositeMode::MinBlend : ElementCompositeMode::Inherit);
+                BabylonNative::UpdateAlphaPremultiplied(isTransparent);
             } else if (propertyName == "antiAliasing")
             {
                 auto value = propertyValue.AsUInt8();

Modules/@babylonjs/react-native-windows/windows/BabylonReactNative/EngineView.cpp

@@ -89,6 +89,7 @@ namespace BabylonNative
                 g_graphics->UpdateSize(width, height);
             }
             g_graphics->UpdateMSAA(mMSAAValue);
+            g_graphics->UpdateAlphaPremultiplied(mAlphaPremultiplied);
 
             g_graphics->EnableRendering();
             m_isRenderingEnabled = true;
@@ -117,6 +118,15 @@ namespace BabylonNative
             }
         }
 
+        void UpdateAlphaPremultiplied(bool enabled)
+        {
+            mAlphaPremultiplied = enabled;
+            if (g_graphics)
+            {
+                g_graphics->UpdateAlphaPremultiplied(enabled);
+            }
+        }
+
         void RenderView()
         {
             // If rendering has not been explicitly enabled, or has been explicitly disabled, then don't try to render.
@@ -236,6 +246,7 @@ namespace BabylonNative
 
         std::shared_ptr<bool> m_isXRActive{};
         uint8_t mMSAAValue{};
+        bool mAlphaPremultiplied{};
     };
 
     namespace
@@ -284,6 +295,18 @@ namespace BabylonNative
         }
     }
 
+    void UpdateAlphaPremultiplied(bool enabled)
+    {
+        if (auto nativeModule{ g_nativeModule.lock() })
+        {
+            nativeModule->UpdateAlphaPremultiplied(enabled);
+        }
+        else
+        {
+            throw std::runtime_error{ "UpdateAlphaPremultiplied must not be called before Initialize." };
+        }
+    }
+
     void RenderView()
     {
         if (auto nativeModule{ g_nativeModule.lock() })

Modules/@babylonjs/react-native/shared/BabylonNative.cpp

@@ -29,6 +29,7 @@ namespace BabylonNative
 
     void UpdateView(WindowType window, size_t width, size_t height);
     void UpdateMSAA(uint8_t value);
+    void UpdateAlphaPremultiplied(bool enabled);
 
     void RenderView();
     void ResetView();