refactors premultiplied alpha (#3189)

With this PR we refactor a `premultiplied alpha` user string set by `characterpreview.cpp` into a more flexible mechanism allowing us to assign any state to GUI textures. We can consider these changes more future proof than the previous approach.

apps/openmw/mwgui/inventorywindow.cpp

@@ -70,7 +70,7 @@ namespace MWGui
         , mTrading(false)
         , mUpdateTimer(0.f)
     {
-        mPreviewTexture.reset(new osgMyGUI::OSGTexture(mPreview->getTexture()));
+        mPreviewTexture.reset(new osgMyGUI::OSGTexture(mPreview->getTexture(), mPreview->getTextureStateSet()));
         mPreview->rebuild();
 
         mMainWidget->castType<MyGUI::Window>()->eventWindowChangeCoord += MyGUI::newDelegate(this, &InventoryWindow::onWindowResize);

apps/openmw/mwgui/race.cpp

@@ -138,7 +138,7 @@ namespace MWGui
         mPreview->rebuild();
         mPreview->setAngle (mCurrentAngle);
 
-        mPreviewTexture.reset(new osgMyGUI::OSGTexture(mPreview->getTexture()));
+        mPreviewTexture.reset(new osgMyGUI::OSGTexture(mPreview->getTexture(), mPreview->getTextureStateSet()));
         mPreviewImage->setRenderItemTexture(mPreviewTexture.get());
         mPreviewImage->getSubWidgetMain()->_setUVSet(MyGUI::FloatRect(0.f, 0.f, 1.f, 1.f));
 

apps/openmw/mwrender/characterpreview.cpp

@@ -190,7 +190,9 @@ namespace MWRender
         mTexture->setInternalFormat(GL_RGBA);
         mTexture->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);
         mTexture->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
-        mTexture->setUserValue("premultiplied alpha", true);
+
+        mTextureStateSet = new osg::StateSet;
+        mTextureStateSet->setAttribute(new osg::BlendFunc(osg::BlendFunc::ONE, osg::BlendFunc::ONE_MINUS_SRC_ALPHA));
 
         mCamera = new osg::Camera;
         // hints that the camera is not relative to the master camera

apps/openmw/mwrender/characterpreview.hpp

@@ -18,6 +18,7 @@ namespace osg
     class Camera;
     class Group;
     class Viewport;
+    class StateSet;
 }
 
 namespace MWRender
@@ -41,6 +42,8 @@ namespace MWRender
         void rebuild();
 
         osg::ref_ptr<osg::Texture2D> getTexture();
+        /// Get the osg::StateSet required to render the texture correctly, if any.
+        osg::StateSet* getTextureStateSet() { return mTextureStateSet; }
 
     private:
         CharacterPreview(const CharacterPreview&);
@@ -54,6 +57,7 @@ namespace MWRender
         osg::ref_ptr<osg::Group> mParent;
         Resource::ResourceSystem* mResourceSystem;
         osg::ref_ptr<osg::Texture2D> mTexture;
+        osg::ref_ptr<osg::StateSet> mTextureStateSet;
         osg::ref_ptr<osg::Camera> mCamera;
         osg::ref_ptr<DrawOnceCallback> mDrawOnceCallback;
 

components/myguiplatform/myguirendermanager.cpp

@@ -4,10 +4,8 @@
 #include <MyGUI_Timer.h>
 
 #include <osg/Drawable>
-#include <osg/BlendFunc>
 #include <osg/Texture2D>
 #include <osg/TexMat>
-#include <osg/ValueObject>
 
 #include <osgViewer/Viewer>
 
@@ -17,8 +15,6 @@
 #include <components/shader/shadermanager.hpp>
 #include <components/sceneutil/nodecallback.hpp>
 
-#include <components/debug/debuglog.hpp>
-
 #include "myguicompat.h"
 #include "myguitexture.hpp"
 
@@ -465,23 +461,17 @@ void RenderManager::doRender(MyGUI::IVertexBuffer *buffer, MyGUI::ITexture *text
     batch.mVertexBuffer = static_cast<OSGVertexBuffer*>(buffer)->getVertexBuffer();
     batch.mArray = static_cast<OSGVertexBuffer*>(buffer)->getVertexArray();
     static_cast<OSGVertexBuffer*>(buffer)->markUsed();
-    bool premultipliedAlpha = false;
-    if (texture)
+
+    if (OSGTexture* osgtexture = static_cast<OSGTexture*>(texture))
     {
-        batch.mTexture = static_cast<OSGTexture*>(texture)->getTexture();
+        batch.mTexture = osgtexture->getTexture();
         if (batch.mTexture->getDataVariance() == osg::Object::DYNAMIC)
             mDrawable->setDataVariance(osg::Object::DYNAMIC); // only for this frame, reset in begin()
-        batch.mTexture->getUserValue("premultiplied alpha", premultipliedAlpha);
+        if (!mInjectState && osgtexture->getInjectState())
+            batch.mStateSet = osgtexture->getInjectState();
     }
     if (mInjectState)
         batch.mStateSet = mInjectState;
-    else if (premultipliedAlpha)
-    {
-        // This is hacky, but MyGUI made it impossible to use a custom layer for a nested node, so state couldn't be injected 'properly'
-        osg::ref_ptr<osg::StateSet> stateSet = new osg::StateSet();
-        stateSet->setAttribute(new osg::BlendFunc(osg::BlendFunc::ONE, osg::BlendFunc::ONE_MINUS_SRC_ALPHA));
-        batch.mStateSet = stateSet;
-    }
 
     mDrawable->addBatch(batch);
 }

components/myguiplatform/myguitexture.cpp

@@ -3,6 +3,7 @@
 #include <stdexcept>
 
 #include <osg/Texture2D>
+#include <osg/StateSet>
 
 #include <components/debug/debuglog.hpp>
 #include <components/resource/imagemanager.hpp>
@@ -21,9 +22,10 @@ namespace osgMyGUI
     {
     }
 
-    OSGTexture::OSGTexture(osg::Texture2D *texture)
+    OSGTexture::OSGTexture(osg::Texture2D *texture, osg::StateSet *injectState)
         : mImageManager(nullptr)
         , mTexture(texture)
+        , mInjectState(injectState)
         , mFormat(MyGUI::PixelFormat::Unknow)
         , mUsage(MyGUI::TextureUsage::Default)
         , mNumElemBytes(0)

components/myguiplatform/myguitexture.hpp

@@ -15,6 +15,7 @@ namespace osg
 {
     class Image;
     class Texture2D;
+    class StateSet;
 }
 
 namespace Resource
@@ -31,6 +32,7 @@ namespace osgMyGUI
 
         osg::ref_ptr<osg::Image> mLockedImage;
         osg::ref_ptr<osg::Texture2D> mTexture;
+        osg::ref_ptr<osg::StateSet> mInjectState;
         MyGUI::PixelFormat mFormat;
         MyGUI::TextureUsage mUsage;
         size_t mNumElemBytes;
@@ -40,9 +42,11 @@ namespace osgMyGUI
 
     public:
         OSGTexture(const std::string &name, Resource::ImageManager* imageManager);
-        OSGTexture(osg::Texture2D* texture);
+        OSGTexture(osg::Texture2D* texture, osg::StateSet* injectState = nullptr);
         virtual ~OSGTexture();
 
+        osg::StateSet* getInjectState() { return mInjectState; }
+
         const std::string& getName() const override { return mName; }
 
         void createManual(int width, int height, MyGUI::TextureUsage usage, MyGUI::PixelFormat format) override;