D3D12: Fix 'ShaderEffect in a ShaderEffectSource as property value'

Import (and clean up) the dropshadow from the shadereffects example.
This is very useful since it tests a lot more paths and cases than
the wobble.

To overcome the issue of not having some of functionality available before
the item is added to a window, make QQuickGenericShaderEffect smarter and
enhance the documentation.

The handling of vertical mirroring is revised. The GLSL and HLSL version of
the dropshadow shaders produce correct, identical output now.

Change-Id: I94800997bfba781140d80720eb6f340cda480747
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/quick/items/qquickgenericshadereffect_p.h b/src/quick/items/qquickgenericshadereffect_p.h
index 5f6652ec32..2af7d1156a 100644
--- a/src/quick/items/qquickgenericshadereffect_p.h
+++ b/src/quick/items/qquickgenericshadereffect_p.h
@@ -105,6 +105,8 @@ private slots:
     void sourceDestroyed(QObject *object);
     void markGeometryDirtyAndUpdate();
     void markGeometryDirtyAndUpdateIfSupportsAtlas();
+    void itemWindowChanged(QQuickWindow *w);
+    void backendChanged();
 
 private:
     QSGGuiThreadShaderEffectManager *shaderEffectManager() const;