use supersampling in Impress if fast opengl scaling is available

So far it's been always disabled, with the exception of the slide preview
extension.

Change-Id: Iaee6fe2d5267c9dfdc31cbf4fb90a9ac0e08e781

include/vcl/bitmap.hxx

@@ -560,6 +560,15 @@ public:
      */
     bool                    Scale( const double& rScaleX, const double& rScaleY, sal_uInt32 nScaleFlag = BMP_SCALE_DEFAULT );
 
+    /**
+      Returns true if bitmap scaling is considered to be fast.
+
+      Currently this returns true if OpenGL is used for scaling, otherwise false (CPU scaling is slower).
+
+      @since 4.5
+    */
+    static bool HasFastScale();
+
     // Adapt the BitCount of rNew to BitCount of lolal, including grey or color paltette
     // Can be used to create alpha/mask bitmaps after their processing in 24bit
     void                    AdaptBitCount(Bitmap& rNew) const;

sd/source/ui/presenter/PresenterPreviewCache.cxx

@@ -96,7 +96,7 @@ PresenterPreviewCache::PresenterPreviewCache (const Reference<XComponentContext>
     : PresenterPreviewCacheInterfaceBase(m_aMutex),
       maPreviewSize(Size(200,200)),
       mpCacheContext(new PresenterCacheContext()),
-      mpCache(new PageCache(maPreviewSize, false, mpCacheContext))
+      mpCache(new PageCache(maPreviewSize, Bitmap::HasFastScale(), mpCacheContext))
 {
     (void)rxContext;
 }
@@ -146,7 +146,7 @@ void SAL_CALL PresenterPreviewCache::setPreviewSize (
     OSL_ASSERT(mpCache.get()!=NULL);
 
     maPreviewSize = Size(rSize.Width, rSize.Height);
-    mpCache->ChangeSize(maPreviewSize, false);
+    mpCache->ChangeSize(maPreviewSize, Bitmap::HasFastScale());
 }
 
 Reference<rendering::XBitmap> SAL_CALL PresenterPreviewCache::getSlidePreview (

sd/source/ui/slidesorter/view/SlideSorterView.cxx

@@ -424,7 +424,7 @@ void SlideSorterView::Layout ()
             const Size aNewPreviewSize (mpLayouter->GetPageObjectLayouter()->GetPreviewSize(PageObjectLayouter::WindowCoordinateSystem));
             if (maPreviewSize != aNewPreviewSize && GetPreviewCache())
             {
-                mpPreviewCache->ChangeSize(aNewPreviewSize, false);
+                mpPreviewCache->ChangeSize(aNewPreviewSize, Bitmap::HasFastScale());
                 maPreviewSize = aNewPreviewSize;
             }
         }
@@ -706,7 +706,7 @@ void SlideSorterView::ConfigurationChanged (
         mpPreviewCache.reset(
             new cache::PageCache(
                 mpLayouter->GetPageObjectSize(),
-                false,
+                Bitmap::HasFastScale(),
                 cache::SharedCacheContext(new ViewCacheContext(mrSlideSorter))));
     }
 

vcl/source/gdi/bitmap3.cxx

@@ -24,6 +24,7 @@
 #include <vcl/bitmapex.hxx>
 #include <vcl/bitmap.hxx>
 #include <vcl/bitmapscalesuper.hxx>
+#include <vcl/opengl/OpenGLHelper.hxx>
 
 #include <boost/scoped_array.hpp>
 
@@ -993,6 +994,11 @@ bool Bitmap::Scale( const Size& rNewSize, sal_uInt32 nScaleFlag )
     return bRet;
 }
 
+bool Bitmap::HasFastScale()
+{
+    return OpenGLHelper::isVCLOpenGLEnabled();
+}
+
 void Bitmap::AdaptBitCount(Bitmap& rNew) const
 {
     ImplAdaptBitCount(rNew);