tdf#120837 File saving at least 5 times slower

The problem here is that we never actually hit the maExportGraphics
cache in SvXMLGraphicHelper, even though we are passing the same image
down repeatedly.

There are two bugs here:

(1) BitmapEx::operator== does not return true if we instantiate 2
Graphic objects from the same XGraphic, so change it to use the more
expensive operator==. To mitigate the cost, move the expensive checks to
the bottom of the method.

(2) in order to use an object in std::unordered_map, the object must
implement an equality function and a hash function. If two objects are
equal THEY MUST have the same hash value. Using the Impl* as the hash
value does not satisfy that condition, so rather use the checksum, which
does.

After these fixes, the save time drops to less than a second.

Also make the checksum method look more like the operator== method,
and add a checksum calculation method for SVG data that more accurately
reflects the underlying SVG data.

Change-Id: I4ca0c7bee60b2efa6fe42301e582c7b278022b46
Reviewed-on: https://gerrit.libreoffice.org/72615
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

include/vcl/graph.hxx

@@ -195,11 +195,6 @@ public:
 
     BitmapChecksum  GetChecksum() const;
 
-    SAL_DLLPRIVATE std::size_t getHash() const
-    {
-        return reinterpret_cast<std::size_t>(ImplGetImpGraphic());
-    }
-
     OUString getOriginURL() const;
     void setOriginURL(OUString const & rOriginURL);
 
@@ -247,7 +242,7 @@ struct hash<Graphic>
 {
     std::size_t operator()(Graphic const & rGraphic) const
     {
-        return rGraphic.getHash();
+        return static_cast<std::size_t>(rGraphic.GetChecksum());
     }
 };
 

include/vcl/vectorgraphicdata.hxx

@@ -104,6 +104,7 @@ public:
     const basegfx::B2DRange& getRange() const;
     const std::deque< css::uno::Reference< css::graphic::XPrimitive2D > >& getPrimitive2DSequence() const;
     const BitmapEx& getReplacement() const;
+    BitmapChecksum GetChecksum() const;
 };
 
 typedef std::shared_ptr< VectorGraphicData > VectorGraphicDataPtr;

vcl/inc/impgraph.hxx

@@ -84,6 +84,8 @@ private:
     bool                         mbSwapOut;
     bool                         mbDummyContext;
     VectorGraphicDataPtr         maVectorGraphicData;
+    // cache checksum computation
+    mutable BitmapChecksum       mnChecksum = 0;
 
     /// The PDF stream from which this Graphic is rendered,
     /// as converted (version downgraded) from the original,

vcl/source/gdi/bitmapex.cxx

@@ -181,9 +181,6 @@ bool BitmapEx::operator==( const BitmapEx& rBitmapEx ) const
     if (meTransparent != rBitmapEx.meTransparent)
         return false;
 
-    if (!maBitmap.ShallowEquals(rBitmapEx.maBitmap))
-        return false;
-
     if (GetSizePixel() != rBitmapEx.GetSizePixel())
         return false;
 
@@ -197,7 +194,10 @@ bool BitmapEx::operator==( const BitmapEx& rBitmapEx ) const
     if (mbAlpha != rBitmapEx.mbAlpha)
         return false;
 
-    return maMask.ShallowEquals(rBitmapEx.maMask);
+    if (maBitmap != rBitmapEx.maBitmap)
+        return false;
+
+    return maMask == rBitmapEx.maMask;
 }
 
 bool BitmapEx::IsEmpty() const

vcl/source/gdi/impgraph.cxx

@@ -1663,6 +1663,9 @@ bool ImpGraphic::ImplIsLink() const
 
 BitmapChecksum ImpGraphic::ImplGetChecksum() const
 {
+    if (mnChecksum != 0)
+        return mnChecksum;
+
     BitmapChecksum nRet = 0;
 
     ensureAvailable();
@@ -1676,25 +1679,16 @@ BitmapChecksum ImpGraphic::ImplGetChecksum() const
 
             case GraphicType::Bitmap:
             {
-                if(maVectorGraphicData.get() && maEx.IsEmpty())
-                {
-                    // use maEx as local buffer for rendered svg
-                    const_cast< ImpGraphic* >(this)->maEx = maVectorGraphicData->getReplacement();
-                }
-
-                if( mpAnimation )
-                {
-                    nRet = mpAnimation->GetChecksum();
-                }
-                else
-                {
-                    nRet = maEx.GetChecksum();
-                }
-
-                if (mpPdfData && mpPdfData->hasElements())
+                if(maVectorGraphicData)
+                    nRet = maVectorGraphicData->GetChecksum();
+                else if (mpPdfData && mpPdfData->hasElements())
                     // Include the PDF data in the checksum, so a metafile with
                     // and without PDF data is considered to be different.
                     nRet = vcl_get_checksum(nRet, mpPdfData->getConstArray(), mpPdfData->getLength());
+                else if( mpAnimation )
+                    nRet = mpAnimation->GetChecksum();
+                else
+                    nRet = maEx.GetChecksum();
             }
             break;
 
@@ -1704,6 +1698,7 @@ BitmapChecksum ImpGraphic::ImplGetChecksum() const
         }
     }
 
+    mnChecksum = nRet;
     return nRet;
 }
 

vcl/source/gdi/vectorgraphicdata.cxx

@@ -288,4 +288,10 @@ const BitmapEx& VectorGraphicData::getReplacement() const
     return maReplacement;
 }
 
+BitmapChecksum VectorGraphicData::GetChecksum() const
+{
+    BitmapChecksum nRet = 0;
+    return vcl_get_checksum(nRet, maVectorGraphicDataArray.getConstArray(), maVectorGraphicDataArray.getLength());
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */