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.

Reviewed-on: https://gerrit.libreoffice.org/72615
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
(cherry picked from commit 319c57d2af5d26d3910db4b02dca145d8881af44)

Change-Id: I4ca0c7bee60b2efa6fe42301e582c7b278022b46
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90843
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

2 files changed, 2 insertions, 6 deletions

diff --git a/include/vcl/graph.hxx b/include/vcl/graph.hxx
index 2ad98c871cae..c8bbccd4574f 100644
--- a/include/vcl/graph.hxx
+++ b/include/vcl/graph.hxx
@@ -199,11 +199,6 @@ 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);
 
@@ -251,7 +246,7 @@ struct hash<Graphic>
 {
     std::size_t operator()(Graphic const & rGraphic) const
     {
-        return rGraphic.getHash();
+        return static_cast<std::size_t>(rGraphic.GetChecksum());
     }
 };
 
diff --git a/include/vcl/vectorgraphicdata.hxx b/include/vcl/vectorgraphicdata.hxx
index ea7615d2bdf6..159dc7afe286 100644
--- a/include/vcl/vectorgraphicdata.hxx
+++ b/include/vcl/vectorgraphicdata.hxx
@@ -103,6 +103,7 @@ 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;