avoid pointless O(N^2) dynamic_cast

I already tried to reduce the cost of this in ef4964a4e598c3c97,
but back then I missed the fact that in fact all the casts guaranteed.
So partially revert the first commit and simply use static_cast.

Change-Id: I4231f698119d56e9f2536f2f0c9d824442d76b09
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/113736
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 38 insertions, 42 deletions

diff --git a/svx/source/sdr/primitive2d/sdrframeborderprimitive2d.cxx b/svx/source/sdr/primitive2d/sdrframeborderprimitive2d.cxx
index 6e289d4be3f1..b87cfcd9342c 100644
--- a/svx/source/sdr/primitive2d/sdrframeborderprimitive2d.cxx
+++ b/svx/source/sdr/primitive2d/sdrframeborderprimitive2d.cxx
@@ -797,55 +797,51 @@ namespace drawinglayer::primitive2d
 
                     for(const auto& aCandidatePartial : aPartial)
                     {
-                        bool bDidMerge(false);
-
-                        // This algorithm is O(N^2) and repeated dynamic_cast inside would be quite costly.
-                        // So check first and skip if the primitives aren't BorderLinePrimitive2D.
-                        const drawinglayer::primitive2d::BorderLinePrimitive2D* candidatePartialAsBorder
-                            = dynamic_cast<const drawinglayer::primitive2d::BorderLinePrimitive2D*>(aCandidatePartial.get());
-                        if(candidatePartialAsBorder)
+                        if(aRetval.empty())
+                        {
+                            // no local data yet, just add as 1st entry, done
+                            aRetval.append(aCandidatePartial);
+                        }
+                        else
                         {
+                            bool bDidMerge(false);
+
                             for(auto& aCandidateRetval : aRetval)
                             {
-                                const drawinglayer::primitive2d::BorderLinePrimitive2D* candidateRetvalAsBorder
-                                    = dynamic_cast<const drawinglayer::primitive2d::BorderLinePrimitive2D*>(aCandidateRetval.get());
-                                if(candidateRetvalAsBorder)
+                                // try to merge by appending new data to existing data
+                                const drawinglayer::primitive2d::Primitive2DReference aMergeRetvalPartial(
+                                    drawinglayer::primitive2d::tryMergeBorderLinePrimitive2D(
+                                        static_cast<BorderLinePrimitive2D*>(aCandidateRetval.get()),
+                                        static_cast<BorderLinePrimitive2D*>(aCandidatePartial.get())));
+
+                                if(aMergeRetvalPartial.is())
+                                {
+                                    // could append, replace existing data with merged data, done
+                                    aCandidateRetval = aMergeRetvalPartial;
+                                    bDidMerge = true;
+                                    break;
+                                }
+
+                                // try to merge by appending existing data to new data
+                                const drawinglayer::primitive2d::Primitive2DReference aMergePartialRetval(
+                                    drawinglayer::primitive2d::tryMergeBorderLinePrimitive2D(
+                                        static_cast<BorderLinePrimitive2D*>(aCandidatePartial.get()),
+                                        static_cast<BorderLinePrimitive2D*>(aCandidateRetval.get())));
+
+                                if(aMergePartialRetval.is())
                                 {
-                                    // try to merge by appending new data to existing data
-                                    const drawinglayer::primitive2d::Primitive2DReference aMergeRetvalPartial(
-                                        drawinglayer::primitive2d::tryMergeBorderLinePrimitive2D(
-                                            candidateRetvalAsBorder,
-                                            candidatePartialAsBorder));
-
-                                    if(aMergeRetvalPartial.is())
-                                    {
-                                        // could append, replace existing data with merged data, done
-                                        aCandidateRetval = aMergeRetvalPartial;
-                                        bDidMerge = true;
-                                        break;
-                                    }
-
-                                    // try to merge by appending existing data to new data
-                                    const drawinglayer::primitive2d::Primitive2DReference aMergePartialRetval(
-                                        drawinglayer::primitive2d::tryMergeBorderLinePrimitive2D(
-                                            candidatePartialAsBorder,
-                                            candidateRetvalAsBorder));
-
-                                    if(aMergePartialRetval.is())
-                                    {
-                                        // could append, replace existing data with merged data, done
-                                        aCandidateRetval = aMergePartialRetval;
-                                        bDidMerge = true;
-                                        break;
-                                    }
+                                    // could append, replace existing data with merged data, done
+                                    aCandidateRetval = aMergePartialRetval;
+                                    bDidMerge = true;
+                                    break;
                                 }
                             }
-                        }
 
-                        if(!bDidMerge)
-                        {
-                            // no merge after checking all existing data, append as new segment
-                            aRetval.append(aCandidatePartial);
+                            if(!bDidMerge)
+                            {
+                                // no merge after checking all existing data, append as new segment
+                                aRetval.append(aCandidatePartial);
+                            }
                         }
                     }
                 }