fdo#70160: Revert "Sidebar: Correcting anomalous mouse behaviour while resizing"

Let's revert this for the time being, before we have the full solution that
works both for sidebars, as well as for the normal docked windows.

This reverts commit 16ea2dc1.

vcl/source/window/splitwin.cxx

@@ -2542,30 +2542,21 @@ void SplitWindow::Tracking( const TrackingEvent& rTEvt )
         {
             sal_Bool    bPropSmaller = (mnMouseModifier & KEY_SHIFT) ? sal_True : sal_False;
             sal_Bool    bPropGreater = (mnMouseModifier & KEY_MOD1) ? sal_True : sal_False;
+            long    nDelta = mnMSplitPos-mnMStartPos;
 
             if ( (mnSplitTest & SPLIT_WINDOW) && !mpMainSet->mpItems )
             {
-                // nDelta corresponds to the direction to which user drags the mouse.
-                // If nDelta > 0, means user has dragged the handle towards the right and vice-versa
-                long nDelta = mnMSplitPos-mnMStartPos;
-
                 if ( (mpSplitSet == mpMainSet) && mbBottomRight )
                     nDelta *= -1;
                 ImplSetWindowSize( nDelta );
             }
             else
             {
-                long nNewSize( 0 );
-
-                // where is the sidebar is attached?
+                long nNewSize = mpSplitSet->mpItems[mnSplitPos].mnPixSize;
                 if ( (mpSplitSet == mpMainSet) && mbBottomRight )
-                    nNewSize = mnMaxSize - mnMStartPos; // right hand side of the screen
+                    nNewSize -= nDelta;
                 else
-                    nNewSize = mnMStartPos; // left hand side of the screen
-
-                // do not make the sidebar wider than mnMaxSize
-                nNewSize = std::min(nNewSize, mpSplitSet->mpItems[mnSplitPos].mnMaxSize);
-
+                    nNewSize += nDelta;
                 SplitItem( mpSplitSet->mpItems[mnSplitPos].mnId, nNewSize,
                            bPropSmaller, bPropGreater );
             }