sc: GetRowForHeight performance improvement.

Instead of just skipping hidden rows, either skip or interpolate
into visible ones.

This method, and it's single caller look rather unusual to me. It is
unclear why we would want to return the results we do, and why the
one caller subtracts a row.

Some surprising proportion of tile rendering was exercising this code
path extremely slowly.

--5.94%--ScDocument::GetPrintArea
          |
          |--5.04%--ScDrawLayer::GetPrintArea
          |          ScTable::GetRowForHeight
          |          |
          |           --4.58%--ScFlatBoolRowSegments::getRangeData
          |                     |
          |                      --2.46%--ScFlatSegmentsImpl<bool, bool>::getRangeData

Change-Id: I75418d6af59a33b99e8bb0c374139e1a4ee6ef87
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/109837
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>
Reviewed-by: Ashod Nakashian <ash@collabora.com>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>

1 files changed, 18 insertions, 5 deletions

diff --git a/sc/source/core/data/table2.cxx b/sc/source/core/data/table2.cxx
index 5a12b0bba520..971c8ad7cd31 100644
--- a/sc/source/core/data/table2.cxx
+++ b/sc/source/core/data/table2.cxx
@@ -3971,16 +3971,25 @@ SCROW ScTable::GetRowForHeight(sal_uLong nHeight) const
                 break;
         }
 
-        nSum += aRowHeightRange.mnValue;
+        // find the last common row between hidden & height spans
+        SCROW nLastCommon = std::min(aData.mnRow2, aRowHeightRange.mnRow2);
+        assert (nLastCommon >= nRow);
+        SCROW nCommon = nLastCommon - nRow + 1;
 
-        if (nSum > nHeight)
+        // how much further to go ?
+        sal_uLong nPixelsLeft = nHeight - nSum;
+        sal_uLong nCommonPixels = aRowHeightRange.mnValue * nCommon;
+
+        // are we in the zone ?
+        if (nCommonPixels > nPixelsLeft)
         {
+            nRow += (nPixelsLeft + aRowHeightRange.mnValue - 1) / aRowHeightRange.mnValue;
+
+            // FIXME: finding this next row is far from elegant,
+            // we have a single caller, which subtracts one as well(!?)
             if (nRow >= pDocument->MaxRow())
                 return pDocument->MaxRow();
 
-            // Find the next visible row.
-            ++nRow;
-
             if (!mpHiddenRows->getRangeData(nRow, aData))
                 // Failed to fetch the range data for whatever reason.
                 break;
@@ -3991,6 +4000,10 @@ SCROW ScTable::GetRowForHeight(sal_uLong nHeight) const
 
             return nRow <= pDocument->MaxRow() ? nRow : pDocument->MaxRow();
         }
+
+        // skip the range and keep hunting
+        nSum += nCommonPixels;
+        nRow = nLastCommon;
     }
     return -1;
 }