🚀 go-pugleaf

> That is not true.  All rows/columns that are removed are freed from
> memory.  There is nothing physically available for the TStringGrid to
> keep displaying for them.
> 
> Try this:
> 
>     void ClearStringGrid(TStringGrid* sgGrid)
>     {
>         sgGrid->RowCount = (sgGrid->FixedRows+1);
>         sgGrid->Rows[sgGrid->FixedRows]->Clear();
>     }
> 

The above doesn't work. Indeed it creates the image that the gridis 
cleared and it 'looks' like everything is gone, but simply set the 
Row/Column count back again and you will see that the strings that were 
entered into the grid are still there.

For example, creating some basic test code like the following including 
three buttons aptly named "ResizeGridButton", "FillGridButton", and 
"ClearGridButton" and one stringgrid named StringGrid1, and you will see 
what I mean when you assign the appropraite events to each:

//---------------------------------------------------------------------------
void __fastcall TForm1::ResizeGridButtonClick(TObject *Sender)
{
   StringGrid1->RowCount = 10;
   StringGrid1->ColCount=10;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FillGridButtonClick(TObject *Sender)
{
    ResizeGridButtonClick(this);
    for (int i=0; i<10;i++)
    {
      for (int j=0; j<10; j++)
      {
        StringGrid1->Cells[i][j] = i+j;
      }
    }
}
//---------------------------------------------------------------------------
void __fastcall TForm1::ClearGridClick(TObject *Sender)
{
ClearStringGrid(StringGrid1);
}
//---------------------------------------------------------------------------

In the GUI, click the FillGrid button, then the ClearGrid button, then 
the ResizeGrid button and you will notice that even though the 'clear 
grid' button cleared the grid visually, when you resize it you will see 
that a large number of values still exist.

Based on the results from above, I did modify the ClearStringGrid code 
to the following:
//---------------------------------------------------------------------------
void ClearStringGrid(TStringGrid* sgGrid)
{
    if (sgGrid->RowCount < sgGrid->ColCount)
    {
     //clear all the rows if there are less rows than columns
      for (int i=0; i<sgGrid->RowCount; i++)
      {
        sgGrid->Rows[i]->Clear();
      }
    }
    else
    {
      //clear all the columns if there are less columns than rows
      for (int i=0; i<sgGrid->ColCount; i++)
      {
        sgGrid->Cols[i]->Clear();
      }
    }

    sgGrid->ColCount=1;
    sgGrid->RowCount=1;
}


Even the above though takes nearly 10 seconds to clear a Grid containing 
  275K rows and only 4 columns on my 2GHz DUO-Core WinXP system with 2GB 
of RAM.  Yes, it's faster than the original code, but I expect faster. 
Am I wrong to expect that this clearing process should be possible in 
less than a second?

Dan