How to find the actual width of grid component with scrollbar in Delphi

问题

I have a grid component (DBGrid) which has lots of columns on it. Because of large number of columns, a scrollbar was created, and thus some part of grid remains hidden. I need to find out what is the real width of DBGrid, including the part which is not shown due to scroll bar. But Width property gives only the width of the component itself. Anybody has any idea?

回答1:

Perhaps this may be helpful. It is part of a class helper for TDBGrid that auto sizes the last column, so that the grid has no empty space. Should be easy to adjust to your needs.

As you may notice, the CalcDrawInfo method is what you are seeking for. As it is protected you can either use a class helper or the usual protected-hack to get hands on it.

procedure TDbGridHelper.AutoSizeLastColumn;
var
  DrawInfo: TGridDrawInfo;
  ColNo: Integer;
begin
  ColNo := ColCount - 1;
  CalcDrawInfo(DrawInfo);
  if (DrawInfo.Horz.LastFullVisibleCell < ColNo - 1) then Exit;

  if (DrawInfo.Horz.LastFullVisibleCell < ColNo) then
    ColWidths[ColNo] := DrawInfo.Horz.GridBoundary - DrawInfo.Horz.FullVisBoundary
  else
    ColWidths[ColNo] := ColWidths[ColNo] + DrawInfo.Horz.GridExtent - DrawInfo.Horz.FullVisBoundary
end;

回答2:

TDBGrid has a Columns property. Each of the columns has its own Width property. So you could loop trought all the columns and sum up their widths.

Like this:

function TotalColumnsWidth(var AGrid: TDBGrid);
var
  i: Integer;
begin
  Result := 0;
  for i := to AGrid.Columns.Count - 1 do
    Result := Result + AGrid.Columns[i].Width;
end;

回答3:

I think I have found a solution (although it seems a little strange). In order to find the difference between column widths and real width of the DBgrid (that means find the width of the empty space left after last column), we need to keep track of which column is shown on the left now (what is current column that is scrolled to). We can do that using OnDrawColumnCell event, since it will draw only columns which are scrolled on now. Then we need to calculate sum of widths of all visible columns, and subtract that from DBGrid's width. P.S. Sorry for bad english

Ex code:

     For i:=0 to Last do
     if Vis[i] then
     Begin
      Sum:=Sum+DBG.Columns[i].Width;
      Inc(Cnt);
     End;

     if dgColLines in DBG.Options then
     Sum := Sum + Cnt;

  //add indicator column width
    if dgIndicator in DBG.Options then
    Sum := Sum + IndicatorWidth;
    Dif:=DBG.ClientWidth - Sum;

回答4:

Here are functions we have used in the past. It takes into account the width of data based on the font and also compensates for vertical lines if they are visible

function GridTextWidth(fntFont : TFont; const sString : OpenString) :
  integer;
var
  f: TForm;
begin
  try
    f:=TForm.Create(nil);
    f.Font:=fntFont;
    result:=f.canvas.textwidth(sstring);
  finally
    f.Free;
    end;
end;




function CalcGridWidth(dbg : TDBGrid { the grid to meaure }): integer; { the "exact" width }
const cMEASURE_CHAR   = '0';
      iEXTRA_COL_PIX  = 4;
      iINDICATOR_WIDE = 11;
var i, iColumns, iColWidth, iTitleWidth, iCharWidth : integer;
begin
  iColumns := 0;
  result   := GetSystemMetrics(SM_CXVSCROLL);

  iCharWidth := GridTextWidth(dbg.font,cMeasure_char);

  with dbg.dataSource.dataSet do begin
    DisableControls;
    for i := 0 to FieldCount - 1 do with Fields[i] do
      if visible then
      begin
        iColWidth := iCharWidth * DisplayWidth;
        if dgTitles in dbg.Options then begin
          ititlewidth:=GridTextWidth(dbg.titlefont,displaylabel);
          if iColWidth < iTitleWidth then
            iColWidth := iTitleWidth;
        end;
        inc(iColumns, 1);
        inc(result, iColWidth + iEXTRA_COL_PIX);
      end;
      EnableControls;
    end;

  if dgIndicator in dbg.Options then
  begin
    inc(iColumns, 1);
    inc(result, iINDICATOR_WIDE);
  end;
  if dgColLines in dbg.Options then
    inc(result, iColumns)
  else
    inc(result, 1);
end;

来源：https://stackoverflow.com/questions/1716870/how-to-find-the-actual-width-of-grid-component-with-scrollbar-in-delphi