How to Fix DBGrid Column Widths Automatically

Designed to enable a user to view and edit data in a tabular grid, the DBGrid provides various ways of customizing the way it represents "its" data. With so much flexibility, a Delphi developer can always find new ways to make it more powerful.

One of the missing features of TDBGrid is that there is no option to automatically adjust the widths of specific columns to completely fit the grid's client width.

When you resize the DBGrid component at runtime, the column widths are not resized.

If the width of the DBGrid is larger than the total width of all the columns, you'll get an empty area right after the last column. On the other hand, if the total width of all the columns is larger than the width of the DBGrid, a horizontal scrollbar will appear.

Automatically Adjust DBGrid Column Widths

There's one handy procedure you can follow that fixes the widths of selective DBGrid columns when the grid is resized at runtime.

It's important to note that, usually, only two to three columns in a DBGrid actually need to be auto-resized; all the other columns display some "static-width" data. For example, you can always specify fixed width for columns displaying values from data fields that are represented with TDateTimeField, TFloatField, TIntegerField, and similar.

What's more, you'll probably create (at design time) persistent field components using the Fields editor, to specify the fields in the dataset, their properties, and their ordering.

With a TField descendant object, you can use the Tag property to indicate that a particular column displaying values for that field must be auto-sized.

This is the idea: If you want a column to auto-fit the available space, assign an integer value for the TField descendant's Tag property that indicates the corresponding column's minimum width.

The FixDBGridColumnsWidth Procedure

Before you begin, in theĀ OnCreate event for the Form object containing the DBGrid, specify what columns need to be auto-resized by assigning a non-zero value for the Tag property of the corresponding TField object.

procedure TForm1.FormCreate(Sender: TObject);
begin
 //setup autoresizable columns by asigning 
 //Minimm Width in the Tag property.
 
 //using fixed value: 40 px
 Table1.FieldByName('FirstName').Tag := 40;

 //using variable value: width of the 
 //default Column title text
 Table1.FieldByName('LastName').Tag :=
 4 + Canvas.TextWidth(
 Table1.FieldByName('LastName').DisplayName);
end;

In the above code, Table1 is a TTable component linked to a DataSource component, which is linked with the DBGrid. The Table1.Table property points to the DBDemos Employee table.

We've marked the columns displaying the values for FirstName and LastName fields to be auto-resizable. The next step is to call our FixDBGridColumnsWidth in the OnResize event handler for the Form:

procedure TForm1.FormResize(Sender: TObject);
begin
 FixDBGridColumnsWidth(DBGrid1);
end;

Note: All of this makes sense if the Align property of the DBGrid includes one of following values: alTop, alBottom, alClient, or alCustom.

Finally, here's the FixDBGridColumnsWidth procedure's code:

procedure FixDBGridColumnsWidth(const DBGrid: TDBGrid);
var
 i : integer;
 TotWidth : integer;
 VarWidth : integer;
 ResizableColumnCount : integer;
 AColumn : TColumn;
begin
 //total width of all columns before resize
 TotWidth := 0;
 //how to divide any extra space in the grid
 VarWidth := 0;
 //how many columns need to be auto-resized
 ResizableColumnCount := 0;

 for i := 0 to -1 + DBGrid.Columns.Count do
 begin
 TotWidth := TotWidth + DBGrid.Columns[i].Width;
 if DBGrid.Columns[i].Field.Tag 0 then 
 Inc(ResizableColumnCount);
 end;

 //add 1px for the column separator line
 if dgColLines in DBGrid.Options then
 TotWidth := TotWidth + DBGrid.Columns.Count;

 //add indicator column width
 if dgIndicator in DBGrid.Options then
 TotWidth := TotWidth + IndicatorWidth;

 //width vale "left"
 VarWidth := DBGrid.ClientWidth - TotWidth;

 //Equally distribute VarWidth
 //to all auto-resizable columns
 if ResizableColumnCount > 0 then
 VarWidth := varWidth div ResizableColumnCount;

 for i := 0 to -1 + DBGrid.Columns.Count do
 begin
 AColumn := DBGrid.Columns[i];
 if AColumn.Field.Tag 0 then
 begin
 AColumn.Width := AColumn.Width + VarWidth;
 if AColumn.Width then
 AColumn.Width := AColumn.Field.Tag;
 end;
 end;
end; (*FixDBGridColumnsWidth*)