Owner-Drawn Cells

For cases where complex per-cell customizations need to be performed you can render the contents of the cell by writing a handler for the OwnerDrawCell event. This event is raised as needed to display the contents of cells that have their OwnerDraw property set to True.

To create the owner-drawn cells in the above illustration:

1. Set the OwnerDraw property to True for the First column either in the designer or in code:

In the Designer

· Open the TrueDBGrid Designer by selecting Designer from the TrueDBGrid Tasks menu.

· Select the First column in the grid by clicking on it in the right pane.

The column can also be selected by choosing First from the drop-down list in the toolbar.

· Click the Display Column tab in the left pane.

· Set the OwnerDraw property to True.

· Click OK to close the editor.

In Code

Add the following code to the Form_Load event:

· Visual Basic

Me.C1TrueDBGrid1.Splits(0).DisplayColumns("First").OwnerDraw = True

· C#

this.c1TrueDBGrid1.Splits(0).DisplayColumns["First"].OwnerDraw = true;

· Delphi

Self.C1TrueDBGrid1.Splits(0).DisplayColumns['First'].OwnerDraw := True;

2. Declare the structure RECT in the general declarations of the form:

· Visual Basic

Public Structure RECT

Dim Left As Long

Dim Top As Long

Dim Right As Long

Dim Bottom As Long

End Structure

· C#

public struct RECT{

long Left;

long Top;

long Right;

long Bottom;

}

· Delphi

type RECT = record

Left: LongInt;

Top: LongInt;

Right: LongInt;

Bottom: LongInt;

end;

3. Implement the OwnerDrawCell event as follows:

· Visual Basic

Private Sub C1TrueDBGrid1_OwnerDrawCell(ByVal sender As Object, ByVal e As C1.Win.C1TrueDBGrid.OwnerDrawCellEventArgs) Handles C1TrueDBGrid1.OwnerDrawCell

If e.Col = 0 Then

' Create a gradient brush, blue to red.

Dim pt1, pt2 As Point

pt1 = New Point(e.CellRect.X, e.CellRect.Y)

pt2 = New Point(e.CellRect.Right, e.CellRect.Y)

Dim linGrBrush As System.Drawing.Drawing2D.LinearGradientBrush

linGrBrush = New System.Drawing.Drawing2D.LinearGradientBrush(pt1, pt2, Color.Blue, Color.Red)

Dim rt As RectangleF

rt = New RectangleF(e.CellRect.X, e.CellRect.Y, e.CellRect.Width, e.CellRect.Height)

' Fill the cell rectangle with the gradient.

e.Graphics.FillRectangle(linGrBrush, e.CellRect)

Dim whiteBR As Brush

whiteBR = New SolidBrush(Color.White)

Dim dispCol As C1.Win.C1TrueDBGrid.C1DisplayColumn

dispCol = Me.C1TrueDBGrid1.Splits(0).DisplayColumns(e.Col)

' Center the text horizontally.

Dim sfmt As New StringFormat()

sfmt.Alignment = StringAlignment.Center

' Draw the text.

e.Graphics.DrawString(dispCol.DataColumn.CellText(e.Row), dispCol.Style.Font, whiteBR, rt, sfmt)

whiteBR.Dispose()

' Let the grid know the event was handled.

e.Handled = True

End If

End Sub

· C#

private void C1TrueDBGrid1_OwnerDrawCell( object sender, C1.Win.C1TrueDBGrid.OwnerDrawCellEventArgs e)

{

if ( e.Col = 0 )

{

// Create a gradient brush, blue to red.

Point pt1, pt2;

pt1 = new Point[e.CellRect.X, e.CellRect.Y];

pt2 = new Point[e.CellRect.Right, e.CellRect.Y];

System.Drawing.Drawing2D.LinearGradientBrush linGrBrush;

linGrBrush = new System.Drawing.Drawing2D.LinearGradientBrush(pt1, pt2, Color.Blue, Color.Red);

RectangleF rt;

rt = new RectangleF(e.CellRect.X, e.CellRect.Y, e.CellRect.Width, e.CellRect.Height);

// Fill the cell rectangle with the gradient.

e.Graphics.FillRectangle(linGrBrush, e.CellRect);

Brush whiteBR;

whiteBR = new SolidBrush(Color.White);

C1.Win.C1TrueDBGrid.C1DisplayColumn dispCol;

dispCol = this.C1TrueDBGrid1.Splits[0].DisplayColumns[e.Col];

// Center the text horizontally.

StringFormat sfmt = new StringFormat();

sfmt.Alignment = StringAlignment.Center;

// Draw the text.

e.Graphics.DrawString(dispCol.DataColumn.CellText[e.Row], dispCol.Style.Font, whiteBR, rt, sfmt);

whiteBR.Dispose();

// Let the grid know the event was handled.

e.Handled = true;

}

· Delphi

procedure TWinForm.C1TrueDBGrid1_OwnerDrawCell(sender: System.Object; e: C1.Win.C1TrueDBGrid.OwnerDrawCellEventArgs);

var pt1, pt2: Point;

linGrBrush: System.Drawing.Drawing2D.LinearGradientBrush;

rt: RectangleF;

whiteBR: Brush;

dispCol: C1.Win.C1TrueDBGrid.C1DisplayColumn;

sfmt: StringFormat;

begin

if e.Col = 0 then

begin

// Create a gradient brush, blue to red.

pt1 := Point.Create(e.CellRect.X, e.CellRect.Y);

pt2 := Point.Create(e.CellRect.Copy, e.CellRect.Y);

linGrBrush := System.Drawing.Drawing2D.LinearGradientBrush.Create(pt1, pt2, Color.Blue, Color.Red);

rt := RectangleF.Create(e.CellRect.X, e.CellRect.Y, e.CellRect.Width, e.CellRect.Height);

// Fill the cell rectangle with the gradient.

e.Graphics.FillRectangle(linGrBrush, e.CellRect);

whiteBR := SolidBrush.Create(Color.White);

dispCol := Self.C1TrueDBGrid1.Splits[0].DisplayColumns[e.Col];

// Center the text horizontally.

sfmt := StringFormat.Create;

sfmt.Alignment := StringAlignment.Center;

// Draw the text.

e.Graphics.DrawString(dispCol.DataColumn.CellText(e.Row), dispCol.Style.Font, whiteBR, rt, sfmt);

whiteBR.Dispose;

// Let the grid know the event was handled.

e.Handled := True;

end;

There are a couple key points worth noting in this example:

· If the Handled property is set to True, the grid will not fill in the cell's background, nor will it display cell text or graphics. Therefore, you are responsible for filling in the entire cell, even if there is no data to display.

· Even a relatively simple example such as the one illustrated here requires a fair amount of coding, so consider using background bitmaps instead of owner-drawn cells if possible.