Customizing events

Events to customize cell’s font attributes and color

There are several events that allow you to customize cell’s font attributes and color before the cell data will be drawn. In the time of calling these events the DataSet is positioned on the record that need to draw, so in the events you can access field values using such methods as TDataSet.FieldByName(..).Value. Do not change grid properties or columns properties in these events. It can bring to recirculation of the program.

TDBGridEh.OnDrawColumnCell

Write OnDrawColumnCell event to overload the standard method of the drawing cell. This event is called after standard drawing, so the information will be drawn above standard-drawn contents of cell. You may print the additional data, using methods of TDBGridEh(Sender).Canvas property.

TDBGridEh.OnDrawDataCell

Do not write an OnDrawDataCell event handler. OnDrawDataCell is obsolete and included for backward compatibility.

TColumnEh.OnAdvDrawDataCell or TDBGridEh.OnAdvDrawDataCell

Write this event to draw data in the grid cell. In code of the event we set Processed parameter in True value to define that the process of drawing was performed in event. Otherwise grid will call method for default drawing of cell data. You may, if necessary, change such parameters as ARect or Params. After changing the parameters call Grid.DefaultDrawColumnDataCell method and set Processed to True value. You can also leave Processed parameter in False state and don’t call Grid.DefaultDrawColumnDataCell. In that case, grid will call default drawing procedure using changed parameters. Use Grid.Canvas property to draw data in the cell by yourself.

TDBGridEh.OnGetCellParams and TColumnEh.OnGetCellParams event

Parameters:

Sender: TObject

Grid, that call the Event

Column: TColumnEh

The column for which the event is called

AFont : TFont

Font that will be used to paint a cell. You can change the font properties to specify properties of the new font rendering

var Background: TColor

The background color that will be used to paint a cell. You can change this parameter to specify a new color

State: TGridDrawState

The status of the cell

Write OnGetCellParams event to set such parameters as Font, cell color or other parameters of cell before cell will be drawn. If it is needed to change parameters only in a specified column then use column event - TColumnEh.OnGetCellParams. In this event you may change Font, Color, Alignment, ImageIndex, Text, checkbox's state and also such properties of a Params parameter as:

BlankCell: Boolean.

Set this property to true to show cell as an empty cell with 3D border.
SuppressActiveCellColor: Boolean.

Set this property to forbid the color of active cell to overlay the color that is set in Background property.

TextEditing: Boolean
Set this property to forbid showing of cell text editor.

These events are also called when grid request Font and Color for inplace editor.
If you want to draw data by yourself use OnAdvDrawDataCell event.

Use this event to replace the cell parameters for particular column before rendering. This event has an expanded set of parameters compared to the TDBGridEh.OnGetCellParams event.
This event is fired, not only before rendering a grid. In some cases, the event is called to request additional cell parameters. For example, before opening InplaceEditor grids causing the event and check Params.TextEditing option to allow you to open InplaceEditor for the current cell.

The TColumnEh.OnGetCellParams event has the following parameters :

Sender: TObject
Grid, which causes Event

EditMode: Boolean
The value is True if the event is caused by cell text editor. This same event is called when rendering a grid cell. In this case EditMode equals False.

Params: TColCellParamsEh
Additional parameters rendering. You can change the properties of this parameter in the event handler to change the format of the rendering of the current cell.

Alignment: TAlignment
Text alignment.

Background: TColor
background color

BlankCell: Boolean
An empty cell with 3D frame

SuppressActiveCellColor: Boolean
Use color Params.Background even if it is a current cell

CheckboxState:TCheckBoxState
Checkbox status if the column is set to show checkboxes

Col: Longint
Column number of the cell, which is drawn at the moment.

CellRect: TRect
The size and the cell borders

Font: TFont
Font to be used for drawing text

ImageIndex: Integer
Number of pictures from Column.ImageList

ReadOnly: Boolean
The cell read-only

Row: Longint
Row cell line number, which is drawn at this point.

State: TGridDrawState
Cell status

Text: String
The text to be rendered in the cell

TextEditing: Boolean
For the current cell, it is allowed to open InplaceEditor

DrawCellByThemes:Boolean
Draw the cell background using the scheme.

TextIsLink: Boolean
The text in the cell is a link reference.

ImageIsLink: Boolean
Picture from Column.ImageList a link reference.