[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'ComCtrls' (#lcl)

# TCustomHeaderControl.OnSectionTrack

Event handler signalled when drag tracking/resizing is activated for the selected header section on the control.

## Declaration

Source position: comctrls.pp line 4108

`published property TCustomHeaderControl.OnSectionTrack : TCustomSectionTrackEvent read FOnSectionTrack write FOnSectionTrack;`

## Description

OnSectionTrack is a TCustomSectionTrackEvent property with the event handler signalled when resize tracking is activated for one of the Sections on the header control. It is signalled (when assigned) from the SectionTrack method. The event occurs when MouseDown, MouseMove, and MouseUp methods handle Shift+Left mouse button events on the control.

An application can implement and assign a handler routine using the signature in TCustomSectionTrackEvent to perform actions related to the resize tracking operation. Arguments passed to the handler routine include the header control and the header section for the notification. The Width and tracking state for the section are also included.

Use OnSectionResize to performs action needed when a resize operation has been completed for one of the header Sections.

Use OnSectionSeparatorDblClick to perform actions when the separator for a header section is double-clicked.

## See also

TCustomHeaderControl.Sections |  | Sections - the short segments of the header separated by vertical bars that function as the elementary selection units of the header.
TCustomHeaderControl.SectionTrack |  | Performs actions needed when the mouse tracking state for a header section has changed.
TCustomHeaderControl.MouseDown |  | Handles a mouse down event for the control.
TCustomHeaderControl.MouseMove |  | Handler for MouseMove events.
TCustomHeaderControl.MouseUp |  | Signals the OnMouseUp handler.
TCustomHeaderControl.OnSectionResize |  | Event handler signalled when a resize operation for a header section has been completed.
TCustomHeaderControl.OnSectionSeparatorDblClick |  | Event handler signalled when a separator between header sections on the control is double-clicked.