[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index]

Reference for unit 'Controls' (#lcl)

TDragImageList

[Properties (by Name)] [Methods (by Name)] [Events (by Name)]

A multi-resolution list of Images used during Drag operations.

Declaration

Source position: controls.pp line 444

`type TDragImageList = class(TCustomImageList)`
`protected`
`function GetResolutionClass; override;`
`procedure Initialize; override;`		initializes the cursor shape and image index for the list.
`public`
`function BeginDrag();`		Start dragging an image; returns True if successful.
`function DragLock();`		Show drag image during drag operation.
`function DragMove();`		Shows the drag image at a new location.
`procedure DragUnlock;`		Hide the drag image.
`function EndDrag;`		Finish dragging of the image, restore the old cursor shape.
`procedure HideDragImage;`		Hides the drag image without unlocking the window.
`function SetDragImage();`		Set index of dragged image and hotspot.
`procedure ShowDragImage;`		Displays the drag image.
`property DragCursor: TCursor; [rw]`		The cursor shape to use while dragging.
`property DragHotspot: TPoint; [rw]`		The position of the HotSpot image, i.e. the offset to the mouse position while dragging.
`property Dragging: Boolean; [r]`		True if dragging in progress.
`property DraggingResolution: TDragImageListResolution; [r]`		Gets the scaled image resolution with the drag images for the list.
`property Resolution []: TDragImageListResolution; [r]`		Gets the image resolution for the specified image width.
`end;`

Inheritance

`TDragImageList`		A multi-resolution list of Images used during Drag operations.
\|
`TCustomImageList`		The base class for TImageList.
\|
`TLCLComponent`		The base class for LCL components which have an associated widget.
\|
`TComponent,IUnknown,IInterfaceComponentReference`
\|
`TPersistent,IFPObserved`
\|
`TObject`

Description

TDragImageList is a TCustomImageList descendant which provides a multi-resolution container for images displayed when a drop-drop operation is active. A drag image is shown when a drag operation is active and a DragImageList has been supplied.

TDragImageList overrides and reimplements methods from the ancestor to support the TDragImageListResolution type used in the image Resolution property. Additional properties and methods are provided to work with a drag image and its hot spot when the operation is started or stopped, and when the mouse position is changed.

In drag-dock operations, a drag image is not typically displayed since the DockRect frame already provides visual feedback.

This is a general overview of the usage of this class:

SetDragImage selects an image from the list, and defines the hotspot within this image. Te hotspot typically is the offset of the mouse position to the origin of the dragged control.
BeginDrag starts dragging, the image is shown at the starting location.
DragMove moves the image.
EndDrag stops dragging, the image is removed from the screen.

TDragImageList is the ancestor for the TImageList class defined in the LCL. It is also the type returned from the GetDragImages method in TControl.

TImageList		Implements a multi-resolution container for images used in an application.
TControl.GetDragImages		Get the list of images used when a drag operation is active.
TCustomImageList		The base class for TImageList.

TDragImageList

Declaration

Inheritance

Description

See also