Moving images while drag and drop - delphi

Question

I have an TImage on a TPanel, and an other (empty) TPanels. I want to drag
the image from the first to the second panel using the drag and drop.
I actually want to see the image while it's moving from one panel to the
other (semi-transparent).
I think I should use TDragObject.GetDragImages but I can't figure out how to construct the whole magic.
procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
Image1.ControlStyle := Image1.ControlStyle + [csDisplayDragImage]; // ???
TImage(Sender).BeginDrag(False);
end;
procedure TForm1.Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
begin
// ???
end;
procedure TForm1.Panel1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
if (Source is TImage) then
Accept := TImage(Source).Parent <> Sender;
end;
procedure TForm1.Panel1DragDrop(Sender, Source: TObject; X, Y: Integer);
begin
if (Source is TImage) then
begin
TImage(Source).Parent := TPanel(Sender);
TImage(Source).Align := alClient;
end;
end;
Update - I found a useful article: Implementing Professional Drag & Drop In VCL/CLX Applications

Answer 1

unit Unit3;
interface
// 2012 Thomas Wassermann - demo
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
TMyDragObject = class(TDragControlObject)
private
FImageList:TImageList;
FDragSource:TControl;
protected
function GetDragImages: TDragImageList; override;
public
Procedure StartDrag(G:TGraphic;p:TPoint;DragSource:TControl);
Constructor Create(AControl: TControl); override;
Destructor Destroy;override;
Property DragSource:TControl read FDragSource;
end;
TForm3 = class(TForm)
Panel1: TPanel;
Panel2: TPanel;
Image1: TImage;
procedure Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
procedure FormCreate(Sender: TObject);
procedure Panel1DragOver(Sender, Source: TObject; X, Y: Integer; State: TDragState; var Accept: Boolean);
procedure FormDestroy(Sender: TObject);
procedure Panel1DragDrop(Sender, Source: TObject; X, Y: Integer);
private
{ Private-Deklarationen }
FDragObject:TMyDragObject;
public
{ Public-Deklarationen }
end;
var
Form3: TForm3;
implementation
constructor TMyDragObject.Create(AControl: TControl);
begin
inherited;
FImageList:=TImageList.Create(nil);
end;
destructor TMyDragObject.Destroy;
begin
FImageList.Free;
inherited;
end;
function TMyDragObject.GetDragImages: TDragImageList;
begin
Result := FImageList;
end;
{$R *.dfm}
procedure TMyDragObject.StartDrag(G: TGraphic;p:TPoint;DragSource:TControl);
var
bmp:TBitMap;
begin
FDragSource := DragSource;
bmp:=TBitMap.Create;
try
FImageList.Width := g.Width;
FImageList.Height := g.Height;
bmp.Width := g.Width;
bmp.Height := g.Height;
bmp.Canvas.Draw(0,0,g);
FImageList.Add(bmp,nil);
finally
bmp.Free;
end;
FImageList.SetDragImage(0,p.x,p.y)
end;
procedure TForm3.FormCreate(Sender: TObject);
var
i:Integer;
begin
ControlStyle := ControlStyle + [csDisplayDragImage];
for I := 0 to ControlCount -1 do
if Controls[i] is TPanel then
TPanel(Controls[i]).ControlStyle := TPanel(Controls[i]).ControlStyle + [csDisplayDragImage];
ReportMemoryLeaksOnShutDown := True;
end;
procedure TForm3.FormDestroy(Sender: TObject);
begin
if Assigned(FDragObject) then FDragObject.Free;
end;
procedure TForm3.Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
var
p:TPoint;
begin
p:=TImage(Sender).ScreenToClient(mouse.cursorpos);
if Assigned(FDragObject) then FDragObject.Free;
FDragObject := TMyDragObject.Create(TImage(Sender));
FDragObject.StartDrag(TImage(Sender).Picture.Graphic,p,TImage(Sender));
DragObject := FDragObject;
end;
procedure TForm3.Panel1DragDrop(Sender, Source: TObject; X, Y: Integer);
begin
if FDragObject.DragSource is TImage then
TImage(FDragObject.DragSource).Parent := TPanel(Sender);
end;
procedure TForm3.Panel1DragOver(Sender, Source: TObject; X, Y: Integer; State: TDragState; var Accept: Boolean);
begin
Accept := Source is TMyDragObject;
end;
end.