Clipboard

Predefined types

TPredefinedClipboardFormat	MIME type
pcfText	text/plain
pcfBitmap	image/bmp
pcfPixmap	image/xpm
pcfIcon	image/lcl.icon
pcfPicture	image/lcl.picture
pcfObject	application/lcl.object
pcfComponent	application/lcl.component
pcfCustomData	application/lcl.customdata
pcfDelphiText	text/plain
pcfDelphiBitmap	text/delphi.bitmap
pcfDelphiPicture	Delphi picture
pcfDelphiMetaFilePict	image/delphimetafilepict
pcfDelphiObject	application/delphi.object
pcfDelphiComponent	Delphi component
pcfKylixPicture	image/delphi.picture
pcfKylixBitmap	image/delphi.bitmap
pcfKylixDrawing	image/delphi.drawing
pcfKylixComponent	application/delphi.component

Text

For use of simple text Clipboard offer property AsText which can be used for reading an writing plain text.

Writing text:

Clipboard.AsText := 'Hello clipboard!';

Reading text:

ShowMessage('Clipboard content: ' + Clipboard.AsText);

Text oriented components

Some visual components like TEdit, TMemo, TStringGrid, TLabeledEdit, TMaskEdit, TSpinEdit and TFloatSpinEdit have ability to select a part of contained text and offer additional functionality for handling clipboard operations on selected text.

  procedure CopyToClipboard; 
  procedure CutToClipboard; 
  procedure PasteFromClipboard;

HTML source

Example of reading HTML source from clipboard:

uses
  Clipbrd, ...;

procedure InsertHTMLSourceFromClipboard(Strings: TString);
var
  Fid: TClipboardFormat
  Str: WideString;
  Stream: TMemoryStream;
begin
  Fid := Clipboard.FindFormatID('text/html');
  if Fid <> 0 then 
  try
    Stream := TMemoryStream.Create;
    if Clipboard.GetFormat(Fid, Stream) then 
    begin
      Stream.Position := 0;
      Str := PWideChar(Stream.Memory);
      Str[(Stream.Size div 2) + 1] := #0;
      Strings.Text := UTF8Encode(Str);
    end;
  finally
    Stream.Free;
  end;
end;

Write html source to clipboard. This can be done with AddFormat either using TStream or memory Buffer.

// register the mime type for text/html. You can do this once at program start:
  ClipbrdFmtHTML := RegisterClipboardFormat('text/html');
...
  // put text and html on the clipboard. Other applications will choose the best format automatically.
  ThePlainUTF8Text := 'Simple text';
  Clipboard.AsText := ThePlainUTF8Text; 
  HTMLSource := '<b>Formatted</b> text'; // text with formatrings
  Clipboard.AddFormat(ClipbrdFmtHTML, HTMLSource[1], Length(HTMLSource));

Image

Load from clipboard

uses 
  Clipbrd, LCLIntf, LCLType, ...;

procedure LoadBitmapFromClipboard(Bitmap: TBitmap);
begin
  if Clipboard.HasFormat(PredefinedClipboardFormat(pcfDelphiBitmap)) then
    Bitmap.LoadFromClipboardFormat(PredefinedClipboardFormat(pcfDelphiBitmap));
  if Clipboard.HasFormat(PredefinedClipboardFormat(pcfBitmap)) then
    Bitmap.LoadFromClipboardFormat(PredefinedClipboardFormat(pcfBitmap));
end;

Save to clipboard

uses 
  Clipbrd, ...;

procedure SaveBitmapToClipboard(Bitmap: TBitmap);
begin
  Clipboard.Assign(Bitmap);
end;

Getting notified of changes

The LCL does not pass on Windows messages. It only passes on messages > WM_USER. This means you have to write your own message handler. Processing non - user messages in your window

Sample code to implement message handler:

unit Unit1;

{$mode delphi}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
  Clipbrd, StdCtrls, Windows, Messages;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    FNextClipboardOwner: HWnd;   // handle to the next viewer
    // Here are the clipboard event handlers
    function WMChangeCBChain(wParam: WParam; lParam: LParam):LRESULT;
    function WMDrawClipboard(wParam: WParam; lParam: LParam):LRESULT;
  public
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}
var
  PrevWndProc:windows.WNDPROC;

function WndCallback(Ahwnd: HWND; uMsg: UINT; wParam: WParam;
  lParam: LParam): LRESULT; stdcall;
begin
  if uMsg = WM_CHANGECBCHAIN then begin
    Result := Form1.WMChangeCBChain(wParam, lParam);
    Exit;
  end 
  else if uMsg=WM_DRAWCLIPBOARD then begin
    Result := Form1.WMDrawClipboard(wParam, lParam);
    Exit;
  end;
  Result := CallWindowProc(PrevWndProc, Ahwnd, uMsg, WParam, LParam);
end;

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
begin
  PrevWndProc := Windows.WNDPROC(SetWindowLong(Self.Handle, GWL_WNDPROC, PtrInt(@WndCallback)));
  FNextClipboardOwner := SetClipboardViewer(Self.Handle);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  ChangeClipboardChain(Handle, FNextClipboardOwner);
end;

function TForm1.WMChangeCBChain(wParam: WParam; lParam: LParam): LRESULT;
var
  Remove, Next: THandle;
begin
  Remove := WParam;
  Next := LParam;
  if FNextClipboardOwner = Remove then FNextClipboardOwner := Next
    else if FNextClipboardOwner <> 0 then
      SendMessage(FNextClipboardOwner, WM_ChangeCBChain, Remove, Next)
end;

function TForm1.WMDrawClipboard(wParam: WParam; lParam: LParam): LRESULT;
begin
  if Clipboard.HasFormat(CF_TEXT) Then Begin
    ShowMessage(Clipboard.AsText);
  end;
  SendMessage(FNextClipboardOwner, WM_DRAWCLIPBOARD, 0, 0);   // VERY IMPORTANT
  Result := 0;
end;

end.

External links

• Basic Clipboard Operations (Cut/Copy/Paste) using the TClipboard object