Clipboard
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Predefined types
TPredefinedClipboardFormat | MIME type |
---|---|
pcfText | text/plain |
pcfBitmap | image/bmp |
pcfPixmap | image/xpm |
pcfIcon | image/lcl.icon |
pcfPicture | image/lcl.picture |
pcfMetaFilePict | image/lcl.metafilepict |
pcfObject | application/lcl.object |
pcfComponent | application/lcl.component |
pcfCustomData | application/lcl.customdata |
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);
Clipboard is a TClipboard variable and the Clipbrd unit should be added in the uses clause in order to use the variable:
uses
..., Clipbrd;
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
The ClipBoard supports reading and writing of HTML.
Example of reading from and writing HTML source to clipboard:
uses
Clipbrd, ...;
var
Html, PlainText: String;
...
begin
Html := ClipBoard.GetAsHtml;
...
Html := '<b>Formatted</b> text';
PlainText := 'Simple Text';
ClipBoard.SetAsHtml(Html, PlainText);
end.
Windows
Handling Html content on the clipboard in Windows requires fidling with headers on Windows.
While in the past users had to do this manually, this now is handled transparently by the ClipBrd unit.
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;
Custom format
Multiple objects
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(AwParam: WParam; AlParam: LParam):LRESULT;
function WMDrawClipboard(AwParam: WParam; AlParam: 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 }
{Don't forget to assign to the OnCreate event.}
procedure TForm1.FormCreate(Sender: TObject);
begin
PrevWndProc := Windows.WNDPROC(SetWindowLongPtr(Self.Handle, GWL_WNDPROC, PtrInt(@WndCallback)));
FNextClipboardOwner := SetClipboardViewer(Self.Handle);
end;
{Don't forget to assign to the OnDestroy event.}
procedure TForm1.FormDestroy(Sender: TObject);
begin
ChangeClipboardChain(Handle, FNextClipboardOwner);
end;
function TForm1.WMChangeCBChain(AwParam: WParam; AlParam: LParam): LRESULT;
var
Remove, Next: THandle;
begin
Remove := AwParam;
Next := AlParam;
if FNextClipboardOwner = Remove then FNextClipboardOwner := Next
else if FNextClipboardOwner <> 0 then
SendMessage(FNextClipboardOwner, WM_ChangeCBChain, Remove, Next)
Result := 0;
end;
function TForm1.WMDrawClipboard(AwParam: WParam; AlParam: 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.
View the clipboard contents
Sometimes its useful to see whats actually in the clipboard at any one time. Here are a couple of methods I use, on a form with a TMemo and a one second timer to do just that -
procedure TForm1.CheckClipboard();
var
I : integer;
List : TStringList;
begin
memo1.clear;
Memo1.Append('[' + Clipboard.AsText + ']');
List := TStringList.Create;
try
ClipBoard.SupportedFormats(List);
for i := 0 to List.Count-1 do begin
//Memo1.Append(List.Strings[i]); // uncomment to see all available formats
case List.Strings[i] of // show these specific ones
'Rich Text Format', 'text/plain', 'UTF8_STRING' :
ReadClip(List.Strings[i]);
end;
end;
finally
List.Free;
end;
end;
function TForm1.ReadClip(TheFormat : ANSIString) : ANSIString;
var
Stream: TMemoryStream;
Fmt : TClipboardFormat;
List : TStringList;
begin
if TheFormat = '' then exit;
Stream := TMemoryStream.Create;
List := TStringList.Create;
try
if Clipboard.HasFormatName(TheFormat) then begin
Memo1.Append(#10+TheFormat);
Fmt := ClipBoard.FindFormatID(TheFormat);
ClipBoard.GetFormat(Fmt, Stream);
if Stream.Size > 0 then begin
Stream.Seek(0, soFromBeginning);
List.LoadFromStream(Stream);
Memo1.Lines.AddStrings(List, False);
end;
end;
finally
List.Free;
Stream.Free;
end;
end;
How to fix empty GTK2 clipboard on exit
Usually when your GTK2 app exits, it's clipboard becomes empty. Bad for usual user. This unit is a dirty fix, add it to "uses" somewhere.
unit fix_gtk_clipboard;
{$mode objfpc}{$H+}
interface
uses
gtk2, gdk2, Clipbrd;
implementation
var
c: PGtkClipboard;
t: string;
finalization
c := gtk_clipboard_get(GDK_SELECTION_CLIPBOARD);
t := Clipboard.AsText;
gtk_clipboard_set_text(c, PChar(t), Length(t));
gtk_clipboard_store(c);
end.
In May 2018 I (dbannon) found that putting this bit of code in a finalization section did fix the problem when the clipboard contents had come from the application itself but if it was there before the application started, that is, the application did not write to the clipboard, it introduces another, similar problem. Clipboard contents are, again, cleared in that case. And appears to happen because by time the finalization clause is executed, the clipboard has already been cleared.
An easy solution is to put that same code into the main form's onClose event. Its early enough that the contents, from either source are still there and late enough not to be subsequently cleared.
uses .... {$ifdef LINUX}gtk2, gdk2, Clipbrd{$endif};
.....
procedure TMainForm.FormClose(Sender: TObject; var CloseAction: TCloseAction);
var
c: PGtkClipboard;
t: string;
begin
{$ifdef LINUX}
c := gtk_clipboard_get(GDK_SELECTION_CLIPBOARD);
t := Clipboard.AsText;
gtk_clipboard_set_text(c, PChar(t), Length(t));
gtk_clipboard_store(c);
{$endif}
end;