How to intercept (detect) a Paste command into a TMemo?
Derive a new control that descends from 'TMemo' to intercept the WM_PASTE
message:
type
TPastelessMemo = class(TMemo)
protected
procedure WMPaste(var Message: TWMPaste); message WM_PASTE;
end;
uses
clipbrd;
procedure TPastelessMemo.WMPaste(var Message: TWMPaste);
var
SaveClipboard: string;
begin
SaveClipboard := Clipboard.AsText;
Clipboard.AsText := 'Simple Question';
inherited;
Clipboard.AsText := SaveClipboard;
end;
If you would like to prohibit any paste operation at all, empty the WMPaste handler.
This is an alternative to Sertac's excellent answer, which is to override the control's WndProc:
// For detecting WM_PASTE messages on the control
OriginalMemoWindowProc: TWndMethod;
procedure NewMemoWindowProc(var Message: TMessage);
//...
// In the form's OnCreate procedure:
// Hijack the control's WindowProc in order to detect WM_PASTE messages
OriginalMemoWindowProc := myMemo.WindowProc;
myMemo.WindowProc := NewMemoWindowProc;
//...
procedure TfrmMyForm.NewMemoWindowProc(var Message: TMessage);
var
bProcessMessage: Boolean;
begin
bProcessMessage := True;
if (Message.Msg = WM_PASTE) then
begin
// Data pasted into the memo!
if (SomeCondition) then
bProcessMessage := False; // Do not process this message any further!
end;
if (bProcessMessage) then
begin
// Ensure all (valid) messages are handled!
OriginalMemoWindowProc(Message);
end;
end;