Mega Code Archive
How to create custom inputquery-messagebox etc without pain
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Using a way that may look like a hack it is possible to modify generic message boxes and change the icon, edit, button, size, etc...
The idea behind this customization is to create a custom message, post it to the queue *before* calling the message box. In the message, you retrieve the handle of the window (if it's messagebox) or the form (if it's inputbox/inputquery/messagedlg) and you modify whatever you want. Let me give two examples, one for a regular api messagebox and another with a inputquery.
1st example: You need to change the default caption of the Yes/No button of a regular messagebox.
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
procedure WMHackBox(var message: TMessage); message WM_USER + 1025;
end;
...
implementation
...
procedure TForm1.Button1Click(Sender: TObject);
begin
// Posting our custom message
PostMessage(Handle, WM_USER + 1025, 0, 0);
// Messagebox call
Application.MessageBox('I'' completely stupid.', 'MyApplication', MB_YESNO or MB_ICONINFORMATION);
end;
procedure TForm1.WMHackBox(var message: TMessage);
var
h: HWND;
begin
// The message box is shown, let's retrieve its handle
h := FindWindow(WC_DIALOG, 'MyApplication');
// If this is the right messagebox, let's modify it
if GetParent(h) = Application.Handle then
begin
SetDlgItemText(h, ID_YES, 'I &agree');
SetDlgItemText(h, ID_NO, 'I &disagree');
end;
end;
Note that if you use MessageDlg, it's not a regular API messagebox but a Form created dynamically by Delphi. See 2nd Example.
2nd example: You need to change the edit property of a InputQuery, for instance the PasswordChar.
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
procedure WMHack(var message: TMessage); message WM_USER + 1024;
end;
...
implementation
...
const
ACaption = 'Caption';
procedure TForm1.Button1Click(Sender: TObject);
begin
PostMessage(Handle, WM_USER + 1024, 0, 0);
InputBox(ACaption, 'Prompt', 'Default');
end;
procedure TForm1.WMHack(var message: TMessage);
var
i: Integer;
j: Integer;
begin
for i := 0 to Screen.FormCount-1 do
if Screen.Forms[i].Caption = ACaption then
begin
for j := 0 to Screen.Forms[i].ControlCount-1 do
if Screen.Forms[i].Controls[j] is TEdit then
begin
TEdit(Screen.Forms[i].Controls[j]).PasswordChar := '#';
TEdit(Screen.Forms[i].Controls[j]).SelectAll;
Exit;
end;
end;
end;
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