Question and Answer Database
FAQ1786D.txt Notifying forms of global changes
Category :VCL
Platform :All
Product :All 32 bit
Question:
How do I tell all created (and even hidden), forms of an
application that some global option has changed?
Answer:
One way is to create a user message, and use the preform method to
send the message to all forms in the Screen.Forms array.
Example:
{Code for Unit1}
const
UM_MyGlobalMessage = WM_USER + 1;
type
TForm1 = class(TForm)
Label1: TLabel;
Button1: TButton;
procedure FormShow(Sender: TObject);
procedure Button1Click(Sender: TObject);
{ Private declarations }
private
procedure UMMyGlobalMessage(var AMessage: TMessage); message
UM_MyGlobalMessage;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
uses Unit2;
procedure TForm1.FormShow(Sender: TObject);
begin
Form2.Show;
end;
procedure TForm1.UMMyGlobalMessage(var AMessage: TMessage);
begin
Label1.Left := AMessage.WParam;
Label1.Top := AMessage.LParam;
Form1.Caption := 'Got It!';
end;
procedure TForm1.Button1Click(Sender: TObject);
var
f: integer;
begin
for f := 0 to Screen.FormCount — 1 do
Screen.Forms[f].Perform(UM_MyGlobalMessage, 42, 42);
end;
{Code for Unit2}
const
UM_MyGlobalMessage = WM_USER + 1;
type
TForm2 = class(TForm)
Label1: TLabel;
private
{ Private declarations }
procedure UMMyGlobalMessage(var AMessage: TMessage); message
UM_MyGlobalMessage;
public
{ Public declarations }
end;
var
Form2: TForm2;
implementation
{$R *.DFM}
procedure TForm2.UMMyGlobalMessage(var AMessage: TMessage);
begin
Label1.Left := AMessage.WParam;
Label1.Top := AMessage.LParam;
Form2.Caption := 'Got It!';
end;
7/16/98 4:31:28 PM
Last Modified: 01-SEP-99