Fake modal dialog using Show? - delphi

Question

My application have several modules, each in one tab on the mainform.
When using a dialog it is convenient to call ShowModal because you know when the dialog is finished. But for the user it is not good as it lock the whole program until the dialog closes.
I want to have a locally modal dialog. So one module can open a dialog and it locks current module only. The user can still switch to another module and continue to work. If the user return to the first module the dialog is there waiting for close before the user can continue to work in that module.
I have to make some kind of framework for this that all dialogs in the application can use.
I have a baseclass for all dialogs TAttracsForm and I think here is the place to add my Show() method.
This should lock access to all wincontrols only in the current module.
It should simulate a call to ShowModal(). How can I achieve this ?
Regards

Answer 1

You will have to do the following:
Have an identity for each module
Have a flag that is active or inactive for each module
Have a flag that stores the modality of the attached dialog. If it is modal and the module is active, then call the show method in the appropriate eventhandler. Remember to update these values in the onshow and onclose events of each dialog.
You may have to fine tune this suggestion till you achieve the exact functionality that you require.

Answer 2

Do you still want to implement this with "you know when the dialog is finished" metaphor?
So like
DoSomethingBeforeDialog();
Form:=TFakeFormDialog.Create(Nil);
try
Form.FakeShowModal();
finally
Form.Free;
end;
DoSomethingAfterDialog();
if the answer is yes, you would try to implement this with threads, like Google Chrome do this with tab pages. But without threads only you can catch message processing with a code like this
function TFakeModalDlg.FakeShowModal(FormParent: TWinControl): boolean;
begin
Parent:=FormParent;
SetBounds((FormParent.Width - Width) div 2, (FormParent.Height - Height) div 2,
Width, Height);
Show;
while NoButtonIsPressed() do
begin
Application.HandleMessage;
end;
Hide;
end;
And you even have code below...
Form:=TFakeModalDlg.Create(Nil);
try
(Sender as TButton).Caption:='Going modal...';
Form.FakeShowModal(TabSheet1);
(Sender as TButton).Caption:='Returned from modal';
finally
Form.Free;
end;
called multiply times from your tabs, but the problem is the these "dialogs" should be closed in "stack order" i.e. reverse to the order they were showed. I think it's impossible to force users to close forms in developers preference order :)

Answer 3

I have actually almost implemented local modal dialogs now.
It is built around that when a TForms Enabled property is set To False the whole Form is locked from input. And my modules is just a descendant from TForm.
My ViewManager class that decide what modules is current add/close modules etc got 2 new methods. LockCurrentView and UnLOckCurrentView.
function TViewManager.LockCurrentView: TChildTemplate;
begin
Result := CurrentView;
Result.Enabled := False;
Result.VMDeactivate; // DeActivate menus and toolbas for this module
end;
procedure TViewManager.UnLockCurrentView(aCallerForm: TChildTemplate);
begin
aCallerForm.VMActivate; // Activate menus and toolbas for this module
aCallerForm.Enabled := True;
end;
TAttracsForm is the baseclass of all dialogs. I Override FormClose and add a new method ShowLocalModal to call instead of ShowModal. I also have to add a TNotifyEvent OnAfterDestruction to be called when the dialog is closed.
procedure TAttracsForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
if Assigned(fCallerForm) then
begin
ClientMainForm.ViewManager.UnLockCurrentView(fCallerForm as TChildTemplate);
if Assigned(OnAfterDestruction) then
OnAfterDestruction(Self);
Action := caFree;
end;
end;
{ Call to make a dialog modal per module.
Limitation is that the creator of the module must be a TChildtemplate.
Several modal dialogs cannot be stacked with this method.}
procedure TAttracsForm.ShowLocalModal(aNotifyAfterClose: TNotifyEvent);
begin
fCallerForm := ClientMainForm.ViewManager.LockCurrentView; // Lock current module and return it
PopupParent := fCallerForm;
OnAfterDestruction := aNotifyAfterClose;
Show;
end;
Some test with simple dialogs looks promising. So the module just have to call ShowLocalModal(myMethod) which have a TNotifyEvent as parameter. This method is called when the dialog is closed.