[DUG] Shellexecute question
John Bird
johnkbird at paradise.net.nz
Fri Jul 25 13:53:51 NZST 2014
I don’t have any ProcessMessages in there! Actually the Program does a very ordered and stable startup, and has to run in sequence so moving the calculations to thread won’t actually gain me anything other than having it responsive to Minimise/maximise. That may be enough reason to do it if is an issue.
Aside – the SW_SHOWNOACTIVE had another oddity to it – the Program B started fine, Program A kept focus, but the window for Program B came up in front of Program A which is just a nuisance. I guess its related in part to the the occasional bugs in Z order that MS never have sorted, where a new form (even modal) will appear sometimes behind the launching form. Still there Windows 7/8.
From: Jolyon Smith
Sent: Friday, July 25, 2014 1:19 PM
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Shellexecute question
It shouldn't be puzzling. It is not the fact that the form is starting minimized, but the fact that Application.Run varies it's behaviour for the SW_SHOWMINNOACTIVE value CmdShow, a variation which does not occur for SW_MINIMIZED.
But NOOOOOoooooo - do NOT add calls to ProcessMessages(). Do not add ANY calls to ProcessMessages(). And remove any you already have !!! :)
ProcessMessages() calls make your application UI code re-entrant in highly unpredictable ways that can have you forever trying to find Heisenbugs, especially in a case like this where a user is likely to click on your launched app icon to see if it has "woken up" yet.
Do blocking work on a background thread, allow the UI to continue to respond on the main thread, and provide whatever feedback to the UI relating to the progress of the background thread via properly marshalled, thread safe mechanisms.
You will get more sleep that way. :)
On 25 July 2014 12:43, John Bird <johnkbird at paradise.net.nz> wrote:
It looks like the code in D2007 Application.Run is the later one. I would like to solve this at some stage out of curiosity so will return. The SW_SHOWMINIMIZED works as expected which is a puzzle. Usual story however, this is not on the list of urgent things to get working so it has to be put aside for now.
Its a good point you make about where to put startup code – my rule of thumb has generally been initialising non component stuff can be done in the form create, but I tend to put anything initialising component stuff on the form show event, and this is where much of it is – there is a bit of setting things visible or not depending on what properties are set and I don’t think this can generally be done before the Show event. This Program B does this general initialisation and then starts a timer which then fires of the rest of the startup code which is long running. Some of the long running code takes 20-40 seconds to run (calculations) and it doesn’t respond to minimising/maximising while that is happening which is another minor issue – I may need to put some extra processmessages calls in there eventually.
This relates to a previous question – the long running calculation sets up some quite large arrays and I tried saving/reading them in from disk to bypass the calculations but it produced a stack overflow. I am presuming that this is not from the code, as Russell’s code to save and load arrays to disk ran standalone, but due to the program using a larger amount of memory. Another investigation for later on the list of priorities!
From: Jolyon Smith
Sent: Friday, July 25, 2014 7:49 AM
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Shellexecute question
If the other Delphi application isn't correctly responding to SW_SHOWMINNOACTIVE then the problem is in the TApplicaiton code of the version of Delphi involved. The fact that your FormShow event isn't firing suggests that it's an older version of Delphi involved, since an inspection of the TApplication.Run method reveals how this behaviour (or lack of) would eventuate....
case CmdShow of
SW_SHOWMINNOACTIVE: FMainForm.FWindowState := wsMinimized;
SW_SHOWMAXIMIZED: MainForm.WindowState := wsMaximized;
end;
if FShowMainForm then
if FMainForm.FWindowState = wsMinimized then
Minimize else
FMainForm.Visible := True;
The internal state is forced to wsMinimize, bypassing normal property setters, resulting in the "show" code simply calling the Minimize method on the main form, rather than making the form visible, which is why the FormShow even isn't fired. The form isn't shown! i.e. the FormShow event will eventually fire only when the user first activates the application and the window becomes shown. You could argue that this is desirable behaviour, but doesn't suit your purposes in this case.
This was changed in later versions of Delphi. The above code is from D7. The version below from XE4 (the only 2 versions I have available on this system):
case CmdShow of
SW_SHOWMINNOACTIVE:
begin
FInitialMainFormState := wsMinimized;
FMainForm.FWindowState := wsMinimized;
end;
SW_SHOWMAXIMIZED: MainForm.WindowState := wsMaximized;
end;
if FShowMainForm then
if (FMainForm.FWindowState = wsMinimized) or (FInitialMainFormState = wsMinimized) then
begin
Minimize;
if (FInitialMainFormState = wsMinimized) then
FMainForm.Show;
end else
FMainForm.Visible := True;
Now it appears that the Show method of your main form should be called, though I haven't tested to see whether this is actually the case. But in theory, SW_SHOWMINNOACTIVE should work for you if you upgrade the target EXE to a more current version of Delphi.
Alternatively, you could move the initialisation code in that EXE, currently triggered by the FormShow event, to a more appropriate initialisation event. After all, this is initialisation that needs to be performed regardless of whether the form is Show'n or not. ;)
It's possible that some of that code cannot be performed in FormCreate, which is a quite common reason to use FormShow instead. If that's the case, then one possible solution is to post a custom message to yourself in FormCreate, to fabricate the create-deferred event you need, without relying on the form being shown to generate the FormShow event:
const
MM_INITIALISE = WM_USER + 1;
TMyForm = class(TForm)
...
procedure MMInitialise(var aMessage: TMessage); message MM_INITIALISE;
end;
TMyForm.FormOnCreate...
begin
PostMessage(Handle, MM_INITIALISE, 0, 0);
....
end;
procedure TMyForm.MMInitialise(var aMessage: TMessage);
begin
// Do initialisation here...
end;
Good luck
On 25 July 2014 00:22, John Bird <johnkbird at paradise.net.nz> wrote:
Hey that should have been perfect, as I already was doing SW_SHOWMINIMIZED which works fine, and so does SW_SHOWNOACTIVE which also does what it should – start the other window but not change focus.
However SW_SHOWMINNOACTIVE doesn’t work. Now the other program is a Delphi program of mine that does some initialisation in the Formshow event (turning on timers etc) and I am wondering if somehow the event doesn’t fire. The process starts, but nothing runs, looks asleep in Task Manager. Not worth messing around with, as its a minor issue.
I toyed with using SW_SHOWINACTIVE and getting the program (Program B) to minimise itself on start, but that is just damned complicated and fiddly/fragile. It also seems prone to ending up with 2 icons on the task bar, as though multiple copies have started even if only one is running – (maybe due to the large amount of work it does on startup – it is unresponsive for a good while) .
I also tried Russells suggestion about setting the foreground window and it don’t work for me (Windows 8.1)
What I did in the end was go back to the SW_SHOWMINIMIZED and then after the ShellExecute (in Program A) I put a ShowMessage saying I had started the other program. Because this gives a modal clue that they have to click on to continue it will do the job of setting the focus back. And its a bit useful for them to be informed it has been started.
From: Jolyon Smith
Sent: Thursday, July 24, 2014 8:21 PM
To: Russell Belding ; NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Shellexecute question
Have you tried passing SW_SHOWMINNOACTIVE instead of SW_MINIMIZED ?
Caveat: The show flag parameter is merely passed to the application being executed. What it chooses to do with that flag is it's own affair, but if you're lucky, it will respect your wishes. If not, then you will have to engage in a focus window arms race/lotto as already suggested. But Route #1 would be to try the officially mandated mechanisms.
Good luck. :)
On 24 July 2014 19:46, russell <russell at belding.co.nz> wrote:
Tyr this after spawning the other program.
SetForegroundWindow(forms.application.mainWindow.handle)
To give the main window of your program focus.
Perhaps modifications of this will take you to the window of the calling program where you want the focus?
Russell
From: delphi-bounces at listserver.123.net.nz [mailto:delphi-bounces at listserver.123.net.nz] On Behalf Of John Bird
Sent: Thursday, 24 July 2014 4:43 p.m.
To: NZ Borland Developers Group - Delphi List
Subject: [DUG] Shellexecute question
I have a program (Program A) that fires up another (program B) via ShellExecute, if its not already running. However even though Program B is started minimised, focus shifts away from Program A, which is a minor nuisance.
Is there any way to stop this within Delphi? Or will I have to do something like delve into the Windows API?
if ShellExecute(Application.Mainform.Handle, 'open', Pchar(aProgName), PChar(aparaml), PChar(aDir), SW_SHOWMINIMIZED) <= 32 then
ShowMessage('Start Minimised error:')
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