[DUG] Odd problem with Tedit

Fri Jun 11 13:30:41 NZST 2010

VCL events being suddenly parallel would be a massively risky and breaking
change, demanding thread synchronisation in any and all events now being
parallelised. 

So I would be very surprised if there was ANY multi-threading in the events.
More likely is that window message order in the OS (or processing in the VCL
of those messages if it is a change that is reflected across different OS's)
has changed in some a subtle fashion and your code contains artefacts which
are only occasionally upset by that change.  i.e. similar to when OnCreate
firing order changed many, many versions ago.

From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On
Behalf Of John Bird
Sent: Friday, 11 June 2010 12:57
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Odd problem with Tedit

The same symptoms showed on computers running XP so it wasn't a Windows 7
change - would multithreading events be there too?

John

Hi John,

This is pure speculation:

I suspect that the events are somehow multi-threaded or not as dependent on
each other as they used to be. This could have something to do with the fact
that you now on Win7 and 2007. The thing pointing me in that direction is
the XP Manifest stuff. I think it alters a lot more under Win7. Oh, and then
there is the fact that you say it works sometimes, and others not...sounds
like two threads running and you want thread 2 to finish before thread
1...99% of the time they do, then the time slicing kicks in and the code
"breaks"

Anyways - well spotted and I like your saying !

Cheers,

Pieter

On 11/06/2010 03:13, John Bird wrote: 

I have solved it.

Had to do bit by bit testing and deductive reasoning to find the cause:  The
bit by bit found nothing but took lots of nice time trying useless things.
The deductive reasoning - this is my oldest program, and was written before
I understood clearly the difference between the form onActivate and onShow
events.   I had some code in the main form onActivate event that did quite a
lot of setups - including showing the second form which in its onActivate
event did some further processing.   I am guessing this is to use a
technical term "asking for weird stuff" .  Moving all the code to the onShow
event in both forms fixed the problem.   Well I think that's what fixed it.

Why did I do it this way with the onActivate event, which fires every time
the main form is returned to?   Well no-one ever told me otherwise, so I had
already put in code that made it only fire most of the code once ever,
effectively it was an onShow event.  And also on the list of events Activate
is right at the top and Show is right at the bottom, and I was teaching
myself this stuff.

The other mystery which I am not going to try to figure is that for over 6
years it has worked fine, and something minor altered recently has thrown
it.  I think it was when I added a combo box to the main form.  Even then
most of the time it worked fine, but often would not.   The main symptom was
the edit not getting proper focus - go figure!

I remember a saying on the door of one of my Physics lecturers - "This
problem - once solved - will be simple"

John

Yes I have tried all sorts of things like setting TabStop  to false, and
most hopefully setting the control second in the Tab Order list with focus
going to another control and then doing a Setfocus to the one I want.   It
still does not fix it.   Also been playing with Autoselect and ShowSelect,
and IMEMode.   Nothing makes any difference - I am convinced its something
in the way the program is built

Is there a way to programatically set the focus more than what Setfocus
does?

John

Hi John,

Have you tried to set the tab order to 1 (or 0 - can't remember which is the
"accepted" first) for this control ?

Cheers,

Pieter

On 10/06/2010 21:20, John Bird wrote: 

This one has me foxed.   I have a standard unit which is a form dialog at
the start of many programs - which gets an access code and a password.

In one program only it misbehaves - the Tedit fields never seem to get focus
properly, so although the users can type text, there is no cursor and the
onexit event of the TEdit does not fire.   Also default text in the Tedit
does not show as selected.   Subsequent returns to this and other edit boxes
do behave properly.

This is Delphi 2007 - problem shows for this program on Windows 7 and XP.
XP Manifest is in use.  Very little processing before this dialog form is
shown...

Note I have already done code like Edit1.Setfocus   -- it does not fix the
problem.

Anyone have any ideas???   Normal build and compile all and deleting all
dcus has not fixed it.

Also is there any way to force a Tedit to have its text selected.   

John

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