Form freezing form

[Ioannis Vranos]

Why in this code the form *does not refresh* when it gets the focus/after some time?

#using <mscorlib.dll >
#using <system.windows .forms.dll>
#using <system.dll>
#using <system.drawing .dll>
#include <windows.h>
#include <cstdlib>
// ==> Just a Form with two labels, one progress bar, opacity 90%.
// ==> label1, and progressBar are public and accessed through main().
// ==> Placed some refreshes but the problem persists.
__gc class Form1: public System::Windows ::Forms::Form
{
private:
System::Windows ::Forms::Label * label2;

public:
System::Windows ::Forms::Progre ssBar * progressBar1;
System::Windows ::Forms::Label * label1;

Form1()
{
this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );

this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );
this->SuspendLayout( );

this->label2->Font = new System::Drawing ::Font(S"Micros oft Sans Serif", 9.75F,
System::Drawing ::FontStyle::Re gular, System::Drawing ::GraphicsUnit: :Point, (System::Byte)1 61);
this->label2->Location = System::Drawing ::Point(14, 16);
this->label2->Name = S"label2";
this->label2->Size = System::Drawing ::Size(264, 40);
this->label2->TabIndex = 1;
this->label2->Text = S"Message 1...";
this->label2->TextAlign = System::Drawing ::ContentAlignm ent::MiddleCent er;

this->progressBar1->Location = System::Drawing ::Point(10, 176);
this->progressBar1->Name = S"progressBar1" ;
this->progressBar1->Size = System::Drawing ::Size(272, 23);
this->progressBar1->TabIndex = 2;

this->label1->Font = new System::Drawing ::Font(S"Micros oft Sans Serif", 8.25F,
System::Drawing ::FontStyle::Re gular, System::Drawing ::GraphicsUnit: :Point, (System::Byte)1 61);
this->label1->Location = System::Drawing ::Point(14, 80);
this->label1->Name = S"label1";
this->label1->Size = System::Drawing ::Size(264, 64);
this->label1->TabIndex = 3;

this->AutoScaleBaseS ize = System::Drawing ::Size(5, 13);
this->ClientSize = System::Drawing ::Size(292, 271);
this->Controls->Add(this->label1);
this->Controls->Add(this->progressBar1 );
this->Controls->Add(this->label2);
this->FormBorderStyl e = System::Windows ::Forms::FormBo rderStyle::Fixe d3D;

this->Name = S"Form1";
this->Opacity = 0.9;
this->ShowInTaskba r = false;
this->Text = S"Some Application";
this->TopMost = true;
this->ResumeLayout(f alse);
}
};
int main()try
{
Form1 *pForm1= __gc new Form1;

pForm1->Show();
pForm1->Refresh();

pForm1->label1->Text= "Diagnostic code";
pForm1->progressBar1->Value= 0;
pForm1->progressBar1->Maximum= 100;

while(true)
{
for(long i= 0; i< 100; ++i)
{
pForm1->progressBar1->Increment(1) ;
pForm1->Refresh();
}

pForm1->progressBar1->Value= 0;
}

}

catch(System::E xception *pe)
{
using namespace System;

Console::WriteL ine("Error: {0}", pe->Message);

return EXIT_FAILURE;
}

[Tamas Demjen]

Ioannis Vranos wrote:

How about calling Application::Do Events() instead of pForm1->Refresh()?
DoEvents processes all messages in the message queue and returns. It's
not nearly as good as multithreading, but it's very simple and prevents
your application from freezing while you are processing something that
lasts more than a 100 milliseconds. Call DoEvents periodically, but not
too often, because it slows down your application.

Why in this code the form *does not refresh* when it gets the
focus/after some time?
while(true)
{
for(long i= 0; i< 100; ++i)
{
pForm1->progressBar1->Increment(1) ;
pForm1->Refresh();
// <<<<<<<<<<<<<<< <<<<<<
Application::Do Events();
// <<<<<<<<<<<<<<< <<<<<<
}

pForm1->progressBar1->Value= 0;
}

}

Tom

[Ioannis Vranos]

Tamas Demjen wrote:

How about calling Application::Do Events() instead of pForm1->Refresh()?
DoEvents processes all messages in the message queue and returns. It's
not nearly as good as multithreading, but it's very simple and prevents
your application from freezing while you are processing something that
lasts more than a 100 milliseconds. Call DoEvents periodically, but not
too often, because it slows down your application.

Thanks for the tip Tamas. It appears that it solves the problem, but another one exists.
When I close the Form by pressing the X button, the application process does not
terminate. Any ideas?
Here is the corrected code:
#using <mscorlib.dll >
#using <system.windows .forms.dll>
#using <system.dll>
#using <system.drawing .dll>
#include <windows.h>
#include <cstdlib>
// ==> Just a Form with two labels, one progress bar, opacity 90%.
// ==> label1, and progressBar are public and accessed through main().
// ==> Placed some refreshes but the problem persists.
__gc class Form1: public System::Windows ::Forms::Form
{
private:
System::Windows ::Forms::Label * label2;

public:
System::Windows ::Forms::Progre ssBar * progressBar1;
System::Windows ::Forms::Label * label1;

Form1()
{
this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );

this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );
this->SuspendLayout( );

this->label2->Font = new System::Drawing ::Font(S"Micros oft Sans Serif",
9.75F, System::Drawing ::FontStyle::Re gular, System::Drawing ::GraphicsUnit: :Point,
(System::Byte)1 61);
this->label2->Location = System::Drawing ::Point(14, 16);
this->label2->Name = S"label2";
this->label2->Size = System::Drawing ::Size(264, 40);
this->label2->TabIndex = 1;
this->label2->Text = S"Message 1...";
this->label2->TextAlign = System::Drawing ::ContentAlignm ent::MiddleCent er;

this->progressBar1->Location = System::Drawing ::Point(10, 176);
this->progressBar1->Name = S"progressBar1" ;
this->progressBar1->Size = System::Drawing ::Size(272, 23);
this->progressBar1->TabIndex = 2;

this->label1->Font = new System::Drawing ::Font(S"Micros oft Sans Serif",
8.25F, System::Drawing ::FontStyle::Re gular, System::Drawing ::GraphicsUnit: :Point,
(System::Byte)1 61);
this->label1->Location = System::Drawing ::Point(14, 80);
this->label1->Name = S"label1";
this->label1->Size = System::Drawing ::Size(264, 64);
this->label1->TabIndex = 3;

this->AutoScaleBaseS ize = System::Drawing ::Size(5, 13);
this->ClientSize = System::Drawing ::Size(292, 271);
this->Controls->Add(this->label1);
this->Controls->Add(this->progressBar1 );
this->Controls->Add(this->label2);
this->FormBorderStyl e = System::Windows ::Forms::FormBo rderStyle::Fixe d3D;

this->Name = S"Form1";
this->Opacity = 0.9;
this->ShowInTaskba r = false;
this->Text = S"Some Application";
this->TopMost = true;
this->ResumeLayout(f alse);
}
};
int main()try
{
using namespace System;
using namespace System::Windows ::Forms;
using namespace System::Threadi ng;

Form1 *pForm1= __gc new Form1;

pForm1->Show();

pForm1->label1->Text= "Diagnostic code";
pForm1->progressBar1->Value= 0;
pForm1->progressBar1->Maximum= 100;

while(true)
{
for(long i= 0; i< 100; ++i)
{
pForm1->progressBar1->Increment(1) ;

if(i%10== 0)
Application::Do Events();

Thread::Sleep(1 00);
}

pForm1->progressBar1->Value= 0;
}

}

catch(System::E xception *pe)
{
using namespace System;

Console::WriteL ine("Error: {0}", pe->Message);

return EXIT_FAILURE;
}

[Tamas Demjen]

Ioannis Vranos wrote:

Thanks for the tip Tamas. It appears that it solves the problem, but
another one exists. When I close the Form by pressing the X button, the
application process does not terminate. Any ideas?

If I'm not mistaken, your main function if in a forever loop. This is
not typical in real-world applications. Usually your processing finishes
sooner or later. If you want to be able to cancel a long lasting
operation, you could have a Cancel button, which would set an
IsCancelled flag on click. Your main loop could then check against this
flag. This is how typical applications work.

I almost always perfer using threads, as opposed to DoEvents, because
threads have automatic load balancing, and you don't have to figure out
how often DoEvents should be called. It's also dangerous to call
DoEvents, because it may call other functions you are not prepared for
(it can have serious side effects, unwanted recursion, etc.).

When using DoEvents, your application won't be as smooth and responsive
as using threads. You either call DoEvents too often, which slows down
your processing, or you call it too rarely, which makes the GUI sluggish
during processing. There is no such problem with threads, as the system
scheduler is very smart, and you can even assign priorities to threads.
Assigning low priority you can instruct the system to "do it if you have
time, otherwise don't".

Tom

[Willy Denoyette [MVP]]

You never give a chance to your application to handle the paint message
posted to the application queue, your infinite loop takes all processing
time.
One bad advise would be to call DoEvents, but he! we are slowly moving to 64
bit OS'ses and this is a something that's been used on 16 bit non-preemptive
windows.
You should run your task (not really a realistic one) on another thread and
update the UI from there using Control::Invoke or BeginInvoke.

Willy.
Willy.

"Ioannis Vranos" <iv*@remove.thi s.grad.com> wrote in message
news:%2******** *******@TK2MSFT NGP12.phx.gbl.. .

Why in this code the form *does not refresh* when it gets the focus/after
some time?

#using <mscorlib.dll >
#using <system.windows .forms.dll>
#using <system.dll>
#using <system.drawing .dll>
#include <windows.h>
#include <cstdlib>
// ==> Just a Form with two labels, one progress bar, opacity 90%.
// ==> label1, and progressBar are public and accessed through main().
// ==> Placed some refreshes but the problem persists.
__gc class Form1: public System::Windows ::Forms::Form
{
private:
System::Windows ::Forms::Label * label2;

public:
System::Windows ::Forms::Progre ssBar * progressBar1;
System::Windows ::Forms::Label * label1;

Form1()
{
this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );

this->label2 = new System::Windows ::Forms::Label( );
this->progressBar1 = new System::Windows ::Forms::Progre ssBar();
this->label1 = new System::Windows ::Forms::Label( );
this->SuspendLayout( );

this->label2->Font = new System::Drawing ::Font(S"Micros oft Sans Serif",
9.75F, System::Drawing ::FontStyle::Re gular,
System::Drawing ::GraphicsUnit: :Point, (System::Byte)1 61);
this->label2->Location = System::Drawing ::Point(14, 16);
this->label2->Name = S"label2";
this->label2->Size = System::Drawing ::Size(264, 40);
this->label2->TabIndex = 1;
this->label2->Text = S"Message 1...";
this->label2->TextAlign = System::Drawing ::ContentAlignm ent::MiddleCent er;

this->progressBar1->Location = System::Drawing ::Point(10, 176);
this->progressBar1->Name = S"progressBar1" ;
this->progressBar1->Size = System::Drawing ::Size(272, 23);
this->progressBar1->TabIndex = 2;

this->label1->Font = new System::Drawing ::Font(S"Micros oft Sans Serif",
8.25F, System::Drawing ::FontStyle::Re gular,
System::Drawing ::GraphicsUnit: :Point, (System::Byte)1 61);
this->label1->Location = System::Drawing ::Point(14, 80);
this->label1->Name = S"label1";
this->label1->Size = System::Drawing ::Size(264, 64);
this->label1->TabIndex = 3;

this->AutoScaleBaseS ize = System::Drawing ::Size(5, 13);
this->ClientSize = System::Drawing ::Size(292, 271);
this->Controls->Add(this->label1);
this->Controls->Add(this->progressBar1 );
this->Controls->Add(this->label2);
this->FormBorderStyl e = System::Windows ::Forms::FormBo rderStyle::Fixe d3D;

this->Name = S"Form1";
this->Opacity = 0.9;
this->ShowInTaskba r = false;
this->Text = S"Some Application";
this->TopMost = true;
this->ResumeLayout(f alse);
}
};
int main()try
{
Form1 *pForm1= __gc new Form1;

pForm1->Show();
pForm1->Refresh();

pForm1->label1->Text= "Diagnostic code";
pForm1->progressBar1->Value= 0;
pForm1->progressBar1->Maximum= 100;

while(true)
{
for(long i= 0; i< 100; ++i)
{
pForm1->progressBar1->Increment(1) ;
pForm1->Refresh();
}

pForm1->progressBar1->Value= 0;
}

}

catch(System::E xception *pe)
{
using namespace System;

Console::WriteL ine("Error: {0}", pe->Message);

return EXIT_FAILURE;
}

[Ioannis Vranos]

Willy Denoyette [MVP] wrote:

You never give a chance to your application to handle the paint message
posted to the application queue, your infinite loop takes all processing
time.
One bad advise would be to call DoEvents, but he! we are slowly moving to 64
bit OS'ses and this is a something that's been used on 16 bit non-preemptive
windows.
You should run your task (not really a realistic one) on another thread and
update the UI from there using Control::Invoke or BeginInvoke.

This is about a window displaying progress of file operations. I assume a form is the only
thing that can be used as a "window". I want to display each file operation. Is your
suggestion that I can't do much else than skipping to display all file operations, but
instead display only from here and there?

The behaviour I am experiencing is exactly the same with this sample application, the form
freezes, but the program itself (a method of the form calling a couple of other methods of
the form) continues normally.

[Ioannis Vranos]

Ioannis Vranos wrote:

This is about a window displaying progress of file operations. I assume
a form is the only thing that can be used as a "window". I want to
display each file operation. Is your suggestion that I can't do much
else than skipping to display all file operations, but instead display
only from here and there?

The behaviour I am experiencing is exactly the same with this sample
application, the form freezes, but the program itself (a method of the
form calling a couple of other methods of the form) continues normally.

It seems that the problem got fixed after placing an Application::Do Events() call at each
iteration.

However if you have some more elegant idea, I would be glad to hear it (executing the file
processing method in a separate thread and letting it modify the Form from there does not
work, the program freezes).

[Ioannis Vranos]

Ioannis Vranos wrote:

It seems that the problem got fixed after placing an
Application::Do Events() call at each iteration.

However if you have some more elegant idea, I would be glad to hear it
(executing the file processing method in a separate thread and letting
it modify the Form from there does not work, the program freezes).

you= you both, or someone else.

[Tamas Demjen]

Ioannis Vranos wrote:

However if you have some more elegant idea, I would be glad to hear it
(executing the file processing method in a separate thread and letting
it modify the Form from there does not work, the program freezes).

Using a separate threads is the only reasonable and elegant solution.
It's not terribly hard to do, but you really have to be careful. Writing
thread safe code is hard, and if you miss something, it will freeze or
crash.

I haven't tried threads in .NET/WinForms, but use them all the time in
unmanaged applications, when a progress dialog is needed for a
long-lasting operation.

When you update the form from the thread, are you taking care of the
synchronization ? Only the main thread is allowed to modify the GUI, you
can't do it directly from the thread, you have to do the update via
Control::Invoke .

There are tutorials out there, although few of them are C++, you can
still get the point from them:
http://samples.gotdotnet.com/quickst...olinvoker.aspx
http://samples.gotdotnet.com/quickst...rshalling.aspx
http://www.dotnetspider.com/technology/kbpages/903.aspx

Tom

[Ioannis Vranos]

Tamas Demjen wrote:

When you update the form from the thread, are you taking care of the
synchronization ? Only the main thread is allowed to modify the GUI, you
can't do it directly from the thread, you have to do the update via
Control::Invoke .

Do you mean I should create a delegate for this? However my question is this, as far as I
understand, before the Application::Do Events() use, the form got "frozen" because of the
frequency of the updates. Why this will not happen when Invoke() is used?