Re: Memory fault when inserting QTableItem into QTable

Oliver Kreuer <[email protected]>
Newsgroups gmane.comp.kde.devel.perl
Message-ID <[email protected]> 
Hello Richard,

I appended two example scripts with input files.
Script "table_fault.pl" reproduces the memory fault whereas 
"table_ok.pl" contains a work around. The work around is not very 
pleasant so I'm still interested why this memory fault occurs.
Due to bug #924345 the work around has to use takeItem insted of removeRow.

Oliver

Richard Dale wrote:
> On Monday 05 July 2004 14:42, Oliver Kreuer wrote:
> 
>>Hello,
>>
>>I've written the following small Perl/Qt program:
>>
>>...
>>table = Qt::Table(frame6, "table");
>>table->setNumRows( int(0) );
>>table->setNumCols( int(0) );
>>table->setReadOnly( 1 );
>>table->setSelectionMode( &Qt::Table::NoSelection() );
>>table->setLeftMargin(0);
>>...
>>open (FILE,"table_example.one") or die;
>>while (defined (my $line = <FILE>))
>>{
>>     chomp($line);
>>     push (@lines,$line);
>>
>>     clearTable();
>>
>>     table->setNumCols(1);
>>     table->horizontalHeader()->setStretchEnabled(1);
>>     table->horizontalHeader()->setLabel(0,"Eine Spalte",-1);
>>     table->setNumRows(scalar(@lines));
>>
>>     my $row = 0;
>>    foreach my $element (@lines)
>>    {
>>
>>table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never,"
>>$element"));
>>        $row++;
>>    }
>>}
>>
> 
> Shouldn't the code above look something like this? I'm not sure if that is the 
> cause of the problem - would you be able to post a complete program/input 
> file that reproduces the bug?
> 
> open (FILE,"table_example.one") or die;
> while (defined (my $line = <FILE>))
>  {
>       chomp($line);
>       push (@lines,$line);
> 
> 
>  }
>       clearTable();
>      table->setNumCols(1);
>       table->horizontalHeader()->setStretchEnabled(1);
>       table->horizontalHeader()->setLabel(0,"Eine Spalte",-1);
>       table->setNumRows(scalar(@lines));
> 
>       my $row = 0;
>      foreach my $element (@lines)
>      {
> 
>  table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never,"
>  $element"));
>          $row++;
>      }
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table_example.one (text/plain, 19 B) 
One
Two
Three
Four
table_example.two (text/plain, 32 B) 
1_1	1_2
2_1	2_2
3_1	3_2
4_1	4_2
table_fault.pl (application/x-perl, 4 KB) 
#!/usr/bin/perl -w

use strict;
use utf8;
#use Qt::debug qw(all);

package table_example;
use Qt;
use Qt::isa qw(Qt::Widget);
use Qt::slots
    tableOneRow => [],
    tableTwoRows => [];
use Qt::attributes qw(
    frame6
    One_Row
    table
    Two_Rows
);


sub NEW
{
    shift->SUPER::NEW(@_[0..2]);

    if ( name() eq "unnamed" )
    {
        setName("table_example" );
    }

    my $table_exampleLayout = Qt::GridLayout(this, 1, 1, 11, 6, '$table_exampleLayout');

    frame6 = Qt::Frame(this, "frame6");
    frame6->setFrameShape( &Qt::Frame::StyledPanel() );
    frame6->setFrameShadow( &Qt::Frame::Raised() );
    my $frame6Layout = Qt::GridLayout(frame6, 1, 1, 11, 6, '$frame6Layout');
    my $spacer = Qt::SpacerItem(190, 20, &Qt::SizePolicy::Expanding, &Qt::SizePolicy::Minimum);
    $frame6Layout->addItem($spacer, 1, 3);

    One_Row = Qt::PushButton(frame6, "One_Row");

    $frame6Layout->addWidget(One_Row, 1, 1);

    table = Qt::Table(frame6, "table");
    table->setNumRows( int(0) );
    table->setNumCols( int(0) );
    table->setReadOnly( 1 );
    table->setSelectionMode( &Qt::Table::NoSelection() );
    table->setLeftMargin(0);                               # don't show left vertical header

    $frame6Layout->addMultiCellWidget(table, 0, 0, 0, 3);

    Two_Rows = Qt::PushButton(frame6, "Two_Rows");

    $frame6Layout->addWidget(Two_Rows, 1, 2);
    my $spacer_2 = Qt::SpacerItem(190, 20, &Qt::SizePolicy::Expanding, &Qt::SizePolicy::Minimum);
    $frame6Layout->addItem($spacer_2, 1, 0);

    $table_exampleLayout->addWidget(frame6, 0, 0);
    languageChange();
    my $resize = Qt::Size(586, 482);
    $resize = $resize->expandedTo(minimumSizeHint());
    resize( $resize );
    clearWState( &Qt::WState_Polished );

    Qt::Object::connect(One_Row, SIGNAL "clicked()", this, SLOT "tableOneRow()");
    Qt::Object::connect(Two_Rows, SIGNAL "clicked()", this, SLOT "tableTwoRows()");
}


#  Sets the strings of the subwidgets using the current
#  language.

sub languageChange
{
    setCaption(trUtf8("Table Test") );
    One_Row->setText( trUtf8("One Row") );
    Two_Rows->setText( trUtf8("Two Rows") );
}


sub tableOneRow
{
		my @lines = ();
		
    open (FILE,"table_example.one") or die;
    while (defined (my $line = <FILE>))
    {
        chomp($line);
        push (@lines,$line);
        
        table->setNumCols(1);
        table->horizontalHeader()->setStretchEnabled(1);
        table->horizontalHeader()->setClickEnabled(0,-1);
        table->horizontalHeader()->setLabel(0,"Eine Spalte",-1);
        table->setNumRows(scalar(@lines));
				table->setFocusPolicy( &Qt::Table::NoFocus() );
        
        my $row = 0;
        foreach my $element (@lines)
        {
            table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }
    }				
}

sub tableTwoRows
{
    my @col1 = ();
		my @col2 = ();

    open (FILE,"table_example.two") or die;
    while (defined (my $line = <FILE>))
    {
        chomp($line);
				my @parts = split/\s+/,$line;
        push (@col1,$parts[0]);
        push (@col2,$parts[1]);
        
        table->setNumCols(2);
        table->horizontalHeader()->setStretchEnabled(1);
        table->horizontalHeader()->setLabel(0,"Erste Spalte",-1);
        table->horizontalHeader()->setLabel(1,"Zweite Spalte",-1);
        table->horizontalHeader()->setClickEnabled(0,-1);
        table->setNumRows(scalar(@col2) > scalar(@col1) ? scalar(@col1) : scalar(@col2));
				table->setFocusPolicy( &Qt::Table::NoFocus() );
        
        my $row = 0;
        foreach my $element (@col1)
        {
            table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }

				$row = 0;
        foreach my $element (@col2)
        {
            table->setItem($row,1,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }				
    }				
}



1;



package main;

use Qt;
use table_example;

my $a = Qt::Application(\@ARGV);
my $w = table_example;
$a->setMainWidget($w);
$w->show;
exit $a->exec;
table_ok.pl (application/x-perl, 4.6 KB) 
#!/usr/bin/perl -w

use strict;
use utf8;
#use Qt::debug qw(all);

package table_example;
use Qt;
use Qt::isa qw(Qt::Widget);
use Qt::slots
    tableOneRow => [],
    tableTwoRows => [];
use Qt::attributes qw(
    frame6
    One_Row
    table
    Two_Rows
);


sub NEW
{
    shift->SUPER::NEW(@_[0..2]);

    if ( name() eq "unnamed" )
    {
        setName("table_example" );
    }

    my $table_exampleLayout = Qt::GridLayout(this, 1, 1, 11, 6, '$table_exampleLayout');

    frame6 = Qt::Frame(this, "frame6");
    frame6->setFrameShape( &Qt::Frame::StyledPanel() );
    frame6->setFrameShadow( &Qt::Frame::Raised() );
    my $frame6Layout = Qt::GridLayout(frame6, 1, 1, 11, 6, '$frame6Layout');
    my $spacer = Qt::SpacerItem(190, 20, &Qt::SizePolicy::Expanding, &Qt::SizePolicy::Minimum);
    $frame6Layout->addItem($spacer, 1, 3);

    One_Row = Qt::PushButton(frame6, "One_Row");

    $frame6Layout->addWidget(One_Row, 1, 1);

    table = Qt::Table(frame6, "table");
    table->setNumRows( int(0) );
    table->setNumCols( int(0) );
    table->setReadOnly( 1 );
    table->setSelectionMode( &Qt::Table::NoSelection() );
    table->setLeftMargin(0);                               # don't show left vertical header

    $frame6Layout->addMultiCellWidget(table, 0, 0, 0, 3);

    Two_Rows = Qt::PushButton(frame6, "Two_Rows");

    $frame6Layout->addWidget(Two_Rows, 1, 2);
    my $spacer_2 = Qt::SpacerItem(190, 20, &Qt::SizePolicy::Expanding, &Qt::SizePolicy::Minimum);
    $frame6Layout->addItem($spacer_2, 1, 0);

    $table_exampleLayout->addWidget(frame6, 0, 0);
    languageChange();
    my $resize = Qt::Size(586, 482);
    $resize = $resize->expandedTo(minimumSizeHint());
    resize( $resize );
    clearWState( &Qt::WState_Polished );

    Qt::Object::connect(One_Row, SIGNAL "clicked()", this, SLOT "tableOneRow()");
    Qt::Object::connect(Two_Rows, SIGNAL "clicked()", this, SLOT "tableTwoRows()");
}


#  Sets the strings of the subwidgets using the current
#  language.

sub languageChange
{
    setCaption(trUtf8("Table Test") );
    One_Row->setText( trUtf8("One Row") );
    Two_Rows->setText( trUtf8("Two Rows") );
}


sub tableOneRow
{
		my @lines = ();
		
    open (FILE,"table_example.one") or die;
    while (defined (my $line = <FILE>))
    {
        chomp($line);
        push (@lines,$line);

####
# Work Around
####
				clearTable();
        
        table->setNumCols(1);
        table->horizontalHeader()->setStretchEnabled(1);
        table->horizontalHeader()->setClickEnabled(0,-1);
        table->horizontalHeader()->setLabel(0,"Eine Spalte",-1);
        table->setNumRows(scalar(@lines));
				table->setFocusPolicy( &Qt::Table::NoFocus() );
        
        my $row = 0;
        foreach my $element (@lines)
        {
            table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }
    }				
}

sub tableTwoRows
{
    my @col1 = ();
		my @col2 = ();

    open (FILE,"table_example.two") or die;
    while (defined (my $line = <FILE>))
    {
        chomp($line);
				my @parts = split/\s+/,$line;
        push (@col1,$parts[0]);
        push (@col2,$parts[1]);

####
# Work Around
####
				clearTable();
        
        table->setNumCols(2);
        table->horizontalHeader()->setStretchEnabled(1);
        table->horizontalHeader()->setLabel(0,"Erste Spalte",-1);
        table->horizontalHeader()->setLabel(1,"Zweite Spalte",-1);
        table->horizontalHeader()->setClickEnabled(0,-1);
        table->setNumRows(scalar(@col2) > scalar(@col1) ? scalar(@col1) : scalar(@col2));
				table->setFocusPolicy( &Qt::Table::NoFocus() );
        
        my $row = 0;
        foreach my $element (@col1)
        {
            table->setItem($row,0,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }

				$row = 0;
        foreach my $element (@col2)
        {
            table->setItem($row,1,Qt::TableItem(table,&Qt::TableItem::Never," $element"));
            $row++;
        }				
    }				
}


####
# Work Around
####

sub clearTable 
{
    if (table->numRows() > 0)
    {
        if (table->numCols() > 1)
        {
            for (my $elem = 0; $elem < table->numRows() ;$elem++ )
            {
                table->takeItem(table->item($elem,0));
                table->takeItem(table->item($elem,1));
            }
        }
        else
        {
            for (my $elem = 0; $elem < table->numRows() ;$elem++ )
            {
                table->takeItem(table->item($elem,0));
            }
        }                       
    }
}



1;



package main;

use Qt;
use table_example;

my $a = Qt::Application(\@ARGV);
my $w = table_example;
$a->setMainWidget($w);
$w->show;
exit $a->exec;
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