[Kde-bindings] Adding more explicit ambiguous method lookup resolution for PerlQt

[Chris Burel]

On Wed, Jun 10, 2009 at 8:34 AM, Richard Dale<rdale at foton.es> wrote:
> On Wednesday 10 June 2009 06:28:33 am Chris Burel wrote:
>> Hey guys,
>> Sorry for double posting, but I wanted to get Ruby's opinion on this too.
>>
>> One thing in PerlQt that can be very frustrating is when the bindings
>> cannot determine which method you intend to call based on the
>> arguments.  A common example of this happens with the QVariant class,
>> because it's essentially a union class that has constructors for a
>> bunch of different data types.  Consider:
>> my $foo = Qt::Variant(1)
>> results in
>>
>> --- Ambiguous method QVariant::QVariant called
>> Candidates are:
>>         QVariant::QVariant( uint )
>>         QVariant::QVariant( int )
>>         QVariant::QVariant( bool )
>> Choosing first one...
>>
>> It's frustrating because the bindings clearly know that the other
>> method exists, and sometimes you really do want to call the other
>> method.  But how should you specify which method you really want?
>>
>> I was thinking that if we already have the method's signature, and it
>> is unique, why not let the coder specify the exact signature they want
>> to call?  Something along the lines of
>> Qt::setSignature( 'QVariant::QVariant( bool )' );
>> my $foo = Qt::Variant(1);
>> That way the coder can force the bindings to call the correct method.
> In QtRuby you can pass an optional second argument to the
> Qt::Variant#fromValue method to indicate the exact type you want:
That works for the case where you make the Variant in Ruby/Perl and
then retrieve data from the Variant also in Ruby/Perl.  But if you're
passing the variant to some function for use by C++, it's not
sufficient.  You have to create the variant with the right type so
that when C++ looks at it to determine it's type, you get the one you
intended.  Consider the following from the widgets/codeeditor example
that ships with Qt-4.5.1:

my $selection = Qt::TextEdit::ExtraSelection();

my $lineColor = Qt::Color(Qt::yellow())->lighter(160);

$selection->format->setBackground( Qt::Brush( $lineColor ) );
# Create a bool or int QVariant?
$selection->format->setProperty(Qt::TextFormat::FullWidthSelection(),
Qt::Variant(1));
$selection->setCursor( this->textCursor() );
$selection->cursor->clearSelection();

this->setExtraSelections([$extraSelections]);

If that creates an int variant, the resulting property is not set as desired.