Qt signals driving me crazy

Below is source of basic window with TreeWidget on left and TabWidget on
the right. I stopped here because there is no way I can get
itemActivated() signal to call my nitem_clicked method. I have tried
practically everything I could find on net (there is very little Qt Ruby
examples beyond basics). Current source shows the most complicated
option, that I could have found ;-(

ruby 1.9.3
qtbindings (4.6.3.4)
kubuntu 10.4

by
TheR

require ‘Qt’

class TreeView < Qt::TreeWidget

slots ‘nitem_clicked(TreeWidgetItem*, int)’

##############################################
def initialize
super
init_ui
end

##############################################
def init_ui
self.header_hidden = true

item = Qt::TreeWidgetItem.new
item.setText(0,‘Mongo’)
addTopLevelItem(item)

item = Qt::TreeWidgetItem.new #Qt::TreeViewItem.new()
item.setText(0,’++ add new Mongo database’)
addTopLevelItem(item)

connect(self, SIGNAL(‘itemActivated( TreeWidgetItem*, int )’), self,
SLOT(‘nitem_clicked(TreeWidgetItem*, int)’))

end

#############################################
def nitem_clicked(item, column)
p item.inspect
end

end

##########################################

Main app

##########################################
class QtApp < Qt::MainWindow
def initialize
super
init_ui
resize 800, 600
move 300, 300
show
end

#############################################
def init_ui
splitter = Qt::Splitter.new
mongo_tree = TreeView.new
splitter.addWidget mongo_tree

mongo_tabs = Qt::TabWidget.new self
tab = Qt::Widget.new
mongo_tabs.addTab tab, ‘Tab1’

splitter.addWidget mongo_tabs
setCentralWidget splitter

quit = Qt::Action.new “&Quit”, self
file = menuBar.addMenu “&File”
file.addAction quit

self.connect(quit, SIGNAL(“triggered()”), Qt::Application.instance,
SLOT(“quit()”))
end

end

app = Qt::Application.new ARGV
QtApp.new
app.exec

On Friday 31 August 2012 Damjan R. wrote

by
TheR

The correct signature for the signal is

‘itemActivated( QTreeWidgetItem*, int )’

while you used

‘itemActivated(TreeWidgetItem*, int )’

without the leading Q. You have the same problem in a couple of other
places.
Generally speaking, when you have problems with a signal-slot
connection, one
of the first things to do is to look at the output on standard error and
see
if you see a warning saying ‘not such a signal’ or ‘not such a slot’
(this
warning is shown even if you’re running ruby with warnings turned off,
since
it is generated from the Qt library on the C++ side. Unfortunately, it
doesn’t
tell you where the wrong signal or slot name is).

I hope this helps

Stefano

Stefano C. wrote in post #1074007:

On Friday 31 August 2012 Damjan R. wrote

by
TheR

The correct signature for the signal is

‘itemActivated( QTreeWidgetItem*, int )’

while you used

‘itemActivated(TreeWidgetItem*, int )’

without the leading Q. You have the same problem in a couple of other
places.
Generally speaking, when you have problems with a signal-slot
connection, one
of the first things to do is to look at the output on standard error and
see
if you see a warning saying ‘not such a signal’ or ‘not such a slot’
(this
warning is shown even if you’re running ruby with warnings turned off,
since
it is generated from the Qt library on the C++ side. Unfortunately, it
doesn’t
tell you where the wrong signal or slot name is).

I hope this helps

Stefano

Thanks for your answer, I have already tried that too.

I oversleep problem a little, looked into source code and found
metaObject().signalNames method. The catch is that if I create
TreeWidget like:

t = Qt::TreeWidget.new
p t.metaObject().signalNames

I get nice output of all available signals, but if I write

p self.metaObject().signalNames

inside my defined TreeView class i get []. Where is the catch?

by
TheR

On Friday 31 August 2012 Damjan R. wrote

while you used
(this
Thanks for your answer, I have already tried that too.
Do you mean that after replacing TreeWidgetItem with QTreeWidgetItem
your
nitem_clicked slot still doesn’t get called? If so, that’s weird, since
I
tried it and it works for me.

p self.metaObject().signalNames

inside my defined TreeView class i get []. Where is the catch?

by
TheR

It may be a bug in qtruby, but I’m not sure. You can ask on the QtRuby
mailing
list (subscribing at
https://mail.kde.org/mailman/listinfo/kde-bindings). If
you don’t, I’ll do that one of the next days, as soon as I have a bit of
free
time. However, I’ve noticed that if I define a new signal in the custom
class,
metaObject#signalNames returns it, but it still doesn’t contain signals
from
the base class.

Stefano

Damjan R. писал 31.08.2012 10:58:

inside my defined TreeView class i get []. Where is the catch?

As far as I understand, #metaObject only describes the exact class it
was called on, not a full ancestor tree. You might need to walk every
superclass to get complete information.

On Saturday 01 September 2012 Damjan R. wrote


)

Posted via http://www.ruby-forum.com/.

setData requires s Qt::Variant as last argument, not a ruby object. In
theory,
with sufficiently recent version of QtRuby, you should be able to create
a
Qt::Variant from any ruby object using

Qt::Variant.from_value my_obj

When I tried it, however, I found out that it sometimes caused crashes.
There
should also be another way to do so, which I haven’t tried. Look at the
first
example at
http://techbase.kde.org/Development/Languages/Ruby#Emitting_Ruby_Classes

If these methods don’t work for you, your only option is to somehow
create a
string or number or something else which you can put in a Qt::Variant
and
which allows you to identify the object (the object_id of the object
itself
could be a good candidate).

I hope this helps

Stefano

Stefano was right. It works now. I must have lost my nerves somewhere in
beetween ;-( The problem is that all three declarations must be the
same:

slots ‘nitem_clicked(QTreeWidgetItem*, int)’

connect(self, SIGNAL(‘itemActivated( QTreeWidgetItem*, int )’),
self, SLOT(‘nitem_clicked(QTreeWidgetItem*, int)’))

Thanks guys.

Now I have another problem. You can add text and icons to
Qt::TreeWidgetItem.

item = Qt::TreeWidgetItem.new
item.setText(0,‘Test’)
item.setIcon(0, Qt::Icon.new(‘pics/test.png’) )

But I would like to add an object. There is a method
QTreeWidgetItem::setData ( int column, int role, const QVariant & value
)

If I use item.setData(0, Qt::UserRole, some_object) I get
method_missing’: undefined method `setData …

which usually means that one of data type is not valid. Is there another
way to add object pointer to QTreeWidgetItem.

by
TheR

Yeah. I was able to overcome the problem. Although it would be nice if
any object could be saved to treeViewItem. It is just a pointer anyway.

But now I have another signal, that doesn’t work. It’s the right mouse
click (context menu) on the same TreeWidget.

slots ‘right_click(QPoint)’

connect(self, SIGNAL(‘customContextMenuRequested(const QPoint)’), self,
SLOT(‘right_click(const QPoint)’) )

def right_click(point)
p ‘right_click’, point
end

by
TheR

And one more thing.

I would like to call my own slot function when main window is closed (to
save some settings when program is closed). How can I accomplish this?

by
TheR

On Monday 03 September 2012 Damjan R. wrote

And one more thing.

I would like to call my own slot function when main window is closed (to
save some settings when program is closed). How can I accomplish this?

by
TheR


Posted via http://www.ruby-forum.com/.

You can have a look at the documentation for
QApplication::lastWindowClosed
and QCoreApplication::AboutToQuit.

Stefano

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