Flicking Qt application using squish - qt

Can anyone please help me in understanding how the flick function works when called flick(objectOrName, x, y, dx, dy, cdx, cdy) using python. When I tried it, it is not working; it is throwing an error:
Cannot call flick with null declarative item

first lets define this flick, applied on objects: http://doc.qt.io/qt-4.8/qml-flickable.html
second, from your error, I only got the feeling that your item, it's not of flickable type. Please go to http://doc.froglogic.com/squish/latest/, and search for flick() .... and you will see that
... It initiates a flick of the specified objectOrName item—which must be a QML Flickable ...
If you have those things cleared, please send an email to contact#froglogic.com, I'm sure it's more quicker this way.

Related

Qt - signal for when QListWidget row is edited?

I am working in Qt4.7, and I have a QListWidget in my dialog. I have a QString that needs to match the current text in the row of this widget (the individual rows are editable). Looking at the signals associated with QListWidget, there seem to be signals for when a different index is selected but none for when the text of a the currently selected row changes. I thought currentTextChanged(QString) would do it, but it didn't. I also thought to try to connect each individual row to something, but QListWidgetItem doesn't have any built-in signals. Does anyone know of a way to do this? Thanks!
At first it seems like QListWidget::itemChanged is the way to go, but soon you run into a problem: the signal is sent for everything - inserts, changing colors, checking boxes, and anything else that "changes" the item! Predelnik pointed that out in his answer. Some people have tried to put in flags and filter everywhere by intercepting various signals to find out if editing was the actual event. It gets very messy.
There is also QAbstractItemModel::dataChanged , which would seem like a good solution. It even has a parameter "const QVector& lstRoles" so you could scan for Qt::EditRole and see if it was really edited. Alas, there's a catch - it gets called for everything just like QListWidget::itemChanged and unfortunately, for QListWidget anyway, the roles parameter is always empty when it's called (I tried it). So much for that idea...
Fortunately, there's still hope... This solution does the trick! :
http://falsinsoft.blogspot.com/2013/11/qlistwidget-and-item-edit-event.html
He uses QAbstractItemDelegate::closeEditor, but I prefer using QAbstractItemDelegate::commitData.
So make a connect like so...
connect(ui.pLstItems->itemDelegate(), &QAbstractItemDelegate::commitData, this, &MyWidget::OnLstItemsCommitData);
Then implement the slot like this...
void MyWidget::OnLstItemsCommitData(QWidget* pLineEdit)
{
QString strNewText = reinterpret_cast<QLineEdit*>(pLineEdit)->text();
int nRow = ui.pLstItems->currentRow();
// do whatever you need here....
}
Now you have a slot that gets called only when the list item's text has been edited!
I guess you need to look into the following signal:
void QListWidget::itemChanged(QListWidgetItem * item)
But be careful because it's being sent every time some property of item changed, not only text. I remember when we ran into the problem once when we changed item colors and got tons of false positive slots called because of that. If you need more fine tuning I guess it's better to write model/view classes yourself and not rely on QListWidget.

crash after QGraphicsProxyWidget is removed from a scene

I have a simple scene with a QGraphicsProxyWidget added to it ( and some widget set on it ).
If I try removing it from the scene, like so:
if ( widget )
{
parentScene->removeItem( m_widget ); // m_widget is a QGraphicsProxyWidget
delete m_widget; // I also tried m_widget->deleteLater() here - same result
m_widget = NULL;
}
I get an instant crash - no descriptive callstack though that would tell me what's wrong ( some windows related calls in the callstack, and that's all ).
I'm using version 5.1.1 of the Qt library, I've searched the manual and the net for an instruction how to actually remove such a widget, and it's not documented at all, so I'm not sure if I'm doing something wrong there, or is there a bug in the library.
I'd appreciate any help.
Cheers,
Piotr
Check your if statement: It says widget when you probably meant m_widget. If widget is non-null and m_widget is null, your program will crash, since the calls to removeItem/delete will attempt to reference a null pointer.
I found the problem - seemingly unrelated call to 'prepareGeometryChange' was to blame here.
My widgets were changing size ( I didn't mention it, 'cause it seemed irrelevant at the time ). However I was calling the aforementioned method AFTER I made the change to the geometry, not before, as the manual instructs.
Apparently that method is very important in order to keep the scene's internal data in order, and due to my calling it incorrectly, it was leaving some invalid references to the deleted items.

Get QWidget absolute position in the MainWindow constructor

I want to get the absolute x and y coordinates of a frame control. I know that there is a QWidget::mapToGlobal function that should give me these coordinates - but it always returns the relative points.
My code is:
int y = ui->frame->mapToGlobal(ui->frame->window()->pos()).y();
Can anyone please help me to understand what I am doing wrong?
EDIT:
Found the problem - I've called this line in the main window class, before it is displayed. So now my Q is how can I get the position that the main window will be displayd in its constructor?
I think you can't, not reliably and portably anyway. The position is not decided yet, and decision is often made by window manager, not the application.
So, what you should do is override moveEvent(), resizeEvent() and/or showEvent() Those are the right place to do stuff like that, instead of constructor.

Qt SLOTS parameters (Beginner)

I'm a beginner to Qt and am making (or at least trying to make) a basic calculator. If I understand correctly, when doing this:
connect(my_button_4, SIGNAL(clicked()), this, SLOT(writeNumberLbl("4")));
The "4" is not accessible (rather, only its type is) in writeNumberLbl. Basically, I would like so that when the button is clicked, the label sets its text to "4". However, I have the numbers 0 to 9, so I wanted to do:
connect(my_button_0, SIGNAL(clicked()), this, SLOT(writeNumberLbl("0")));
connect(my_button_1, SIGNAL(clicked()), this, SLOT(writeNumberLbl("1")));
...
connect(my_button_9, SIGNAL(clicked()), this, SLOT(writeNumberLbl("9")));
My writeNumberLbl function is:
void Calculator::preWriteVal(QChar val)
{
QString curVal = ui.lbl_output->text();
curVal += val;
ui.lbl_output->setText(curVal);
}
However, I can see that this will not work due to the parameter, 'val'. Could someone please point me in the right direction? Thank you. I did look to see if this question had already been answered and couldn't find anything. If it has, please provide me a link.
Also, is it possible, using Qt Designer 4, to connect a widget to a custom slot?
Thank you.
As far as I know,Qt's signal/slot system requires that the number of parameters of signal function is not less than that of slots function.
In your example,the signal function click() have zero parameters and slot function writeNumberLbl("4") have one parameter,this will not be accepted by the Qt's signal/slot system and if you run your program in debug mode of Qt creator,the qDebug will show you a message like 'Incompatiable signal/slot' blalbalba~. To solve this problem, just read the article given by Arnold Spence. It is quite clear.
There are a number of ways to tackle this problem and they are outlined very nicely here. Although that page is a bit old, I think it is still quite valid. I would recommend using a signal mapper.
For your second question, yes. You can connect signals and slots using Qt Designer by setting the designer in "Edit Signals/Slots" mode. Once in this mode, for example, you can drag a connection line from a button to the form. A dialog will open up allowing you to choose the signal and slot to connect. If you haven't already implemented a slot in code, you can specify the name of a slot and then add the code for it afterward.
The number of parameters in Slot can not exit those in Signal? and pressed() has none. You have two choices (three, counting the dumb one):
Use QSignalMapper. Its help is self-explanatory.
Connect all your buttons to single slot. In it, find out what button has been pressed. QObject::sender() function helps.
There are even more ways, but more complicated.

Flex - Is there a way to specify what direction a ComboBox will open?

Maybe I should further qualify this - Is there a way to specify which direction a ComboBox will open without copying and pasting the entire ComboBox class and ripping out the code where it determines which direction it will open in...
I'm my specific case - I need it to open upwards - always.
UPDATE: You can't fix this by subclassing it because the function that handles the direction of the opening is:
private function displayDropdown(show:Boolean, trigger:Event = null):void
And that bad boy uses a fair amount of private variables which my subclass wouldn't have access to...
If you build up the Menu object yourself, you can place the menu anywhere you want by simply setting the x,y coordinates of the menu object. You'll need to calculate those coordinates, but you might be able to do this easily without subclassing ComboBox.
I am doing something similar with PopUpButton; you might find it easier to work with PopUpButton. This is based on real code from my current project:
private function initMenu(): void {
var m:Menu = new Menu();
m.dataProvider = theMenuData;
m.addEventListener(MenuEvent.ITEM_CLICK, menuClick);
m.showRoot = false;
// m.x = ... <-- probably don't need to tweak this.
// m.y = ... <-- this is really the interesting one :-)
theMenu.popUp = m;
}
<mx:PopUpButton id="theMenu" creationComplete="initMenu()" ... />
BTW, to get the PopUpButton to act more like I wanted it (always popup, no matter where the click), setting openAlways=true in the MXML works like a charm.
I doubt it - you'd need to subclass the control (which isn't that big a deal.)
Maybe you could mess with the real estate so it's placed in such a fashion (e.g. crowded into the lower right corner) that up is naturally coerced?
I would recommend checking out this post. Yes, you do have to grab the ComboBox code and modify it, but at least now you have an idea where the modifications need to go.
You could set the MaxDropDownHeight, if you set it big enough Windows will automatically set the direction upwards.
This irritated me no end. I have uploaded a solution, its a simple Class that extends the PopUpButton and removes the logic of stage bounds detection as it failed 50% of the time anyway. My code just allows you to simply specify whether you want to open the menu up or down:
http://gist.github.com/505255

Resources