qtconcurent imagescaling example upgrade

hello.

i look at the example "imagescaling" and done some upgrade.

well:

image.h (image.cpp has all the implementation)

Code:

---

class ImageData
{
  //... some data for the image size and path
}
 
class MyImage: public QWidget, public ImageData
{
// some function for working with images
}

---

Then I have another class for working with all loaded images.

imagelist.h

Code:

---

class MyLsit:public QWidget
{
//...
}

---

imageList.cpp

Code:

---

// my function for loading image
MyImage loadImage(const ImageData &data)
{
 MyImage m;
//... things to do on loading images
 return m;
}
 
void MyList::FirstStep()
{
 QList<ImageData> datalist;
 // load data
collection= new QFutureWatcher<Image>((QObject*)this);
collection->setFuture(QtConcurrent::mapped(datalist,loadImage));
// etc
}

---

when I compile the project it returns the error:

Quote:

---

/usr/lib64/qt-4.4.1/include/QtGui/qwidget.h: In copy constructor ‘MyImage::MyImage(const MyImage&)’:
/usr/lib64/qt-4.4.1/include/QtGui/qwidget.h:750: error: ‘QWidget::QWidget(const QWidget&)’ is private
../qt4/Tools/ShowImg/image.h:18: error: within this context
../qt4/Tools/imgsched.cpp: In function ‘Image LoadImage(ImageData&)’:
../qt4/Tools/imgsched.cpp:12: note: synthesized method ‘MyImage::MyImage(const MyImage&)’ first required here

---

if I change MyImage with QImage:

Code:

---

QImage loadImage(const ImageData &data){...}

---

it compiles.

I think this is an C++ feature, but i can not work it out.
Any suggestion on how to implement this would be appreciate.
thx!

why does MyImage (need to) inherit from QWidget?

(QWidget -as all QObjects- can not be copied or copy-constructed, which is what your compiler is trying to tell you.)

i forgot to write a detail:
in MyImage I have overwriten the paintEvent function, because i don't use in my main widget a QLabel object where to put the image.

Is there an another way for displaying image?

you have to separate the scaling from the drawing, ie make a class that contains the image (and associated data), and, if needed, one for displaying the data

Two reasons:
* QWidgets can't be copied (no way about that) - see above
* you must access QWidgets only in the main thread (which means no using QWidgets in QtConcurrent either!)

ok. thanks for the explanation....
i'll will rework my code

Quote:

---

you must access QWidgets only in the main thread (which means no using QWidgets in QtConcurrent either!)

---

could you tell me where can i read more about this? i have a big hole about this topic.

just read threads