this is weird...

[SGaist]

To add to @mrjj, allocating QColor on the heap is rather unusual, if you take a look at Qt's classes which are using QColor, you'll see they all take const references. So you'll be dereferencing your heap allocated objects all the time if you use them with Qt classes which essentially wastes CPU cycles.

[harry]

i finally had some time to return to this project, and now i have 2 more problems:

as i said above, i have an array of QColors. the problem is that when i try to access one of them with

return mycolor[n];

the compiler gives me the following error:

invalid conversion from QColor* to Qrgb.

wait, what? where does this Qrgb come from? the array contains Qcolors, and the function (or method?) is supposed to return a QColor. so what am i doing wrong here?

the other problem is that the paintEvent() function of that class is not called. i change the size (both by dragging the edge of the window and by calling resize()), i call update() but paintEvent does not run, the background does not turn green, and the breakpoint is not hit. what's going on here? it is a subclass of QWidget, in case that matters.

[SGaist]

You don't have an array of QColor, you have an array of QColor pointers. Since your function returns a QColor object, a conversion must be done and the constructor that matches best is the one taking a Qrgb, but still, it's not valid.

As suggested before, use a vector of QColor rather than a vector of pointers to QColor.

As for paintEvent, can you post your code ?

[harry]

@SGaist said:

You don't have an array of QColor, you have an array of QColor pointers. Since your function returns a QColor object, a conversion must be done and the constructor that matches best is the one taking a Qrgb, but still, it's not valid.

As suggested before, use a vector of QColor rather than a vector of pointers to QColor.

i put in a QVector, nd now it seems to work ok. i'm gonna find out when i get to the point where i get the button to request a color from the screen.

As for paintEvent, can you post your code ?

what code are you referring to? the code in my paintEvent() method is irrelevant right now because it does not get called. yes, i have confirmed that by setting a breakpoint on the first line.

my main() method looks like this:

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyScreen w;
w.show();
return a.exec();
}

did i mention that the paintEvent() problem is with MyScreen?

in myscreen.h i had these lines:

public slots:
void paintEvent();

and then i saw these lines in an example program:

protected:
void paintEvent();

and i tried them out but that change made no difference.

[Jakob]

@harry You should read, learn, and remember this: http://www.cplusplus.com/doc/tutorial/arrays/

[SGaist]

Your paintEvent signature is wrong, it's missing the parameter.

[harry]

@harry said:

@SGaist said:

You don't have an array of QColor, you have an array of QColor pointers. Since your function returns a QColor object, a conversion must be done and the constructor that matches best is the one taking a Qrgb, but still, it's not valid.

As suggested before, use a vector of QColor rather than a vector of pointers to QColor.

i put in a QVector, nd now it seems to work ok. i'm gonna find out when i get to the point where i get the button to request a color from the screen.

ok, i'm trying to access that array now, and when i say something like

Qcolor c = MyColor[index];

i get a little window with an error message about a segmentation fault.

this line is in the header:

QVector<QColor> MyColor;

what am i doing wrong?

[mrjj]

Hi
QVector<QColor> MyColor;
means, dynamic list of colors. (it just defines it)
But unless do you
MyColor.append( QColor(255,0,0) );

Then
Qcolor c = MyColor[index];
will crash your program as the list is empty.

[harry]

@mrjj said:

Hi
QVector<QColor> MyColor;
means, dynamic list of colors. (it just defines it)
But unless do you
MyColor.append( QColor(255,0,0) );

i guess i should have mentioned that i have a couple of lines like this:

MyColor[3] = QColor( 0, 255, 255);

in my initcolors method. and i have confirmed that this method gets called when i launch the app, and it assigns the colors as intended.

should i try the append thing instead? but then how can i be sure which color ends up at which index?

[mrjj]

hi
if u have
MyColor[3] = QColor( 0, 255, 255);
then list is not empty
maybe index just too high for what u got in list.
use the .size() to check if index is ok

[harry]

@mrjj said:

hi
if u have
MyColor[3] = QColor( 0, 255, 255);
then list is not empty
maybe index just too high for what u got in list.
use the .size() to check if index is ok

just checked: size is 10 as it should be
index is 1, well within limits.

[mrjj]

but did u do
MyColor[0] = QColor( 0, 255, 255);
MyColor[1] = QColor( 0, 255, 255);
MyColor[2] = QColor( 0, 255, 255);
MyColor[3] = QColor( 0, 255, 255);
MyColor[4] = QColor( 0, 255, 255);
etc
does it have one at 1 ?

update:
if I do
QVector<QColor> colors;
colors[0]= QColor(244,0,0); <<< crash here.
qDebug() << colors.size();

So not sure why it seems to work for you.
But if u have size() 10 then it must have.
I would use append.
just append in the order you want.

[harry]

@mrjj said:

but did u do
MyColor[0] = QColor( 0, 255, 255);
MyColor[1] = QColor( 0, 255, 255);
MyColor[2] = QColor( 0, 255, 255);
MyColor[3] = QColor( 0, 255, 255);
MyColor[4] = QColor( 0, 255, 255);
etc
does it have one at 1 ?

yes, i fill the array with 10 different colors.

update:
if I do
QVector<QColor> colors;
colors[0]= QColor(244,0,0); <<< crash here.
qDebug() << colors.size();

So not sure why it seems to work for you.
But if u have size() 10 then it must have.
I would use append.
just append in the order you want.

i tried append. it seems to work, but i still have the same problem: when i try to get a qcolor from the qvector like this:

return myColor.at(1);

i get that little window with the segmentation fault. SIGSEGV, if that makes a difference.

i just thought of something. gotta try it out...

[harry]

@harry said:

i just thought of something. gotta try it out...

i have all my mycolor.append() lines in initColors(), and there they work nomally. but when i copy one of them into getColor(), i get a segmentation fault. i guess that means initColors() can access the QVector but getColor() can not. question is, why? both methods (or functions or whatever) are part of the same class, so what's going on here? weird.

[mrjj]

Ok it does sound strange.
so
QVector<QColor> myColors;
is defined in class .h ?
And only there. ?

So when ever you use myColor, its the same one, the one and only?
can u show all the code of the place where u use
return myColor.at(1);

is it just a access function like
QColor GetColor(index ) {
return myColor.at(index);
}

This should work with no issues so something strange is going on :)

so what ever u are doing with myColors we need to know

[harry]

@mrjj said:

Ok it does sound strange.
so
QVector<QColor> myColors;
is defined in class .h ?

check. that should make it available to all methods of that class, right?

And only there. ?

check

So when ever you use myColor, its the same one, the one and only?

it should be. how can i find out?

can u show all the code of the place where u use
return myColor.at(1);

i'm running OSX right now which is why i can't access my code. i'll post some code when i boot into ubuntu again.

is it just a access function like
QColor GetColor(index ) {
return myColor.at(index);
}

check. actually i make sure the index is within acceptable limits first. but yeah, that function is there to return one of those 10 colors to any UI element that requests one.

This should work with no issues so something strange is going on :)

so what ever u are doing with myColors we need to know

[mrjj]

Ok
Yes if defined in class
it is available to all methods of that class.
Its defined in the class, yes ?
Not outside, like global variable ?

It sounds it should just work. So must be something
unexpected .
Looking forward to code.

[SGaist]

An additional check: do you have something like QVector<QColor> myColors; in your constructor ?

[harry]

@SGaist said:

An additional check: do you have something like QVector<QColor> myColor; in your constructor ?

nope, that line is in the header file. would i be right in assuming that if that line was in the constructor, no other method would have access to the qvector? IOW, wouldn't the append lines in initcolors() also give me segmentation faults? the qvector is declared in the header file and initialized to 10 elements in the constructor (see below).

ok, so much for the header file. now the implementation file:

in the constructor i have this line:
myColor = QVector<QColor>(10);

in my initcolors() method i have 10 lines like
myColor.append(QColor(0,0,0));
and
qDebug() << myColor.at(1);
and they work normally.

my getcolors() method (just after initcolors(), in the same class) ends with this line:
return myColor.at(index);
and that's the one that gives me the segmentation fault.

[mrjj]

So you have something like

class MainWindow : public QMainWindow {
  Q_OBJECT

 public:
  explicit MainWindow(QWidget* parent = 0);
  ~MainWindow();
 public:
  void initcolors() {
    myColor = QVector<QColor>(10);
    myColor[0] = (QColor(0, 0, 0));
    myColor[1] = (QColor(244, 0, 0));
    myColor[2] = (QColor(255, 0, 0));
  }

  QColor GetColor(int index) {
    return myColor.at(index);
  }
  void Test() {
    qDebug() << GetColor(2);
  }
 private slots:
  void on_pushButton_released();

 private:
  Ui::MainWindow* ui;
  QVector<QColor> myColor;

};

And you call initcolors from constructor.

If I call Test, it works as expected.

So can you show how you call your
getcolors ?
Should be something like class->getcolors() if outside the class