[SOLVED] application segfaults when assigning pixmap for Label

SGaist

Hi and welcome to devnet,

Can you check that the QImage is valid ? e.g. do you have Tux.png in the same folder as your application executable ?

dqqw

i'm pretty sure that it loads the image, because when i run it in debug mode, in the locals it displays the resolution of the image

SGaist

You should confirm it with a test like

@
if (!renderedImage.isNull())
qDebug() << "invalid image";
@

On a related note, you can create a QPixmap from a file, that would save you the conversion there

dqqw

modified the code as follows:
@void RaytracerMainWindow::on_actionRender_triggered()
{
QImage renderedImage;
renderedImage.load("Tux.png");
if(!renderedImage.isNull()){
qDebug() << "invalid image";
}else{
qDebug() << "image loaded";
}

raytracerRenderDialog->renderedImageContainer->show();

//raytracerRenderDialog->renderedImageContainer->setPixmap(QPixmap::fromImage(renderedImage));

ui->actionShow_render->setChecked(true);

}@

it outputs "image loaded "

and on a sidenote raytracerRenderDialog->renderedImageContainer->show(); crashes the application

could you please take a look at the RaytracerRenderDialog class?
i think the problem comes from there.

see i created a mainwindow (RaytracerMainWindow) and a dialog (RenderDialog), the creator generated the correct headers and classes for them.
but when i tried to instanciate a RaytracerRenderDialog inside RaytracerMainWindow, the compiler threw all kinds of redefinition error and such.
so i read somewhere i must derive a class to be able to instantiate it.
i think something is messed up in the constructor of RaytracerRenderDialog.

in the past few yeard i coded mostly strictly in C, so it is hard for me to get back to the C++ mentality, let aloge getting used to QT's own mechanisms.

thanks

SGaist

You are doing the test wrong, if isNull() is true you have an invalid image

Are you sure renderedImageContainer is initialized correctly ?

dqqw

yeah, that was a copy-paste problem, and it did not have the tux.png next to it because i moved the project folder and the build folder changed too...
yeah and i copy pasted your code without actually checking... :D

i THINK i initialize it correctly:
@RaytracerMainWindow::RaytracerMainWindow(QWidget *parent):
QMainWindow(parent),
ui(new Ui::RaytracerMainWindow)
{
ui->setupUi(this);
raytracerRenderDialog= new RaytracerRenderDialog(parent);
}@

which calls this:
@RaytracerRenderDialog::RaytracerRenderDialog(QWidget *parent):
QDialog(parent),
renderDialog(new Ui::RenderDialog)
{
renderDialog->setupUi(this);
}@

somewhere in the middle i realized that qt widget classes keep a reference to themselves as a pointer of ther class, but some things are not very clean to me

if it would help i could upload an archive of the project itself

SGaist

Where is renderedImageContainer declared ?

dqqw

since it was added with the desginer:

<widget class="QLabel" name="renderedImageContainer">
<property name="styleSheet">
<string notr="true">background-color: rgb(128, 128, 128);</string>
</property>
<property name="text">
<string/>
</property>
</widget>

so it is declared in the intermediary ui_renderdialog.h, which is generated.

i assumed it should be initialized since i call the setuUi method for RenderDialog from RaytracerRenderDialog

SGaist

Did you run your application through the debugger ?

dqqw

solved it.

added
@void RenderDialog::setRenderedImage(QPixmap pixmap)
{
ui->renderedImageContainer->setPixmap(pixmap);
}@

to RenderDialog

and called it like this from raytreacermainwindow:
@void RaytracerMainWindow::on_actionRender_triggered()
{
QImage renderedImage;
renderedImage.load("Tux.png");
if(renderedImage.isNull()){
qDebug() << "invalid image";
}else{
qDebug() << "image loaded";
}

RenderDialog *renderDialog= new RenderDialog();

renderDialog->setRenderedImage(QPixmap::fromImage(renderedImage));

renderDialog->show();

}@