Dynamically created buttons and connecting signal to slot

Kris Revi

So i thought i was done with this! but then i forgot to connect button click to a slot!

void MainWindow::updateImageFolder()
{
    //assume the directory exists and contains some files grab every image file there
    QDir directory("./Matrix Images/32 x 32/");
    QStringList images = directory.entryList(QStringList() << "*.*" << "*.*",QDir::Files);

    QLayoutItem *child;
    while ((child = ui->GRID_IMAGEFOLDER_DISPLAY->takeAt(0)) != nullptr) {
        delete child->widget(); // delete the widget
        delete child;   // delete the layout item
    }

    signalMapper = new QSignalMapper(this);

    foreach(QString filename, images) {

        QPushButton *button = new QPushButton(this);


        connect(button, SIGNAL(clicked()), this, SLOT(selectedImageDisplay(filename)));

        button->setMinimumSize(32, 32);
        button->setMaximumSize(32, 32);
        button->setFixedSize(32, 32);
        button->setIcon(QIcon("./Matrix Images/32 x 32/" + filename));
        button->setIconSize(QSize(32, 32));
        button->setCursor(Qt::PointingHandCursor);
        button->setObjectName(filename);

        ui->GRID_IMAGEFOLDER_DISPLAY->addWidget(button);

    }
}

but i get this error

QObject::connect: No such slot MainWindow::selectedImageDisplay(filename) in ..\NEONCONTROLLER\mainwindow.cpp:333
QObject::connect:  (receiver name: 'MainWindow')

and yes i have added void selectedImageDisplay(QString img); to mainwindow.h so :S

JonB

@Kris-Revi said in Dynamically created buttons and connecting signal to slot:

connect(button, SIGNAL(clicked()), this, SLOT(selectedImageDisplay(filename)));

To the best of my knowledge you need the parameter type not name in these macros?
connect(button, SIGNAL(clicked()), this, SLOT(selectedImageDisplay(QString)));

However, if you would please move over to the new style signal/slot syntax instead of these macros your QoL (& ours) would be better!

Even when you have done that, you will find you can't do it like you're trying. You are going to need to use a C++ lambda here for the slot so as to pass the filename parameter from the local variable, because the clicked() signal does not pass such a string. Start from e.g.
https://forum.qt.io/topic/96163/lambda-that-uses-signal-argument-to-connect-to-a-slot
https://artandlogic.com/2013/09/qt-5-and-c11-lambdas-are-your-friend/amp/
https://medium.com/genymobile/how-c-lambda-expressions-can-improve-your-qt-code-8cd524f4ed9f

Kris Revi

@JonB ooh noo... lambda in C++ is a pain compared to python version :|

btw i'll switch to the new connect()

JonB

@Kris-Revi
I have just appended some reference links for the lambda stuff to my previous post.

Kris Revi

@JonB so i got it working

connect(button, &QPushButton::clicked, [=]() { selectedImageDisplay("./Matrix Images/32 x 32/" + filename); });

having 1 problem tho

void MainWindow::selectedImageDisplay(QString img)
{
    imageObject = new QImage();           // Make a new imageObject
    imageObject->load(img);          // Load the image from path

    QJsonArray RGB565;
    for(int y = 0; y < imageObject->height(); y++) {
        const quint16 *line = reinterpret_cast<const quint16*>(imageObject->constScanLine(y));
        for(int x = 0; x < imageObject->width(); x++)
            RGB565 << *(line++);
    }

    socket.sendCommandStrip(QString("pixArt"), RGB565);
}

when it gets sent to the Matrix the pixels are out of order and the colors are way off for some reason :S can you spot why? cause i cant :S

JonB

@Kris-Revi
I believe you got that loop-packing code from @Bonnie in another thread, so he can come and sort it out ;-)

While you wait for him/inspiration, do some debugging yourself: look at the first so-many byte values sent, compare against the values of those received, is there a difference-pattern? Do you even end up with same number received as sent? Your problem might be in retrieving them, packing/unpacking them, or JSONifying them.

[P.S. You had a QSignalMapper earlier: if you're going to go down lambda route (much more powerful) you can probably get rid of that.]

Kris Revi

@JonB that's true! i googled and got som sugestion for my problem but yea! :) removed now!

Kris Revi

@JonB i fixed it! so i mentioned that the colors was off and pixel order so i thought why not just try

*imageObject = imageObject->convertToFormat(QImage::Format_RGB16);

and that was the problem :) even if i saved the image as RGB16 upen uploading it and converting it it was not saved as RGB16 apparently

Christian Ehrlicher

@Kris-Revi said in Dynamically created buttons and connecting signal to slot:

imageObject = new QImage();

You leak this image object. Better create it on the stack.

Kris Revi

@Christian-Ehrlicher leak? stack what now?

JonB

@Kris-Revi
"leak" means the memory used by your new QImage() is never returned to the pool. Either delete it at the end, or @Christian-Ehrlicher is suggesting easiest is make it a QImage imageObject; variable here, which means it is on the "stack" (instead of the "heap" for newed objects). Then it gets thrown away at end of the method for sure.

Kris Revi

@JonB so make a QImage imageObject; not imageObject = new QImage() ?,

mrjj

@Kris-Revi
Yes exactly.

Solved Dynamically created buttons and connecting signal to slot