Multiple data in QT Signal

Xav12358

Hello
I use PySide2 and I want to create a custom signal which send (str, QImage) data.

But I get that error:

Value types used on meta functions (including signals) need to be registered on meta type: str

So I decided to use QLineEdit instead because QString doesn't exist. Here is the program I use:

from typing import Callable, List, Dict

import cv2
from PySide2.QtGui import QImage, QPixmap
from PySide2.QtWidgets import QWidget, QPushButton, QStackedWidget, QLineEdit, QMessageBox, QGroupBox, QLabel
from PySide2.QtWidgets import QTreeWidget, QTreeWidgetItem, QTreeWidgetItemIterator
from PySide2.QtCore import QFile, Signal, Slot, SIGNAL, QObject, QLine
from PySide2 import QtCore
from PySide2.QtUiTools import QUiLoader

import os

from cv_bridge import CvBridge

from datalog_parser import DatalogParser


class View(QWidget):
    classifier_groupbox : QGroupBox
    datalog_tree_widget: QTreeWidget
    environmental_groupbox : QGroupBox

    label_dict : Dict[str, QLabel]
    new_image : QtCore.Signal(QImage)

    item_signal = QtCore.Signal(QLineEdit, QImage)

    def __init__(self):
        self.label_dict =  dict()

        super(View, self).__init__()
        self.window = None

        QtCore.QObject.connect(self,  QtCore.SIGNAL("item_signal(QLineEdit, QImage)"), self, QtCore.SLOT("new_image_callback(QLineEdit, QImage)"))
        # self.new_image.emit("dada")
        # QObject.connect(self.new_image, SIGNAL("new_image_callback(QImage)"), self.new_image_callback)

        self.load_ui()
        self.classifier_groupbox = self.window.findChild(QGroupBox, 'classifier_groupbox')
        self.datalog_tree_widget = self.window.findChild(QTreeWidget, 'datalog_tree_widget')
        self.environmental_groupbox = self.window.findChild(QGroupBox, 'environmental_groupbox')
        self.label = self.window.findChild(QLabel, 'label')
        self.window.show()

    def load_ui(self):
            loader = QUiLoader()
            path = os.path.join(os.path.dirname(__file__), "form.ui")
            print(f'ui path {path}')
            ui_file = QFile(path)
            ui_file.open(QFile.ReadOnly)
            self.window = loader.load(ui_file, self)
            ui_file.close()

    @Slot( QLineEdit,QImage)
    def new_image_callback(self,line: QLineEdit, image: QImage):
        print(f'new_image_callback arg ')

        # self.label.setPixmap(QPixmap.fromImage(image))

        data_name = line.text()
        if not data_name in self.label_dict:
            self.label_dict[data_name] = QLabel()
            self.environmental_groupbox.layout().addWidget(self.label_dict[data_name])
            # self.label_dict[data_name].setPixmap(QPixmap.fromImage(q_image))
            self.label.setPixmap(QPixmap.fromImage(image))
            # print(f"image data type {type(data)} data{data}")

    def player_callback(self, data, data_name:str):
        print(f"here dataname {data_name}")

        try:
            image_data = CvBridge().imgmsg_to_cv2(data.message)

            q_image = QImage(image_data, image_data.shape[1], image_data.shape[0],
                             QImage.Format_RGB888)

            # self.new_image.emit((q_image, data_name))
            self.emit(SIGNAL("item_signal(QLine,QImage)"),   QLineEdit(), q_image)
            # self.item_signal.emit( q_image)

            print("done")

        except Exception as err:
            print(err)
            pass

    def update_tree(self, datalogs: DatalogParser):
        for product, datalog_list in datalogs.datalogs.items():
            parent_item = QTreeWidgetItem(self.datalog_tree_widget)
            print(f"add {product}")
            parent_item.setText(0, product)

            for datalog in datalog_list:
                print(f'child {datalog}')
                child = QTreeWidgetItem(parent_item)
                child.setText(0, datalog.name)

        self.datalog_tree_widget.expandAll()

I get no error but no callback is called. When I use signal/slot with only one argument, it works properly but with the previous program, no error and no callback.

Pl45m4

@Xav12358 said in Multiple data in QT Signal:

need to be registered on meta type: str

You can register the type str and then use it with signals

JonB

@Xav12358
Unless Python/PySide2 magically lets you do it somehow, you cannot have QLineEdit as a parameter to anything in C++, whether signal, slot or any other function.

QtCore.QObject.connect(self, QtCore.SIGNAL("item_signal(QLineEdit, QImage)"), self, QtCore.SLOT("new_image_callback(QLineEdit, QImage)"))

self.emit(SIGNAL("item_signal(QLine,QImage)"), QLineEdit(), q_image)

Do you have any evidence either of these lines work?

You should be able to define a signal passing a str in PySide2. The Examples section at https://wiki.qt.io/Qt_for_Python_Signals_and_Slots includes:

import sys                                                                  
from PySide2.QtWidgets import QApplication, QPushButton                     
from PySide2.QtCore import QObject, Signal, Slot                            
                                                                            
app = QApplication(sys.argv)                                                
                                                                            
# define a new slot that receives a string and has                          
# 'saySomeWords' as its name                                                
@Slot(str)                                                                  
def say_some_words(words):                                                  
    print(words)                                                               
                                                                            
class Communicate(QObject):                                                 
 # create a new signal on the fly and name it 'speak'                       
 speak = Signal(str)                                                        
                                                                            
someone = Communicate()                                                     
# connect signal and slot                                                   
someone.speak.connect(say_some_words)                                         
# emit 'speak' signal                                                         
someone.speak.emit("Hello everybody!")

So does that work for you?

Xav12358

@Pl45m4
How can I register str ?

Xav12358

@JonB said in Multiple data in QT Signal:

import sys
from PySide2.QtWidgets import QApplication, QPushButton
from PySide2.QtCore import QObject, Signal, Slot

app = QApplication(sys.argv)

define a new slot that receives a string and has

'saySomeWords' as its name

@Slot(str)
def say_some_words(words):
print(words)

class Communicate(QObject):

create a new signal on the fly and name it 'speak'

speak = Signal(str)

someone = Communicate()

connect signal and slot

someone.speak.connect(say_some_words)

emit 'speak' signal

someone.speak.emit("Hello everybody!")

The example works properly. I don't understand why I get that error in my code

Value types used on meta functions (including signals) need to be registered on meta type: str

I try to send only str, and I also get the same trouble.

Xav12358

In fact, it comes from the connect signal function. When I connect the signal inside my View, it does works.

Now I connect the signal and the slot outside the View class and it works.

JonB

@Xav12358
So you have it working now, right? I have no idea about the QtCore.SIGNAL("...") syntax you are trying to employ, never used it and would not use it.

I tried with your original syntax involving

self.emit(SIGNAL("item_signal(str, QImage)"),  "hello", QImage())

and got the same error as you about str needing to be registered.

Threw that away and replaced with "proper"/"normal" syntax:

self.item_signal.connect(self.new_image_callback)
...
self.item_signal.emit("hello", QImage())

and all is well.