<![CDATA[logmessage from another thread to the mainwindow slot]]>i have two classes that im trying to log a message to a textbrowser

  1. The main thread works
  2. But if i call the slot and try to emit the singal it does work.
  3. is there a way to debug it
MainWindow::MainWindow(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::MainWindow)
    , m_window2(new Editor(this))
, m_window3(new T_Editor(this))
{
    ui->setupUi(this);
    connect(m_window2, & Editor::logMessage, this, &MainWindow::logMessage);
// new thread editor 
connect(m_window3, & T_Editor::logMessage, this, &MainWindow::logMessage);
}

If i try to emit logmessage from the other thread it doesnt work. But if i emit from editor class it works. (both in the same thread)

]]>https://forum.qt.io/topic/102253/logmessage-from-another-thread-to-the-mainwindow-slotRSS for NodeSat, 18 Apr 2026 14:37:52 GMTMon, 29 Apr 2019 13:03:22 GMT60<![CDATA[Reply to logmessage from another thread to the mainwindow slot on Mon, 29 Apr 2019 19:09:48 GMT]]>Hi,

If you want to log from different threads. You should rather have a dedicated object for that with proper protections in place.

]]>https://forum.qt.io/post/525988https://forum.qt.io/post/525988Mon, 29 Apr 2019 19:09:48 GMT<![CDATA[Reply to logmessage from another thread to the mainwindow slot on Mon, 29 Apr 2019 18:49:54 GMT]]>@Sunfluxgames said in logmessage from another thread to the mainwindow slot:

m_window3(new T_Editor(this))

I don't think this object (m_window3) lives in another thread at all...

]]>https://forum.qt.io/post/525981https://forum.qt.io/post/525981Mon, 29 Apr 2019 18:49:54 GMT<![CDATA[Reply to logmessage from another thread to the mainwindow slot on Mon, 29 Apr 2019 14:30:49 GMT]]>m_window3 to another thread after calling connect()? In that case, it may not work.

belive this is what it is.

mainwindow logMessage is a private member but guess i will have to make it public to access it from the other thread object

create a connect in the T_editor class that connects the signal logmessage with slot of mainwindow slot.

Editor/mainwindow both run on the same thread
Editor create a thread for T_editor that creates its own object etc..

]]>https://forum.qt.io/post/525938https://forum.qt.io/post/525938Mon, 29 Apr 2019 14:30:49 GMT<![CDATA[Reply to logmessage from another thread to the mainwindow slot on Mon, 29 Apr 2019 13:12:50 GMT]]>In Qt, whether signal-slot connection crosses a thread boundary or not does not matter - it works same regardless of threads. The only thing which might not work is when custom objects are sent - but then all that is needed is to properly register them. Qt warns about it at compile time - so it's not a problem in this case.

  • are you sure the signal logMessage is emitted?
  • if you are using a worker object, are you sure it emits the signal and that you connect to that signal, and not the encompassing thread?
  • are you moving m_window3 to another thread after calling connect()? In that case, it may not work
  • does it work when you hard-code connection type to Qt::QueuedConnection?
  • is your main window performing some CPU-intensive task, like a long loop or something?
]]>https://forum.qt.io/post/525931https://forum.qt.io/post/525931Mon, 29 Apr 2019 13:12:50 GMT