Add icon to top left corner of all windows and taskbar icon

[why_bother]

I've been trying to get a custom icon I created to display in the top left corner of a Qt application I've been writing, and no matter what I try, I cannot get it to display. It will only display the default icon no matter what I do. I created a test app to try and just get it to work without doing it in my app, but even that won't work.
I can get it to display the same icon within a window with QPixmap, so it's not a path issue.

I've even tried deleting the Makefile created by qmake and the .qmake.stash files and running

qmake test_icon.pro

qmake test_icon.pro

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again. But it still will not display my icon no matter what I try.

I would like to display the same icon in all windows of my Qt app, as well as the taskbar icon as well.

I'm new to programming with Qt, so I have no idea what I'm doing wrong.

I'm using Manjaro Linux with Qt5.

My main.cpp file:

#include <QApplication>
#include <QMainWindow>
#include <QIcon>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    // Set the application icon using the resource path (:/myicon.png)
    app.setWindowIcon(QIcon(":/myicon.png"));
 
    // Create main window (and any other windows)
    QMainWindow mainWindow;
    mainWindow.setWindowTitle("My App");
    mainWindow.show();
 
    // Any other top-level windows you create will automatically use this icon
    // unless you set a different icon on them individually using setWindowIcon()
    // on the widget instance itself.
 
    return app.exec();
}

#include <QApplication>
#include <QMainWindow>
#include <QIcon>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    // Set the application icon using the resource path (:/myicon.png)
    app.setWindowIcon(QIcon(":/myicon.png"));

    // Create main window (and any other windows)
    QMainWindow mainWindow;
    mainWindow.setWindowTitle("My App");
    mainWindow.show();

    // Any other top-level windows you create will automatically use this icon
    // unless you set a different icon on them individually using setWindowIcon()
    // on the widget instance itself.

    return app.exec();
}

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My resources.qrc file:

<!DOCTYPE RCC>
<RCC version="1.0">
<qresource prefix="/">
    <file>myicon.png</file>
</qresource>
</RCC>

<!DOCTYPE RCC>
<RCC version="1.0">
<qresource prefix="/">
    <file>myicon.png</file>
</qresource>
</RCC>

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My test_icon.pro file:

######################################################################
# Automatically generated by qmake (3.1) Fri Jan 16 16:35:33 2026
######################################################################
 
TEMPLATE = app
TARGET = test_icon
QT += widgets
INCLUDEPATH += .
RESOURCES += resources.qrc
 
# You can make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# Please consult the documentation of the deprecated API in order to know
# how to port your code away from it.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
 
# Input
SOURCES += main.cpp

######################################################################
# Automatically generated by qmake (3.1) Fri Jan 16 16:35:33 2026
######################################################################

TEMPLATE = app
TARGET = test_icon
QT += widgets
INCLUDEPATH += .
RESOURCES += resources.qrc

# You can make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# Please consult the documentation of the deprecated API in order to know
# how to port your code away from it.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

# Input
SOURCES += main.cpp

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What in the f**king hell am I missing?? I don't understand what I'm doing wrong. I'm at my wits end with this.

Can someone please tell me what I'm doing wrong in plain simple english?

Thanks in advance for any help.

[d_stranz]

I am not all that familiar with various linux flavors, but quite often the window frame and its decorations are controlled by whatever window manager is being used for the PC desktop. This is the case for Windows.

This bit from the Qt docs on Setting the Application Icon might provide more help.

[why_bother]

I am not all that familiar with various linux flavors, but quite often the window frame and its decorations are controlled by whatever window manager is being used for the PC desktop. This is the case for Windows.

This bit from the Qt docs on Setting the Application Icon might provide more help.

Then why respond if you're "not familiar" with "linux flavors"? This isn't helpful. I'm not interested in Windows, that's not relevant.

I've already looked at that and it's just confusing, as it mentions setIcon(); so what's the difference between setWindowIcon() and setIcon() ?
What am I supposed to use, setIcon() or setWindowIcon() ?

I'm sorry, but I don't understand what the difference between the two is, and the more I read, more confused I'm getting. Can someone please just explain it in plain simple english so I can understand it, please.

Again, I'm new to Qt programming, so can someone who actually knows please enlighten me?

Again, I'm trying to set a custom icon I created for top left corner of the window title bar (for all windows) and the icon displayed in the taskbar (being the same icon), instead of the default icon that's currently displayed. I would like to do this in code rather than using Qt Creator. Surely there must be a way to do this, and clearly I'm too thick to understand how to do it. Can someone please enlighten me in plain simple english.

[why_bother]

Can this thread be deleted? As I cannot find any option to do it myself. If it can't be, can a moderator please close it.

I've decided to seek help elsewhere, as I think I'd get better help elsewhere.

Sorry for the trouble.

[d_stranz]

I will close this thread at your request. I hope if you do look elsewhere for help, your rudeness in responding to an answer from someone trying to give you some help won't follow you there.