Emoji on button labels causes a silent crash

Joel Santos

Hi,

I'm new to Qt, and I'm using Qt Creator to lay out my GUI. I wanted to get some emoji in my button labels to break the monotony of a very text-heavy app, but when I do, the app silently crashes. I managed to track the point were it fails and replicate it with a minimum app that shows the issue (I attach the ui file below, that should be enough to generate the issue). I'm using PySide6 (6.9.2), Python 3.13 on Windows 11.

The issue is in the autogenerated code from .ui to .py. On it, retranslateUI() is called on the widgets that have text on it, which in turn calls setText() with QCoreApplication.translate() and a escaped sequence for the emoji, which triggers the crash.

In the minimal app I attach, my main widget is EmojiButton, defined in emojibutton.py

# in emojybutton.py
class EmojiButton(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.ui = Ui_EmojiButton()
        self.ui.setupUi(self)

Ui_EmojiButton is autogenerated from the ui file:

# in autogenerated ui_form.py
class Ui_EmojiButton(object):
    def setupUi(self, EmojiButton):
        [...]
        self.retranslateUi(EmojiButton)
        [...]
    def retranslateUi(self, EmojiButton):
        EmojiButton.setWindowTitle(QCoreApplication.translate("EmojiButton", u"EmojiButton", None))
        self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me \ud83d\ude80", None))

If I change the autogenerated code from a escaped sequence to a literal emoji, the app works

# changing
self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me \ud83d\ude80", None)) # doesn't work 
# for
self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me 🚀", None)) # works!

But because it's autogenerated code, next time I generate it, it will revert back.

I've noticed a "translatable" property that I can uncheck, which also fixes the issue, as QCoreApplication.translate() is not called with an escaped sequence. I asked in stack overflow and people pointed out that this would also work, while still maintaining a "escape sequence" style, but again, can't change it as it's part of the autogenerated code

self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me \U0001f680", None)) # this scape sequence works too

For now, the solution seems to be to uncheck the "translatable" property, which is good for me, but it seems like a bug to me, and I wasn't capable of finding anything related to it in the forum.

PS: while writing this post, I just noticed that the "escape sequence" of 🚀 is \U0001f680, which doesn't seem to have any relation to the \ud83d\ude80 generated by pyside6-uic, so maybe the error is there?
If I change the autogenerated

# changing
self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me \ud83d\ude80", None)) # doesn't work 
# for
self.pushButton.setText(QCoreApplication.translate("EmojiButton", u"Click me \u0001\uf680", None)) # no emoji on the button (shows two squares) but at least runs

Here's the ui file that generates the issue and should be enough to replicate it

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>EmojiButton</class>
 <widget class="QWidget" name="EmojiButton">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>287</width>
    <height>198</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>EmojiButton</string>
  </property>
  <widget class="QPushButton" name="pushButton">
   <property name="geometry">
    <rect>
     <x>80</x>
     <y>80</y>
     <width>111</width>
     <height>31</height>
    </rect>
   </property>
   <property name="font">
    <font>
     <pointsize>16</pointsize>
    </font>
   </property>
   <property name="text">
    <string>Click me 🚀</string>
   </property>
  </widget>
 </widget>
 <resources/>
 <connections/>
</ui>

SimonSchroeder

@Joel-Santos said in Emoji on button labels causes a silent crash:

PS: while writing this post, I just noticed that the "escape sequence" of 🚀 is \U0001f680, which doesn't seem to have any relation to the \ud83d\ude80 generated by pyside6-uic, so maybe the error is there?

In UTF-16 (which Qt uses internally), Unicode code points starting from \U00010000 don't fit into 16 bits anymore. This is why your emoji needs a so-called surrogate pair in UTF-16. You cannot easily see how the surrogate pair relates to the original code point. But, \ud83d\ude80 is the Unicode character encoded as UTF-16. Qt decided to use 16 bits when Unicode didn't have that many characters (back then it was called UCS-2; Windows has the same problem). Maybe this is from back in the day when 16 bits were enough.

This is certainly a bug. However, this is a user forum and you'll not reach developers through this. You should file an official bugreport instead (https://bugreports.qt.io).

@Joel-Santos said in Emoji on button labels causes a silent crash:

I asked in stack overflow and people pointed out that this would also work, while still maintaining a "escape sequence" style, but again, can't change it as it's part of the autogenerated code

Can you write \U0001f680 inside the .ui-file directly? It might not show up in the Qt Designer correctly or might even be destroyed when saving from the Designer again.

Joel Santos

@SimonSchroeder thanks for your reply. I filled a bug. I wanted to ask the opinion of more expert users before doing it.

Regarding your suggestion, I tried, but then it prints the string \U0001f680, so the parser in pyside6-uic doesn't allow to work around it.

I'll close this as it seems to be a bug, any poor soul that encounters this and is not tranlsating their app, they can deselect the translatable check in the QAbstractMethod properties.

Thanks!

SGaist

@Joel-Santos hi,

Did you open a ticket about this ?

SimonSchroeder

@SGaist https://bugreports.qt.io/browse/PYSIDE-3173

SGaist

Thank you !