[PyQt] Properties in PyQt5

[Florian Bruhin]

* Glenn Ramsey <gr at componic.co.nz> [2014-09-24 16:03:30 +1200]:
> Hi,
> 
> I have a dialog that has been created in Qt Designer and I would like to
> be able to set a red border on a QLineEdit based on its contents (or lack thereof).
> 
> Below is what I have tried, based on the PyQt4 version in Mark Summerfield's
> book "Rapid GUI programming with Python and Qt", but it doesn't work.

It'd be useful if you said which page/snippet so I could take a look
at that as well ;)

> What have I done wrong here?

AFAIK you need to call setStyleSheet again after a property changed.
I do something like this (from memory, untested):


class MyWidget(QWidget):

    STYLESHEET = """
        QWidget#MyWidget[error="true"] {
            color: red;
        }

        QWidget#MyWidget[error="false"] {
            color: green;
        }
    """
    _error = False

    def __init__(self, parent=None):
        super().__init__(parent)
        self.setStyleSheet(self.STYLESHEET)

    @pyqtProperty(bool):
    def error(self):
        return self._error

    @error.setter
    def error(self, val):
        if self._error == val:
            # Updating the stylesheet is rather expensive so we want
            # to avoid it if it's unnecessary
            return
        self._error = val
        self.setStyleSheet(self.STYLESHEET)

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