BreezeStyleSheets/ISSUES.md

Issues

There are limitations to what can be styled with stylesheets, as well as rare bugs that prevent certain styles or widgets from rendering properly. This is a list of known issues, as well as suitable workarounds. THese issues are organized by the widget type, then the description of the properties/styles they affect.

• QCompleter
  • Menu Hover Background Color
• QDial
  • Custom Style
• QSlider
  • Invisible Ticks
• QTabBar
  • Triangular Tab Color
  • Triangular Tab Hover Background Color
  • Triangular Tab Padding
• QTextDocument
  • Placeholder Text
• QToolButton
  • Menu Button Padding
• [QWidget]
  • Standard Icons

QCompleter

Menu Hover Background Color

QCompleter doesn't have a hover background color in Qt5 on the drop-down menu. This works fine in Qt6, and changing rules for QListView (the drop-down menu) changes the drop-down menu in Qt6, but not Qt5.

QDial

Custom Style

QDial cannot be customized via a stylesheet, which is a known bug in QTBUG-1160. An example of how to style a QDial is available in dial.py. This works out-of-the-box, and can be a drop-in replacement for QDial.

QSlider

Invisible Ticks

QSlider ticks disappear when using stylesheets, which is a known bug referenced in QTBUG-3304 and QTBUG-3564. An example of how to style a QSlider is available in slider.py, however, this does not work with a stylesheet applied to a QSlider.

QTabBar

Triangular Tab Color

The text and border colors of a triangular QTabBar must be the same. This cannot be modified via a stylesheet.

Triangular Tab Hover Background Color

Triangular tab bars do not have :hover pseudo-states for non-selected tabs. Only the selected tab has a :hover pseudo-state, defeating the purpose. This could be fixed by installing an event filter for a HoverEnter or HoverMove event.

Triangular Tab Padding

Custom padding for triangular QTabBars on the bottom is ignored. All other tab positions work.

QTextDocument

Placeholder Text

For the widgets QTextEdit, QPlainTextEdit, and QLineEdit, which use an internal QTextDocument, you can set placeholder text for when no text is present. In Qt5, this is correctly grayed out when the placeholder text is present, which is not respected in Qt6 (as of Qt version 6.3.0).

An example of a workaround placeholder_text.py, which only works currently for Qt5 or Qt6 without a stylesheet. Using the native stylesheet shows it uses hard-coded colors for Qt6, so this is almost certainly a Qt bug. This is likely referenced in QTBUG-92947 and QTCREATORBUG-25444.

An example workaround setting the placeholder text at palette at the application level (for all widgets) is as follows. You can also set the placeholder text color for each individual widget.

C++

#include <QApplication>
#include <QColor>
#include <QPalette>

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

    auto palette = app.palette();
    QColor red(255, 0, 0);
    palette.setColor(QPalette::PlaceholderText, red);
    app.setPalette(palette);

    ...

    return app.exec();
}

Python

import sys
from PyQt6 import QtGui, QtWidgets

ColorRole = QtGui.QPalette.ColorRole

def main():
    app = QtWidgets.QApplication(sys.argv)

    palette = app.palette()
    red = QtGui.QColor(255, 0, 0)
    palette.setColor(ColorRole.PlaceholderText, red)
    app.setPalette(palette)

    ...

    return app.exec()

QToolButton

Menu Button Padding

QToolButton may have extra padding or clip the menu indicator in some cases. Auto-raised QToolButtons will clip the menu indicator, as will QToolButtons without text. Other cases will always add padding, whether there is a menu indicator or not. In order to force padding or no-padding for the menu indicator, set the Qt property of hasMenu to true or false. For example, to force additional padding for a menu indicator, use button->setProperty("hasMenu", true);.

A simple example of creating a QToolButton with text and with no menu drop-down is as follows:

C++

#include <QApplication>
#include <QString>
#include <QToolButton>

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

    ... // Get our window, central widget, layout, etc.

    auto *button = new QToolButton(widget);
    button->setText(QString("Button 1"));
    button->setProperty(QString("hasMenu"), false);

    ... // Add button to layout, show window, etc.

    return app.exec();
}

Python

import sys
from PyQt6 import QtGui, QtWidgets

def main():
    app = QtWidgets.QApplication(sys.argv)

    ... # Get our window, central widget, layout, etc.

    button = QtWidgets.QToolButton(widget)
    button.setText('Button 1')
    button.setProperty('hasMenu', False)

    ... # Add button to layout, show window, etc.

    return app.exec()

QCommandLink Icon

The default icon for QCommandLinkButton is platform-dependent, and depends on the standard icon SP_CommandLink (which cannot be specified in a stylesheet). See Standard Icons for an explanation on how to override this standard icon.

QWidget

Standard Icons

Certain standard icons cannot be overwritten in the stylesheet, and therefore a custom style must be installed in the Qt application. The standard-icons plugin comes with a set of custom standard icons, and the standard_icons.py example shows a complete application for how to override the default standard icons.

A simple example of overriding the command link icon for a PyQt6 application is as follows. First, configure with the standard-icons plugin.

python configure.py --extensions=standard-icons

Next, set the application stylesheet, subclass QCommonStyle to get custom standard icons, and install the style globally in the Qt application.

from PyQt6 import QtCore, QtGui, QtWidgets

StandardPixmap = QtWidgets.QStyle.StandardPixmap
OpenModeFlag = QtCore.QFile.OpenModeFlag

# Create a map of registered icons, so we can efficiently query if we
# should override the icon or use the pre-packaged standard icons.
ICON_MAP = {
    ...
    StandardPixmap.SP_CommandLink: 'right_arrow.svg',
    ...
}

def stylesheet_icon(style, icon, option=None, widget=None):
    '''Get a standard icon for the stylesheet style'''

    # See if we've registered a custom icon in the stylesheet
    path = ICON_MAP.get(icon, None)
    if path is not None:
        resource = f'dark:{path}'
        if QtCore.QFile.exists(resource):
            return QtGui.QIcon(resource)

    # No custom icon: return the default for the style.
    return QtWidgets.QCommonStyle.standardIcon(style, icon, option, widget)


class ApplicationStyle(QtWidgets.QCommonStyle):
    def __init__(self, style):
        super().__init__()
        # Store an instance for the default style, so we can query that.
        # Avoids an infinite, recursive loop.
        self.style = style

    def __getattribute__(self, item):
        '''
        Override for standardIcon. Everything else should default to the
        system default. We cannot have `style_icon` be a member of
        `ApplicationStyle`, since this will cause an infinite recursive loop.
        '''

        if item == 'standardIcon':
            return lambda *x: stylesheet_icon(self, *x)
        return getattr(self.style, item)

def main():
    app = QtWidgets.QApplication(sys.argv)

    # Install our custom style globally. QCommonStyle, unlike QProxyStyle,
    # actually works nicely with stylesheets. `Fusion` is available
    # on all platforms, but you can use any style you want. We
    # just need a created style, because `app.style()` will be 
    # deleted by he garbage collector.
    style = QtWidgets.QStyleFactory.create('Fusion')
    app.setStyle(ApplicationStyle(style))

    # Set our stylesheet. 
    # NOTE: this must occur after setting the application style.
    file = QtCore.QFile('dark:stylesheet.qss')
    file.open(OpenModeFlag.ReadOnly | OpenModeFlag.Text)
    stream = QtCore.QTextStream(file)
    app.setStyleSheet(stream.readAll())

    ...

    return app.exec()