Using Qt to create the OS X Yosemite Translucency effect - macos

Question

We're trying to make a QMainWindow with the Mac OSX Yosemite translucency effect. We're using PyQt, but the problem is a Qt issue. With what we've tried so far, it's always either fully transparent or fully opaque (like a normal window). If we turn on Qt.WA_TranslucentBackground, the window background becomes 100% completely transparent.
Additionally, the QGraphicsView we're displaying on it then leaves trails behind when you scroll. The mouse input also "passes through" the transparent parts - clicking on a transparent portion of the graphics view will register as a click on the window behind it. Setting a stylesheet with any custom background color then has no effect. If we turn it off, the window remains opaque. Then we can change the background color using a style sheet, but it's still opaque. Turing WA_FramelessWindowHint on and off doesn't seem to fix anything, either. Nor does setAutoFillBackground(). Do you know how to make a window with the Yosemite translucency effect?
Here's a sample Python program to test this: -
# Attempt at Mac OSX Translucency (example code)
import sys
from PyQt5 import QtCore, QtGui, QtWidgets
Qt = QtCore.Qt
class ExampleMainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.testWidget = QtWidgets.QLabel('Test label, which should be transparent')
# Make sure the testWidget is transparent
self.testWidget.setStyleSheet('background: transparent')
self.testWidget.setAttribute(Qt.WA_TranslucentBackground, True)
self.testWidget.setAutoFillBackground(True)
self.setStyleSheet('background: rgba(255, 255, 255, 0.8)')
self.setAttribute(Qt.WA_TranslucentBackground, True)
self.setAutoFillBackground(True)
#self.setWindowFlags(Qt.FramelessWindowHint) # Doesn't seem to help
self.setCentralWidget(self.testWidget)
def main():
global app, exWindow
app = QtWidgets.QApplication(sys.argv)
exWindow = ExampleMainWindow()
exWindow.show()
exitcodesys = app.exec_()
app.deleteLater()
sys.exit(exitcodesys)
if __name__ == '__main__': main()

Answer 1

Your stylesheet isn't valid. Qt's rgba expects an integer in range 0-255 or a percentage for the values only. So use 80% instead of 0.8. Along with WA_TranslucentBackground that should get you going.
And please post your code in the question, as your pastes expire in a few days and this question will then be unusable.
Here is code that is working for me; I see my other applications' windows underneath. It's C++. I'm using Qt4 rather than 5; perhaps this matters.
#include <QMainWindow>
#include <QApplication>
#include <QLabel>
class MyMain : public QMainWindow
{
Q_OBJECT
public:
MyMain(QWidget* parent = 0);
};
MyMain::MyMain(QWidget* parent)
: QMainWindow(parent)
{
setAttribute(Qt::WA_TranslucentBackground, true);
setStyleSheet("background: rgba(0,0,0,80%);");
QLabel* foo = new QLabel();
foo->setText("hello");
foo->setStyleSheet("color: white;");
setCentralWidget(foo);
}
#include "main.moc"
int main(int argc, char** argv)
{
QApplication app(argc, argv);
MyMain m;
m.show();
return app.exec();
}