Is there a way to overlay multiple elements on the parent widget (PySide / Qt)

Question

I have a main parent widget and I want some layouts on top of the parent widget.

Initializing the layout using the parent widget will place the layout on top of the parent widget. I like it and would like to do it several times (left, top, bottom and right) for the same parent widget.

I used QGridLayout with different layouts, but this made the layouts resize and made them small. No matter what Overlay is added, the latter should be on top of other elements.

Below is a very simple example of what I want.

import sys
from PySide import QtGui, QtCore


class Overlay(QtGui.QBoxLayout):
    """Overlay widgets on a parent widget."""

    def __init__(self, parent=None, location="left"):
        super().__init__(QtGui.QBoxLayout.TopToBottom, parent)

        if location == "left" or location == "right":
            self.setDirection(QtGui.QBoxLayout.TopToBottom)
            if location == "right":
                self.setAlignment(QtCore.Qt.AlignRight)
        elif location == "top" or location == "bottom":
            self.setDirection(QtGui.QBoxLayout.LeftToRight)
            if location == "bottom":
                self.setAlignment(QtCore.Qt.AlignBottom)

        self.css = "QWidget {background-color: lightskyblue; color: white}"
    # end Constructor

    def addWidget(self, widget):
        super().addWidget(widget)

        widget.setStyleSheet(self.css)
    # end addWidget
# end class Overlay

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

    window = QtGui.QMainWindow()
    window.show()

    widg = QtGui.QTreeView()
    window.setCentralWidget(widg)

    left = Overlay(widg, "left")
    left.addWidget(QtGui.QLabel("HELLO"))
    left.addWidget(QtGui.QLabel("WORLD!"))

    top = Overlay(widg, "top")
    top.addWidget(QtGui.QLabel("Hello"))
    top.addWidget(QtGui.QLabel("World!"))

    right = Overlay(location="right")
    right.setParent(widg)
    right.addWidget(QtGui.QLabel("hello"))
    right.addWidget(QtGui.QLabel("world!"))

    return app.exec_()
# end main

if __name__ == '__main__':
    sys.exit(main())

? , , Overlays ?

layout = QtGui.QBoxLayout(QtGui.QBoxLayout.TopToBottom, parent_widget)

,

layout = QtGui.QBoxLayout(QtGui.QBoxLayout.TopToBottom)
layout.setParent(parent_widget)

, ?

Answer 1

, . OverlayCenter , , .

import sys
from PySide import QtGui, QtCore


class OverlayCenter(QtGui.QLayout):
    """Layout for managing overlays."""

    def __init__(self, parent):
        super().__init__(parent)

        # Properties
        self.setContentsMargins(0, 0, 0, 0)

        self.items = []
    # end Constructor

    def addLayout(self, layout):
        """Add a new layout to overlay on top of the other layouts and widgets."""
        self.addChildLayout(layout)
        self.addItem(layout)
    # end addLayout

    def __del__(self):
        """Destructor for garbage collection."""
        item = self.takeAt(0)
        while item:
            item = self.takeAt(0)
    # end Destructor

    def addItem(self, item):
        """Add an item (widget/layout) to the list."""
        self.items.append(item)
    # end addItem

    def count(self):
        """Return the number of items."""
        return len(self.items)
    # end Count

    def itemAt(self, index):
        """Return the item at the given index."""
        if index >= 0 and index < len(self.items):
            return self.items[index]

        return None
    # end itemAt

    def takeAt(self, index):
        """Remove and return the item at the given index."""
        if index >= 0 and index < len(self.items):
            return self.items.pop(index)

        return None
    # end takeAt

    def setGeometry(self, rect):
        """Set the main geometry and the item geometry."""
        super().setGeometry(rect)

        for item in self.items:
            item.setGeometry(rect)
    # end setGeometry
# end class OverlayCenter


class Overlay(QtGui.QBoxLayout):
    """Overlay widgets on a parent widget."""

    def __init__(self, location="left", parent=None):
        super().__init__(QtGui.QBoxLayout.TopToBottom, parent)

        if location == "left":
            self.setDirection(QtGui.QBoxLayout.TopToBottom)
            self.setAlignment(QtCore.Qt.AlignLeft | QtCore.Qt.AlignVCenter)
        elif location == "right":
            self.setDirection(QtGui.QBoxLayout.TopToBottom)
            self.setAlignment(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
        elif location == "top":
            self.setDirection(QtGui.QBoxLayout.LeftToRight)
            self.setAlignment(QtCore.Qt.AlignTop | QtCore.Qt.AlignHCenter)
        elif location == "bottom":
            self.setDirection(QtGui.QBoxLayout.LeftToRight)
            self.setAlignment(QtCore.Qt.AlignBottom | QtCore.Qt.AlignHCenter)


        self.css = "QWidget {background-color: lightskyblue; color: white}"
    # end Constructor

    def addWidget(self, widget):
        super().addWidget(widget)

        widget.setStyleSheet(self.css)
    # end addWidget
# end class Overlay

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

    window = QtGui.QMainWindow()
    window.show()

    widg = QtGui.QTreeView()
    window.setCentralWidget(widg)

    left = Overlay("left")
    lhlbl = QtGui.QLabel("Hello")
    lwlbl = QtGui.QLabel("World!")
    lhlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    lwlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    left.addWidget(lhlbl)
    left.addWidget(lwlbl)

    top = Overlay("top")
    lhlbl = QtGui.QLabel("HELLO")
    lwlbl = QtGui.QLabel("WORLD!")
    lhlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    lwlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    top.addWidget(lhlbl)
    top.addWidget(lwlbl)

    right = Overlay("right")
    lhlbl = QtGui.QLabel("hellO")
    lwlbl = QtGui.QLabel("worlD!")
    lhlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    lwlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    right.addWidget(lhlbl)
    right.addWidget(lwlbl)

    bottom = Overlay("bottom")
    lhlbl = QtGui.QLabel("hello")
    lwlbl = QtGui.QLabel("world!")
    lhlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    lwlbl.setSizePolicy(QtGui.QSizePolicy.Maximum, QtGui.QSizePolicy.Maximum)
    bottom.addWidget(lhlbl)
    bottom.addWidget(lwlbl)

    center = OverlayCenter(widg)
    center.addLayout(left)
    center.addLayout(top)
    center.addLayout(right)
    center.addLayout(bottom)

    return app.exec_()
# end main

if __name__ == '__main__':
    sys.exit(main())