PyQt: wrap-around layout of widgets inside a QScrollArea

Question

I am developing an app for memorizing text using PyQt4. I want to show all the words in bubbles so that you see how long the word is. But when I have all the bubbles in my QScrollArea, they are aligned one under the other. I would like to have them aligned side-by-side, but with word-wrap.

I got the bubbles to work using a QLabel with rounded borders. But now that I have the words in QLabel's, PyQt doesn't consider them as words - but as widgets. So PyQt puts one widget under the other. I would like the widgets to be aligned side-by-side until they reach the end of the line, and then they should wrap around to the next line - meaning the QLabel's should act like words in a text document.

Here is my code so far:

f = open(r'myFile.txt')

class Bubble(QtGui.QLabel):
    def __init__(self, text):
        super(Bubble, self).__init__(text)
        self.word = text
        self.setContentsMargins(5, 5, 5, 5)

    def paintEvent(self, e):
        p = QtGui.QPainter(self)
        p.setRenderHint(QtGui.QPainter.Antialiasing,True)
        p.drawRoundedRect(0,0,self.width()-1,self.height()-1,5,5)
        super(Bubble, self).paintEvent(e)


class MainWindow(QtGui.QMainWindow):
    def __init__(self, text, parent=None):
        QtGui.QMainWindow.__init__(self, parent)
        self.setupUi(self)
        self.MainArea = QtGui.QScrollArea
        self.widget = QtGui.QWidget()
        vbox = QtGui.QVBoxLayout()
        self.words = []
        for t in re.findall(r'\b\w+\b', text):
            label = Bubble(t)
            label.setFont(QtGui.QFont('SblHebrew', 18))
            label.setFixedWidth(label.sizeHint().width())
            self.words.append(label)
            vbox.addWidget(label)
        self.widget.setLayout(vbox)
        self.MainArea.setWidget(self.widget)

if __name__ == '__main__':
    import sys
    app = QtGui.QApplication(sys.argv)
    myWindow = MainWindow(f.read(), None)
    myWindow.show()
    sys.exit(app.exec_())

When I run this I get:

But I would like the words (the Qlabel's containing the words) to be next to each other, not under each other, like this (photoshopped):

I've been doing a lot of research, but no answers help me align the widgets next to each other.

Redcoat

Why aren't you using html? – Medrano

explain your question please – Floatable

@ekhumoro, I am writing a computer app. Isn't html for web pages? besides, I'm still learning html. – Redcoat

@eyllanesc, I have explained the question better in an edit. – Redcoat

@CheynShmuel You could display an image of how you want the result. Another thing, PyQt supports HTML for desktop applications. – Floatable

@Floatable I added a photoshoped picture of how I would like it to look – Redcoat

I don't know why I now use from PyQt5 import QtWidgets , and replace all widgets of QtGui.xxxx to QtWidgets.xxx. after running the codes, the box cannot show anything related to the text I put in myFile.txt – Mcabee

Answer 1

I thought it might be possible to use html in a QTextBrowser widget for this, but Qt's rich-text engine doesn't support the border-radius CSS property which would be needed for the bubble labels.

So it looks like you need a PyQt port of the Flow Layout example. This can "word-wrap" a collection of widgets inside a container, and also allows the margins and horizontal/vertical spacing to be adjusted.

Here is a demo script that implements the FlowLayout class and shows how to use it with your example:

import sys
from PyQt4 import QtCore, QtGui

class FlowLayout(QtGui.QLayout):
    def __init__(self, parent=None, margin=-1, hspacing=-1, vspacing=-1):
        super(FlowLayout, self).__init__(parent)
        self._hspacing = hspacing
        self._vspacing = vspacing
        self._items = []
        self.setContentsMargins(margin, margin, margin, margin)

    def __del__(self):
        del self._items[:]

    def addItem(self, item):
        self._items.append(item)

    def horizontalSpacing(self):
        if self._hspacing >= 0:
            return self._hspacing
        else:
            return self.smartSpacing(
                QtGui.QStyle.PM_LayoutHorizontalSpacing)

    def verticalSpacing(self):
        if self._vspacing >= 0:
            return self._vspacing
        else:
            return self.smartSpacing(
                QtGui.QStyle.PM_LayoutVerticalSpacing)

    def count(self):
        return len(self._items)

    def itemAt(self, index):
        if 0 <= index < len(self._items):
            return self._items[index]

    def takeAt(self, index):
        if 0 <= index < len(self._items):
            return self._items.pop(index)

    def expandingDirections(self):
        return QtCore.Qt.Orientations(0)

    def hasHeightForWidth(self):
        return True

    def heightForWidth(self, width):
        return self.doLayout(QtCore.QRect(0, 0, width, 0), True)

    def setGeometry(self, rect):
        super(FlowLayout, self).setGeometry(rect)
        self.doLayout(rect, False)

    def sizeHint(self):
        return self.minimumSize()

    def minimumSize(self):
        size = QtCore.QSize()
        for item in self._items:
            size = size.expandedTo(item.minimumSize())
        left, top, right, bottom = self.getContentsMargins()
        size += QtCore.QSize(left + right, top + bottom)
        return size

    def doLayout(self, rect, testonly):
        left, top, right, bottom = self.getContentsMargins()
        effective = rect.adjusted(+left, +top, -right, -bottom)
        x = effective.x()
        y = effective.y()
        lineheight = 0
        for item in self._items:
            widget = item.widget()
            hspace = self.horizontalSpacing()
            if hspace == -1:
                hspace = widget.style().layoutSpacing(
                    QtGui.QSizePolicy.PushButton,
                    QtGui.QSizePolicy.PushButton, QtCore.Qt.Horizontal)
            vspace = self.verticalSpacing()
            if vspace == -1:
                vspace = widget.style().layoutSpacing(
                    QtGui.QSizePolicy.PushButton,
                    QtGui.QSizePolicy.PushButton, QtCore.Qt.Vertical)
            nextX = x + item.sizeHint().width() + hspace
            if nextX - hspace > effective.right() and lineheight > 0:
                x = effective.x()
                y = y + lineheight + vspace
                nextX = x + item.sizeHint().width() + hspace
                lineheight = 0
            if not testonly:
                item.setGeometry(
                    QtCore.QRect(QtCore.QPoint(x, y), item.sizeHint()))
            x = nextX
            lineheight = max(lineheight, item.sizeHint().height())
        return y + lineheight - rect.y() + bottom

    def smartSpacing(self, pm):
        parent = self.parent()
        if parent is None:
            return -1
        elif parent.isWidgetType():
            return parent.style().pixelMetric(pm, None, parent)
        else:
            return parent.spacing()

class Bubble(QtGui.QLabel):
    def __init__(self, text):
        super(Bubble, self).__init__(text)
        self.word = text
        self.setContentsMargins(5, 5, 5, 5)

    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        painter.drawRoundedRect(
            0, 0, self.width() - 1, self.height() - 1, 5, 5)
        super(Bubble, self).paintEvent(event)

class MainWindow(QtGui.QMainWindow):
    def __init__(self, text, parent=None):
        super(MainWindow, self).__init__(parent)
        self.mainArea = QtGui.QScrollArea(self)
        self.mainArea.setWidgetResizable(True)
        widget = QtGui.QWidget(self.mainArea)
        widget.setMinimumWidth(50)
        layout = FlowLayout(widget)
        self.words = []
        for word in text.split():
            label = Bubble(word)
            label.setFont(QtGui.QFont('SblHebrew', 18))
            label.setFixedWidth(label.sizeHint().width())
            self.words.append(label)
            layout.addWidget(label)
        self.mainArea.setWidget(widget)
        self.setCentralWidget(self.mainArea)

if __name__ == '__main__':

    app = QtGui.QApplication(sys.argv)
    window = MainWindow('Harry Potter is a series of fantasy literature')
    window.show()
    sys.exit(app.exec_())

Medrano

Thank you so much! This did just what I wanted to! Though I am very sad to say I do not understand why. Two questions: (1) Is there a way to display the widgets Right to Left? (2) Is there a way to align the widgets to any direction, or to justify them, maybe? – Redcoat

@CheynShmuel. Maybe - but it would require a lot of extra work. That is why I suggested using html earlier - it solves all the difficulties of laying out the document, and it makes it easy to format the words in a variety of different ways. Unfortunately, the QTextEdit and QTextBrowser classes don't support the full feature set of modern html/css, so you can't get fancy stuff like rounded corners. But right-to-left and justification are supported. – Medrano

I understand it could be hard, but at least it's possible. Could you at least point me in the right direction? I understand it could be hard, so could you help a little, at least? – Redcoat

@CheynShmuel. The original FlowLayout class that I ported to PyQt was written by the Qt devs, who know how to write custom layouts. I have no experience of that myself. The Qt docs have this: How to Write A Custom Layout Manager. But really, this is way too much work for one SO question. My advice would be to get your program working with html (which will be quick and easy), and then worry about fancy stuff like rounded corners later. If you do some web-searching, you'll probably even find work-rounds for that. – Medrano

Thank you. I will try to do that – Redcoat

The tutorial to writing a custom layout manager you linked me too is in Java. Could you find one that's for python, please? – Redcoat

It's C++, which is the language Qt is written in. See my answer above for an example of a custom layout manager written in python (which I ported from C++). I don't know of any others. – Medrano

Let us continue this discussion in chat. – Redcoat

Answer 2

Here's a PyQt5 version of the Flow Layout demo script:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class FlowLayout(QtWidgets.QLayout):
    def __init__(self, parent=None, margin=-1, hspacing=-1, vspacing=-1):
        super(FlowLayout, self).__init__(parent)
        self._hspacing = hspacing
        self._vspacing = vspacing
        self._items = []
        self.setContentsMargins(margin, margin, margin, margin)

    def __del__(self):
        del self._items[:]

    def addItem(self, item):
        self._items.append(item)

    def horizontalSpacing(self):
        if self._hspacing >= 0:
            return self._hspacing
        else:
            return self.smartSpacing(
                QtWidgets.QStyle.PM_LayoutHorizontalSpacing)

    def verticalSpacing(self):
        if self._vspacing >= 0:
            return self._vspacing
        else:
            return self.smartSpacing(
                QtWidgets.QStyle.PM_LayoutVerticalSpacing)

    def count(self):
        return len(self._items)

    def itemAt(self, index):
        if 0 <= index < len(self._items):
            return self._items[index]

    def takeAt(self, index):
        if 0 <= index < len(self._items):
            return self._items.pop(index)

    def expandingDirections(self):
        return QtCore.Qt.Orientations(0)

    def hasHeightForWidth(self):
        return True

    def heightForWidth(self, width):
        return self.doLayout(QtCore.QRect(0, 0, width, 0), True)

    def setGeometry(self, rect):
        super(FlowLayout, self).setGeometry(rect)
        self.doLayout(rect, False)

    def sizeHint(self):
        return self.minimumSize()

    def minimumSize(self):
        size = QtCore.QSize()
        for item in self._items:
            size = size.expandedTo(item.minimumSize())
        left, top, right, bottom = self.getContentsMargins()
        size += QtCore.QSize(left + right, top + bottom)
        return size

    def doLayout(self, rect, testonly):
        left, top, right, bottom = self.getContentsMargins()
        effective = rect.adjusted(+left, +top, -right, -bottom)
        x = effective.x()
        y = effective.y()
        lineheight = 0
        for item in self._items:
            widget = item.widget()
            hspace = self.horizontalSpacing()
            if hspace == -1:
                hspace = widget.style().layoutSpacing(
                    QtWidgets.QSizePolicy.PushButton,
                    QtWidgets.QSizePolicy.PushButton, QtCore.Qt.Horizontal)
            vspace = self.verticalSpacing()
            if vspace == -1:
                vspace = widget.style().layoutSpacing(
                    QtWidgets.QSizePolicy.PushButton,
                    QtWidgets.QSizePolicy.PushButton, QtCore.Qt.Vertical)
            nextX = x + item.sizeHint().width() + hspace
            if nextX - hspace > effective.right() and lineheight > 0:
                x = effective.x()
                y = y + lineheight + vspace
                nextX = x + item.sizeHint().width() + hspace
                lineheight = 0
            if not testonly:
                item.setGeometry(
                    QtCore.QRect(QtCore.QPoint(x, y), item.sizeHint()))
            x = nextX
            lineheight = max(lineheight, item.sizeHint().height())
        return y + lineheight - rect.y() + bottom

    def smartSpacing(self, pm):
        parent = self.parent()
        if parent is None:
            return -1
        elif parent.isWidgetType():
            return parent.style().pixelMetric(pm, None, parent)
        else:
            return parent.spacing()

class Bubble(QtWidgets.QLabel):
    def __init__(self, text):
        super(Bubble, self).__init__(text)
        self.word = text
        self.setContentsMargins(5, 5, 5, 5)

    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        painter.drawRoundedRect(
            0, 0, self.width() - 1, self.height() - 1, 5, 5)
        super(Bubble, self).paintEvent(event)

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, text, parent=None):
        super(MainWindow, self).__init__(parent)
        self.mainArea = QtWidgets.QScrollArea(self)
        self.mainArea.setWidgetResizable(True)
        widget = QtWidgets.QWidget(self.mainArea)
        widget.setMinimumWidth(50)
        layout = FlowLayout(widget)
        self.words = []
        for word in text.split():
            label = Bubble(word)
            label.setFont(QtGui.QFont('SblHebrew', 18))
            label.setFixedWidth(label.sizeHint().width())
            self.words.append(label)
            layout.addWidget(label)
        self.mainArea.setWidget(widget)
        self.setCentralWidget(self.mainArea)

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = MainWindow('Harry Potter is a series of fantasy literature')
    window.show()
    sys.exit(app.exec_())

Medrano