[FIXED] Increasing addAction icon size PyQt5

Issue

I have QLineEdit in which I wanted to add a clear button at the end of it. I enabled clear button in QLineEdit, it was working fine. I need to add a custom clear button at the end of the QLineEdit, so I used addAction() of QLineEdit and added my custom icon. The problem is that I can't find a solution to increase the size, I tried increasing the image size and it's not working.

class TextBox(QFrame):
    def __init__(self, parent):
        super(TextBox, self).__init__(parent=parent)
        self.setObjectName("textBox")

        self.isActive = False

        self.lineEdit = QLineEdit()

        self.lineEdit.addAction(QIcon("assets/icons/[email protected]"), QLineEdit.TrailingPosition)

Solution

A QIcon does not have a specific size, as it's only "decided" by the widget that uses it. While most widgets that use icons have a iconSize property, the icons of actions in a QLineEdit are shown in a different way.

Up until Qt 5.11 (excluded), the size was hardcoded to 16 pixels if the line edit was smaller than 34 pixels or 32 if it was taller.

Starting from Qt 5.11 the size is retrieved using the style (through pixelMetric()), and this can be overridden using a proxy style:

class Proxy(QtWidgets.QProxyStyle):
    def pixelMetric(self, metric, opt=None, widget=None):
        if (metric == self.PM_SmallIconSize and 
            isinstance(widget, QtWidgets.QLineEdit)):
                size = widget.property('iconSize')
                if size is not None:
                    return size
                return widget.fontMetrics().height()
        return super().pixelMetric(metric, opt, widget)


class LineEdit(QtWidgets.QLineEdit):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.setProperty('iconSize', 64)
        # ...

For previous versions of Qt, though, things are a bit tricky. The only solution I came up with is to install event filters on all QToolButton that are children of the line edit (every action uses an internal QToolButton, including the clear action), manually set their geometry (required for correct click actions) and paint it in the event filter.

The following includes the proxystyle implementation in case the current version correctly supports it as explained before:

from PyQt5 import QtWidgets, QtCore, QtGui

if int(QtCore.QT_VERSION_STR.split('.')[1]) > 11:
    IconSizeFix = False
else:
    IconSizeFix = True


class Proxy(QtWidgets.QProxyStyle):
    def pixelMetric(self, metric, opt=None, widget=None):
        if (metric == self.PM_SmallIconSize and 
            isinstance(widget, QtWidgets.QLineEdit)):
                size = widget.property('iconSize')
                if size is not None:
                    return size
                return widget.fontMetrics().height()
        return super().pixelMetric(metric, opt, widget)


class LineEdit(QtWidgets.QLineEdit):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.setProperty('iconSize', 64)
        self.setClearButtonEnabled(True)
        self.addAction(QtGui.QIcon("icon.png"), self.TrailingPosition)
        font = self.font()
        font.setPointSize(48)
        self.setFont(font)

    def checkButtons(self):
        for button in self.findChildren(QtWidgets.QToolButton):
            button.installEventFilter(self)

    def actionEvent(self, event):
        super().actionEvent(event)
        if IconSizeFix:
            self.checkButtons()

    def eventFilter(self, source, event):
        if event.type() == QtCore.QEvent.Paint:
            if (source.defaultAction().objectName() == '_q_qlineeditclearaction' and 
                not self.text()):
                    return True
            qp = QtGui.QPainter(source)
            state = QtGui.QIcon.Disabled
            if source.isEnabled():
                state = QtGui.QIcon.Active if source.isDown() else QtGui.QIcon.Normal
            iconSize = QtCore.QSize(*[self.property('iconSize')] * 2)
            qp.drawPixmap(source.rect(), source.icon().pixmap(
                self.windowHandle(), iconSize, state, QtGui.QIcon.Off))
            return True
        return super().eventFilter(source, event)

    def resizeEvent(self, event):
        if not IconSizeFix:
            return
        self.checkButtons()
        buttons = self.findChildren(QtWidgets.QToolButton)
        if not buttons:
            return

        left = []
        right = []
        center = self.rect().center().x()
        for button in buttons:
            geo = button.geometry()
            if geo.center().x() < center:
                left.append(button)
            else:
                right.append(button)
        
        left.sort(key=lambda x: x.geometry().x())
        right.sort(key=lambda x: x.geometry().x())

        iconSize = self.property('iconSize')

        margin = iconSize / 4
        top = (self.height() - iconSize) / 2
        leftMargin = rightMargin = 0
        if left:
            x = margin
            leftEdge = left[-1].geometry().right()
            for button in left:
                geo = QtCore.QRect(x, top, iconSize, iconSize)
                button.setGeometry(geo)
                x += iconSize + margin
            leftMargin = x - leftEdge - margin
        if right:
            rightEdge = self.width() - margin
            x = rightEdge - len(right) * iconSize - (len(right) - 1) * margin
            rightMargin = self.width() - rightEdge + margin
            for button in right:
                geo = QtCore.QRect(x, top, iconSize, iconSize)
                button.setGeometry(geo)
                x += iconSize + margin
        self.setTextMargins(leftMargin, 0, rightMargin, 0)


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle(Proxy())
    w = LineEdit()
    w.show()
    sys.exit(app.exec_())

Consider the following:

• using the pre-5.11 workaround the positioning is not pixel-perfect, I tried to mimic what QLineEdit does to keep the code as simple as possible;
• the painting is not exactly the same, most importantly the icon is missing the "highlight" shade when clicked, and if the style uses fade in/out effects for the clear button those effects won't be available;
• the QProxyStyle method also affects the sizeHint of the QLineEdit, so it can not be smaller than the icon size, so use it with care;

Answered By - musicamante