Custom widget with frame like QLineEdit

[cil]

Hi All.

I would like to build a custom widget that appears with the same frame and background of QLineEdit, whatever they are. The inner content of the widget will be drawn by my paintEvent method.

Till now I was able to draw the same frame, inheriting my widget from QFrame (instead of QWidget) and setting the frame style to StyledPanel | Sunken. This isn't enough, because I have no background (QLineEdit has a background, usually white).

There's a way to tell Qt "draw this widget like QLineEdit"?

I'm doing this through PyQt4 (if matters...).

Thank you.

[wysota]

If it is just about background then you need to tell the frame it should draw one (QWidget::autoFillBackground) and what colour it should use for it (QWidget::setBackgroundRole(QPalette::Base)).

[cil]

I tried this (python code):

palette = self.palette()
palette.setColor(QPalette.Window, Qt.white)
self.setPalette(palette)
self.setAutoFillBackground(True)

palette = self.palette()
palette.setColor(QPalette.Window, Qt.white)
self.setPalette(palette)
self.setAutoFillBackground(True)

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and this, like you suggested:

self.setBackgroundRole(QPalette.Base)
self.setAutoFillBackground(True)

self.setBackgroundRole(QPalette.Base)
self.setAutoFillBackground(True)

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both draw a white filled rectangle under the widget's frame, but this rectangle is slightly bigger than the frame and this is awful (at least with my KDE4/Oxygen widget style, which has rounded corners for all widgets; the white background of QLineEdit is, obviously, well contained inside the frame).

thank you for your help.

[borisbn]

see QStyle::drawPrimitive ( QStyle::PE_PanelLineEdit, ... )

[faldzip]

There's a way to tell Qt "draw this widget like QLineEdit"?

Yes, you can derive your class from QLineEdit.
On the other hand you can draw whole controls with QStyle or QStylePainter. Read about those classes in Assistant.

[cil]

Deriving from QLineEdit seems to me a little forced, because I don't want to modify/extend the QLineEdit behaviour but I want only its appearance. Anyway, If there are no technical reasons to don't derive from QLineEdit for a totally different scope, this could be the simpliest solution.

QStyle seems promising! But not so easy to understand... I'll look for some examples. Thank you.

[aamer4yu]

What if you set the stylesheet with a thick border ?
something like myLineEdit->setStyleSheet("border : 2px solid black;");

Check the stylesheet example in Qt demos...

[wysota]

Go for QStyle as faldżip suggested, it's easy, really.

[cil]

I think this is the right direction... and now I understand the borisbn suggestion.

in my paintEvent method (python code):

def paintEvent(self, event):
 
        painter = QPainter(self)
 
        option = QStyleOption()
        option.initFrom(self)
        self.style().drawPrimitive(QStyle.PE_PanelLineEdit, option, painter)
        ... other drawing operations...

def paintEvent(self, event):

        painter = QPainter(self)

        option = QStyleOption()
        option.initFrom(self)
        self.style().drawPrimitive(QStyle.PE_PanelLineEdit, option, painter)
        ... other drawing operations...

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but this has no effect. I get only my drawing operations.
I have some troubles to understand what to do with the QStyleOption object. Maybe the problem is this.

[wysota]

I think you should be using QStyleOptionFrame(V3). It's best to look into QLineEdit source code and verify that instead of guessing.

[cil]

I read qlineedit.cpp, as you wisely suggest. Doing this gave me the inspiration
for this solution (python code):

class MyWidget(QWidget):
 
    def __init__(self, parent=None):
 
        super(MyWidget, self).__init__(parent)
 
        self.styleoption = QStyleOptionFrameV2()
        qle = QLineEdit()
        qle.initStyleOption(self.styleoption)
 
 
    def paintEvent(self, event):
 
        painter = QPainter(self)
        self.styleoption.rect = self.contentsRect()
        self.style().drawPrimitive(QStyle.PE_PanelLineEdit, self.styleoption, painter)

class MyWidget(QWidget):

    def __init__(self, parent=None):

        super(MyWidget, self).__init__(parent)

        self.styleoption = QStyleOptionFrameV2()
        qle = QLineEdit()
        qle.initStyleOption(self.styleoption)


    def paintEvent(self, event):

        painter = QPainter(self)
        self.styleoption.rect = self.contentsRect()
        self.style().drawPrimitive(QStyle.PE_PanelLineEdit, self.styleoption, painter)

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In other words, I use a QLineEdit to fill in the QStyleOption object for me.
Then I can use drawPrimitive (borisbn's hint) to have my widget drawn as
I like.

Thank you for you patience, I learned some useful things.

[wysota]

Hmm... Not very efficient to create a line edit just to fill in a few properties.

[cil]

It's true, but there aren't any visibile performance problems and my code is really simple and compact. I can always explode initStyleOption() whenever it becomes necessary.

[wysota]

Yeah, but it's still ugly