Draw a PE_IndicatorBranch in a QLabel

[mrjj]

Hi
I think it needs a rect also, but not sure its the only thing.

class NodeWidget : public QLabel
{
public:
    NodeWidget(QWidget *parent = nullptr) :
        QLabel("this text is displayed", parent) { }
private:
    void paintEvent(QPaintEvent *e)
    {
        
        QLabel::paintEvent(e);
        
        QStyleOption branchOption;
        QPainter painter(this);
        //painter.setBrush( Qt::white);
        //painter.drawRect(0, 0, width() - 1, height() - 1);
        branchOption.initFrom(this);
        branchOption.state = QStyle::State_Item | QStyle::State_Children;
        //  branchOption.state |= QStyle::State_Open; // if to draw open
        branchOption.rect = rect();// adjust this
        style()->drawPrimitive(QStyle::PE_IndicatorBranch, &branchOption, &painter, this);

    }
};

[oberluz]

@mrjj thanks

When I read you reply I was in fact playing around setting the option.rect which you correctly identified as not having been sent, although I still haven't been able to display the indicator branch.

I think it may have to do with the fact that the label is within a layout in a QListwidget row item. Just assigning the QLabel rect doesn't seem enough in my case.

I'll keep on trying...

[mrjj]

@oberluz
Hi
well if you look at the test code, it seems that
style()->drawPrimitive(QStyle::PE_IndicatorBranch draws the
the indicator in the center of the rect given.
It should not matter if inside a QListwidget but you might want to
check the rect label.

[oberluz]

@mrjj Yes I noticed that. I've replicated your test example and I can now get it to display in the row of a QListWidget. Thanks

[mrjj]

@oberluz
You can simply calculate a new rect for the beginning of the text line and
then ask QLabel to center text or similar.
If you want complete control you should draw both text and PE_IndicatorBranch
with painter.
(and not call QLabel::paintEvent(e); )
However, if you use rich text in Label or mutliple lines it is slightly more complicated.

[oberluz]

@mrjj thanks. I was able to get it to work if the QListWidget was the central widget in the QApplicaiton as per your example. However if I add it to a dock widget they fail to draw:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    QWidget* createListWidget();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "MainWindow.h"
#include "ui_MainWindow.h"
#include <QListWidget>
#include <QLabel>
#include <QPainter>
#include <QHBoxLayout>
#include <QApplication>
#include <iostream>
#include <QDockWidget>

class NodeWidget : public QLabel
{
public:
    NodeWidget(QWidget *parent = NULL) :
        QLabel("", parent)
    {
    }

private:
     void paintEvent(QPaintEvent *);
};

void NodeWidget::paintEvent(QPaintEvent *e)
{
    QLabel::paintEvent(e);
    QPainter painter(this);
    QStyleOption option;
    option.initFrom(this);
    option.rect = rect();
    option.state = QStyle::State_Item | QStyle::State_Children;
    style()->drawPrimitive(QStyle::PE_IndicatorBranch, &option, &painter, this);
}

class RowWidget : public QWidget
{
public:
    RowWidget(const QString& text, QWidget *parent = NULL);
};


RowWidget::RowWidget(const QString &text, QWidget *parent) :
    QWidget(parent)
{
    QHBoxLayout* layout = new QHBoxLayout(this);
    layout->setContentsMargins(0,0,0,0);

    layout->addWidget(new NodeWidget(this));
    layout->addWidget(new QLabel(text, this));
    layout->addWidget(new QLabel("text", this));

    setLayout(layout);
}


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    layout()->setContentsMargins(0,0,0,0);

    QString styleSheet("QDockWidget::title { font: 75 11pt \"ubuntu\"; text-align: left; background: darkgray; }");

    QDockWidget* m_dockWidget;
    m_dockWidget = new QDockWidget(" Dock Window", this);
    m_dockWidget->setObjectName(QString::fromUtf8("DockWidget"));
    QSizePolicy sizePolicy6(QSizePolicy::Minimum, QSizePolicy::Minimum);
    sizePolicy6.setHorizontalStretch(0);
    sizePolicy6.setVerticalStretch(0);
    sizePolicy6.setHeightForWidth(m_dockWidget->sizePolicy().hasHeightForWidth());
    m_dockWidget->setSizePolicy(sizePolicy6);
    m_dockWidget->setAllowedAreas(Qt::LeftDockWidgetArea|Qt::RightDockWidgetArea|Qt::TopDockWidgetArea|Qt::BottomDockWidgetArea);

    m_dockWidget->layout()->setContentsMargins(0,0,0,0);
    m_dockWidget->setStyleSheet(styleSheet);

    addDockWidget(Qt::BottomDockWidgetArea, m_dockWidget);

    QWidget* list = createListWidget();
    m_dockWidget->setWidget(list);

    {
        QWidget* list = createListWidget();
        setCentralWidget(list);
    }
}

MainWindow::~MainWindow()
{
    delete ui;
}

QWidget *MainWindow::createListWidget()
{
    QListWidget* list = new QListWidget(this);
    list->setAlternatingRowColors(true);

    RowWidget* widget = new RowWidget("one", list);
    QListWidgetItem* item = new QListWidgetItem(list);
    item->setSizeHint(widget->minimumSizeHint());
    list->addItem(item);
    list->setItemWidget(item, widget);

    widget = new RowWidget("two", list);
    item = new QListWidgetItem(list);
    item->setSizeHint(widget->minimumSizeHint());
    list->addItem(item);
    list->setItemWidget(item, widget);

    widget = new RowWidget("three", list);
    item = new QListWidgetItem(list);
    item->setSizeHint(widget->minimumSizeHint());
    list->addItem(item);
    list->setItemWidget(item, widget);

    return list;
}

[oberluz]

@oberluz said in Draw a PE_IndicatorBranch in a QLabel:

drawPrimitive

my bad: the style sheet is causing the issue. Can't see why that could cause it?

[mrjj]

Hi
What does the stylesheet target?
margins and such can affect lots of stuff if not
target using names or concrete types as selectors

[oberluz]

@mrjj I only intended it to darken the dock window title bar:

QString styleSheet("QDockWidget::title { font: 75 11pt \"ubuntu\"; text-align: left; background: darkgray; }");

[mrjj]

@oberluz
so if you do use styleSheet it looks as you expect?
you are right, im not sure either how that should affect NodeWidget

[oberluz]

@mrjj yes, without the stylesheet its fine:

Is its possible I need to get the current style sheet, then somehow add the title, and then set it ? I'm thinking that by just setting it rather than modifying it I might be deleting something

[mrjj]

@oberluz
Hi
Unless you manually set a stylesheet, its empty pr default.
so if that is the ONLY stylesheet you set, i dont get it.

[oberluz]

@mrjj its the only one, the example I posted is complete

[mrjj]

@oberluz
Sorry, i really cant guess.
It seems not very connected.
and should only affect Title

[oberluz]

@mrjj Maybe a bug.. I might raise one with this example

[mrjj]

@oberluz
Could be.
Please make a small sample that can reproduce it.
Makes it far more likely we discover what it is. :)

[oberluz]

@mrjj will do and I'll run it under 5.13 before submititng

[mrjj]

@oberluz
Super.
and please post link to bug here :)

[oberluz]

@mrjj https://bugreports.qt.io/browse/QTBUG-76947
as promised. reproduced it with 5.13.