QStyle::drawControl() not correctly painting enabled/disabled state

peter.thompson

I have a custom delegate that is subclassed from QStyledItemDelegate. In the paint() method for this delegate, I'm using QStyle::drawControl() to draw a check box in the current application's style. I would like to have this check box appear disabled (i.e. grayed out) if the current index is uneditable. However, I can't figure out how to get this to work.

Here is what I have currently:

void MyCheckBoxDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
    this->QStyledItemDelegate::paint(painter, option, index);

    QStyleOptionButton buttonOption;
    buttonOption.rect = MyCheckBoxDelegate::getCheckBoxRectangle(option);

    buttonOption.palette = option.palette;
    buttonOption.direction = option.direction;
    buttonOption.fontMetrics = option.fontMetrics;
    buttonOption.styleObject = option.styleObject;

    buttonOption.state = QStyle::State_None;
    buttonOption.state |= index.data().toBool() ? QStyle::State_On : QStyle::State_Off;
    if (index.flags().testFlag(Qt::ItemIsEditable))
        buttonOption.state |= QStyle::State_Enabled;

    QApplication::style()->drawControl(QStyle::CE_CheckBox, &buttonOption, painter, option.widget);
}

Right now, the check box always appears to be enabled. For reference, here's a comparison with an actual check box widget in the application:

	Enabled, On	Enabled, Off	Disabled, On	Disabled, Off
Widget
Delegate

Am I doing something wrong? Or does QStyle->drawControl() not consider the enabled state when drawing?

peter.thompson

Some more information: I put a breakpoint on drawControl() and followed it through the Qt source code. The application style is a QWindows11Style, but it eventually gets down to QCommonStyle::drawControl(). There's a large switch statement, and it gets to this case for CE_CheckBox. I don't see anything directly in that code that compares the state with State_Enabled.

That code then calls drawPrimitive() with PE_IndicatorCheckBox. That method also has a large switch statement, and it gets to this case for PE_IndicatorCheckBox. I don't see anything here that compares the state with State_Enabled.

Going back up to the case in QCommonStyle::drawControl(), it next recursively calls itself with CE_CheckBoxLabel. That takes us to this case for CE_CheckBoxLabel. I'm only seeing that it compares with State_Enabled to adjust how the icon or text are displayed, but both are null/empty in my case.

SGaist

Hi,

Might be a silly question but did you check the value of state in each of these cases ?

peter.thompson

@SGaist The incoming state for option is State_Enabled|State_Children|State_Sibling. The state on buttonOption is being set to State_On / State_Off when the index is not editable and set to State_On|State_Enabled / State_Off|State_Enabled when the index is editable.

peter.thompson

Some more information: I put a breakpoint on drawControl() and followed it through the Qt source code. The application style is a QWindows11Style, but it eventually gets down to QCommonStyle::drawControl(). There's a large switch statement, and it gets to this case for CE_CheckBox. I don't see anything directly in that code that compares the state with State_Enabled.

That code then calls drawPrimitive() with PE_IndicatorCheckBox. That method also has a large switch statement, and it gets to this case for PE_IndicatorCheckBox. I don't see anything here that compares the state with State_Enabled.

Going back up to the case in QCommonStyle::drawControl(), it next recursively calls itself with CE_CheckBoxLabel. That takes us to this case for CE_CheckBoxLabel. I'm only seeing that it compares with State_Enabled to adjust how the icon or text are displayed, but both are null/empty in my case.

peter.thompson

Turns out it was the palette. You have to set the "current color group" for the palette to QPalette::Disabled. In fact, setting the state doesn't seem to have any effect whatsoever. Setting the palette alone is enough to control the color (and make it appear disabled). But I think I'll keep setting the state just in case it has an effect in other styles.

void MyCheckBoxDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
    this->QStyledItemDelegate::paint(painter, option, index);

    QStyleOptionButton buttonOption;
    buttonOption.rect = MyCheckBoxDelegate::getCheckBoxRectangle(option);

    buttonOption.palette = option.palette;
    buttonOption.direction = option.direction;
    buttonOption.fontMetrics = option.fontMetrics;
    buttonOption.styleObject = option.styleObject;

    buttonOption.state = QStyle::State_None;
    buttonOption.state |= index.data().toBool() ? QStyle::State_On : QStyle::State_Off;

    if (index.flags().testFlag(Qt::ItemIsEditable))
    {
        buttonOption.state |= QStyle::State_Enabled;
        buttonOption.palette.setCurrentColorGroup(QPalette::Normal);
    }
    else
    {
        buttonOption.palette.setCurrentColorGroup(QPalette::Disabled);
    }

    QApplication::style()->drawControl(QStyle::CE_CheckBox, &buttonOption, painter, option.widget);
}

Christian Ehrlicher

This problem is fixed with Qt6.10, maybe also with 6.9 but don't know exactly since there are a lot of changes in the windows11 style as it is not yet finished. This works fine for me with git HEAD:

class Delegate : public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;

    void paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
    {
        QStyleOptionButton buttonOption;
        buttonOption.rect = option.rect;
        buttonOption.palette = option.palette;
        buttonOption.direction = option.direction;
        buttonOption.fontMetrics = option.fontMetrics;
        buttonOption.styleObject = option.styleObject;
        buttonOption.state = QStyle::State_None;
        buttonOption.state |= index.column() % 2 == 0 ? QStyle::State_On : QStyle::State_Off;
        if (index.column() < 2)
            buttonOption.state |= QStyle::State_Enabled;

        option.widget->style()->drawControl(QStyle::CE_CheckBox, &buttonOption, painter, option.widget);
    }
};