[Qt-interest] Styling QStyledItemDelegate checkboxes in a QAbstractItemView with Qt Style Sheets

[Pradeep K Vijayan]

Hi Ryan,

If you are still looking for an answer, I managed to make it work with:

QTableView::indicator:checked
{
     background: url(":checkbox/checked");
}

QTableView::indicator:unchecked
{
     background: url(":checkbox/unchecked");
}

Cheers,
Pradeep
-- 
Pradeep K Vijayan
EditShare EMEA
United Kingdom
www.editshare.co.uk

On 22/10/2010 09:37, RJ Ryan wrote:
> Hello all,
>
> I have a QTableView in which I use the Qt::CheckStateRole to show
> checkboxes in one of the columns. How can I style these checkboxes with
> Qt style sheets?
>
> I have tried the following selectors:
> - QCheckBox::indicator
> - QTableView QCheckBox::indicator
> - QTableView::item QCheckBox::indicator
> - QTableView::item::indicator
>
> Once I select the indicator, I give it a rule like so:
>
> {
>    image: url(:/foo.png);
> }
>
> None of the above selectors work. I've confirmed that the same settings
> work fine on a regular QCheckBox that is not in my table.
>
> I've tried to dig through the Qt source to find out how the checkbox is
> being rendered. It looks to me like QStyledItemDelegate checks for the
> flags to see if Qt::ItemIsUserCheckable, and then checks the
> Qt::CheckStateRole of the cells. If it turns out the item is checkable,
> then it paints the widget like so:
>
> qstyleditemdelegate.cpp:422
> const QWidget *widget = QStyledItemDelegatePrivate::widget(option);
> QStyle *style = widget ? widget->style() : QApplication::style();
> style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);
>
> Looking at QStyleSheetStyle::drawControl, I can see that
> QStyle::CE_ItemViewItem is handled like so:
>
> qstylesheetstyle.cpp:3952
> QRenderRule subRule = renderRule(w, opt, PseudoElement_ViewItem);
> if (subRule.hasDrawable() || hasStyleRule(w, PseudoElement_Indicator)) {
>      QStyleOptionViewItemV4 optCopy(*vopt);
>      subRule.configurePalette(&optCopy.palette, vopt->state &
> QStyle::State_Selected ? QPalette::HighlightedText : QPalette::Text,
>                               vopt->state & QStyle::State_Selected ?
> QPalette::Highlight : QPalette::Base);
>      QWindowsStyle::drawControl(ce, &optCopy, p, w);
> } else {
>      QStyleOptionViewItemV4 voptCopy(*vopt);
>      subRule.configurePalette(&voptCopy.palette, QPalette::Text,
> QPalette::NoRole);
>      baseStyle()->drawControl(ce, &voptCopy, p, w);
> }
>
>  From this, it appears that the QAbstractItemView::item is checked for a
> drawable (e.g. background-image?) and also if the widget itself has an
> ::indicator style, then it is passed through
> QWindowsStyle::drawControl(), while otherwise it is passed through
> baseStyle()->drawControl().
>
> Since no other styles (on my platform) handle CE_ItemViewItem, this
> makes it to QCommonStyle. The handling for CE_ItemViewItem in
> QCommonStyle draws the check-box like this:
>
> proxy()->drawPrimitive(QStyle::PE_IndicatorViewItemCheck, &option, p,
> widget);
>
> I don't know this code so well, so I'm assuming proxy() goes right back
> to the top of the chain of styles, back to QStyleSheetStyle.
> drawPrimitive() for QStyleSheetStyle with PE_IndicatorViewItemCheck sets
> pseudoElement to PseudoElement_ViewItemIndicator and then does this:
>
>
> qstylesheetstyle.cpp:4398
> if (pseudoElement != PseudoElement_None) {
>      QRenderRule subRule = renderRule(w, opt, pseudoElement);
>      if (subRule.hasDrawable()) {
>          subRule.drawRule(p, rect);
>      } else {
>          baseStyle()->drawPrimitive(pe, opt, p, w);
>      }
> }
>
> So it looks to me like this checkbox should be rendered with the rule
> indicated by PseudoElement_ViewItemIndicator. From the PseudoElement
> info structure, I can tell that the selector for this is "indicator".
> This leads me to believe that a selector like these should work:
>
> QTableView::item::indicator
> or
> QTableView::item::indicator::checked
>
> I've tried these and none of them seem to work. I'm using Qt 4.6.2 on
> Ubuntu 10.04, so I'm not sure if this is a bug or not. I've reached the
> limit of my knowledge of how QStyle works, so it'd be really helpful if
> someone who knows what is going on here could help me out.
>
> Thanks for your time,
> RJ Ryan
>
>