HowTo draw different backgrounds with QStyledItemDelegate?

Question

Problem:

• I have QTreeView object, and a QStandardItemModel as model to view widget;
• For some item's I have set data with setData method to split them with a parameter;
• So I need to draw different background pixmap for QStandardItem items, which are with icon's and some text data;
• And don't want to redraw all the items objects, I mean icon and text. Just change background.

First, I was thinking that:

• I could set CSS stylesheets in Qt Designer for the object with 2 different background pictures, BUT QStandardItem doesn't have setProperty method...

Example:

QTreeView#treeView::item[ROLE="AAA"],
QTreeView#treeView::branch[ROLE="AAA"]
{
    height: 25px;
    border: none;
    color: #564f5b;
    background-image: url(:/backgrounds/images/row1.png);
    background-position: top left;
}

QTreeView#treeView::item[ROLE="BBB"],
QTreeView#treeView::branch[ROLE="BBB"]
{
    height: 25px;
    border: none;
    color: #564f5b;
    background-image: url(:/backgrounds/images/row2.png);
    background-position: top left;
}

• then I created my own delegate, inherited from QStyledItemDelegate class, and reimplement paint method, BUT I can't just change background, because QStyledItemDelegate::paint( painter, opt, index ); code will overdraw my drawPixmap...

Example:

QStyleOptionViewItemV4 opt = option; // Для обхода QTBUG-4310
opt.state &= ~QStyle::State_HasFocus; // Чтобы не рисовался прямоугольник фокуса 

QStyledItemDelegate::paint( painter, opt, index );    

// HERE I WANT TO CHANGE BACKGROUND (DEFAULT IS ALREADY SET IN DESIGNER WITH ABOVE CODE)
if( index.data( SORT_ROLE ).toBool() )
{
    const QPixmap pixmap( ":/backgrounds/images/backgrounds/contractor_row__high_priority.png" );
    painter->drawPixmap( option.rect, pixmap, pixmap.rect() );

    QStyledItemDelegate::paint( painter, opt, index );
}

So I'm stuck...

Answer 1

Here is my trick:

The Designer's stylesheet part:

QTreeView#treeView
{
    border: none;
    background-color:#f0f0f1;
}   

QTreeView#treeView::item,
QTreeView#treeView::branch
{
    height: 25px;
    border: none;
    color: #564f5b;
}

QTreeView#treeView::item:selected,
QTreeView#treeView::branch:selected
{
    border-bottom: none;
    color: #ffffff;    
    background-image: url(:/backgrounds/images/backgrounds/kontragents_row_selection.png);
    background-position: top left;  

}

QTreeView#treeView::item:selected:!active,
QTreeView#treeView::branch:selected:!active
{
    color: #ffffff;
}

Delegate reimplemented paint() method:

void paint( QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index ) const
 {
      QStyleOptionViewItemV4 opt = option; // Для обхода QTBUG-4310
      opt.state &= ~QStyle::State_HasFocus; // Чтобы не рисовался прямоугольник фокуса

      QBrush brush = opt.backgroundBrush;
      brush.setTexture( QPixmap( index.data( SORT_ROLE ).toBool()
           ? BACKGROUND_HIGH_PRIORITY
           : BACKGROUND_STANDARD ) );

      // FILL BACKGROUND     
      painter->save();
      painter->fillRect( opt.rect, brush );
      painter->restore();

      // DRAW ICON & TEXT
      QStyledItemDelegate::paint( painter, opt, index );

      // IF ( CHILD ) THEN PAINT OVER ONLY! BRANCH RECT
      bool isIndexParent = !index.parent().isValid();
      if( !isIndexParent )
      {
           QRect rect( 0, opt.rect.y(), 20, opt.rect.height() );

           if( opt.state & QStyle::State_Selected )
           {
                brush.setTexture( QPixmap( BACKGROUND_SELECTED ) );
           }

           painter->save();
           painter->fillRect( rect, brush );
           painter->restore();
      }
 }

Resulting QTreeView view:

Have a nice day! :)

PS: no need redrawing icons, text, selection...

Answer 2

The delegate's paint method is all or nothing, so you won't be able to mix your background with the default implementation's.

However, if you're competent enough to even consider writing a custom delegate, you should have no problem implementing one that can draw your background plus icon and text.