Using QStyledItemDelegate::paint() on a table cell (alignment issues)

[graffy]

Hello,

I'm overloading the QStyledItemDelegate::paint() function to enable the display of text and/or icons (depending on user preference) in a table column. I have the feature working exactly as I intended. However, getting the text and icons to align with the other data in the row required me to add / subtract pixels from the rect position (denoted by the "Offset" variables in the code below).

I suppose this will work, but it makes me nervous, as I fear I may have implemented a device-dependent solution, thus different video cards or platforms may render everything differently, making my adjustments worthless. Is there a device independent way to match the alignment of painted text / graphics to the alignemnt of values of the adjacent cells? Or can anyone assuage my fears that my approach is going to be ok, regardless of platform / video hardware?

Obligatory code:

void CSVWorld::RecordStatusDelegate::paint (QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
   painter->save();
 
   QFont font = QApplication::font();
   font.setPointSize(10);
 
   QFontMetrics fm(font);
 
   QString text = "";
   QIcon *icon = 0;
 
   switch (index.data().toInt())
   {
        //ICON SELECTION LOGIC HERE
   }
 
   QRect textRect = option.rect;
   QRect iconRect = option.rect;
    int displayables = 0;
 
   //for icon-only (1), default option.rect centers icon left-to-right
   //otherwise, size option.rect to fit the icon, forcing left-alignment with text
 
    iconRect.setTop (iconRect.top() + mIconTopOffset);   //device-dependent?
    iconRect.setBottom (iconRect.top() + mIconSize);
 
    if (displayables == 0 && (icon) )
    {
        iconRect.setRight (iconRect.left() + mIconSize);
        textRect.setLeft (iconRect.right() + (mIconSize/4) * 3);
        textRect.setRight (textRect.left() + fm.width(text));
    }
    else
        textRect.setLeft (textRect.left() + mTextLeftOffset );   //device-dependent?
 
    textRect.setTop (textRect.top() + ((option.rect.height() - fm.height()) / 2) + mTextTopOffset);   //device-dependent?
 
   if (displayables == 0 || displayables == 1)
   {
        if (icon)
           painter->drawPixmap(iconRect.center(),icon->pixmap(mIconSize, mIconSize));
   }
 
   // icon + text or text only, or force text if no icon exists for status
   if (displayables == 0 || displayables == 2 || !(icon) )
   {
        painter->setFont(font);
        painter->drawText(textRect,text);
   }
 
   painter->restore();
 
}

void CSVWorld::RecordStatusDelegate::paint (QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
   painter->save();

   QFont font = QApplication::font();
   font.setPointSize(10);

   QFontMetrics fm(font);

   QString text = "";
   QIcon *icon = 0;

   switch (index.data().toInt())
   {
        //ICON SELECTION LOGIC HERE
   }

   QRect textRect = option.rect;
   QRect iconRect = option.rect;
    int displayables = 0;

   //for icon-only (1), default option.rect centers icon left-to-right
   //otherwise, size option.rect to fit the icon, forcing left-alignment with text

    iconRect.setTop (iconRect.top() + mIconTopOffset);   //device-dependent?
    iconRect.setBottom (iconRect.top() + mIconSize);

    if (displayables == 0 && (icon) )
    {
        iconRect.setRight (iconRect.left() + mIconSize);
        textRect.setLeft (iconRect.right() + (mIconSize/4) * 3);
        textRect.setRight (textRect.left() + fm.width(text));
    }
    else
        textRect.setLeft (textRect.left() + mTextLeftOffset );   //device-dependent?

    textRect.setTop (textRect.top() + ((option.rect.height() - fm.height()) / 2) + mTextTopOffset);   //device-dependent?

   if (displayables == 0 || displayables == 1)
   {
        if (icon)
           painter->drawPixmap(iconRect.center(),icon->pixmap(mIconSize, mIconSize));
   }

   // icon + text or text only, or force text if no icon exists for status
   if (displayables == 0 || displayables == 2 || !(icon) )
   {
        painter->setFont(font);
        painter->drawText(textRect,text);
   }

   painter->restore();

}

To copy to clipboard, switch view to plain text mode 

[Santosh Reddy]

Instead of mTextLeftOffset and mTextTopOffset can't you use text alignment options while painting?

QTextOption o;
o.setAlignment(Qt::AlignHCenter| Qt::AlignVCenter);
painter->drawText(textRect, text, o);

QTextOption o;
o.setAlignment(Qt::AlignHCenter| Qt::AlignVCenter);
painter->drawText(textRect, text, o);

To copy to clipboard, switch view to plain text mode 

[graffy]

Hmmm.. That seemed to work pretty well. Eliminates all of the text alignment issues, anyway. It's still not quite lined up vertically, but I may leave it at that if I get no complaints. At least it's device-independent at my level that way.