How to simplify a complex item delegate?

[Lykurg]

I need to know the size for QStyledItemDelegate::sizeHint as well...

Yes, but only the height and width, not every exact position of the elements. Also I guess the count of labels is known and static, so you can cache that information. So it would be easy:

int countOfLabels = 3; // or whatever
int h = 0;
h = countOfLabels * (fontmetrics.height() + padding)
h = qMax(h, heightOfThumbnail);

int countOfLabels = 3; // or whatever
int h = 0;
h = countOfLabels * (fontmetrics.height() + padding)
h = qMax(h, heightOfThumbnail);

To copy to clipboard, switch view to plain text mode 

Also I considered using columns.

Also that doesn't change much of my example:

QList<QPair<QString,QString> > labels; // a pair has "label:value"
// Draw the pixmap
int currentX = pixmap.width() + padding /* +... */;
 
// then drawing
int height = fontmetrics.height() + padding;
for(int i = /*...*/) {
    painter->drawText(QRect(currentX, i*height, maxDescWidth, height), Qt::AlignRight, labels.at(i).first);
    // same for the text.
}

QList<QPair<QString,QString> > labels; // a pair has "label:value"
// Draw the pixmap
int currentX = pixmap.width() + padding /* +... */;

// then drawing
int height = fontmetrics.height() + padding;
for(int i = /*...*/) {
    painter->drawText(QRect(currentX, i*height, maxDescWidth, height), Qt::AlignRight, labels.at(i).first);
    // same for the text.
}

To copy to clipboard, switch view to plain text mode 

The solution with a QWidget is possible but then you could simply use Q***Widget. And also the delegate functions are called quite a lot so it isn't with good performance.

[Adam Badura]

This should work (not tested but you should get the picture...)

void paint ( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const {
  QPixmap px = index.data(Qt::DecorationRole).toPixmap();
  painter->drawPixmap(option.rect.topLeft()+QPoint(1,1), px);
  painter->drawText(option.rect.adjusted(px.width+1+5, 1, -1, -1), Qt::AlighLeft|Qt::AlignTop, QString("%1\n%2\n%3").arg(index.data(Qt::DisplayRole).toString()).arg(index.data(...).toString()).arg(index.data(...).toString()));
}

void paint ( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const {
  QPixmap px = index.data(Qt::DecorationRole).toPixmap();
  painter->drawPixmap(option.rect.topLeft()+QPoint(1,1), px);
  painter->drawText(option.rect.adjusted(px.width+1+5, 1, -1, -1), Qt::AlighLeft|Qt::AlignTop, QString("%1\n%2\n%3").arg(index.data(Qt::DisplayRole).toString()).arg(index.data(...).toString()).arg(index.data(...).toString()));
}

To copy to clipboard, switch view to plain text mode 

Only that this does not do what I wanted. The 3 text fields consist of two columns which have to be aligned properly. I did mention that and it was visible on the image of current state I posted in the mean time.

Although I do like the idea of drawing multiline text. I wasn't aware this is possible. Some simplification at least.

The solution with a QWidget is possible but then you could simply use Q***Widget. And also the delegate functions are called quite a lot so it isn't with good performance.

Why do you think this is bad? I am actually very attracted to this idea as it would allow me to do what I indeed wanted: use UI for designing the items. Also this might ease styling. After all the QWidget drawing/layout would do the same thing that I would do "by hand".

[wysota]

Only that this does not do what I wanted. The 3 text fields consist of two columns which have to be aligned properly. I did mention that and it was visible on the image of current state I posted in the mean time.

I don't see any "two columns" on the image you posted (http://stackoverflow.com/questions/4...tyled-listview). Could you elaborate what you mean? I can see a thumbnail and four rows of single word strings.

Why do you think this is bad?

This is really bad, trust me Try having more than 10 rows with cell widgets and notice how performance drops. If you need anything complex I would really consider using QtQuick for the view.

Anyway I will think about some mechanism for simplified delegate layout. I think for static cases such as yours this is possible. It's much more complicated if you want to do animations (e.g. like in QProgressBar on modern Windows). I used to tutor a bachelor thesis that aimed to work around this problem.

If you don't hear back from me in a couple of days, send me a PM or bump the thread.

[Adam Badura]

I don't see any "two columns" on the image you posted (http://stackoverflow.com/questions/4...tyled-listview). Could you elaborate what you mean? I can see a thumbnail and four rows of single word strings.

See second paragraph of my first post. Then second paragraph of the post in which I asked you for sample. Then the post in which I provided my current code and a snapshot of what it does. The Windows Media Player example was just that. An example of similar layout which I found quickly. I didn't know any better example and didn't want to spend to much time looking for one.

This is really bad, trust me Try having more than 10 rows with cell widgets and notice how performance drops. If you need anything complex I would really consider using QtQuick for the view.

I didn't want to have QWidget for every item. (This way I could use QTreeWidget instead...) I wanted to have just one object hidden behind the scenes which I would feed with data (either directly or by sharing model and changing "active index") to than size/paint through it. Would that be bad to? Why? What more would it do (as compared to ordinary delegate) that it would influence performance so much?

I cannot switch to QtQuick. I would like but the decision is not up to me.

[wysota]

See second paragraph of my first post. Then second paragraph of the post in which I asked you for sample. Then the post in which I provided my current code and a snapshot of what it does. The Windows Media Player example was just that. An example of similar layout which I found quickly. I didn't know any better example and didn't want to spend to much time looking for one.

Your delegate is still pretty simple.

I didn't want to have QWidget for every item. (This way I could use QTreeWidget instead...)

I don't understand how using QTreeWidget influences anything here.

I wanted to have just one object hidden behind the scenes which I would feed with data (either directly or by sharing model and changing "active index") to than size/paint through it. Would that be bad to? Why?

You would have to modify most properties of that object during every paint which is quite heavy.

I cannot switch to QtQuick.

Not even for this single view?

[wysota]

Just to let you know, I already have a preliminary working solution. It's not pixel-perfect yet, but it already gives acceptable results.

delegatelayout.jpg

DelegateLayout *l = new DelegateLayoutFrame(Qt::Horizontal);
l->setSpacing(10);
l->setMargins(QMargins(5,5,5,5));
DelegatePixmap *p1 = new DelegatePixmap(l);
DelegateText *t1 = new DelegateText(l);
t1->setRole(Qt::UserRole+1);
t1->setMargins(QMargins(5,5,5,5));
t1->setMinimumSize(QSize(QFontMetrics(f).width("MMMM"), 1));
 
DelegateLayout *headersl = new DelegateLayout(Qt::Vertical, l);
DelegateStaticText *h1 = new DelegateStaticText(headersl);
h1->setText("Name:");
DelegateStaticText *h2 = new DelegateStaticText(headersl);
h2->setText("Created:");
 
DelegateLayout *valuesl = new DelegateLayout(Qt::Vertical, l);
DelegateText *t2 = new DelegateText(valuesl);
t2->setRole(Qt::DisplayRole);
t2->setForegroundColor(Qt::darkGreen);
DelegateText *t3 = new DelegateText(valuesl);
t3->setRole(Qt::UserRole);
QListView v;
 
LayoutDelegate *ld = new LayoutDelegate(&v);
ld->setLayout(l);
v.setItemDelegate(ld);
v.setModel(&model);
 
v.show();

DelegateLayout *l = new DelegateLayoutFrame(Qt::Horizontal);
l->setSpacing(10);
l->setMargins(QMargins(5,5,5,5));
DelegatePixmap *p1 = new DelegatePixmap(l);
DelegateText *t1 = new DelegateText(l);
t1->setRole(Qt::UserRole+1);
t1->setMargins(QMargins(5,5,5,5));
t1->setMinimumSize(QSize(QFontMetrics(f).width("MMMM"), 1));

DelegateLayout *headersl = new DelegateLayout(Qt::Vertical, l);
DelegateStaticText *h1 = new DelegateStaticText(headersl);
h1->setText("Name:");
DelegateStaticText *h2 = new DelegateStaticText(headersl);
h2->setText("Created:");

DelegateLayout *valuesl = new DelegateLayout(Qt::Vertical, l);
DelegateText *t2 = new DelegateText(valuesl);
t2->setRole(Qt::DisplayRole);
t2->setForegroundColor(Qt::darkGreen);
DelegateText *t3 = new DelegateText(valuesl);
t3->setRole(Qt::UserRole);
QListView v;

LayoutDelegate *ld = new LayoutDelegate(&v);
ld->setLayout(l);
v.setItemDelegate(ld);
v.setModel(&model);

v.show();

To copy to clipboard, switch view to plain text mode 

[Adam Badura]

I'm waiting. Looks very promising. Those Delegate* types are your own, are they?

[wysota]

I'm waiting. Looks very promising. Those Delegate* types are your own, are they?

Yes, they are mine.

Here is the current state:

delegatelayout1.png

[Adam Badura]

How is this going? I got assigned back to the task at least for some time so I can now introduce improvements.

[wysota]

Are you interested only in the display of items or also about editing and interaction?

[Adam Badura]

Are you interested only in the display of items or also about editing and interaction?

Only display for now.

[wysota]

In that case I will post my current solution and provide a link to it during the weekend. You want to use it in a commercial project?