QDirModel curiosity

It appears that QDirModel uses rows to store directory entries, which means that columns are not useful at all. So I have a simple hierarchy:

Code:

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ls -R
 
A	C
 
./A:
B
 
./A/B:
 
./C:

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If I run the following code to browse the hierarchy:

Code:

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void
MyClass::Browse(QModelIndex idx, int indent)
{
  QFileInfo info = this->fileInfo(idx);
  for (int i=indent ; i>0 ; i--)
    this->Print(" \r");
  this->Print("%d %d %s", idx.row(), idx.column(), info.fileName().toAscii().constData());
  for (int i=0 ; idx.child(i, 0).isValid() ; i++)
    this->ComputeSizes(idx.child(i, 0), indent+2);
}

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I get the expected output:

Code:

---

MyClass: 38 0 test
MyClass:   0 0 A
MyClass:     0 0 B
MyClass:   1 0 C

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But if I change the code so as to browse columns rather that rows as follow:

Code:

---

void
MyClass::Browse(QModelIndex idx, int indent)
{
  QFileInfo info = this->fileInfo(idx);
  for (int i=indent ; i>0 ; i--)
    this->Print(" \r");
  this->Print("%d %d %s", idx.row(), idx.column(), info.fileName().toAscii().constData());
  for (int i=0 ; idx.child(0, i).isValid() ; i++)
    this->ComputeSizes(idx.child(0, i), indent+2);
}

---

I get an unexpected output:

Code:

---

MyClass: 38 0 test
MyClass:   0 0 A
MyClass:     0 0 B
MyClass:     0 1 B
MyClass:     0 2 B
MyClass:     0 3 B
MyClass:   0 1 A
MyClass:   0 2 A
MyClass:   0 3 A

---

I would have expected that idx.child(0, i>0) be unvalid!

I have one more question: what is the difference between QDirModel::sibling() and QDirModel::child()?