PyQt: How Can I set row heights of QTreeView - qt

Question

In PyQt, I am looking for a way to set the height of rows in a QTreeView (similarly to QTableView.setRowHeight(row, row_height), but QTreeView does not have this function). QAbstractItemModel is used to set the tree model. I read some suggestions here using and sub-classing QAbstractItemDelegate.sizeHint(option, index) but I don't know exactly how to call them correctly within my tree model.
Any minimal code or suggestion would be greatly appreciated. Thanks.

Answer 1

The QTreeView works out a height for each row based on the data and size hints returned for each item. I think you probably just need to return size hints, either for all your items, or at least the first row (if you have setUniformRowHeights(True)). Incidentally this can significantly improve performance and so you should set it if you can.
So you just need to implement your AbstractItemModel.data() method to return a size hint in the SizeHintRole. Something like this:
def data(self, index, role = QtCore.Qt.DisplayRole):
# Check the index, possibly return None
if role == QtCore.Qt.DisplayRole:
# Return the data
elif role == QtCore.Qt.SizeHintRole:
return QtCore.QSize(item_width,item_height)
# Other roles - maybe return None if you don't use them.
EDIT: Big example
You say you are still having trouble so here is a complete working example, based on the standard QT itemviews example. Try varying the QSize returned in the data method to see how the view changes:
import sys
from PySide import QtCore,QtGui
class TreeItem(object):
def __init__(self, data, parent=None):
self.parentItem = parent
self.data = data
self.childItems = []
def appendChild(self, item):
self.childItems.append(item)
def row(self):
if self.parentItem:
return self.parentItem.childItems.index(self)
return 0
class TreeModel(QtCore.QAbstractItemModel):
def __init__(self, parent=None):
super(TreeModel, self).__init__(parent)
self.rootItem = TreeItem(None)
for i,c in enumerate("abcdefg"):
child = TreeItem([i,c],self.rootItem)
self.rootItem.appendChild(child)
parent = self.rootItem.childItems[1]
child = TreeItem(["down","down"],parent)
parent.appendChild(child)
def columnCount(self, parent):
return 2
def data(self, index, role):
if not index.isValid():
return None
if role == QtCore.Qt.DisplayRole:
item = index.internalPointer()
return item.data[index.column()]
elif role == QtCore.Qt.SizeHintRole:
print "giving size hint"
return QtCore.QSize(40,40)
return None
def flags(self, index):
if not index.isValid():
return QtCore.Qt.NoItemFlags
return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable
def headerData(self, section, orientation, role):
if orientation == QtCore.Qt.Horizontal and role == QtCore.Qt.DisplayRole:
return ["A","B"][section]
return None
def index(self, row, column, parent):
if not self.hasIndex(row, column, parent):
return QtCore.QModelIndex()
if not parent.isValid():
parentItem = self.rootItem
else:
parentItem = parent.internalPointer()
childItem = parentItem.childItems[row]
if childItem:
return self.createIndex(row, column, childItem)
else:
return QtCore.QModelIndex()
def parent(self, index):
if not index.isValid():
return QtCore.QModelIndex()
parentItem = index.internalPointer().parentItem
if parentItem == self.rootItem:
return QtCore.QModelIndex()
return self.createIndex(parentItem.row(), 0, parentItem)
def rowCount(self, parent):
if parent.column() > 0:
return 0
if not parent.isValid():
parentItem = self.rootItem
else:
parentItem = parent.internalPointer()
return len(parentItem.childItems)
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
model = TreeModel()
view = QtGui.QTreeView()
view.setModel(model)
view.setWindowTitle("Simple Tree Model")
view.show()
sys.exit(app.exec_())

Answer 2

It's pretty simple to do this with stylesheet :
self.setStyleSheet("QTreeView::item { padding: 10px }")

Answer 3

Don't know about Python, but C++ code would be like this:
model->setData(model->index(/*your index*/), QSize(20, 20), Qt::SizeHintRole);
And you need to set it for all items in your tree.
If you want use QItemDelegate - you no need to call this function, you just set your delegate to view, like this (C++ code again, but main idea is the same):
treeView->setItemDelegate(new MyDelegate(this));
Than view will use it when it need it.

Answer 4

For the PySide bindings, here's the Python code for the custom delegate on the AbstractItemModel.
from PySide import QtCore, QtGui
tree = QTreeView()
tree.model = QtGui.QAbstractItemModel()
tree.setModel(tree.model)
size = QtCore.QSize(20, 20)
index = tree.model.index(row, col) # row, col are your own
tree.model.setData(index, size, QtCore.Qt.SizeHintRole)
delegate = MyDelegate()
tree.setItemDelegate(delegate)
This is just translating the code from #RazrFalcon to Python, and was requested by another user.

Answer 5

With Qt 5.9.2, I had trouble with simultaneously getting QTreeView auto-sizing columns and custom row heights. Using SizeHintRole worked for height but seemingly wrecked auto-width. The solution for me was to set the rows to have uniform heights and then do something like this in Python 3.7:
self._tree = QTreeView()
self._tree.setAlternatingRowColors(True)
self._tree.setUniformRowHeights(True)
...
fi = QFontInfo(self.font())
self._tree.setStyleSheet(
f'''
QTreeView {{
alternate-background-color: #E6FFFF;
}}
QTreeView::Item{{
height:{fi.pixelSize() * 2}px;
}}
''')
I'll speculate that setting colors and heights this way provides a tiny bit of a performance improvement.