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Using QScrollArea collapses children widgets

I am trying to create a dynamic GUI with multiple Groupbox objects in a QVBoxLayout. As there are a lot of them, I will be needing a scroll area to make them available to the end user.
So I tried to change to top widget of this tab from a QWidget to a QScrollArea.
Before the change:
This is the kind of result I want but with a scroll bar because the window is too high.
After the change to QScrollArea:
My GroupBoxs are now "collapsed" and there is not scrollbar. I tried setting their size but it is not adequate because they are not fixed. I searched the documentation and tried to use WidgetResizable or I tried to set a fixed height or the sizehint but nothing worked as I wanted.
After creating the the Groupbox, the sizeHint for my QScrollArea is already very low (around 150px of height) so I think I'm missing a parameter.
It would be complicated to provide code as it is intricate. If necessary I could recreate the problem in a simpler way.
How to reproduce:
from PyQt5 import QtWidgets, QtGui, QtCore
from PyQt5.QtWidgets import *
import sys
class Example(QMainWindow):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
v_layout = QVBoxLayout()
scroll_area = QScrollArea()
self.layout().addWidget(scroll_area)
scroll_area.setLayout(v_layout)
# v_layout.setSizeConstraint(QLayout.SetMinimumSize)
for i in range(50):
box = QGroupBox()
grid = QGridLayout()
box.setLayout(grid)
grid.addWidget(QLabel("totototo"), 0, 0)
grid.addWidget(QLineEdit(), 1, 0)
grid.addWidget(QPushButton(), 2, 0)
v_layout.addWidget(box)
self.show()
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
Uncommenting # v_layout.setSizeConstraint(QLayout.SetMinimumSize) allows the content of the group boxes to deploy and fixes the first part of the issue. But there is still not scroll bar.

You have 2 errors:
A widget should not be added to the layout of a QMainWindow, but the setCentralWidget method should be used.
You should not add the layout to the QScrollArea but use a widget as a container for the other widgets, also if you use layouts then you have to activate the widgetResizable property.
Considering the above, the solution is:
def initUI(self):
scroll_area = QScrollArea(widgetResizable=True)
self.setCentralWidget(scroll_area)
container = QWidget()
scroll_area.setWidget(container)
v_layout = QVBoxLayout(container)
for i in range(50):
box = QGroupBox()
grid = QGridLayout()
box.setLayout(grid)
grid.addWidget(QLabel("totototo"), 0, 0)
grid.addWidget(QLineEdit(), 1, 0)
grid.addWidget(QPushButton(), 2, 0)
v_layout.addWidget(box)
self.show()

How to align widgets in PyQt5

I am trying to use PyQt5 for one of my GUI application. I could be able to add widgets as I want, but couldn't align them properly. I want to align my widgets as below:
But, My code is working something like this,
Following is my code, can anyone help me please?
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtCore import QRect
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import QDesktopWidget, QLabel
class GroupBox(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.setGeometry(QtCore.QRect(20, 20, 900, 700))
self.setWindowTitle("InvoiceMee - Split Documents")
layout = QtWidgets.QGridLayout(self)
groupbox = QtWidgets.QGroupBox("Files to Convert", checkable=False)
layout.addWidget(groupbox)
hbox = QtWidgets.QHBoxLayout()
groupbox.setLayout(hbox)
label = QLabel()
pixmap = QPixmap('images.jpg')
label.setPixmap(pixmap)
label.resize(pixmap.width(), pixmap.height())
pathBox = QtWidgets.QLineEdit(self)
pathBox.setPlaceholderText("Enter the Path Here")
pathBox.setGeometry(QRect(160, 150, 201, 20))
selectFileBtn = QtWidgets.QPushButton("Select")
convertButton = QtWidgets.QPushButton("Convert")
good_radiobutton = QtWidgets.QRadioButton("Invoices")
naive_radiobutton = QtWidgets.QRadioButton("Credit Notes")
hbox.addWidget(pathBox, alignment=QtCore.Qt.AlignCenter)
hbox.addWidget(selectFileBtn, alignment=QtCore.Qt.AlignCenter)
hbox.addWidget(convertButton, alignment=QtCore.Qt.AlignCenter)
hbox.addWidget(good_radiobutton, alignment=QtCore.Qt.AlignCenter)
hbox.addWidget(naive_radiobutton, alignment=QtCore.Qt.AlignCenter)
hbox.addWidget(label,alignment=QtCore.Qt.AlignCenter)
hbox.addStretch()
self.center()
def center(self):
# geometry of the main window
qr = self.frameGeometry()
# center point of screen
cp = QDesktopWidget().availableGeometry().center()
# move rectangle's center point to screen's center point
qr.moveCenter(cp)
# top left of rectangle becomes top left of window centering it
self.move(qr.topLeft())

Use QGridLayout instead of QHBoxLayout. Grid Layout gives you the option to layout your widgets in a grid like struture. Here's the official documentation for QGridLayout.
You can change your layout like this:
grid = QtWidgets.QGridLayout()
groupbox.setLayout(grid)
grid.addWidget(label,0,0,1,0,QtCore.Qt.AlignCenter)
grid.addWidget(pathBox,1,0,QtCore.Qt.AlignRight)
grid.addWidget(selectFileBtn,1,1,QtCore.Qt.AlignLeft)
grid.addWidget(good_radiobutton,2,0,QtCore.Qt.AlignRight)
grid.addWidget(naive_radiobutton,2,1,QtCore.Qt.AlignLeft)
grid.addWidget(convertButton,3,0,1,0,QtCore.Qt.AlignCenter)
Add a vertical spacer item if you want to remove space between your widgets:
verticalSpacer = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
grid.addItem(verticalSpacer, 6, 0, QtCore.Qt.AlignTop)

You are using a QHBoxLayout (which stands for horizontal box layout). This means that all widgets that you added will be always displayed side by side, horizontally, according to the order of insertion.
You should use a layout that allows vertical orientation, instead.
You're using more than a widget per row, so you could use a QGridLayout, but, since some of those widgets have different horizontal sizes, the result might not be what you showed us.
The solution is to use nested layouts, with a main grid layout with stretch sets for first/third row and column and a "central" layout added to the second row/column of the grid. Then, whenever you need more than one widget in a row, add a nested QHBoxLayout.
class GroupBox(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.setGeometry(QtCore.QRect(20, 20, 900, 700))
self.setWindowTitle("InvoiceMee - Split Documents")
layout = QtWidgets.QGridLayout(self)
groupbox = QtWidgets.QGroupBox("Files to Convert", checkable=False)
layout.addWidget(groupbox)
# the "main" layout, used to ensure that the actual layout containing
# all widgets stays in the center
groupLayout = QtWidgets.QGridLayout()
groupbox.setLayout(groupLayout)
groupLayout.setColumnStretch(0, 1)
groupLayout.setColumnStretch(2, 1)
groupLayout.setRowStretch(0, 1)
groupLayout.setRowStretch(2, 1)
# this is the actual layout used to add widgets
centerLayout = QtWidgets.QVBoxLayout()
groupLayout.addLayout(centerLayout, 1, 1)
label = QLabel()
pixmap = QPixmap('images.jpg')
label.setPixmap(pixmap)
# this won't work
# label.resize(pixmap.width(), pixmap.height())
pathBox = QtWidgets.QLineEdit(self)
pathBox.setPlaceholderText("Enter the Path Here")
# this won't work either, the layout will try to move and resize it anyway
# pathBox.setGeometry(QRect(160, 150, 201, 20))
# use minimum width instead
pathBox.setMinimumWidth(200)
selectFileBtn = QtWidgets.QPushButton("Select")
convertButton = QtWidgets.QPushButton("Convert")
good_radiobutton = QtWidgets.QRadioButton("Invoices")
naive_radiobutton = QtWidgets.QRadioButton("Credit Notes")
centerLayout.addWidget(label, alignment=QtCore.Qt.AlignCenter)
# the second row has more than one widget, use a nested horizontal layout
inputLayout = QtWidgets.QHBoxLayout()
centerLayout.addLayout(inputLayout)
inputLayout.addWidget(pathBox)
inputLayout.addWidget(selectFileBtn)
# the same for the radio buttons
radioLayout = QtWidgets.QHBoxLayout()
centerLayout.addLayout(radioLayout)
# use horizontal alignment to keep buttons closer, otherwise the layout
# will try to expand them as much as possible (depending on the other
# widgets in the centerLayout)
radioLayout.addWidget(good_radiobutton, alignment=QtCore.Qt.AlignRight)
radioLayout.addWidget(naive_radiobutton, alignment=QtCore.Qt.AlignLeft)
# use center alignment so that the button doesn't expand
centerLayout.addWidget(convertButton, alignment=QtCore.Qt.AlignCenter)
I'd suggest you to carefully study how layout work and behave, make some experiments and also use Qt Designer to easily see how nested layout can work.
Also, consider that in some cases it might be necessary to set a specific size policy to avoid widgets expanding too much, and use a QWidget "container" can make things easier.
For example, instead of using the horizontal alignment when you add the radio buttons, you can use a QWidget container:
# ...
radioContainer = QtWidgets.QWidget()
centerLayout.addWidget(radioContainer, alignment=QtCore.Qt.AlignCenter)
radioContainer.setSizePolicy(QtWidgets.QSizePolicy.Maximum,
QtWidgets.QSizePolicy.Preferred)
radioLayout = QtWidgets.QHBoxLayout(radioContainer)
radioLayout.addWidget(good_radiobutton)
radioLayout.addWidget(naive_radiobutton)
# ...

How does stretch factor work in Qt?

I'm working on a GUI application with pyqt5. At a certain dialog I need many components, being one of those a QWebEngineView as a canvas for plotting data, which should take most of the space available even if the chart is not ready when creating the dialog.
I expect it to look something like this:
I investigated and found about the stretch factor. I saw that QSizePolicy is directly applicable only to widgets and not to layouts, as shown in this SO answer. But then I saw that the methods addWidget and addLayout allow me to set the stretch factor in the direction of the QBoxLayout, and that seemed ideal for my intentions.
So I tried with:
from PyQt5.QtWidgets import QWidget, QLabel, QVBoxLayout, QHBoxLayout
from strategy_table import StrategyTable
layout = QVBoxLayout()
layout.addWidget(QLabel("Strategy components"))
# Upper layout for a table. Using a 30% of vertical space
upper_layout = QHBoxLayout() # I'm using a HBox because I also want a small button at the right side of the table
self.table = StrategyTable(self) # Own class derived from QTableWidget
upper_layout.addWidget(self.table)
add_button = QPushButton('Add')
add_button.clicked.connect(self._show_add_dialog)
upper_layout.addWidget(add_button)
layout.addLayout(upper_layout, 3) # Setting 20% of size with the stretch factor
# Then the plot area, using 60% of vertical space
layout.addWidget(QLabel("Plot area"))
canvas = QWebEngineView()
layout.addWidget(self.canvas, 6)
# Finally, a small are of 10% of vertical size to show numerical results
layout.addWidget(QLabel("Results"))
params_layout = self._create_results_labels() # A column with several QLabel-QTextArea pairs, returned as a QHBoxLayout
layout.addLayout(params_layout, 1)
self.setLayout(layout)
But it looked exactly the same as before:
It looked quite ok before adding the results Layout at the bottom, I guess because the upper table is empty at the beginning, and therefore took very little space and left the rest to the canvas.
Anyway, it seems that the stretch factor is being ignored, so I don't know if I am missing something here, or that I didn't fully understand the stretch factor.
BTW, I know I would use the QtEditor for designing the GUI, but I kind of prefer doing these things manually.

The problem is simple, the layouts handle the position and size of the widgets, but it has limits, among them the minimum size of the widgets, and in your case the last element has a height higher than 10%, so physically it is impossible. We can see that by removing the content or using a QScrollArea:
import sys
from PyQt5 import QtCore, QtGui, QtWidgets, QtWebEngineWidgets
class StrategyTable(QtWidgets.QTableWidget):
pass
class Widget(QtWidgets.QWidget):
def __init__(self, parent=None):
super(Widget, self).__init__(parent)
lay = QtWidgets.QVBoxLayout(self)
table = StrategyTable()
button = QtWidgets.QPushButton("Add")
hlay = QtWidgets.QHBoxLayout()
hlay.addWidget(table)
hlay.addWidget(button)
canvas = QtWebEngineWidgets.QWebEngineView()
canvas.setUrl(QtCore.QUrl("http://www.google.com/"))
scroll = QtWidgets.QScrollArea()
content_widget = QtWidgets.QWidget()
scroll.setWidgetResizable(True)
scroll.setWidget(content_widget)
vlay = QtWidgets.QVBoxLayout()
vlay.addWidget(QtWidgets.QLabel("Results:"))
params_layout = self._create_results_labels()
content_widget.setLayout(params_layout)
vlay.addWidget(scroll)
lay.addLayout(hlay, 3)
lay.addWidget(canvas, 6)
lay.addLayout(vlay, 1)
def _create_results_labels(self):
flay = QtWidgets.QFormLayout()
for text in ("Delta", "Gamma", "Rho", "Theta", "Vega"):
flay.addRow(text, QtWidgets.QTextEdit())
return flay
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
w = Widget()
w.show()
sys.exit(app.exec_())

Hope this will be useful to understand Layouts along with stretch factor
Sample Layout based on percentages (CPP)
QVBoxLayout *topMostVerticalLayout = new QVBoxLayout(this);
QHBoxLayout *upperHorznLayout = new QHBoxLayout();
QHBoxLayout *bottomHorznLayout = new QHBoxLayout();
QVBoxLayout *InnerVerticalLayout1 = new QVBoxLayout(this);
QVBoxLayout *InnerVerticalLayout2 = new QVBoxLayout(this);
QVBoxLayout *InnerVerticalLayout3 = new QVBoxLayout(this);
QVBoxLayout *InnerVerticalLayout4 = new QVBoxLayout(this);
QVBoxLayout *InnerVerticalLayout5 = new QVBoxLayout(this);
bottomHorznLayout->addLayout(InnerVerticalLayout1,15); //(15% stretch)
bottomHorznLayout->addLayout(InnerVerticalLayout2,15); //(15% stretch)
bottomHorznLayout->addLayout(InnerVerticalLayout3,15); //(15% stretch)
bottomHorznLayout->addLayout(InnerVerticalLayout4,15); //(15% stretch)
bottomHorznLayout->addLayout(InnerVerticalLayout5,40); //(40% stretch)
topMostVerticalLayout->addLayout(upperHorznLayout,3); //(30% stretch)
topMostVerticalLayout->addLayout(bottomHorznLayout,7); //(70% stretch)
this->setLayout(topMostVerticalLayout);

Creating a 'Page View' style layout for a rich text editor with the scroll-bar aligned to the right edge

I'm trying to create a rich-text editor with a layout similar to Microsoft Word's 'Page View' or 'Print Layout.' I'd like to have a QTextEdit horizontally centered in the main window, with the scroll-bar aligned against the far right edge of the main window.
I couldn't find a way to move a QTextEdit's default scroll-bar independent of the QTextEdit itself. Instead, I tried creating a separate scroll-bar, and making the QTextEdit grow vertically using the solution found here: A QWidget like QTextEdit that wraps its height automatically to its contents?
Here is my attempt:
import sys
from PySide import QtGui, QtCore
class MainWindow(QtGui.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.initUI()
def initUI(self):
cw = CentralWidget()
self.setCentralWidget(cw)
self.setGeometry(200, 200, 1000, 600)
self.show()
def resizeEvent(self, event):
self.centralWidget().setFixedHeight(event.size().height())
class CentralWidget(QtGui.QWidget):
def __init__(self):
super(CentralWidget, self).__init__()
self.initUI()
def initUI(self):
text = MainTextEdit()
text.setMinimumWidth(850)
text.setStyleSheet('border: 0;')
pageWidget = QtGui.QWidget()
scroll = QtGui.QScrollArea()
scroll.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
scroll.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
scroll.setMaximumWidth(18)
# If you change setWidgetResizeable to False,
# the textedit will center, but scrolling will not work.
scroll.setWidgetResizable(True)
scroll.setWidget(pageWidget)
hbox = QtGui.QHBoxLayout()
hbox.setContentsMargins(0,0,0,0)
hbox.addStretch(0.5)
hbox.addWidget(text)
hbox.addStretch(0.5)
pageWidget.setLayout(hbox)
hbox2 = QtGui.QHBoxLayout()
hbox2.setContentsMargins(0,0,0,0)
hbox2.addWidget(pageWidget)
hbox2.addWidget(scroll)
self.setLayout(hbox2)
class MainTextEdit(QtGui.QTextEdit):
def __init__(self, *args, **kwargs):
super(MainTextEdit, self).__init__(*args, **kwargs)
self.document().contentsChanged.connect(self.sizeChange)
self.setFontPointSize(80)
self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
def sizeChange(self):
docHeight = self.document().size().height()
self.setMinimumHeight(docHeight)
def main():
app = QtGui.QApplication(sys.argv)
mw = MainWindow()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
There are at least two problems with this:
Problem #1
As is, the code above does not horizontally center the QTextEdit in the main window, but the scroll bar at the far-right does work. If you change scroll.setWidgetResizable(True) to scroll.setWidgetResizable(False) on line 41, the QTextEdit will center horizontally, but the scroll-bar does not work. It seems you can get one feature or the other, but not both.
Problem #2
In order to keep the MainWindow from auto-expanding when the QTextEdit grows, the MainWindow assigns a fixed height to the CentralWidget whenever the MainWindow is resized (see line 19 of the code above). This works well until the user tries to vertically shrink the main window. The window can be vertically expanded by clicking and dragging the bottom border, but it can't be vertically shrunk.
Conclusion
Maybe this is the wrong approach all-together. Any suggestions?

Set a symmetrical margin via setViewportMargins on the QTextEdit which inherits from QAbstractScrollArea.
Example:
from PySide import QtGui, QtCore
app = QtGui.QApplication([])
window = QtGui.QWidget()
layout = QtGui.QVBoxLayout(window)
edit = QtGui.QTextEdit('jfdh afdhgfkjg fdnvfh vklkfjvkflj lddkl ljklfjkl jvkldjfkvljfgvjldf ll dl dljvklj ljljlbl llkb jbgl')
edit.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
edit.setViewportMargins(30, 0, 30, 30)
layout.addWidget(edit)
window.show()
app.exec_()
Gives:

How to add a fixed header to a QScrollArea?

I currently have a QScrollArea defined by:
self.results_grid_scrollarea = QScrollArea()
self.results_grid_widget = QWidget()
self.results_grid_layout = QGridLayout()
self.results_grid_layout.setSizeConstraint(QLayout.SetMinAndMaxSize)
self.results_grid_widget.setLayout(self.results_grid_layout)
self.results_grid_scrollarea.setWidgetResizable(True)
self.results_grid_scrollarea.setWidget(self.results_grid_widget)
self.results_grid_scrollarea.setViewportMargins(0,20,0,0)
which sits quite happily nested within other layouts/widgets, resizes as expected, etc.
To provide headings for the grid columns, I'm using another QGridLayout positioned directly above the scroll area - this works... but looks a little odd, even when styled appropriately, especially when the on-demand (vertical) scrollbar appears or disappears as needed and the headers no longer line up correctly with the grid columns. It's an aesthetic thing I know... but I'm kinda picky ;)
Other widgets are added/removed to the self.results_grid_layout programatically elsewhere. The last line above I've just recently added as I thought it would be easy to use the created margin area, the docs for setViewportMargins state:
Sets margins around the scrolling area. This is useful for applications such as spreadsheets with "locked" rows and columns. The marginal space is is left blank; put widgets in the unused area.
But I cannot for the life of me work out how to actually achieve this, and either my GoogleFu has deserted me today, or there's little information/examples out there on how to actually achieve this.
My head is telling me I can assign just one widget, controlled by a layout (containing any number of other widgets) to the scrollarea - as I have done. If I add say a QHeaderview for example to row 0 of the gridlayout, it will just appear below the viewport's margin and scroll with the rest of the layout? Or am I missing something and just can't see the wood for the trees?
I'm just learning Python/Qt, so any help, pointers and/or examples (preferably with Python but not essential) would be appreciated!
Edit: Having followed the advice given so far (I think), I came up with the following little test program to try things out:
import sys
from PySide.QtCore import *
from PySide.QtGui import *
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setMinimumSize(640, 480)
self.container_widget = QWidget()
self.container_layout = QVBoxLayout()
self.container_widget.setLayout(self.container_layout)
self.setCentralWidget(self.container_widget)
self.info_label = QLabel(
"Here you can see the problem.... I hope!\n"
"Once the window is resized everything behaves itself.")
self.info_label.setWordWrap(True)
self.headings_widget = QWidget()
self.headings_layout = QGridLayout()
self.headings_widget.setLayout(self.headings_layout)
self.headings_layout.setContentsMargins(1,1,0,0)
self.heading_label1 = QLabel("Column 1")
self.heading_label1.setContentsMargins(16,0,0,0)
self.heading_label2 = QLabel("Col 2")
self.heading_label2.setAlignment(Qt.AlignCenter)
self.heading_label2.setMaximumWidth(65)
self.heading_label3 = QLabel("Column 3")
self.heading_label3.setContentsMargins(8,0,0,0)
self.headings_layout.addWidget(self.heading_label1,0,0)
self.headings_layout.addWidget(self.heading_label2,0,1)
self.headings_layout.addWidget(self.heading_label3,0,2)
self.headings_widget.setStyleSheet(
"background: green; border-bottom: 1px solid black;" )
self.grid_scrollarea = QScrollArea()
self.grid_widget = QWidget()
self.grid_layout = QGridLayout()
self.grid_layout.setSizeConstraint(QLayout.SetMinAndMaxSize)
self.grid_widget.setLayout(self.grid_layout)
self.grid_scrollarea.setWidgetResizable(True)
self.grid_scrollarea.setWidget(self.grid_widget)
self.grid_scrollarea.setViewportMargins(0,30,0,0)
self.headings_widget.setParent(self.grid_scrollarea)
### Add some linedits to the scrollarea just to test
rows_to_add = 10
## Setting the above to a value greater than will fit in the initial
## window will cause the lineedits added below to display correctly,
## however - using the 10 above, the lineedits do not expand to fill
## the scrollarea's width until you resize the window horizontally.
## What's the best way to fix this odd initial behaviour?
for i in range(rows_to_add):
col1 = QLineEdit()
col2 = QLineEdit()
col2.setMaximumWidth(65)
col3 = QLineEdit()
row = self.grid_layout.rowCount()
self.grid_layout.addWidget(col1,row,0)
self.grid_layout.addWidget(col2,row,1)
self.grid_layout.addWidget(col3,row,2)
### Define Results group to hold the above sections
self.test_group = QGroupBox("Results")
self.test_layout = QVBoxLayout()
self.test_group.setLayout(self.test_layout)
self.test_layout.addWidget(self.info_label)
self.test_layout.addWidget(self.grid_scrollarea)
### Add everything to the main layout
self.container_layout.addWidget(self.test_group)
def resizeEvent(self, event):
scrollarea_vpsize = self.grid_scrollarea.viewport().size()
scrollarea_visible_size = self.grid_scrollarea.rect()
desired_width = scrollarea_vpsize.width()
desired_height = scrollarea_visible_size.height()
desired_height = desired_height - scrollarea_vpsize.height()
new_geom = QRect(0,0,desired_width+1,desired_height-1)
self.headings_widget.setGeometry(new_geom)
def main():
app = QApplication(sys.argv)
form = MainWindow()
form.show()
app.exec_()
if __name__ == '__main__':
main()
Is something along these lines the method to which you were pointing? Everything works as expected as is exactly what I was after, except for some odd initial behaviour before the window is resized by the user, once it is resized everything lines up and is fine.
I'm probably over-thinking again or at least overlooking something... any thoughts?

I had a similar problem and solved it a little differently. Instead of using one QScrollArea I use two and forward a movement of the lower scroll area to the top one. What the code below does is
It creates two QScrollArea widgets in a QVBoxLayout.
It disables the visibility of the scroll bars of the top QScrollArea and assigns it a fixed height.
Using the valueChanged signal of the horizontal scroll bar of the lower QScrollArea it is possible to "forward" the horizontal scroll bar value from the lower QScrollArea to the top one resulting a fixed header at the top of the window.
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
widget = QWidget()
self.setCentralWidget(widget)
vLayout = QVBoxLayout()
widget.setLayout(vLayout)
# TOP
scrollAreaTop = QScrollArea()
scrollAreaTop.setWidgetResizable(True)
scrollAreaTop.setFixedHeight(30)
scrollAreaTop.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
scrollAreaTop.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
scrollAreaTop.setWidget(QLabel(" ".join([str(i) for i in range(100)])))
# BOTTOM
scrollAreaBottom = QScrollArea()
scrollAreaBottom.setWidgetResizable(True)
scrollAreaBottom.setWidget(QLabel("\n".join([" ".join([str(i) for i in range(100)]) for _ in range(10)])))
scrollAreaBottom.horizontalScrollBar().valueChanged.connect(lambda value: scrollAreaTop.horizontalScrollBar().setValue(value))
vLayout.addWidget(scrollAreaTop)
vLayout.addWidget(scrollAreaBottom)

You may be over-thinking things slightly.
All you need to do is use the geometry of the scrollarea's viewport and the current margins to calculate the geometry of any widgets you want to place in the margins.
The geometry of these widgets would also need to be updated in the resizeEvent of the scrollarea.
If you look at the source code for QTableView, I think you'll find it uses this method to manage its header-views (or something very similar).
EDIT
To deal with the minor resizing problems in your test case, I would advise you to read the Coordinates section in the docs for QRect (in particular, the third paragraph onwards).
I was able to get more accurate resizing by rewriting your test case like this:
import sys
from PySide.QtCore import *
from PySide.QtGui import *
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setMinimumSize(640, 480)
self.container_widget = QWidget()
self.container_layout = QVBoxLayout()
self.container_widget.setLayout(self.container_layout)
self.setCentralWidget(self.container_widget)
self.grid_scrollarea = ScrollArea(self)
self.test_group = QGroupBox("Results")
self.test_layout = QVBoxLayout()
self.test_group.setLayout(self.test_layout)
self.test_layout.addWidget(self.grid_scrollarea)
self.container_layout.addWidget(self.test_group)
class ScrollArea(QScrollArea):
def __init__(self, parent=None):
QScrollArea.__init__(self, parent)
self.grid_widget = QWidget()
self.grid_layout = QGridLayout()
self.grid_widget.setLayout(self.grid_layout)
self.setWidgetResizable(True)
self.setWidget(self.grid_widget)
# save the margin values
self.margins = QMargins(0, 30, 0, 0)
self.setViewportMargins(self.margins)
self.headings_widget = QWidget(self)
self.headings_layout = QGridLayout()
self.headings_widget.setLayout(self.headings_layout)
self.headings_layout.setContentsMargins(1,1,0,0)
self.heading_label1 = QLabel("Column 1")
self.heading_label1.setContentsMargins(16,0,0,0)
self.heading_label2 = QLabel("Col 2")
self.heading_label2.setAlignment(Qt.AlignCenter)
self.heading_label2.setMaximumWidth(65)
self.heading_label3 = QLabel("Column 3")
self.heading_label3.setContentsMargins(8,0,0,0)
self.headings_layout.addWidget(self.heading_label1,0,0)
self.headings_layout.addWidget(self.heading_label2,0,1)
self.headings_layout.addWidget(self.heading_label3,0,2)
self.headings_widget.setStyleSheet(
"background: green; border-bottom: 1px solid black;" )
rows_to_add = 10
for i in range(rows_to_add):
col1 = QLineEdit()
col2 = QLineEdit()
col2.setMaximumWidth(65)
col3 = QLineEdit()
row = self.grid_layout.rowCount()
self.grid_layout.addWidget(col1,row,0)
self.grid_layout.addWidget(col2,row,1)
self.grid_layout.addWidget(col3,row,2)
def resizeEvent(self, event):
rect = self.viewport().geometry()
self.headings_widget.setGeometry(
rect.x(), rect.y() - self.margins.top(),
rect.width() - 1, self.margins.top())
QScrollArea.resizeEvent(self, event)
if __name__ == '__main__':
app = QApplication(sys.argv)
form = MainWindow()
form.show()
sys.exit(app.exec_())