How to make one tab bar in QTabWidget expendable? - pyqt

Question

I need to customize my QTabWidget so that one of its tab bars (lets say there are 4 tabs overall) has expanding property and will fill the remaining space between other tabs. Any ideas?

Answer 1

you can subclass QTabBar, set it to the width of your tabwidget (the height depends on the fontsize) and overwrite tabSizeHint():
class tabBar(QTabBar):
def __init__(self, width, height, parent=None):
QTabBar.__init__(self, parent)
self.setFixedSize(width, height)
def tabSizeHint(self, i):
f = 3 # Tab3 shall be f times wider then the other tabs
tw = int(self.width()/(self.count() + f -1)) # width per Tab
if i == 2: # Tab3
# return QSize(tw*f, self.height()) edited -> rounding error possible
return QSize(self.width() - (self.count() - 1)*tw, self.height())
return QSize(tw, self.height()) # all other tabs
and set this tabBar to your tabwidget:
tb = tabBar(tabWidget.width(), 34) # tabBars height depends on fontSize
tabwidget..setTabBar(tb)
looks like this:
edit:
if the tabWidget is resized, a resizeEvent() occurs. In this moment the tabWidget already has its new size and is repainted immediatedly after the resizeEvent(),
see QT-Doc QTabWidget.resizeEvent
So if the width() of the tabBar is adapted in resizeEvent(), the tabBar will always have the same width as the tabwidget. Because the tabSizeHint() depends on the width, all tabs will have the correct width too. So You can subclass QTabWidget() and overwrite resizeEvent() for a dynamical solution:
class tabWidget(QTabWidget):
def __init__(self, parent=None):
QTabWidget.__init__(self, parent)
def resizeEvent(self, event):
self.tabBar().setFixedWidth(self.width())
QTabWidget.resizeEvent(self, event)

Answer 2

To do this correctly, it's necessary to work backwards from the existing sizes of the tabs. This is because the tab sizes are affected by the current style, and by other features such as tab close buttons. It's also important to set a minimum size for the tab which is exandable (otherwise it could be resized to nothing).
Here is a simple demo that does all that:
from PyQt4 import QtCore, QtGui
class TabBar(QtGui.QTabBar):
def __init__(self, expanded=-1, parent=None):
super(TabBar, self).__init__(parent)
self._expanded = expanded
def tabSizeHint(self, index):
size = super(TabBar, self).tabSizeHint(index)
if index == self._expanded:
offset = self.width()
for index in range(self.count()):
offset -= super(TabBar, self).tabSizeHint(index).width()
size.setWidth(max(size.width(), size.width() + offset))
return size
class TabWidget(QtGui.QTabWidget):
def __init__(self, expanded=-1, parent=None):
super(TabWidget, self).__init__(parent)
self.setTabBar(TabBar(expanded, self))
def resizeEvent(self, event):
self.tabBar().setMinimumWidth(self.width())
super(TabWidget, self).resizeEvent(event)
class Window(QtGui.QWidget):
def __init__(self):
super(Window, self).__init__()
self.tabs = TabWidget(2, self)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.tabs)
for text in 'One Two Three Four'.split():
self.tabs.addTab(QtGui.QWidget(self), text)
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Window()
window.setGeometry(500, 300, 400, 200)
window.show()
sys.exit(app.exec_())