Context Layouts

This is how Qt expects you to build user interfaces with code:

window = QWidget()
button1 = QPushButton("One")
button2 = QPushButton("Two")
button3 = QPushButton("Three")
button4 = QPushButton("Four")

layout = QVBoxLayout()
window.setLayout(layout)

hbox1 = QHBoxLayout()
layout.addLayout(hbox1)
hbox1.addWidget(button1)
hbox1.addWidget(button2)

hbox2 = QHBoxLayout()
layout.addLayout(hbox2)
hbox2.addWidget(button3)
hbox2.addWidget(button4)

This is only 4 buttons and it's already extremely ugly. Each nested layout needs a unique name. Every time you create a new layout you have to shift gears to add it to its parent. Don't even get me started on how pointless the distinction between .addWidget() and .addLayout() is. There isn't even a hint about what this layout will look like when it's built. We haven't even started messing with attributes like margins or alignments yet!

This is definitely not pythonic.

Enter, the Context Layout:

window = QWidget()
button1 = QPushButton("One")
button2 = QPushButton("Two")
button3 = QPushButton("Three")
button4 = QPushButton("Four")

with CVBoxLayout(window) as layout:
    with layout.hbox():
        layout.add(button1)
        layout.add(button2)
    with layout.hbox():
        layout.add(button3)
        layout.add(button4)

All of the backtracking and repetition is gone. The pointless effort of naming each layout is gone. The indentation helps show the structure of the layout.

The top level CVBoxLayout adds itself to its parent correctly and automatically. The .add() method can handle a layout or a widget or even a mixed list of both.

The .add() method also returns the item you give it, which allows us to remove even more duplication in some situations:

# note that a with block does not create a new scope
with CHBoxLayout(QWidget()) as layout:
    button1 = layout.add(QPushButton("One"))
    button2 = layout.add(QPushButton("Two"))

# so these references are available after the with block closes
print(button1) 

Context layouts also support more advanced usages:

with CVBoxLayout(QWidget()) as layout:
    # supports '+='
    layout += QLabel('Title') 
    # supports '+', which returns the added widget
    button1 = layout + QPushButton("One")
    # All add() methods also support lists and tuples of widgets
    button2, button3 = layout.add((QPushButton("Two"), QPushButton("Three")))
    button4, button5 = layout + [QPushButton("Four"), QPushButton("Five")]

Advanced Layouts

Other Qt layout types are supported:

• Forms: py with CFormLayout(QWidget()) as layout: layout.add('label', QPushButton('')) layout += ['label', QPushButton('')] layout += { 'label': QPushButton(''), 'label': QPushButton(''), }
• Splitters: py with CSplitter(QWidget()) as split: # coming soon pass
• Scroll Areas: py with CScrollArea(QWidget()) as layout: # coming soon pass