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# QGraphicsLinearLayout Class Reference
[QtGui module]

The QGraphicsLinearLayout class provides a horizontal or vertical layout for managing widgets in Graphics View. More...

Inherits QGraphicsLayout.

### Methods

- __init__ (self, QGraphicsLayoutItem parent = None)
- __init__ (self, Qt.Orientation orientation, QGraphicsLayoutItem parent = None)
- addItem (self, QGraphicsLayoutItem item)
- addStretch (self, int stretch = 1)
- Qt.Alignment alignment (self, QGraphicsLayoutItem item)
- int count (self)
- insertItem (self, int index, QGraphicsLayoutItem item)
- insertStretch (self, int index, int stretch = 1)
- invalidate (self)
- QGraphicsLayoutItem itemAt (self, int index)
- float itemSpacing (self, int index)
- Qt.Orientation orientation (self)
- removeAt (self, int index)
- removeItem (self, QGraphicsLayoutItem item)
- setAlignment (self, QGraphicsLayoutItem item, Qt.Alignment alignment)
- setGeometry (self, QRectF rect)
- setItemSpacing (self, int index, float spacing)
- setOrientation (self, Qt.Orientation orientation)
- setSpacing (self, float spacing)
- setStretchFactor (self, QGraphicsLayoutItem item, int stretch)
- QSizeF sizeHint (self, Qt.SizeHint which, QSizeF constraint = QSizeF())
- float spacing (self)
- int stretchFactor (self, QGraphicsLayoutItem item)

## Detailed Description

The QGraphicsLinearLayout class provides a horizontal or vertical layout for managing widgets in Graphics View.

The default orientation for a linear layout is Qt.Horizontal. You can choose a vertical orientation either by calling setOrientation(), or by passing Qt.Vertical to QGraphicsLinearLayout's constructor.

The most common way to use QGraphicsLinearLayout is to construct an object on the heap with no parent, add widgets and layouts by calling addItem(), and finally assign the layout to a widget by calling QGraphicsWidget.setLayout().

     QGraphicsScene scene;
     QGraphicsWidget *textEdit = scene.addWidget(new QTextEdit);
     QGraphicsWidget *pushButton = scene.addWidget(new QPushButton);

     QGraphicsLinearLayout *layout = new QGraphicsLinearLayout;
     layout->addItem(textEdit);
     layout->addItem(pushButton);

     QGraphicsWidget *form = new QGraphicsWidget;
     form->setLayout(layout);
     scene.addItem(form);

You can add widgets, layouts, stretches (addStretch(), insertStretch() or setStretchFactor()), and spacings (setItemSpacing()) to a linear layout. The layout takes ownership of the items. In some cases when the layout item also inherits from QGraphicsItem (such as QGraphicsWidget) there will be a ambiguity in ownership because the layout item belongs to two ownership hierarchies. See the documentation of QGraphicsLayoutItem.setOwnedByLayout() how to handle this. You can access each item in the layout by calling count() and itemAt(). Calling removeAt() or removeItem() will remove an item from the layout, without destroying it.

### Size Hints and Size Policies in QGraphicsLinearLayout

QGraphicsLinearLayout respects each item's size hints and size policies, and when the layout contains more space than the items can fill, each item is arranged according to the layout's alignment for that item. You can set an alignment for each item by calling setAlignment(), and check the alignment for any item by calling alignment(). By default, items are centered both vertically and horizontally.

### Spacing within QGraphicsLinearLayout

Between the items, the layout distributes some space. The actual amount of space depends on the managed widget's current style, but the common spacing is 4. You can also set your own spacing by calling setSpacing(), and get the current spacing value by calling spacing(). If you want to configure individual spacing for your items, you can call setItemSpacing().

### Stretch Factor in QGraphicsLinearLayout

You can assign a stretch factor to each item to control how much space it will get compared to the other items. By default, two identical widgets arranged in a linear layout will have the same size, but if the first widget has a stretch factor of 1 and the second widget has a stretch factor of 2, the first widget will get 1/3 of the available space, and the second will get 2/3.

QGraphicsLinearLayout calculates the distribution of sizes by adding up the stretch factors of all items, and then dividing the available space accordingly. The default stretch factor is 0 for all items; a factor of 0 means the item does not have any defined stretch factor; effectively this is the same as setting the stretch factor to 1. The stretch factor only applies to the available space in the lengthwise direction of the layout (following its orientation). If you want to control both the item's horizontal and vertical stretch, you can use QGraphicsGridLayout instead.

### QGraphicsLinearLayout Compared to Other Layouts

QGraphicsLinearLayout is very similar to QVBoxLayout and QHBoxLayout, but in contrast to these classes, it is used to manage QGraphicsWidget and QGraphicsLayout instead of QWidget and QLayout.

See also QGraphicsGridLayout and QGraphicsWidget.

## Method Documentation

### QGraphicsLinearLayout.__init__ (self, QGraphicsLayoutItem parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QGraphicsLinearLayout instance using Qt.Horizontal orientation. parent is passed to QGraphicsLayout's constructor.

### QGraphicsLinearLayout.__init__ (self, Qt.Orientation orientation, QGraphicsLayoutItem parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QGraphicsLinearLayout instance. You can pass the orientation for the layout, either horizontal or vertical, and parent is passed to QGraphicsLayout's constructor.

### QGraphicsLinearLayout.addItem (self, QGraphicsLayoutItem item)

The item argument has it's ownership transferred to Qt.

This convenience function is equivalent to calling insertItem(-1, item).

### QGraphicsLinearLayout.addStretch (self, int stretch = 1)

This convenience function is equivalent to calling insertStretch(-1, stretch).

### Qt.Alignment QGraphicsLinearLayout.alignment (self, QGraphicsLayoutItem item)

Returns the alignment for item. The default alignment is Qt.AlignCenter.

The alignment decides how the item is positioned within its assigned space in the case where there's more space available in the layout than the widgets can occupy.

See also setAlignment().

### int QGraphicsLinearLayout.count (self)

### QGraphicsLinearLayout.insertItem (self, int index, QGraphicsLayoutItem item)

The item argument has it's ownership transferred to Qt.

Inserts item into the layout at index, or before any item that is currently at index.

See also addItem(), itemAt(), insertStretch(), and setItemSpacing().

### QGraphicsLinearLayout.insertStretch (self, int index, int stretch = 1)

Inserts a stretch of stretch at index, or before any item that is currently at index.

See also addStretch(), setStretchFactor(), setItemSpacing(), and insertItem().

### QGraphicsLinearLayout.invalidate (self)

### QGraphicsLayoutItem QGraphicsLinearLayout.itemAt (self, int index)

### float QGraphicsLinearLayout.itemSpacing (self, int index)

Returns the spacing after item at index.

See also setItemSpacing().

### Qt.Orientation QGraphicsLinearLayout.orientation (self)

Returns the layout orientation.

See also setOrientation().

### QGraphicsLinearLayout.removeAt (self, int index)

Removes the item at index without destroying it. Ownership of the item is transferred to the caller.

Reimplemented from QGraphicsLayout.

See also removeItem() and insertItem().

### QGraphicsLinearLayout.removeItem (self, QGraphicsLayoutItem item)

The item argument

Removes item from the layout without destroying it. Ownership of item is transferred to the caller.

See also removeAt() and insertItem().

### QGraphicsLinearLayout.setAlignment (self, QGraphicsLayoutItem item, Qt.Alignment alignment)

Sets the alignment of item to alignment. If item's alignment changes, the layout is automatically invalidated.

See also alignment() and invalidate().

### QGraphicsLinearLayout.setGeometry (self, QRectF rect)

### QGraphicsLinearLayout.setItemSpacing (self, int index, float spacing)

Sets the spacing after item at index to spacing.

See also itemSpacing().

### QGraphicsLinearLayout.setOrientation (self, Qt.Orientation orientation)

Change the layout orientation to orientation. Changing the layout orientation will automatically invalidate the layout.

See also orientation().

### QGraphicsLinearLayout.setSpacing (self, float spacing)

Sets the layout's spacing to spacing. Spacing refers to the vertical and horizontal distances between items.

See also spacing(), setItemSpacing(), setStretchFactor(), and QGraphicsGridLayout.setSpacing().

### QGraphicsLinearLayout.setStretchFactor (self, QGraphicsLayoutItem item, int stretch)

Sets the stretch factor for item to stretch. If an item's stretch factor changes, this function will invalidate the layout.

Setting stretch to 0 removes the stretch factor from the item, and is effectively equivalent to setting stretch to 1.

See also stretchFactor().

### QSizeF QGraphicsLinearLayout.sizeHint (self, Qt.SizeHint which, QSizeF constraint = QSizeF())

### float QGraphicsLinearLayout.spacing (self)

Returns the layout's spacing. Spacing refers to the vertical and horizontal distances between items.

See also setSpacing().

### int QGraphicsLinearLayout.stretchFactor (self, QGraphicsLayoutItem item)

Returns the stretch factor for item. The default stretch factor is 0, meaning that the item has no assigned stretch factor.

See also setStretchFactor().