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QtGui.IQLayoutItem Interface Reference

The QLayoutItem class provides an abstract item that a QLayout manipulates. More...

Inheritance diagram for QtGui.IQLayoutItem:

Public Member Functions

int HeightForWidth (int w)
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void Invalidate ()
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int MinimumHeightForWidth (int w)
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Properties

Qt.AlignmentFlag Alignment [get, set]
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QRect Geometry [get, set]
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QSizePolicy.ControlType ControlTypes [get]
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Qt.Orientation ExpandingDirections [get]
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System.Boolean HasHeightForWidth [get]
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System.Boolean IsEmpty [get]
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QLayout Layout [get]
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QSize MaximumSize [get]
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QSize MinimumSize [get]
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QSize SizeHint [get]
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QSpacerItem SpacerItem [get]
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QWidget Widget [get]
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Detailed Description

The QLayoutItem class provides an abstract item that a QLayout manipulates.

This is used by custom layouts.

Pure virtual functions are provided to return information about the layout, including, sizeHint(), minimumSize(), maximumSize() and expanding().

The layout's geometry can be set and retrieved with setGeometry() and geometry(), and its alignment with setAlignment() and alignment().

isEmpty() returns whether the layout item is empty. If the concrete item is a QWidget, it can be retrieved using widget(). Similarly for layout() and spacerItem().

Some layouts have width and height interdependencies. These can be expressed using hasHeightForWidth(), heightForWidth(), and minimumHeightForWidth(). For more explanation see the Qt Quarterly article Trading Height for Width.

See also QLayout.

Member Function Documentation

int QtGui.IQLayoutItem.HeightForWidth ( int  w)

Returns the preferred height for this layout item, given the width w.

The default implementation returns -1, indicating that the preferred height is independent of the width of the item. Using the function hasHeightForWidth() will typically be much faster than calling this function and testing for -1.

Reimplement this function in layout managers that support height for width. A typical implementation will look like this:

int MyLayout::heightForWidth(int w) const

{

if (cache_dirty || cached_width != w) {

// not all C++ compilers support "mutable"

MyLayout that = (MyLayout)this;

int h = calculateHeightForWidth(w);

that->cached_hfw = h;

return h;

}

return cached_hfw;

}

Caching is strongly recommended; without it layout will take exponential time.

See also hasHeightForWidth().

Implemented in QtGui.QWidgetItemV2, QtGui.QWidgetItem, QtGui.QLayoutItem, QtGui.QLayout, QtGui.QGridLayout, QtGui.QFormLayout, and QtGui.QBoxLayout.

void QtGui.IQLayoutItem.Invalidate ( )

Invalidates any cached information in this layout item.

Implemented in QtGui.QLayoutItem, QtGui.QLayout, QtGui.QGridLayout, QtGui.QFormLayout, and QtGui.QBoxLayout.

int QtGui.IQLayoutItem.MinimumHeightForWidth ( int  w)

Returns the minimum height this widget needs for the given width, w. The default implementation simply returns heightForWidth(w).

Implemented in QtGui.QLayoutItem, QtGui.QLayout, QtGui.QGridLayout, and QtGui.QBoxLayout.

Property Documentation

Qt.AlignmentFlag QtGui.IQLayoutItem.Alignment
getset

Returns the alignment of this item.

Sets the alignment of this item to alignment.

Note: Item alignment is only supported by QLayoutItem subclasses where it would have a visual effect. Except for QSpacerItem, which provides blank space for layouts, all public Qt classes that inherit QLayoutItem support item alignment.

QSizePolicy.ControlType QtGui.IQLayoutItem.ControlTypes
get

Returns the control type(s) for the layout item. For a QWidgetItem, the control type comes from the widget's size policy; for a QLayoutItem, the control types is derived from the layout's contents.

See also QSizePolicy::controlType().

Qt.Orientation QtGui.IQLayoutItem.ExpandingDirections
get

Returns whether this layout item can make use of more space than sizeHint(). A value of Qt::Vertical or Qt::Horizontal means that it wants to grow in only one dimension, whereas Qt::Vertical | Qt::Horizontal means that it wants to grow in both dimensions.

QRect QtGui.IQLayoutItem.Geometry
getset

Returns the rectangle covered by this layout item.

Implemented in subclasses to set this item's geometry to r.

System.Boolean QtGui.IQLayoutItem.HasHeightForWidth
get

Returns true if this layout's preferred height depends on its width; otherwise returns false. The default implementation returns false.

Reimplement this function in layout managers that support height for width.

See also heightForWidth() and QWidget::heightForWidth().

System.Boolean QtGui.IQLayoutItem.IsEmpty
get

Implemented in subclasses to return whether this item is empty, i.e. whether it contains any widgets.

QLayout QtGui.IQLayoutItem.Layout
get

If this item is a QLayout, it is returned as a QLayout; otherwise 0 is returned. This function provides type-safe casting.

QSize QtGui.IQLayoutItem.MaximumSize
get

Implemented in subclasses to return the maximum size of this item.

QSize QtGui.IQLayoutItem.MinimumSize
get

Implemented in subclasses to return the minimum size of this item.

QSize QtGui.IQLayoutItem.SizeHint
get

Implemented in subclasses to return the preferred size of this item.

QSpacerItem QtGui.IQLayoutItem.SpacerItem
get

If this item is a QSpacerItem, it is returned as a QSpacerItem; otherwise 0 is returned. This function provides type-safe casting.

QWidget QtGui.IQLayoutItem.Widget
get

If this item is a QWidget, it is returned as a QWidget; otherwise 0 is returned. This function provides type-safe casting.