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The QLayoutItem class provides an abstract item that a QLayout manipulates. More...
#include <QLayoutItem>
Inherited by QLayout, QSpacerItem, and QWidgetItem.
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.
Constructs a layout item with an alignment. Not all subclasses support alignment.
Destroys the QLayoutItem.
Returns the alignment of this item.
See also setAlignment().
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.
Returns the rectangle covered by this layout item.
See also setGeometry().
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().
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().
Invalidates any cached information in this layout item.
Implemented in subclasses to return whether this item is empty, i.e. whether it contains any widgets.
If this item is a QLayout, it is returned as a QLayout; otherwise 0 is returned. This function provides type-safe casting.
Implemented in subclasses to return the maximum size of this item.
Returns the minimum height this widget needs for the given width, w. The default implementation simply returns heightForWidth(w).
Implemented in subclasses to return the minimum size of this item.
Sets the alignment of this item to alignment. Not all subclasses support alignment.
See also alignment().
Implemented in subclasses to set this item's geometry to r.
See also geometry().
Implemented in subclasses to return the preferred size of this item.
If this item is a QSpacerItem, it is returned as a QSpacerItem; otherwise 0 is returned. This function provides type-safe casting.
If this item is a QWidget, it is returned as a QWidget; otherwise 0 is returned. This function provides type-safe casting.
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