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public interface QLayoutItemInterface
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.
QLayout
.
Method Summary | |
---|---|
Qt.Alignment |
alignment()
Returns the alignment of this item. |
QSizePolicy.ControlTypes |
controlTypes()
Returns the control type(s) for the layout item. |
Qt.Orientations |
expandingDirections()
Returns whether this layout item can make use of more space than sizeHint() . |
QRect |
geometry()
Returns the rectangle covered by this layout item. |
boolean |
hasHeightForWidth()
Returns true if this layout's preferred height depends on its width; otherwise returns false. |
int |
heightForWidth(int arg__1)
Returns the preferred height for this layout item, given the width w. |
void |
invalidate()
Invalidates any cached information in this layout item. |
boolean |
isEmpty()
|
QLayout |
layout()
If this item is a QLayout , it is returned as a QLayout ; otherwise 0 is returned. |
QSize |
maximumSize()
Implemented in subclasses to return the maximum size of this item. |
int |
minimumHeightForWidth(int arg__1)
Returns the minimum height this widget needs for the given width, w. |
QSize |
minimumSize()
Implemented in subclasses to return the minimum size of this item. |
void |
setAlignment(Qt.Alignment a)
Sets the alignment of this item to alignment. |
void |
setGeometry(QRect arg__1)
|
QSize |
sizeHint()
Implemented in subclasses to return the preferred size of this item. |
QSpacerItem |
spacerItem()
If this item is a QSpacerItem , it is returned as a QSpacerItem ; otherwise 0 is returned. |
QWidget |
widget()
If this item is a QWidget , it is returned as a QWidget ; otherwise 0 is returned. |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
---|
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Method Detail |
---|
Qt.Alignment alignment()
setAlignment()
.
QSizePolicy.ControlTypes controlTypes()
QWidgetItem
, the control type comes from the widget's size policy; for a QLayoutItem
, the control types is derived from the layout's contents. QSizePolicy::controlType()
.
void setAlignment(Qt.Alignment a)
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.
alignment()
.
Qt.Orientations expandingDirections()
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 geometry()
setGeometry()
.
boolean hasHeightForWidth()
Reimplement this function in layout managers that support height for width.
heightForWidth()
, and QWidget::heightForWidth()
.
int heightForWidth(int arg__1)
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:
The following code example is written in c++.
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.
hasHeightForWidth()
.
void invalidate()
boolean isEmpty()
QLayout layout()
QLayout
, it is returned as a QLayout
; otherwise 0 is returned. This function provides type-safe casting.
QSize maximumSize()
int minimumHeightForWidth(int arg__1)
heightForWidth
(w).
QSize minimumSize()
void setGeometry(QRect arg__1)
QSize sizeHint()
QSpacerItem spacerItem()
QSpacerItem
, it is returned as a QSpacerItem
; otherwise 0 is returned. This function provides type-safe casting.
QWidget widget()
QWidget
, it is returned as a QWidget
; otherwise 0 is returned. This function provides type-safe casting.
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