Wt
3.3.8
|
A widget that holds and manages child widgets. More...
#include <Wt/WContainerWidget>
Public Types | |
Public Types inherited from Wt::WObject | |
typedef void(WObject::* | Method) () |
Typedef for a WObject method without arguments. | |
Public Member Functions | |
WContainerWidget (WContainerWidget *parent=0) | |
Creates a container with optional parent. | |
~WContainerWidget () | |
Destructor. | |
void | setLayout (WLayout *layout) |
Sets a layout manager for the container. More... | |
void | setLayout (WLayout *layout, WFlags< AlignmentFlag > alignment) |
Sets a layout manager for the container (deprecated). More... | |
WLayout * | layout () |
Returns the layout manager that was set for the container. More... | |
virtual void | addWidget (WWidget *widget) |
Adds a child widget to this container. More... | |
virtual void | insertBefore (WWidget *widget, WWidget *before) |
Inserts a child widget in this container, before another widget. More... | |
virtual void | insertWidget (int index, WWidget *widget) |
Inserts a child widget in this container at given index. More... | |
virtual void | removeWidget (WWidget *widget) |
Removes a child widget from this container. More... | |
virtual void | clear () |
Removes and deletes all child widgets. More... | |
virtual int | indexOf (WWidget *widget) const |
Returns the index of a widget. | |
virtual WWidget * | widget (int index) const |
Returns the widget at index | |
virtual int | count () const |
Returns the number of widgets in this container. | |
void | setContentAlignment (WFlags< AlignmentFlag > contentAlignment) |
Specifies how child widgets must be aligned within the container. More... | |
void | setPadding (const WLength &padding, WFlags< Side > sides=All) |
Sets padding inside the widget. More... | |
WLength | padding (Side side) const |
Returns the padding set for the widget. More... | |
WFlags< AlignmentFlag > | contentAlignment () const |
Returns the alignment of children. More... | |
void | setOverflow (Overflow overflow, WFlags< Orientation > orientation=(Horizontal|Vertical)) |
Sets how overflow of contained children must be handled. More... | |
void | setList (bool list, bool ordered=false) |
Renders the container as an HTML list. More... | |
bool | isList () const |
Returns if this container is rendered as a List. More... | |
bool | isUnorderedList () const |
Returns if this container is rendered as an Unordered List. More... | |
bool | isOrderedList () const |
Returns if this container is rendered as an Ordered List. More... | |
EventSignal< WScrollEvent > & | scrolled () |
Event signal emitted when scrolling in the widget. More... | |
int | scrollTop () const |
return the number of pixels the container is scrolled horizontally More... | |
int | scrollLeft () const |
return the number of pixels the container is scrolled vertically More... | |
Public Member Functions inherited from Wt::WInteractWidget | |
WInteractWidget (WContainerWidget *parent=0) | |
Create an InteractWidget with optional parent. | |
EventSignal< WKeyEvent > & | keyWentDown () |
Event signal emitted when a keyboard key is pushed down. More... | |
EventSignal< WKeyEvent > & | keyPressed () |
Event signal emitted when a "character" was entered. More... | |
EventSignal< WKeyEvent > & | keyWentUp () |
Event signal emitted when a keyboard key is released. More... | |
EventSignal & | enterPressed () |
Event signal emitted when enter was pressed. More... | |
EventSignal & | escapePressed () |
Event signal emitted when escape was pressed. More... | |
EventSignal< WMouseEvent > & | clicked () |
Event signal emitted when a mouse key was clicked on this widget. More... | |
EventSignal< WMouseEvent > & | doubleClicked () |
Event signal emitted when a mouse key was double clicked on this widget. More... | |
EventSignal< WMouseEvent > & | mouseWentDown () |
Event signal emitted when a mouse key was pushed down on this widget. More... | |
EventSignal< WMouseEvent > & | mouseWentUp () |
Event signal emitted when a mouse key was released on this widget. More... | |
EventSignal< WMouseEvent > & | mouseWentOut () |
Event signal emitted when the mouse went out of this widget. More... | |
EventSignal< WMouseEvent > & | mouseWentOver () |
Event signal emitted when the mouse entered this widget. More... | |
EventSignal< WMouseEvent > & | mouseMoved () |
Event signal emitted when the mouse moved over this widget. More... | |
EventSignal< WMouseEvent > & | mouseDragged () |
Event signal emitted when the mouse is dragged over this widget. More... | |
EventSignal< WMouseEvent > & | mouseWheel () |
Event signal emitted when the mouse scroll wheel was used. More... | |
EventSignal< WTouchEvent > & | touchStarted () |
Event signal emitted when a finger is placed on the screen. More... | |
EventSignal< WTouchEvent > & | touchEnded () |
Event signal emitted when a finger is removed from the screen. More... | |
EventSignal< WTouchEvent > & | touchMoved () |
Event signal emitted when a finger, which is already placed on the screen, is moved across the screen. More... | |
EventSignal< WGestureEvent > & | gestureStarted () |
Event signal emitted when a gesture is started. More... | |
EventSignal< WGestureEvent > & | gestureChanged () |
Event signal emitted when a gesture is changed. More... | |
EventSignal< WGestureEvent > & | gestureEnded () |
Event signal emitted when a gesture is ended. More... | |
void | setDraggable (const std::string &mimeType, WWidget *dragWidget=0, bool isDragWidgetOnly=false, WObject *sourceWidget=0) |
Configure dragging for drag and drop. More... | |
void | unsetDraggable () |
Disable drag & drop for this widget. More... | |
void | setMouseOverDelay (int delay) |
Sets a delay for the mouse over event. More... | |
int | mouseOverDelay () const |
Returns the mouse over signal delay. More... | |
virtual void | setPopup (bool popup) |
Lets the widget overlay over other sibling widgets. More... | |
virtual void | load () |
Loads content just before the widget is used. More... | |
virtual bool | isEnabled () const |
Returns whether the widget is enabled. More... | |
Public Member Functions inherited from Wt::WWebWidget | |
WWebWidget (WContainerWidget *parent=0) | |
Construct a WebWidget with a given parent. More... | |
virtual void | setPositionScheme (PositionScheme scheme) |
Sets the CSS position scheme. More... | |
virtual PositionScheme | positionScheme () const |
Returns the CSS position scheme. More... | |
virtual void | setOffsets (const WLength &offset, WFlags< Side > sides=All) |
Sets CSS offsets for a non-statically positioned widget. More... | |
virtual WLength | offset (Side s) const |
Returns a CSS offset. More... | |
virtual void | resize (const WLength &width, const WLength &height) |
Resizes the widget. More... | |
virtual WLength | width () const |
Returns the width. More... | |
virtual WLength | height () const |
Returns the height. More... | |
virtual void | setMinimumSize (const WLength &width, const WLength &height) |
Sets a minimum size. More... | |
virtual WLength | minimumWidth () const |
Returns the minimum width. More... | |
virtual WLength | minimumHeight () const |
Returns the minimum height. More... | |
virtual void | setMaximumSize (const WLength &width, const WLength &height) |
Sets a maximum size. More... | |
virtual WLength | maximumWidth () const |
Returns the maximum width. More... | |
virtual WLength | maximumHeight () const |
Returns the maximum height. More... | |
virtual void | setLineHeight (const WLength &height) |
Sets the CSS line height for contained text. | |
virtual WLength | lineHeight () const |
Returns the CSS line height for contained text. More... | |
virtual void | setFloatSide (Side s) |
Specifies a CSS float side. More... | |
virtual Side | floatSide () const |
Returns the CSS float side. More... | |
virtual void | setClearSides (WFlags< Side > sides) |
Sets the sides that should be cleared of floats. More... | |
virtual WFlags< Side > | clearSides () const |
Returns the sides that should remain empty. More... | |
virtual void | setMargin (const WLength &margin, WFlags< Side > sides=All) |
Sets CSS margins around the widget. More... | |
virtual WLength | margin (Side side) const |
Returns a CSS margin set. More... | |
virtual void | setHiddenKeepsGeometry (bool enabled) |
Sets whether the widget keeps its geometry when hidden. More... | |
virtual bool | hiddenKeepsGeometry () const |
Returns whether the widget keeps its geometry when hidden. More... | |
virtual void | setHidden (bool hidden, const WAnimation &animation=WAnimation()) |
Hides or shows the widget. More... | |
virtual bool | isHidden () const |
Returns whether the widget is set hidden. More... | |
virtual bool | isVisible () const |
Returns whether the widget is visible. More... | |
virtual void | setDisabled (bool disabled) |
Sets whether the widget is disabled. More... | |
virtual bool | isDisabled () const |
Returns whether the widget is set disabled. More... | |
virtual bool | isPopup () const |
Returns whether the widget is overlayed. More... | |
virtual void | setInline (bool isInline) |
Sets whether the widget is displayed inline or as a block. More... | |
virtual bool | isInline () const |
Returns whether the widget is displayed inline or as block. More... | |
virtual void | setDecorationStyle (const WCssDecorationStyle &style) |
Sets a CSS decoration style. More... | |
virtual WCssDecorationStyle & | decorationStyle () |
Returns the decoration style of this widget. More... | |
virtual void | setStyleClass (const WString &styleClass) |
Sets (one or more) CSS style classes. More... | |
virtual WString | styleClass () const |
Returns the CSS style class. More... | |
virtual void | addStyleClass (const WString &styleClass, bool force=false) |
Adds a CSS style class. More... | |
virtual void | removeStyleClass (const WString &styleClass, bool force=false) |
Removes a CSS style class. More... | |
virtual bool | hasStyleClass (const WString &styleClass) const |
Returns whether the widget has a style class. | |
virtual void | setVerticalAlignment (AlignmentFlag alignment, const WLength &length=WLength()) |
Sets the vertical alignment. More... | |
virtual AlignmentFlag | verticalAlignment () const |
Returns the vertical alignment. More... | |
virtual WLength | verticalAlignmentLength () const |
Returns the fixed vertical alignment that was set. More... | |
virtual void | setToolTip (const WString &text, TextFormat textFormat=PlainText) |
Sets a tooltip. More... | |
virtual void | setDeferredToolTip (bool enable, TextFormat textFormat=PlainText) |
Enable deferred tooltip. More... | |
virtual WString | toolTip () const |
Returns the tooltip. | |
virtual void | refresh () |
Refresh the widget. More... | |
virtual void | setAttributeValue (const std::string &name, const WString &value) |
Sets an attribute value. More... | |
virtual WString | attributeValue (const std::string &name) const |
Returns an attribute value. More... | |
virtual void | setJavaScriptMember (const std::string &name, const std::string &value) |
Sets a JavaScript member. More... | |
virtual std::string | javaScriptMember (const std::string &name) const |
Returns the value of a JavaScript member. More... | |
virtual void | callJavaScriptMember (const std::string &name, const std::string &args) |
Calls a JavaScript member. More... | |
virtual bool | loaded () const |
Returns whether this widget has been loaded. More... | |
virtual void | setId (const std::string &id) |
Sets the CSS Id. More... | |
virtual WWidget * | find (const std::string &name) |
Finds a descendent widget by name. More... | |
virtual WWidget * | findById (const std::string &id) |
Finds a descendent widget by id. | |
virtual void | setSelectable (bool selectable) |
Sets as selectable. More... | |
virtual void | doJavaScript (const std::string &javascript) |
Executes the given JavaScript statements when the widget is rendered or updated. More... | |
virtual const std::string | id () const |
Returns the (unique) identifier for this object. More... | |
void | setLoadLaterWhenInvisible (bool) |
Change the way the widget is loaded when invisible. More... | |
std::string | htmlTagName () const |
returns the current html tag name More... | |
void | setHtmlTagName (const std::string &tag) |
set the custom HTML tag name More... | |
const std::vector< WWidget * > & | children () const |
Returns contained widgets. More... | |
Signal & | childrenChanged () |
Signal emitted when children have been added or removed. More... | |
virtual void | setCanReceiveFocus (bool enabled) |
Sets whether the widget can receive focus. More... | |
virtual bool | canReceiveFocus () const |
Returns whether the widget can receive focus. More... | |
virtual bool | setFirstFocus () |
Set focus on the widget's first descendant. More... | |
virtual void | setFocus (bool focus) |
Sets focus. More... | |
virtual bool | hasFocus () const |
Returns whether the widget currently has the focus. | |
virtual void | setTabIndex (int index) |
Sets the tab index. More... | |
virtual int | tabIndex () const |
Returns the tab index. More... | |
EventSignal & | blurred () |
Signal emitted when the widget lost focus. More... | |
EventSignal & | focussed () |
Signal emitted when the widget recieved focus. More... | |
virtual bool | scrollVisibilityEnabled () const WT_CXX11ONLY(finaloverride) |
Returns whether scroll visibility detection is enabled for this widget. More... | |
virtual void | setScrollVisibilityEnabled (bool enabled) WT_CXX11ONLY(finaloverride) |
Sets whether scroll visibility detection is enabled for this widget. More... | |
virtual int | scrollVisibilityMargin () const WT_CXX11ONLY(finaloverride) |
Returns the margin around the viewport within which the widget is considered visible. More... | |
virtual void | setScrollVisibilityMargin (int margin) WT_CXX11ONLY(finaloverride) |
Sets the margin around the viewport within which the widget is considered visible. More... | |
virtual Signal< bool > & | scrollVisibilityChanged () WT_CXX11ONLY(finaloverride) |
Signal triggered when the scroll visibility of this widget changes. More... | |
virtual bool | isScrollVisible () const WT_CXX11ONLY(finaloverride) |
Returns whether this widget is currently considered scroll visible. More... | |
virtual void | setThemeStyleEnabled (bool enabled) |
Sets whether theme styling for a widget is enabled or disabled. More... | |
virtual bool | isThemeStyleEnabled () const |
Returns whether this widget is currently styled by the chosen theme. More... | |
Public Member Functions inherited from Wt::WWidget | |
virtual | ~WWidget () |
Destructor. More... | |
WWidget * | parent () const |
Returns the parent widget. More... | |
virtual void | removeChild (WObject *child) |
Removes a child object. More... | |
void | setWidth (const WLength &width) |
Sets the width. More... | |
void | setHeight (const WLength &height) |
Sets the height. More... | |
virtual void | positionAt (const WWidget *widget, Orientation orientation=Vertical) |
Positions a widget next to another widget. More... | |
virtual void | toggleStyleClass (const WString &styleClass, bool add, bool force=false) |
Toggles a CSS style class. | |
std::string | jsRef () const |
Returns a JavaScript expression to the corresponding DOM node. More... | |
void | setFocus () |
Sets focus. More... | |
virtual void | acceptDrops (const std::string &mimeType, const WString &hoverStyleClass=WString()) |
Sets a mime type to be accepted for dropping. More... | |
virtual void | stopAcceptDrops (const std::string &mimeType) |
Indicates that a mime type is no longer accepted for dropping. More... | |
virtual void | setObjectName (const std::string &name) |
Sets an object name. More... | |
virtual void | htmlText (std::ostream &out) |
Streams the (X)HTML representation. More... | |
bool | isRendered () const |
Returns whether the widget is rendered. More... | |
void | hide () |
Hides the widget. More... | |
void | animateHide (const WAnimation &animation) |
Hides the widget using an animation. More... | |
void | show () |
Shows the widget. More... | |
void | animateShow (const WAnimation &animation) |
Shows the widget using an animation. More... | |
void | enable () |
Enables the widget. More... | |
void | disable () |
Disable thes widget. More... | |
bool | layoutSizeAware () const |
Returns whether the widget is layout size aware. More... | |
Public Member Functions inherited from Wt::WObject | |
WObject (WObject *parent=0) | |
Create a WObject with a given parent object. More... | |
virtual | ~WObject () |
Destructor. More... | |
virtual std::string | objectName () const |
Returns the object name. More... | |
void | resetLearnedSlots () |
Resets learned stateless slot implementations. More... | |
template<class T > | |
void | resetLearnedSlot (void(T::*method)()) |
Resets a learned stateless slot implementation. More... | |
template<class T > | |
WStatelessSlot * | implementStateless (void(T::*method)()) |
Declares a slot to be stateless and learn client-side behaviour on first invocation. More... | |
template<class T > | |
WStatelessSlot * | implementStateless (void(T::*method)(), void(T::*undoMethod)()) |
Declares a slot to be stateless and learn client-side behaviour in advance. More... | |
void | isNotStateless () |
Marks the current function as not stateless. More... | |
template<class T > | |
WStatelessSlot * | implementJavaScript (void(T::*method)(), const std::string &jsCode) |
Provides a JavaScript implementation for a method. More... | |
void | addChild (WObject *child) |
Adds a child object. More... | |
const std::vector< WObject * > & | children () const |
Returns the children. | |
WObject * | parent () const |
Returns the parent object. | |
Additional Inherited Members | |
Static Public Member Functions inherited from Wt::WWebWidget | |
static WString | escapeText (const WString &text, bool newlinesToo=false) |
Escape HTML control characters in the text, to display literally (deprecated). More... | |
static std::string & | escapeText (std::string &text, bool newlinestoo=false) |
Escape HTML control characters in the text, to display literally (deprecated). More... | |
static bool | removeScript (WString &text) |
Remove tags/attributes from text that are not passive (deprecated). More... | |
static std::string | jsStringLiteral (const std::string &v, char delimiter= '\'') |
Turn a UTF8 encoded string into a JavaScript string literal. More... | |
Static Public Member Functions inherited from Wt::WWidget | |
static WString | tr (const char *key) |
Short hand for WString::tr() More... | |
Protected Member Functions inherited from Wt::WInteractWidget | |
virtual void | propagateSetEnabled (bool enabled) |
Propagates that a widget was enabled or disabled through children. More... | |
Protected Member Functions inherited from Wt::WWebWidget | |
virtual void | enableAjax () |
Progresses to an Ajax-enabled widget. More... | |
virtual WStatelessSlot * | getStateless (Method method) |
On-demand stateless slot implementation. More... | |
virtual void | render (WFlags< RenderFlag > flags) |
Renders the widget. More... | |
Protected Member Functions inherited from Wt::WWidget | |
void | setLayoutSizeAware (bool sizeAware) |
Sets the widget to be aware of its size set by a layout manager. More... | |
virtual void | layoutSizeChanged (int width, int height) |
Virtual method that indicates a size change. More... | |
WWidget (WContainerWidget *parent=0) | |
Creates a widget. More... | |
virtual void | dropEvent (WDropEvent dropEvent) |
Handles a drop event. More... | |
virtual int | boxPadding (Orientation orientation) const |
Returns the widget's built-in padding. More... | |
virtual int | boxBorder (Orientation orientation) const |
Returns the widget's built-in border width. More... | |
void | scheduleRender (WFlags< RepaintFlag > flags=0) |
Schedules rerendering of the widget. More... | |
Static Protected Member Functions inherited from Wt::WObject | |
static WObject * | sender () |
Returns the sender of the current slot call. More... | |
A widget that holds and manages child widgets.
A WContainerWidget acts as a container for child widgets. Child widgets may be added directly to the container or using a layout manager.
Use addWidget() or pass the container as constructor argument to a widget to directly add children to the container, without using a layout manager. In that case, CSS-based layout is used, and the resulting display is determined by properties of the children and the container. By default, a WContainerWidget is displayed as a block and manages its children within a rectangle. Inline child widgets are layed out in lines, wrapping around as needed, while block child widgets are stacked vertically. The container may add padding at the container edges using setPadding(), and provide alignment of contents using setContentAlignment(). A container is rendered by default using a HTML div
tag, but this may be changed to an HTML ul
or ol
tag to make use of other CSS layout techniques, using setList(). In addition, specializations of this class as implemented by WAnchor, WGroupBox, WStackedWidget and WTableCell provide other alternative rendering of the container.
When setting the WContainerWidget inline the container only acts as a conceptual container, offering a common style to its children. Inline children are still layed out inline within the flow of the parent container of this container, as if they were inserted directly into that parent container. Block children are then not allowed (according to the HTML specification).
To use a layout manager instead of CSS-based layout, use setLayout() or pass the container as constructor argument to a layout manager. In that case you should not define any padding for the container, and widgets and nested layout managers must be added to the layout manager, instead of to the container directly.
Usage example:
When using a layout manager, you need to carefully consider the alignment of the layout manager with respect to the container: when the container's height is unconstrained (not specified explicitly using resize() or a style class, and the container is not included in a layout manager), you should pass AlignTop to setLayout().
Depending on its configuration and usage, the widget corresponds to the following HTML tags:
<div>
tag.<span>
.<ul>
.<ol>
.<li>
.This widget does not provide styling, and can be styled using inline or external CSS as appropriate.
|
virtual |
Adds a child widget to this container.
This is equivalent to passing this container as the parent when constructing the child. The widget is appended to the list of children, and thus also layed-out at the end.
Reimplemented in Wt::Ext::Splitter, and Wt::WStackedWidget.
|
virtual |
Removes and deletes all child widgets.
This deletes all children that have been added to this container.
If a layout was set, also the layout manager is deleted.
WFlags<AlignmentFlag> Wt::WContainerWidget::contentAlignment | ( | ) | const |
Returns the alignment of children.
Inserts a child widget in this container, before another widget.
The widget is inserted at the place of the before
widget, and subsequent widgets are shifted.
Reimplemented in Wt::Ext::Splitter.
|
virtual |
Inserts a child widget in this container at given index.
The widget is inserted at the given index
, and subsequent widgets are shifted.
Reimplemented in Wt::Ext::Splitter, and Wt::WStackedWidget.
bool Wt::WContainerWidget::isList | ( | ) | const |
Returns if this container is rendered as a List.
bool Wt::WContainerWidget::isOrderedList | ( | ) | const |
Returns if this container is rendered as an Ordered List.
bool Wt::WContainerWidget::isUnorderedList | ( | ) | const |
Returns if this container is rendered as an Unordered List.
|
virtual |
Returns the layout manager that was set for the container.
If no layout manager was previously set using setLayout(WLayout *), 0 is returned.
Reimplemented from Wt::WWidget.
Returns the padding set for the widget.
|
virtual |
Removes a child widget from this container.
This removes the widget from this container, but does not delete the widget !
EventSignal< WScrollEvent > & Wt::WContainerWidget::scrolled | ( | ) |
Event signal emitted when scrolling in the widget.
This event is emitted when the user scrolls in the widget (for setting the scroll bar policy, see setOverflow()). The event conveys details such as the new scroll bar position, the total contents height and the current widget height.
int Wt::WContainerWidget::scrollLeft | ( | ) | const |
return the number of pixels the container is scrolled vertically
This value is only set if setOverflow() has been called
int Wt::WContainerWidget::scrollTop | ( | ) | const |
return the number of pixels the container is scrolled horizontally
This value is only set if setOverflow() has been called
void Wt::WContainerWidget::setContentAlignment | ( | WFlags< AlignmentFlag > | contentAlignment | ) |
Specifies how child widgets must be aligned within the container.
For a WContainerWidget, only specifes the horizontal alignment of child widgets. Note that there is no way to specify vertical alignment: children are always pushed to the top of the container.
For a WTableCell, this may also specify the vertical alignment. The default alignment is (Wt::AlignTop | Wt::AlignLeft).
|
virtual |
Sets a layout manager for the container.
Note that you can nest layout managers inside each other, to create a complex layout hierarchy.
If a previous layout manager was already set, it is first deleted. In that case, you will need to make sure that you either readd all widgets that were part of the previous layout to the new layout, or delete them, to avoid memory leaks.
Reimplemented from Wt::WWidget.
void Wt::WContainerWidget::setLayout | ( | WLayout * | layout, |
WFlags< AlignmentFlag > | alignment | ||
) |
Sets a layout manager for the container (deprecated).
The alignment
argument determines how the layout is aligned inside the container. By default, the layout manager arranges children over the entire width and height of the container, corresponding to a value of AlignJustify.
In general, alignment
is the logical OR of a horizontal and a vertical flag:
When using a horizontal alignment different from Wt::AlignJustify, and a vertical alignment different from '0', the widget is sized in that direction to fit the contents, instead of the contents being adjusted to the widget size. This is useful when the container does not have a specific size in that direction and when the layout manager does not contain any widgets that wish to consume all remaining space in that direction.
The widget will take ownership of layout
.
void Wt::WContainerWidget::setList | ( | bool | list, |
bool | ordered = false |
||
) |
Renders the container as an HTML list.
Setting renderList
to true
will cause the container to be using an HTML <ul>
or <ol>
type, depending on the value of orderedList
. This must be set before the initial render of the container. When set, any contained WContainerWidget will be rendered as an HTML <li>
. Adding non-WContainerWidget children results in unspecified behaviour.
Note that CSS default layout rules for <ul>
and <ol>
add margin and padding to the container, which may look odd if you do not use bullets.
By default, a container is rendered using a <div>
element.
void Wt::WContainerWidget::setOverflow | ( | Overflow | overflow, |
WFlags< Orientation > | orientation = (Horizontal | Vertical) |
||
) |
Sets how overflow of contained children must be handled.
This is an alternative (CSS-ish) way to configure scroll bars on a container widget, compared to wrapping inside a WScrollArea.
Unlike WScrollArea, horizontal scrolling does not work reliably when the container widget is inserted in a layout manager: the layout manager will overflow rather than use scrollbars for this container widget. A solution then is to use WScrollArea instead.