WidgetScrollbarDecorator : Adds scrollbar functionality to a QWidget. More...

#include <WidgetScrollbarDecorator.h>

Public Member Functions
bool	enabled () const
	Check whether the target is currently scrollable. More...

WidgetScrollbarDecorator &	operator= (WidgetScrollbarDecorator)=delete

void	setEnabled (bool enable)
	Enable or disable scrollable behaviour. More...

void	setThresholdHeight (int height)
	Set the height, in pixels, at which scrollbars should appear. More...

void	setThresholdSize (int width, int height)
	Set the size, in pixels, at which scrollbars should appear. More...

void	setThresholdWidth (int width)
	Set the width, in pixels, at which scrollbars should appear. More...

	WidgetScrollbarDecorator (const WidgetScrollbarDecorator &)=delete

	WidgetScrollbarDecorator (QWidget *target)
	Constructor. More...

virtual	~WidgetScrollbarDecorator ()
	Destructor. More...

Private Attributes
bool	m_enabled
	Whether the target is currently scrollable. More...

QVBoxLayout *	m_layout
	Main layout used when scrollable. More...

QWidget *	m_offscreen
	Used to hold above widgets when disabled. More...

QScrollArea *	m_scrollarea
	Used to provide scrolling functionality. More...

QWidget *	m_target
	The target widget that is given scrollbars. More...

QWidget *	m_viewport
	Single widget inside QScrollArea. More...

Detailed Description

WidgetScrollbarDecorator : Adds scrollbar functionality to a QWidget.

Mainly intended to make QDialogs and QMainWindows scrollable since this feature is missing in Qt. This allows particularly large dialogs to be used on laptops and other devices with small screens.

Both horizontal and vertical scrollbars are provided. Scrollbars are only visible when needed (when the dialog/widget is too small to display all widgets at their minimum size). Qt automatically attempts to resize dialogs to fit on the screen that they show up on.

Usage:

Create an instance of this class (usually as a class member)

private:

WidgetScrollbarDecorator m_scrollbars;

MantidQt::API::WidgetScrollbarDecorator

WidgetScrollbarDecorator : Adds scrollbar functionality to a QWidget.

Definition: WidgetScrollbarDecorator.h:77

Initialise with the widget that needs scrollbars (usually this )

ExampleDialog::ExampleDialog() : m_scrollbars(this) {}

Enable scrollbars (only after the UI has been set up!)

ui->setupUi(this); // MUST happen first

m_scrollbars.setEnabled(true);

MantidQt::API::WidgetScrollbarDecorator::setEnabled

void setEnabled(bool enable)

Enable or disable scrollable behaviour.

Definition: WidgetScrollbarDecorator.cpp:87

Details:

The reason scrollbars should only be enabled after the UI is set up is that this decorator works by pulling the main layout of the target widget out (along with all widgets inside of it), adding its own layout and scrollarea widgets to the target, and finally placing the original layout inside of the scrollarea.

For Designer-created dialogs, this means that setupUi(this) must be called before scrollbars are enabled. Widgets can still be accessed as usual via the ui object. This includes adding, removing, moving, etc widgets, as long as it is done using ui->mainLayout rather than this->layout().

For manually created dialogs, this means that you have to at least create a main layout for your dialog before enabling the scrollbars. Note that after enabling scrollbars, this->layout() will no longer be the layout that you created. So, if you want to access your layout or add more widgets later, you should keep a pointer to it and work with that.

Definition at line 77 of file WidgetScrollbarDecorator.h.

Constructor & Destructor Documentation

◆ WidgetScrollbarDecorator() [1/2]

WidgetScrollbarDecorator::WidgetScrollbarDecorator ( QWidget * target )

explicit

Constructor.

Parameters

target The target widget to be extended with scrollbar functionality.

Definition at line 22 of file WidgetScrollbarDecorator.cpp.

References m_layout, m_offscreen, m_scrollarea, m_target, and m_viewport.

◆ ~WidgetScrollbarDecorator()

WidgetScrollbarDecorator::~WidgetScrollbarDecorator ( )

virtual

Destructor.

Definition at line 50 of file WidgetScrollbarDecorator.cpp.

References m_offscreen.

◆ WidgetScrollbarDecorator() [2/2]

MantidQt::API::WidgetScrollbarDecorator::WidgetScrollbarDecorator ( const WidgetScrollbarDecorator & )

delete

Member Function Documentation

◆ enabled()

bool WidgetScrollbarDecorator::enabled ( ) const

Check whether the target is currently scrollable.

Returns: true if the target is currently scrollable, false otherwise.

Definition at line 61 of file WidgetScrollbarDecorator.cpp.

References m_enabled.

Referenced by setEnabled().

◆ operator=()

WidgetScrollbarDecorator & MantidQt::API::WidgetScrollbarDecorator::operator= ( WidgetScrollbarDecorator )

delete

◆ setEnabled()

void WidgetScrollbarDecorator::setEnabled ( bool enable )

Enable or disable scrollable behaviour.

Enable or disable scrollable behaviour on the target.

This works by shuffling layouts using a sparsely documented feature of QWidget::setLayout(). Normally, you cannot remove a layout once it is set without deleting it (and all contained widgets along with it). You also cannot call setLayout() on a widget that already has a layout.

However, if the layout you pass to setLayout() is already set on a different widget, that layout and all contained widgets are reparented, effectively removing it from the widget it was on. But, for this to work, you need a layout-less widget to call setLayout() on.

Since this class works with three widgets (the target widget, the viewport inside of the scrollable area, and an offscreen dummy widget) and only two layouts (the layout of the target widget and the layout that contains the scrollarea), there is always one widget that has no layout.

When scrolling is enabled, m_offscreen is empty. When scrolling is disabled, m_viewport is empty.

Parameters

enable Whether the target should be scrollable or not.

Definition at line 87 of file WidgetScrollbarDecorator.cpp.

References enabled(), m_enabled, m_layout, m_offscreen, m_target, and m_viewport.

Referenced by MantidQt::CustomDialogs::StartLiveDataDialog::initLayout().

◆ setThresholdHeight()

void WidgetScrollbarDecorator::setThresholdHeight ( int height )

Set the height, in pixels, at which scrollbars should appear.

This overrides the default behaviour of preferring to shrink widgets until they reach their minimum size before enabling scrollbars. Note that scrollbars will be enabled before reaching this size setting if the minimum size of all widgets is reached first.

Set to 0 to reset to default behaviour.

Parameters

height Minimum height target may shrink to before scrollbars appear

Definition at line 131 of file WidgetScrollbarDecorator.cpp.

References height, and m_viewport.

◆ setThresholdSize()

void WidgetScrollbarDecorator::setThresholdSize	(	int	width,
		int	height
	)

Set the size, in pixels, at which scrollbars should appear.

This overrides the default behaviour of preferring to shrink widgets until they reach their minimum size before enabling scrollbars. Note that scrollbars will be enabled before reaching this size setting if the minimum size of all widgets is reached first.

Set to (0, 0) to reset to default behaviour.

Parameters

width	Minimum width target may shrink to before scrollbars appear
height	Minimum height target may shrink to before scrollbars appear

Definition at line 147 of file WidgetScrollbarDecorator.cpp.

References height, and m_viewport.

◆ setThresholdWidth()

void WidgetScrollbarDecorator::setThresholdWidth ( int width )

Set the width, in pixels, at which scrollbars should appear.

This overrides the default behaviour of preferring to shrink widgets until they reach their minimum size before enabling scrollbars. Note that scrollbars will be enabled before reaching this size setting if the minimum size of all widgets is reached first.

Set to 0 to reset to default behaviour.

Parameters

width Minimum width target may shrink to before scrollbars appear

Definition at line 116 of file WidgetScrollbarDecorator.cpp.

References m_viewport.