# wx.ScrollBar¶

A wx.ScrollBar is a control that represents a horizontal or vertical scrollbar.

It is distinct from the two scrollbars that some windows provide automatically, but the two types of scrollbar share the way events are received.

## Window Styles¶

This class supports the following styles:

• wx.SB_HORIZONTAL: Specifies a horizontal scrollbar.

• wx.SB_VERTICAL: Specifies a vertical scrollbar.

## Events Emitted by this Class¶

Handlers bound for the following event types will receive a wx.ScrollEvent parameter.

• EVT_SCROLL: Process all scroll events.

• EVT_SCROLL_TOP: Process wxEVT_SCROLL_TOP scroll to top or leftmost (minimum) position events.

• EVT_SCROLL_BOTTOM: Process wxEVT_SCROLL_BOTTOM scroll to bottom or rightmost (maximum) position events.

• EVT_SCROLL_LINEUP: Process wxEVT_SCROLL_LINEUP line up or left events.

• EVT_SCROLL_LINEDOWN: Process wxEVT_SCROLL_LINEDOWN line down or right events.

• EVT_SCROLL_PAGEUP: Process wxEVT_SCROLL_PAGEUP page up or left events.

• EVT_SCROLL_PAGEDOWN: Process wxEVT_SCROLL_PAGEDOWN page down or right events.

• EVT_SCROLL_THUMBTRACK: Process wxEVT_SCROLL_THUMBTRACK thumbtrack events (frequent events sent as the user drags the thumbtrack).

• EVT_SCROLL_THUMBRELEASE: Process wxEVT_SCROLL_THUMBRELEASE thumb release events.

• EVT_SCROLL_CHANGED: Process wxEVT_SCROLL_CHANGED end of scrolling events (MSW only).

• EVT_COMMAND_SCROLL: Process all scroll events.

• EVT_COMMAND_SCROLL_TOP: Process wxEVT_SCROLL_TOP scroll to top or leftmost (minimum) position events.

• EVT_COMMAND_SCROLL_BOTTOM: Process wxEVT_SCROLL_BOTTOM scroll to bottom or rightmost (maximum) position events.

• EVT_COMMAND_SCROLL_LINEUP: Process wxEVT_SCROLL_LINEUP line up or left events.

• EVT_COMMAND_SCROLL_LINEDOWN: Process wxEVT_SCROLL_LINEDOWN line down or right events.

• EVT_COMMAND_SCROLL_PAGEUP: Process wxEVT_SCROLL_PAGEUP page up or left events.

• EVT_COMMAND_SCROLL_PAGEDOWN: Process wxEVT_SCROLL_PAGEDOWN page down or right events.

• EVT_COMMAND_SCROLL_THUMBTRACK: Process wxEVT_SCROLL_THUMBTRACK thumbtrack events (frequent events sent as the user drags the thumbtrack).

• EVT_COMMAND_SCROLL_THUMBRELEASE: Process wxEVT_SCROLL_THUMBRELEASE thumb release events.

• EVT_COMMAND_SCROLL_CHANGED: Process wxEVT_SCROLL_CHANGED end of scrolling events (MSW only).

## The difference between EVT_SCROLL_THUMBRELEASE and EVT_SCROLL_CHANGED¶

The EVT_SCROLL_THUMBRELEASE event is only emitted when actually dragging the thumb using the mouse and releasing it (This EVT_SCROLL_THUMBRELEASE event is also followed by an EVT_SCROLL_CHANGED event). The EVT_SCROLL_CHANGED event also occurs when using the keyboard to change the thumb position, and when clicking next to the thumb (In all these cases the EVT_SCROLL_THUMBRELEASE event does not happen). In short, the EVT_SCROLL_CHANGED event is triggered when scrolling/moving has finished independently of the way it had started. Please see the Widgets Sample (“Slider” page) to see the difference between EVT_SCROLL_THUMBRELEASE and EVT_SCROLL_CHANGED in action.

Note

A scrollbar has the following main attributes: range, thumb size, page size, and position. The range is the total number of units associated with the view represented by the scrollbar. For a table with 15 columns, the range would be 15. The thumb size is the number of units that are currently visible. For the table example, the window might be sized so that only 5 columns are currently visible, in which case the application would set the thumb size to 5. When the thumb size becomes the same as or greater than the range, the scrollbar will be automatically hidden on most platforms. The page size is the number of units that the scrollbar should scroll by, when ‘paging’ through the data. This value is normally the same as the thumb size length, because it is natural to assume that the visible window size defines a page. The scrollbar position is the current thumb position. Most applications will find it convenient to provide a function called AdjustScrollbars() which can be called initially, from an OnSize event handler, and whenever the application data changes in size. It will adjust the view, object and page size according to the size of the window and the size of the data.

## Class Hierarchy¶

Inheritance diagram for class ScrollBar:

wxMSW

wxMAC

wxGTK

## Methods Summary¶

 __init__ Default constructor. Create Scrollbar creation function called by the scrollbar constructor. GetClassDefaultAttributes GetPageSize Returns the page size of the scrollbar. GetRange Returns the length of the scrollbar. GetThumbPosition Returns the current position of the scrollbar thumb. GetThumbSize Returns the thumb or ‘view’ size. IsVertical Returns True for scrollbars that have the vertical style set. SetScrollbar Sets the scrollbar properties. SetThumbPosition Sets the position of the scrollbar.

## Class API¶

class wx.ScrollBar(Control)

Possible constructors:

ScrollBar()

ScrollBar(parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize,
style=SB_HORIZONTAL, validator=DefaultValidator, name=ScrollBarNameStr)


A ScrollBar is a control that represents a horizontal or vertical scrollbar.

### Methods¶

__init__(self, *args, **kw)

__init__ (self)

Default constructor.

__init__ (self, parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize, style=SB_HORIZONTAL, validator=DefaultValidator, name=ScrollBarNameStr)

Constructor, creating and showing a scrollbar.

Parameters
• parent (wx.Window) – Parent window. Must be not None.

• id (wx.WindowID) – Window identifier. The value wx.ID_ANY indicates a default value.

• pos (wx.Point) – Window position. If wx.DefaultPosition is specified then a default position is chosen.

• size (wx.Size) – Window size. If wx.DefaultSize is specified then a default size is chosen.

• style (long) – Window style. See wx.ScrollBar.

• validator (wx.Validator) – Window validator.

• name (string) – Window name.

Create(self, parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize, style=SB_HORIZONTAL, validator=DefaultValidator, name=ScrollBarNameStr)

Scrollbar creation function called by the scrollbar constructor.

See wx.ScrollBar for details.

Parameters
Return type

bool

static GetClassDefaultAttributes(variant=WINDOW_VARIANT_NORMAL)
Parameters

variant (WindowVariant) –

Return type

wx.VisualAttributes

GetPageSize(self)

Returns the page size of the scrollbar.

This is the number of scroll units that will be scrolled when the user pages up or down. Often it is the same as the thumb size.

Return type

int

GetRange(self)

Returns the length of the scrollbar.

Return type

int

GetThumbPosition(self)

Returns the current position of the scrollbar thumb.

Return type

int

GetThumbSize(self)

Returns the thumb or ‘view’ size.

Return type

int

IsVertical(self)

Returns True for scrollbars that have the vertical style set.

Return type

bool

SetScrollbar(self, position, thumbSize, range, pageSize, refresh=True)

Sets the scrollbar properties.

Parameters
• position (int) – The position of the scrollbar in scroll units.

• thumbSize (int) – The size of the thumb, or visible portion of the scrollbar, in scroll units.

• range (int) – The maximum position of the scrollbar.

• pageSize (int) – The size of the page size in scroll units. This is the number of units the scrollbar will scroll when it is paged up or down. Often it is the same as the thumb size.

• refresh (bool) – True to redraw the scrollbar, False otherwise.

Note

Let’s say you wish to display 50 lines of text, using the same font. The window is sized so that you can only see 16 lines at a time. You would use:

scrollbar.SetScrollbar(0, 16, 50, 15)


The page size is 1 less than the thumb size so that the last line of the previous page will be visible on the next page, to help orient the user. Note that with the window at this size, the thumb position can never go above 50 minus 16, or 34. You can determine how many lines are currently visible by dividing the current view size by the character height in pixels. When defining your own scrollbar behaviour, you will always need to recalculate the scrollbar settings when the window size changes. You could therefore put your scrollbar calculations and SetScrollbar call into a function named AdjustScrollbars, which can be called initially and also from a wx.SizeEvent event handler function.

SetThumbPosition(self, viewStart)

Sets the position of the scrollbar.

Parameters

viewStart (int) – The position of the scrollbar thumb.

### Properties¶

PageSize

Range

ThumbPosition

ThumbSize